EGU Leonardo Conference Series on the Hydrological Cycle
FLOODS IN 3D: PROCESSES, PATTERNS, PREDICTIONS
EGU Leonardo Conference
23-25 November 2011
Bratislava, Slovakia
Edited by: J. Szolgay, M. Danáčová, K. Hlavčová, S. Kohnová, V. Pišteková Published by: Slovak University of Technology in Bratislava
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© Department of Land and Water Resources Management,
Faculty of Civil Engineering, Slovak University of Technology,
Radlinského 11, 813 68 Bratislava, Slovakia
Number of prints: 120 copies
Number of pages: 110
ISBN 978-80-227-3596-4
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EGU Leonardo Topical Conference Series on the Hydrological Cycle
FLOODS IN 3D: PROCESSES, PATTERNS, PREDICTIONS
ORGANISED BY: Department of Land and Water Resources Management,
Faculty of Civil Engineering, Slovak University of Technology in Bratislava.
INTERNATIONAL SCIENTIFIC COMMITTEE
Alberto Montanari Università di Bologna, Bologna, Italy Attilio Castellarin Università di Bologna, Bologna, Italy Bob Moore Centre for Ecology & Hydrology, Wallingford, Oxfordshire, UK Bruno Merz The Helmholtz Research Centre for Geosciences GFZ, Potsdam,
Germany G. di Baldassarre Institute for Water Education, Delft, The Netherlands G.T. Aronica University of Messina, Messina, Italy Henrik Madsen DHI, Hørsholm, Denmark Marco Borga University of Padua, Padova, Italy Pierluigi Claps Politecnico di Torino, Torino, Italy Ralf Merz The Helmholtz Centre for Environmental Research, Leipzig, Germany Roger Moussa Institut National de la Recherche Agronomique, Montpellier, France Thomas Kjeldsen Centre for Ecology & Hydrology, Wallingford, Oxfordshire, UK
CONFERENCE CHAIR Jan Szolgay Slovak University of Technology in Bratislava, Bratislava, Slovakia
LOCAL ORGANIZING COMITTEE AT FACULTY OF CIVIL ENGINEERING, SLOVAK UNIVERSITY OF TECHNOLOGY
Kamila Hlavčová
Silvia Kohnová
Michaela Danáčová
Jana Daneková
Katarína Juričeková
Silvia Stasselová
Viera Pišteková
Gabriela Babiaková
Editorial
This book of abstracts contains 100 contributions submitted by more than 90
registered authors from 19 countries. The authors take full responsibility for all
content.
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PREFACE
The frequency of disastrous floods, number of fatalities, as well as the economic damage,
caused by floods is globally increasing. In this respect environmental changes (such as land-
use change, inappropriate river management, and climate variability) have raised increasing
concern. Defining reliable and robust flood-risk assessment strategies for emerging and
developing countries is also a pressing need because of the lack of data and inappropriate
land-use and developments.
For these reasons, predicting current and future flood risks continues to be a major challenge
for society and science when considering strategies for mitigating and coping with the impact
of flooding. As natural phenomena caused by meteorological factors, floods are governed by
various landscape properties and modified by human influence. Successful strategies for
living with and coping with floods must therefore be based on a sound understanding of the
main generating processes of extreme flows, including their spatial and temporal patterns.
Incorporating this kind of understanding into predictive models is needed for the reduction of
flood risks, and for addressing the potential impacts of global changes on hydrological
extremes, including climate and land-use changes.
The 2011 Leonardo Conference therefore had the ambition of looking at Floods in 3D:
• Processes
• Patterns
• Predictions
To assess and compare developments and impacts, a better understanding of flood
processes is essential. This is not an easy task as human activities have disrupted the
natural hydrological regimes. Nowadays most river basins cannot be considered pristine. The
scientific literature clearly points to the importance of detecting and understanding of
hydrological change, especially through improving process-understanding and separating of
anthropogenic from natural variations, possibly avoiding an overemphasis on trends.
Spatial patterns of flood processes exist on different scales, from small-scale patterns
resulting from different runoff production mechanisms operating within a single catchment, to
large-scale patterns, caused by the regional variability in hydrometeorology. There has been
an increasing need to assess uncertainties when studying spatial and temporal patterns of
floods and analysing their possible impact on flood management. The analysis of spatial
patterns is central to any regional flood frequency analysis procedure. The analysis of
temporal patterns of floods is fundamental to the understanding and assessment of
variations in flood frequency.
The complex nature of flood risk challenges has established risk assessment methodologies
along with their modelling components, such as hydrological and hydraulic simulation
methods. Predicting current and future flood risk continues to be a major challenge for
climatology, hydrology and water resources engineering. While we have a good qualitative
understanding of factors which may lead to changes in flood frequency and flood risk (such
as climatic change, land-use effects and human interference in river channels and on flood
plains), our quantitative understanding of changes in flood hazard and flood risk is still in
need of improvement.
These three dimensions of floods were addressed at the 2011 EGU Leonardo Conference,
which offered a forum within which the most recent advances for investigating flood
processes, patterns and predictions were debated.
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TABLE OF CONTENTS
LEONARDO LECTURE
LOOKING AT FLOODS IN 3D - PROCESSES, PATTERNS, PREDICTIONS: Blöschl, G.
..................................................................................................................................... 1
Session: PROCESSES
WHY IT CAN BE WORTH USING A DIFFUSIVE MODEL INSTEAD OF A FULLY DYNAMIC ONE: Aricò, C. - Sinagra, M. - Tucciarelli, T. ................................................................ 5
INFLUENCE OF MICROTOPOGRAHY FOR "UNCERTAIN" FLOOD HAZARD ESTIMATION IN URBAN AREAS: Aronica, G.T. - Neal, J. - Candela, A. - Bates, P.D. ............................. 6
APPLICABILITY OF THE NRCS CURVE NUMBER METHOD TO SMALL LOWLAND CATCHMENT IN POLAND: Banasik, K. - Woodward, D. .................................................... 7
HYDROMETEOROLOGICAL, HYDROLOGICAL AND HYDRAULIC ANALYSIS FOR THE NOV 1, 2010 FLOOD EVENT IN THE VENETO REGION OF ITALY: Borga, M. - Zoccatelli, D. - Marra, F. - Penna, D. - Marchi, L. - Frank, E. ................................................................ 8
(FLASH) FLOODS ON 27 AUGUST 2010 IN LOWLAND CATCHMENTS IN THE NETHERLANDS AND GERMANY: Brauer, C.C. - Teuling, A.J. - Overeem, A. - Van der Velde, Y. - Hazenberg, P. - Warmerdam, P.M.M - Uijlenhoet, R. - Hobbelt, L.G. .................. 9
ASSIMILATION OF ASCAT, AMSR-E AND ECMWF DERIVED SOIL MOISTURE PRODUCT FOR FLOOD FORECASTING: Brocca, L. - Melone, F. - Moramarco, T. - Zucco, G. - Wagner, W. - Hasenauer, S. - De Rosnay, P. - Albergel, C. - Matgen, P. - Martin, C. .... 10
DEFINITION OF SOIL MOISTURE INITIAL CONDITION INTO A DISTRIBUTED HYDROLOGICAL MODEL THROUGH LAND SURFACE TEMPERATURE FROM REMOTE SENSING IN THE UPPER YANGTZE RIVER BASIN: Corbari, C. - Mancini, M. - Li, J. - Bob Su ................................................................................................................................... 11
CASE STUDY OF USING HYDROLOGIC FLOW ROUTING FOR ESTIMATING THE RELATIONSHIP BETWEEN THE TRAVEL TIME OF FLOOD PEAKS AND DISCHARGE: Danáčová, M. - Šúrek, P. - Szolgay, J. ........................................................................ 12
ESTIMATION OF FUTURE FLOOD RISK FOR FLOOD WARNING SYSTEMS IN TORYSA RIVER BASIN: Daneková, J. - Výleta, R. - Hlavčová, K. ................................................. 13
EVALUATING THE PERFORMANCE OF METEOROLOGICAL FORECASTS AND RE-ANALYSIS USING GLOBAL RIVER ROUTING: Dutra, E. - Dai Yamazaki - Wetterhall, F. - Pappenberger, F. - Balsamo, G. ..................................................................................... 14
A NEW MODELLING TOOL FOR DETERMINING THE CATCHMENT HYDROLOGICAL RESPONSE (CASE STUDY: ISONZO RIVER): Ferri, M. - Monego, M. - Norbiato, D. - Bauruffi, F. ........................................................................................................................ 15
ANALYSES OF THE DEPENDENCE STRUCTURE OF SIMULATED FLOOD PEAK-VOLUME DATA USING COPULAS: Gaál, L. – Bacigál, T. – Viglione, A. – Szolgay, J. ..... 16
APPLICATION OF BAYESIAN MCMC METHODS FOR INCLUSION OF HISTORICAL FLOODS IN A STATISTICAL ESTIMATION OF DESIGN MAXIMUM FLOODS: Gaál, L. - Kohnová, S. - Szolgay, J. ................................................................................................. 17
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WHAT HAS BEEN LEARNED FROM THE POST FLASH FLOOD SURVEYS RECENTLY CONDUCTED IN EUROPE?: Gaume, E. - Borga, M. - Marchi, L. .................................... 18
RETROSPECTIVE CASE STUDIES OF FLOOD SIMULATIONS TO ADDRESS THE SOCIOPOLITICAL ISSUES: Hoes, O. - Tariq, M.A.U.R ................................................. 19
TOWARDS ADVANCED SOLUTIONS FOR THE CALIBRATION OF HEAVY METAL DISPERSION CONTAMINATION MODELLING IN FLOODPLAIN: Hostache, R. - Matgen, P.
- Hissler, C. - Kies, T. - Tosheva, Z. - Stille, P. - David, E. - Bates, P. ........................... 20
OPERATIVE EVALUATION OF PEAK OUTFLOW DURING FLASH FLOOD USING ARTIFICIAL INTELLIGENCE METHODS: Janál, P. - Stary, M. ....................................... 21
URBAN FOOTPRINTS ON CATCHMENT STORM RUNOFF: Kjeldsen, T.R. - Miller, J.D. - Packman, J.C. ............................................................................................................ 22
ESTIMATING CATCHMENT SCALE RETENTION CAPACITY FROM SCATTEROMETER SOIL MOISTURE DATA: Komma, J. - Merz, R. - Blöschl, G. - Wagner, W. ................ 23
3-DIMENSIONAL MODELING OF RUNOFF GENERATION OF A MOUNTAINOUS RIVER: Kuchment, L.S. - Demidov, V.N. ..................................................................................... 24
ON THE VALUE OF MULTIOBJECTIVE OPTIMISATION FOR PROFITING FROM SOFT INFORMATION IN UNGAUGED BASINS: Lombardi, L. - Montosi, E. - Toth, E. - Castellarin, A. - Montanari, A. ............................................................................................................ 25
RECONSTRUCTION OF THE HYDRAULIC CONDITIONS OF THE 1951 INUNDATION OF THE POLESINE REGION, ITALY: Masoero, A. - Claps, P. - Di Baldassarre, G. - Asselman, N. ................................................................................................................................... 26
2D HYDRODYNAMIC FLOOD MODELLING IN A GRAVEL BED BRAIDED RIVER: Molnar, P.- Boehringer, D. - Wanner, P. - Burlando, P. .............................................................. 27
EVALUATION AND MODELLING OF THE IMPACT OF LAND USE ON DISCHARGE, NITRATE AND SUSPENDED SOLIDS CONCENTRATION BY FLOOD EVENTS IN SMALL CATCHMENTS: Moravcova, J. - Pavlicek, T. - Ondr, P. - Koupilova, M. - Kvitek, T. .... 28
ON THE USE OF THE DIFFUSIVE WAVE MODEL FOR MODELLING EXTREME FLOOD EVENTS IN THE FLOODPLAIN: NATURAL vs ANTHROPOGENIC CATCHMENTS: Moussa, R. - Ghesquière, J. - Bocquillon, C. .............................................................. 29
A COMPARISON OF DIFFERENT APPROACHES TO DESIGN FLOOD ESTIMATION IN ALPINE CATCHMENTS: Rogger, M. - Kohl, B. - Merz, R. - Viglione, A. - Blöschl, G. .... 30
WOODY DEBRIS TRANSPORT DURING FLOODS: 2D HYDRODYNAMIC MODELLING APPROACH: Ruiz Villanueva, V. - Bladé Castellet, E. - Sánchez Juny, M. - Bodoque del Pozo, J.M. - Díez Herrero, A. ..................................................................................... 31
DISCHARGE HYDROGRAPH ESTIMATION USING 2D DIFFUSIVE MODEL AND SYNCRONOUS WATER LEVEL MEASUREMENTS: Sinagra, M. - Nasello, C. - Moramarco, T. - Tucciarelli, T. ............................................................................................................ 32
SNOWMELT RUNOFF PREDICTION IN THE UPPER EUPHRATES BASIN, TURKEY: Sorman, A.A. - Gozel, E. - Sensoy, A. ......................................................................... 33
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INFORMATION EXPANSION FOR UNDERSTANDING TRANS-BASIN FLOODS: Uhlemann, S. - Thieken, A. - Merz, B. ......................................................................... 34
FLOOD INUNDATION MODELLING IN LARGE RIVERS UNDER UNCERTAINTY USING GLOBALLY AND FREELY AVAILABLE REMOTE SENSING DATA: Yan, K. - Di Baldassarre, G. - Solomatine, D. - Dottori, F. .............................................................. 35
Session: PATTERNS
DESIGN FLOOD GENERATION FOR LOWLAND RIVER SECTIONS ACCOUNTING THE UNCERTAINTY GENERATED BY SUPERPOSITION AND COINCIDENCE OF FLOODS: Bálint, G. - Lipták, G. - Szilágyi, J. - Zempléni, A. .............................................................. 39
INDIRECT ESTIMATION OF DESIGN VALUES OF HEAVY RAINFALL IN THE ALPINE REGION OF SLOVAKIA: A CASE STUDY: Bara, M. - Látečková, J. - Kohnová, S. - Gaál, L. - Szolgay, J. - Hlavčová, K. ................................................................................................. 40
FLOOD POTENTIAL IN SMALL BASINS OF SLOVAKIA: Barka, I. - Minár, J. - Trizna, M. - Bonk, R. ........................................................................................................................ 41
THE SURFACE WATER OCEAN TOPOGRAPHY SATELLITE MISSION: PROSPECTS FOR FLOOD SCIENCE: Bates, P. ..................................................................................... 42
EUROPEAN FLOOD DATA AVAILABILITY AND PARENT DISTRIBUTION OF ANNUAL FLOODS: Castellarin, A. - Kohnova, S. - ES0901 – WG2 Team ....................................... 43
ACCOUNTING FOR EXTREME FLOODS OCCURRED AT UNGAUGED SITES IN REGIONAL FLOOD FREQUENCY STUDIES: Cong, N.C. - Payrastre, O. - Gaume, E. .... 44
INFLUENCE OF OCEANIC PHENOMENA ON FLOODS: Diez, J.J. - Esteban, M.D. - López-Gutiérrez, J.S. - Negro, V. ................................................................................................. 45
INVESTIGATING RUNOFF GENERATION MECHANISMS IN A SWISS PRE ALPINE CATCHMENT BY SPATIAL INTERCOMPARISON: Fischer, Benjamin, M.C. - Seibert, J. .. 46
SCENARIOS OF HEAVY, FLOOD-TRIGGERING PRECIPITATION IN THE CARPATHIAN AREA, ON THE BASIS OF HIGH RESOLUTION REGIONAL CLIMATE MODELS: Gaál, L. - Beranová, R. - Kyselý, J. - Hlavčová, K. ......................................................................... 47
CLIMATOLOGICAL AND GEOLOGICAL CONTROLS OF REGIONAL PATTERNS OF FLOOD TIME SCALES IN AUSTRIA: Gaál, L. - Szolgay, J. - Kohnová, S. - Parajka, J. - Merz, R. - Blöschl, G. ................................................................................................. 48
USING PROXIMITY ALONG THE RIVER NETWORK TO IMPROVE DESIGN FLOOD ESTIMATION AT UNGAUGED SITES: Ganora, D. - Laio, F. - Claps, P. ........................... 49
IMPROVING SIMULATIONS OF INUNDATION PATTERNS BY AIRBORNE LASER SCANNING ANALYSES - A CASE STUDY IN A DANUBE WETLAND: Gschöpf C. - Vetter M. - Blöschl, G. ............................................................................................................ 50
CAN WE ATTRIBUTE FLOOD TRENDS?: Merz, B. - Delgado, J. - Hundecha, Y. - Nguyen, D. - Uhlemann, S. - Vorogushyn, S. ..................................................................................... 51
CROSS-CALIBRATION AT REGIONAL SCALE FOR RAINFALL-RUNOFF MODELING IN UNGAUGED CATCHMENTS: Montosi, E. - Montanari , A. - Toth, E. - Parajka, J. - Blöschl, G. ................................................................................................................................... 52
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ANTICIPATORY FLOOD RISK ASSESSMENT - CASE STUDIES FROM AUSTRIA: Neuhold, C. ........................................................................................................................... 53
ELBE 3D – A SPATIO-TEMPORAL ANALYSIS OF SOIL MOISTURE PATTERNS LINKED TO EXTREME FLOODS IN THE ELBE RIVER BASIN: Nied, M, - Hundecha, Y. - Merz, B. ................................................................................................................................... 54
THE GRADEX-KC AND GRADEX-ZN METHODS FOR COMPUTING MAXIMUM FLOODS WITH T-YEAR RETURN PERIOD WHERE DISCHARGE MEASUREMENT SERIES ARE INCOMPLETE: Ozga-Zieliński, B. ................................................................................................................................... 55
DECADES OF FLOOD SEASONALITY ACROSS THE ALPINE-CARPATHIAN RANGE: Parajka, J. - Kohnová, S. - Szolgay, J. - Merz, R. - Hlavčová, K. - Blöschl, G. ................ 56
AN ANALYSIS OF CHANGE IN ALPINE ANNUAL MAXIMUM DISCHARGES: IMPLICATIONS FOR THE SELECTION OF DESIGN DISCHARGES: Pistocchi, A. - Castellarin, A. ............................................................................................................ 57
T-YEAR MAXIMUM DISCHARGES ON WATER COURSES IN SLOVAKIA: Podolinská, J. - Šipikalová, H. - Kohnová, S. ................................................................................................. 58
FLOOD PREDICTION IN UNGAUGED CATCHMENTS: REDUCING UNCERTAINTY WITH AN OPTIMUM USE OF REGIONAL INFORMATION: Randrianasolo, A. - Ramos, M-H - Andréassian, V. ............................................................................................................ 59
STOCHASTIC MODELING OF LARGE FLOODS - SPATIAL DEPENDENCE BETWEEN LOCAL RUNOFFS: Raschke, M. ..................................................................................... 60
A NEW QUALITATIVE FIELD METHOD TO CAPTURE SHALLOW SOIL MOISTURE PATTERNS IN WET ENVIRONMENTS: Rinderer, M. - Kollegger, A. - Fischer, B. - Seibert, J. ................................................................................................................................... 61
COMPARISON AND COMBINATION OF FLOOD REGIONALIZATION METHODS IN SAXONY, GERMANY: Salinas, J.L. - Merz, R. - Laaha, G. - Walther, J. - Büttner, U. .... 62
COUPLING TOPOLOGICAL AND CANONICAL KRIGING FOR DESIGN-FLOOD PREDICTION IN UNGAUGED BASINS IN THE SOUTHEASTERN UNITED STATES: Stacey A. Archfield - Castellarin, A. - Jon O. Skøien - Julie E. Kiang ........................... 63
POTENTIAL OF HIGH RESOLUTION MODELLING OF RUNOFF GENERATION PROCESSES: Steinbrich, A. - Weiler, M. ......................................................................... 64
A THREE STEP APPROACH TO ANALYSIS OF FLOOD HAZARDS IN COASTAL BASINS: CASE SAR-ULLA RIVER, GALICIA-SPAIN: Vegas, E. - García, E. - Álvarez, C. - Listen, M. ................................................................................................................................... 65
EXTREME RAINSTORMS: TESTING REGIONAL ENVELOPE CURVES AGAINST STOCHASTICALLY GENERATED EVENTS: Viglione, A. - Castellarin, A. - Rogger, M. - Merz, R. - Blöschl, G. ................................................................................................. 66
MECHANISMS OF CLIMATE CHANGE EFFECTS ON FLOODS: Viglione, A. - Salinas, J.L. - Merz, R. - Blöschl, G. ................................................................................................. 67
BIVARIATE FLOOD ESTIMATION BY DIFFERENT THRESHOLD MODELS: Zempléni, A. - Bálint, G. ........................................................................................................................ 68
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ON THE RELATIVE ROLES OF HILLSLOPE PROCESSES AND RIVER NETWORK IN THE HYDROLOGIC RESPONSE TO SPACE-TIME VARIABLE RAINFALL FIELDS: Zoccatelli, D. - Borga, M. ........................................................................................................................ 69
Session: PREDICTIONS
TOWARDS A SEAMLESS FLOOD EARLY WARNING SYSTEM: FROM FLASH FLOODS TO GLOBAL FORECASTING: Alfieri, L. - Salamon, P. - Pappenberger, F. - Burek, P. - Krzeminski, B. - Muraro, D. - Thielen, J. - de Roo, A. .................................................. 73
THE MULTIVARIATE STATISTICAL ANALYSIS OF THE EXTREME HYDROLOGICAL EVENTS: Bačová Mitková, V. ..................................................................................... 74
ON THE JOINT ESTIMATION OF FLOOD FREQUENCY DISTRIBUTIONS AT SEASONAL AND ANNUAL TIME SCALE: Baratti, E. - Montanari, A. - Castellarin, A. - Bezzi, A. - Di Giulio, A. - Ruzzante, E. ................................................................................................. 75
MODELLING OF CLIMATE CHANGE IMPACTS ON FLOODS BY CONTINUOUS SIMULATION WITH UNCERTAINTY: Blazkova, S. - Beven, K. - Martinkova, M. ................ 76
PERSISTENCE AS A FACTOR OF FLOOD HAZARD FOR EMBANKED RIVERS: Bogdanowicz, E. - Strupczewski, W.G. - Kochanek, K. .................................................. 77
DESIGN FLOOD PROFILES ESTIMATION: FREEBOARD VERSUS UNCERTAINTY BOUNDS: Brandimarte, L. - Di Baldassarre, G. .............................................................. 78
PROBABILISTIC FORECASTING OF ANTECEDENT SOIL MOISTURE CONDITION AS FLASH FLOOD PRECURSOR VARIABLES: Brigandì, G. - Aronica, G.T. - Loukas, A. - Vasiliades, L. - Papaioannou, G. ..................................................................................... 79
FLOOD PROTECTION OF THE CITY OF LJUBLJANA AND EXPERIENCES GAINED DURING THE SEPTEMBER 2010 FLOOD: Brilly, M. - Vidmar, A. - Rusjan, S. ................ 80
NEW METHODS OF FLASH FLOOD FORECASTING AT THE CZECH HYDROMETEOROLOGICAL INSTITUTE: Březková, L. - Novák, P. - Jonov, M. - Kyznarová, H. - Šálek, M. - Frolík, P. - Janál, P. .............................................................. 81
EFFECTS OF UNCERTAINTY IN BOUNDARY CONDITIONS ON FLOOD HAZARD ASSESSMENT: Domeneghetti, A. - Vorogushyn, S. - Castellarin, A. - Merz, B. - Brath, A. ................................................................................................................................... 82
THE VALUE OF URBAN FLOOD MAPPING: APPLICATION TO THE CASE STUDY OF BARCELONNETTE (FRANCE): Dottori, F. - Di Baldassarre, G. - Alfonso, L. ................ 83
OPEN SOURCE GIS TOOLS FOR FLOOD HAZARD MAPPING WITHIN THE DANUBE FLOOD RISK PROJECT: Franceschi, S. - Monacelli, G. - Rigon, R. ........................... 84
UNCERTAINTY ESTIMATION OF SIMULATED WATER LEVELS FOR THE MITCH FLOOD EVENT IN TEGUCIGALPA : Fuentes, D.C. - Halldin, S. - Xu, C-Y. - Lundin, L-C .... 85
INTEGRATION OF TIME SERIES MANAGEMENT SYSTEM AND DATA SERVING FOR MODELLING APPLICATIONS: Gál, R. ......................................................................... 86
ASSESSMENT OF PROJECTED CHANGES IN PRECIPITATION EXTREMES IN THE CZECH REPUBLIC USING A NON-STATIONARY INDEX FLOOD MODEL: Hanel, M. - Vizina, A. - Martínková, M. ................................................................................................. 87
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SAFEFTY CRITERIA FOR FLOOD PROTECTION STRUCTURES IN SLOVENIA: Humar, N. - Kryžanowski, A. - Brilly, M. - Schnabl, S. ......................................................................... 88
SPRING FLOOD FREQUENCY ANALYSIS OF LITHUANIAN RIVERS: Kriaučiūnienė, J. - Šarauskienė, D. ............................................................................................................ 89
ESTIMATION OF FLOOD FREQUENCY CURVES IN POORLY GAUGED MEDITERRANEAN WATERSHEDS USING A DERIVED DISTRIBUTION PROCEDURE: Loukas, A. - Vasiliades, L. - Papaioannou, G. - Aronica, G.T. ....................................... 90
CLIMATE CHANGE IMPACT ASSESSMENT OF FLOOD RISK. CASE STUDY: VIDAA RIVER BASIN: Madsen, H. - Larsen, J. - Madsen, M.N. .................................................. 91
FLOOD RISK MAPPING UNDER UNCERTAINTY: APPLICATION TO SUNGAI JOHOR BASIN MALAYSIA: Md. Ali, A. – Di Baldassare, G. – Solomatine, D. ...................................92
FLOOD IN TOWN – DECISION SUPPORT TOOL (VESNA): Mišík, M. - Kučera, M. - Fridrich Tegelhoffová, M. - Mrnčo, I. ................................................................................................. 93
UNCERTAINTY IN 1D HYDRAULIC MODELLING CAUSED BY PARAMETERIZATION AND INFLOW INACCURACY: Mukolwe, M.M. - Di Baldassarre, G. - Werner, M. - Solomatine, D. ................................................................................................................................... 94
UNCERTAINTY ASSESSMENT OF STREAMFLOW SIMULATION ON UNGAUGED CATCHMENTS USING A DISTRIBUTED MODEL AND THE KALMAN FILTER BASED MISP ALGORITHM: Múnera, J.C. - Francés, F. - Todini, E. ....................................... 95
TOWARDS SPATIALLY DISTRIBUTED FLOOD FORECASTS IN FLASH FLOOD PRONE AREAS: RESULTS OF A FIRST TEST IN THE SOUTH OF FRANCE: Naulin, J-P - Payrastre, O. - Gaume, E. - Delrieu, G. - Arnaud, P. - Lutoff, C. - Vincendon, B. ................ 96
PROBABILISTIC FLOOD RISK MAPPING INCLUDING SPATIAL DEPENDENCE: Neal, J. - Keef, C. - Bates, P. - Beven, K. - Leedal, D. .............................................................. 97
ENSEMBLE PREDICTION OF FLOODS – PROCESS CONTROLS: Nester, T. - Blöschl, G. ................................................................................................................................... 98
FLOOD HAZARD UNDER CLIMATE CHANGE IN THE MEKONG DELTA: Nguyen, V.D. - Delgado, J.M. - Merz, B. - Bárdossy, A. - Apel, H. .............................................................. 99
FLOOD PRONE AREAS MAPPING THROUGH GIS AND MULTI-CRITERIA ANALYSIS: Papaioannou, G. - Loukas, A. - Vasiliades, L. - Aronica, G.T. ..................................... 100
VISUALISING PROBABILISTIC FLOOD FORECAST INFORMATION: EXPERT PREFERENCES AND PERCEPTIONS OF BEST PRACTICE IN UNCERTAINTY COMMUNICATION: Pappenberger, F. - Stephens, E. - Thielen, J. - Salamon, P. - Demeritt, D. - van Andel, S.J. - Wetterhall, F. - Alfieri, L. ............................................................ 101
DEVELOPMENT OF DECISION SUPPORT SYSTEMS FOR FLASH FLOOD FORECASTING IN SMALL CATCHMENTS: Poma, S. - Brigandì, G. - Aronica, G.T. - Candela, A. ...................................................................................................................... 102
AN ENTROPY APPROACH FOR THE OPTIMIZATION OF RIVER CROSS-SECTIONAL SPACING: Ridolfi, E. – Alfonso,L. - Di Baldassarre, G. – Dottori, F. – Russo, F. – Napolitano, F. ................................................................................................................................. 103
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FLOOD-RISK MAPPING – A NEW INSIGHT INTO A MAJOR ENVIRONMENTAL PROBLEM: Romanowicz, R. - Kiczko, A. - Osuch, M. ................................................ 104
BAYESIAN UNCERTAINTY ASSESSMENT OF FLOOD PREDICTIONS IN UNGAUGED URBAN BASIS FOR CONCEPTUAL RAINFALL-RUNOFF MODELS: Sikorska A. - Scheidegger A. - Banasik K. - Rieckermann J. ............................................................ 105
DEVELOPMENT OF EXPECTED ANNUAL DAMAGE CURVES AND MAPS AS A BASIC TOOL FOR THE RISK-BASED DESIGNING OF STRUCTURAL AND NON-STRUCTURAL MEASURES: Tariq, M.A.U.R. - Van de Giesen, N.C. - Hoes, O. ..................................... 106
FLOOD FORECASTING WITH CONSTRAINED DOWNSTREAM CONDITION IN YUVACIK BASIN, TURKEY: Uysal, G. - Yavuz, Ö. – Şensoy, A. - Şorman, A.A. - Akgün, T. - Gezgin, T. ................................................................................................................................. 107
UNCERTAINTY ANALYSIS OF HEAVY RAINFALL EVENTS REPRESENTED BY A HYDROMETEOROLOGICAL MODEL AND SATELLITE RAINFALL ALGORITHM FOR FLOOD FORECASTING: Yucel, I. - Mert, I. ............................................................ 108
UNCERTAINTY ASSESSMENT OF CLIMATE CHANGE ADAPTATION OPTIONS IN URBAN FLASH FLOODS: Zhou, Q. - Arnbjerg-Nielsen, K. ..................................... 109
LEONARDO LECTURE
1
LOOKING AT FLOODS IN 3D - PROCESSES, PATTERNS, PREDICTIONS
Blöschl, G.
Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Vienna,
Austria
E-mail: [email protected]
Obtaining flood discharge values, be it for design purposes or operational flood
management, has traditionally focused on the estimation problem. In flood frequency
statistics we have developed ever more refined techniques for exploiting the information of
the flood sample, and in flood forecasting we have focused on sophisticated updating
procedures based on control theory. In this presentation I will argue that a fresh look is
needed at the flood estimation problem from three perspectives – processes, patterns,
predictions - to make better use of the wealth of hydrological knowledge gained in the past
century. From a process perspective, understanding the causal mechanisms of flood
generation at the catchment scale is the key. Analysing spatial patterns of dynamic flood
characteristics helps learn from the rich diversity of flood processes across the landscape. In
prediction it is essential to combine the causal, spatial and temporal information that may be
available on floods in the catchment of interest. I will present a number of examples from
Austria to illustrate the rich diversity of flood processes that are often site specific and difficult
to capture by formal methods. On the basis of these examples, and the various sources of
information, I will illustrate that hydrological reasoning and Bayesian methods give a more
complete representation of flood processes at a given site than the traditional estimation
methods alone. I propose the term ‘‘flood frequency hydrology,’’ as opposed to flood
frequency statistics, to reflect the focus on hydrological processes and hydrological
reasoning. By accounting for processes and patterns in the predictions, the single
dimensional estimation problem is transformed into a three dimensional hydrological
problem.
3
EGU Leonardo Conference Series on the Hydrological Cycle
SESSION: PROCESSES
Conveners: G. di Baldassare, M. Borga, A. Montanari, R. Moussa
This session focused on a number of gaps in scientific understanding and
modelling of flood processes and in predicting flood severity, such as:
• Understanding of coupled human and natural flood systems;
• Comparison (and integration) of hydraulic, hydrological and stochastic flood
models;
• Development of techniques for the assimilation of ground and remote sensing
data.
SESSION: PROCESSES
5
WHY IT CAN BE WORTH USING A DIFFUSIVE MODEL INSTEAD OF A FULLY
DYNAMIC ONE
Aricò, C., Sinagra, M. and Tucciarelli, T.
Department of Civil, Environmental and Aerospace Engineering, University of Palermo, Viale delle Scienze 90128
Palermo, Italy
Email: [email protected], [email protected], [email protected]
The paper is aimed to revise the traditional idea that the choice of a diffusive model instead
of the fully dynamic one, for the solution of the continuity and momentum equations
according to the shallow water hypothesis, is only a question of computational effort.
Additional, often prevailing motivations can be that: 1) in the Diffusive Shallow Water (DSW)
models only one boundary condition (b. c.) is required at each boundary point, where the
appropriate number of b. c. in the Fully dynamic Shallow Water (FSW) models can be zero,
two or three depending on the local Froude number, 2) most important, the sensitivity of the
computed water depth to the topographic error is much higher in the FSW models than in the
DSW ones.
Motivation (1) is often based on data limitation. For example, the availability of data regarding
supercritical flows entering the upstream domain boundary is often missing and in the FSW
solution the normal (i.e. uniform) flow condition is usually adopted to relate water depth to
discharge. Motivation (2) can be the most important one. Guinot and Cappallaere have
recently analyzed the sensitivity of a FSW 2D model with respect to the parameter errors,
where parameters are the topographic elevation, the Manning coefficient and the bed slope.
They have shown that, in the very simple case of frictionless, horizontal bed with uniform
steady-state flow, the sensitivity of the water depth with respect to the bed elevation error
can be computed as the solution of a Laplace equation, where the source term is inversely
proportional to the local Froude number. Because a diffusive model can be thought as a fully
dynamic one where the gravity force goes to infinity, the sensitivity of the DSW model is
always smaller than the sensitivity of the FSW one. The same conclusions can be obtained
for the 1D case by observing the behaviour of the water depth when a topographic change is
given for a constant energy value.
Several numerical tests are presented, where the real geometry of the channel bed is
simplified according to different approximation levels. Comparing the results of the diffusive
MAST-2D model with the results of the fully dynamic MAST-2C and BreZo models, it is
shown that the results of the FSW models are superior to the results of the DSW models only
for very detailed geometry reconstructions and mesh densities.
SESSION: PROCESSES
6
INFLUENCE OF MICROTOPOGRAHY FOR “UNCERTAIN” FLOOD HAZARD
ESTIMATION IN URBAN AREAS
Aronica, G.T.1, Neal, J.2, Candela, A.3 and Bates, P.D.2
1 Dipartimento di Ingegneria Civile, University of Messina, Italy
2 School of Geographical Sciences, University of Bristol, UK
3 Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, University of Palermo, Italy
Email: [email protected]
Floods are considered the most frequent natural disaster worldwide and may have serious
socio economic impacts in a community. Properties worth several billion euros are located on
floodplains in Europe, and many of these are classified as being at risk. The majority of these
properties are in urbanised areas. This is a problem as not only are properties located next to
river channels which may flood, but also because the rapid increase in the area covered by
impervious surfaces has increased runoff and led to enhanced local flooding as a
consequence of excess rainfall (pluvial flooding). Such floods have high spatial and temporal
variability and are strongly controlled by micro-scale features (depressions, walls, culverts)
within the catchment such that they are extremely difficult to predict. The above-described
phenomena make the estimation of flood risk in urban areas complex, since it must deal with
both main river flooding and flooding due to excess rainfall.
Local failures in inlets or culverts are often observed as a consequence of precipitation
events with even lower intensities than the design rainfall. Micro-topography effects are
usually responsible for those local failures, and their potential in terms of local flooding can
be investigated by taking a proper degree of topographic details into consideration.
Here, we test the ability of two computationally efficient hydraulic models: a two-dimensional
hyperbolic finite element model and a recently developed version of the LISFLOOD-FP
model which solves a reduced form of the full shallow water equations in a highly efficient
manner in analysing the effects of micro-topography for producing local flooding with
significant water depth and velocity in zones of flow concentration. These models are applied
to a case study in the city of Glasgow.
SESSION: PROCESSES
7
APPLICABILITY OF THE NRCS CURVE NUMBER METHOD TO SMALL
LOWLAND CATCHMENT IN POLAND
Banasik, K.1 and Woodward, D.2
1 Warsaw University of Life Sciences - SGGW, Department of Water Engineering, Sedimentation Laboratory, ul.
Nowoursynowska 166, PL-02-787 Warsaw, Poland 2 Natural Resources Conservation Service USDA, Washington D.C.
E-mail: [email protected], mailto:[email protected]
The NRCS Curve Number (known also as SCS-CN) method is well known as a tool in
predicting flood runoff from small ungauged catchment. The traditional way of determination
the CNs, based on soil characteristics, land use and hydrological conditions, seemed to have
tendency to overpredict the floods in some cases. A few year rainfall-runoff data, collected in
a small (A=82.4 km^2 ), lowland, agricultural catchment in Central Poland, were used to
determine runoff Curve Number and to check a tendency of changing. The date was
collected using an electronic system with a time step of recording of 10 minutes.
The analysis concluded, that using CN value according to the procedure described in USDA-
SCS Handbook one receives representative value for estimating runoff from high rainfall
depths. This has been confirmed by applying “asymptotic approach” for estimating the
watershed curve number from the rainfall-runoff data. Furthermore, the analysis indicated
that CN, estimated from mean retention parameter S of recorded events with rainfall depth
higher than initial abstraction, is also approaching the theoretical CN. The observed CN,
ranging from 52.3 to 95.5, declines with increasing storm size, which has been classified as a
standard response of watershed (Hawkins 1992). The investigation demonstrated also
changeability of the CN during the year, with much lower values during the growing season.
SESSION: PROCESSES
8
HYDROMETEOROLOGICAL, HYDROLOGICAL AND HYDRAULIC ANALYSIS
FOR THE NOV 1, 2010 FLOOD EVENT IN THE VENETO REGION OF ITALY
Borga, M. 1, Zoccatelli, D.1, Marra, F.1, Penna, D.1, Marchi, L.2 and Frank, E.3
1 Department of Land and Agroforest Environment, University of Padova, Legnaro, Italy
2 CNR IRPI - National Research Council of Italy, Research Institute for Hydrogeological Protection, Padova, Italy
3 BETA Studio s.r.l., Ponte San Nicolò (PD) – Italy
Email: [email protected], [email protected], [email protected]
Hydrometeorological analyses of rainfall and flood response are presented for the flood
event occurred over the Veneto Region in November 2010. The event – lasting three days -
produced localized storm total rainfall accumulation exceeding 500 mm. Hydrometeorological
and hydrologic studies illustrate the important role of orography in controlling the flood
response. Analyses of high-resolution radar rainfall fields are presented, with special
emphasis on radar rainfall error structure and the spatial and temporal variations of flood-
producing rainfall. Diagnostic and hydrologic model studies in a number of headwater
catchments were made possible thanks to availability of data from post-event surveys
executed just after the flood. The consistency of data from post-event surveys and from
conventional stream gauge stations is examined. Diagnostic studies over the Posina, Leogra
and Agno basins are carried out to examine the controls of orographic enhancement of
precipitation, space-time rainfall distribution and land surface processes on extreme flood
response. Land surface processes and the contrasting distribution of rainfall in space and
time from the storm systems, mainly due to the orographic control, combine to shape the
scale-dependent distribution of extreme floods in the study basins. Results are reported from
a hydraulic diagnostic analysis, based on a 2D hydrodynamic model, aimed to assess the
numerical description of the inundation in selected areas of the floodplains and its effect on
flood attenuation.
SESSION: PROCESSES
9
(FLASH) FLOODS ON 27 AUGUST 2010 IN LOWLAND CATCHMENTS IN THE
NETHERLANDS AND GERMANY
Brauer, C.C.1, Teuling, A.J.1,2, Overeem, A.1,3, Van der Velde, Y.1,4,5, Hazenberg, P.1,
Warmerdam, P.M.M.1, Uijlenhoet, R.1 and Hobbelt, L.G.1
1Hydrology and Quantitative Water Management Group, Wageningen University, P.O.Box 47, 6700AA
Wageningen, The Netherlands, 2formerly at: Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
3now at: Royal Netherlands Meteorological Institute, De Bilt, The Netherlands
4Soil Physics, Ecohydrology and Ground Water Management Group, Wageningen University, Wageningen, The
Netherlands 5now at: Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden
E-mail: [email protected]
On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany
were struck by a series of heavy rainfall events. Over an area of 740 km2 more than 120 mm
of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres,
highways and agricultural fields, and considerable financial loss.
We investigated the unprecedented flash flood triggered by this exceptionally heavy rainfall
event in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed
employed by Wageningen University since the 1960s. This study aims to improve our
understanding of the dynamics of such lowland flash floods. We present a detailed
hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological
characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar
and a microwave link, as well as the measured soil moisture, groundwater and discharge
response of the catchment.
We found that the response of the Hupsel Brook catchment can be divided into four phases:
(1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and
surface runoff and (4) backwater feedback. During this extreme event some thresholds
became apparent that do not play a role under average conditions and are not incorporated
in rainfall-runoff models.
Because of the large spatial extent of the rainfall event, many brooks and rivers in the
Netherlands and Germany flooded. With data from several catchments we investigated the
influence of rainfall and catchment characteristics (such as slope, size and land use) on the
response of discharge to rainfall.
SESSION: PROCESSES
10
ASSIMILATION OF ASCAT, AMSR-E AND ECMWF DERIVED SOIL MOISTURE
PRODUCT FOR FLOOD FORECASTING
Brocca, L.1, Melone, F.1, Moramarco, T.1, Zucco, G.1, Wagner, W.2, Hasenauer, S.2, De
Rosnay, P.3, Albergel, C.3, Matgen, P.4, Martin, C.5
1 Research Institute for Geo-Hydrological Protection, National Research Council, Perugia, Italy
2 Institute of Photogrammetry and Remote Sensing, Vienna University of Technology, Vienna, Austria
3 European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom
4 Public Research Centre - Gabriel Lippmann, CRP, Belvaux, Luxembourg
5 UMR -6012 ESPACE, Département de Géographie, Université de Nice-Sophia-Antipolis, Nice, France
E-mail: [email protected]; [email protected], [email protected],
[email protected], [email protected], [email protected], [email protected],
[email protected], [email protected], [email protected]
In recent years, steady increases in flood damages have led to a growing interest in the
development of flood forecasting systems operating in near real-time. Flood forecasting has
been widely approached by using rainfall-runoff models. However, uncertainties in model
structure, model parameters and input/output observations strongly impact the accuracy of
the predictions. To reduce this limitation, hydrological data assimilation has become an
important issue for research and applications. In particular, the assimilation of soil moisture
observations has the potential to provide great benefits for runoff prediction.
Nowadays, soil moisture estimates from satellite sensors and global meteorological models
are becoming more readily available with a spatial and temporal resolution that is suitable for
hydrological applications. On the other hand, different data assimilation techniques have
been developed and proposed for the optimal use of soil moisture observations in rainfall-
runoff modelling. Notwithstanding these large efforts, even after a decade of attempts to
improve hydrological predictions through the process of data assimilation, genuine 'success
stories' continue to be rare, arguably due to differences in the quality of data and models
used in different applications. Therefore, the following aspects have still to be addressed: the
improvement of the hydrological information retrieval from remotely sensed data, the choice
of the optimum data assimilation method, the quantitative description of model and
observation errors, the choice of assimilated data and the evaluation of data assimilation
effectiveness.
In this study, the soil moisture products derived from two different satellite sensors, the
Advanced Scatterometer and the Advanced Microwave Scanning Radiometer, and from the
ECMWF Integrated Forecasting System are employed. A multi-layer continuous and
distributed rainfall-runoff model, named MISDc-ML, is used to test and compare the
effectiveness of the different products for improving flood prediction. The Ensemble Kalman
filter is adopted to optimally incorporate the soil moisture data into MISDc-ML. Several
catchments located in different climatic regions over Europe are used as case studies.
The use of different soil moisture products, model structures (i.e. variable number of soil
layers) and study areas provides an in-depth understanding of the value of soil moisture data
assimilation in rainfall-runoff modelling. Results reveal that the three soil moisture products
can be conveniently used to improve runoff prediction. However, reliability differs according
to the climatic region of the catchment under investigation. Moreover, a detailed
characterization of the water movement in the soil through the structure of the rainfall-runoff
model is necessary in order to have a significant impact of the assimilated data in the model
itself.
SESSION: PROCESSES
11
DEFINITION OF SOIL MOISTURE INITIAL CONDITION INTO A DISTRIBUTED
HYDROLOGICAL MODEL THROUGH LAND SURFACE TEMPERATURE FROM
REMOTE SENSING IN THE UPPER YANGTZE RIVER BASIN
Corbari, C.1, Mancini, M.1, Li, J.2 and Bob Su3
1 Politecnico di Milano, Milano, Italy
2 China Institute of Water Resources and Hydropower Research, Beijing, China
3 University of Twente, Twente, The Netherlands
E-mail: [email protected]
This work investigates the potentiality of the use of operative remote sensing land surface
temperature observations (LST) as a proxy of surface soil moisture, which as well-known,
constitutes the soil initial condition before any storm event in real time flood forecasting
model, to improve real time flash flood forecast modeling in order to reduce and to manage
flood risk.
The application of distributed hydrological models, both in operative and scientific research,
is limited by the difficulties to verify evaporative fluxes and soil water content at the basin
scale. In fact, calibration and validation of distributed models generally depend on
comparison between simulated and observed discharges at the available river cross
sections, which are usually very few.
The use of thermal infrared data integrated with a hydrological model seems to solve the
limitation of microwave remote sensor in determining the surface soil moisture. LST from
remote sensing will be used for distributed hydrological model internal validation of the mass
and energy balance as a complementary method to the traditional discharge measurements.
A thermodynamic model for energy and mass balance computation will be implemented and
included into the distributed hydrological model FEST-EWB (Flash–flood Event–based
Spatially–distributed rainfall–runoff Transformation - Energy Water Balance). The energy
balance is solved looking for the representative thermodynamic equilibrium temperature
defined as the land surface temperature that closes the energy balance equation. This
temperature is an integral temperature, which is representative of a volume and of the
heterogeneity of the thermodynamic exchanges.
This scheme is applied from 2000 to 2010 in the Upper Yangtze River basin (China) with an
area of about 1 000 000 km2 where few ground hydrological and meteorological data are
available. Land surface temperature from MODIS and AATSR sensors will be used for the
validation of the distributed hydrological model FEST-EWB.
SESSION: PROCESSES
12
CASE STUDY OF USING HYDROLOGIC FLOW ROUTING FOR ESTIMATING
THE RELATIONSHIP BETWEEN THE TRAVEL TIME OF FLOOD PEAKS AND
DISCHARGE
Danáčová, M., Šúrek, P. and Szolgay, J.
Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Radlinskeho 11, 813 68 Bratislava, Slovakia
E-mail: [email protected], [email protected], [email protected]
The relationship between the travel time of flood peaks and discharge can be obtained
directly from historical hydrographs; however this method is time-consuming and requires
analysis of several dozens of such waves. To overcome this, an automatic parameter
optimisation technique was developed using hydrologic flow routing model for estimating the
relationship between the travel time of flood peaks and discharge. The practical applicability
of the concept was tested on the Morava River between Moravský Svätý Jan and Záhorská
Ves, the Laborec River between Krásny Brod, on the Torysa River between Brezovica –
Sabinov and on the Hron River between Brezno – Banská Bystrica. The travel-time
discharge relationship was assumed as being composed from chained successive linear
segments. Both the length and number of segments was allowed to vary. This relationship
was used to assess the travel time parameter in the discrete multilinear cascade model. The
modelled travel-time parameter vs. discharge relationships were estimated by optimisation of
the model performance with the help of a genetic algorithm and ANN. The relationships
between travel-time of flood peaks and peak discharge were also studied on these river
reaches based on data from several floods. The performance of the proposed method was
compared against relationships obtained from empirical data, and also by genetic
optimization of the flood routing model performance on a small set of floods, respectively.
The optimised piecewise linear relationship fitted well the empirical data on travel-times of
flood peaks and was also consistent with the findings in the literature. It was shown that the
relationships detected by the genetic optimisation exhibit the same behaviour as those
gained from the empirical data.
SESSION: PROCESSES
13
ESTIMATION OF FUTURE FLOOD RISK FOR FLOOD WARNING
SYSTEMS IN TORYSA RIVER BASIN
Daneková, J., Výleta, R. and Hlavčová, K.
Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Radlinskeho 11, 813 68 Bratislava, Slovakia
E-mail: [email protected], [email protected], [email protected]
The planning for flood-related emergencies could be supported by an estimate of the return
period of a forthcoming extreme flood event. A study of the relationship between the return
periods of floods and flood-causing precipitation on the Torysa River basin to the outlet at
Prešov located in the eastern part of Slovakia with an area of 673.89 km2 was taken as the
basis for such an estimate in this poster. A methodological framework for such an estimate,
based on a combination of statistical methods with a real time estimation of the soil moisture
index of the basin with the help of a lumped mathematical rainfall runoff model, was
proposed. A conceptual rainfall-runoff model with a daily time step was adopted for runoff
modelling. The study of the relationship between the modelled soil moisture index of river
basin at the beginning of the annual maximum floods and the flood-causing precipitation
totals showed no dependence between these two quantities. Using event-based flood
simulations, synthetic flood waves were generated for rainfall scenarios with the rainfall-
runoff model. The relationships between the return periods of the synthetic precipitation and
the return periods of the simulated floods were analysed, and the effect of antecedent basin
saturation index on the extremity of the floods was quantified. Critical values of the basin
saturation index leading to floods with higher return periods than the return period of flood-
causing precipitation were suggested.
SESSION: PROCESSES
14
EVALUATING THE PERFORMANCE OF METEOROLOGICAL FORECASTS AND
RE-ANALYSIS USING GLOBAL RIVER ROUTING
Dutra, E.1, Dai Yamazaki2, Wetterhall, F.1, Pappenberger, F.1 and Balsamo, G.1
1
European Centre for Medium-Range Weather Forecasts, Reading, UK 2
Institute of Industrial Science, University of Tokyo, Tokyo, Japan
E-mail: [email protected]
River discharge is a natural integrator of meteorological variables. The integration is made
over a spatial domain (catchment) which is geophysically appropriate, and over time. It takes
into account the correlations and covariances between several meteorological variables in a
meaningful way, integrating information from a multidimensional variable space.
Furthermore, river discharge observations are available and generally reliable. Therefore,
river discharge is an important variable to consider in verifying forecast performance, not only
from a meteorological standpoint but also for its relevance to applications. A river routing
scheme describing floodplain inundation dynamics is applied in the verification of
meteorological forecast and reanalysis. The scheme is forced by daily runoff fields generated
by the ECMWF land surface model HTESSEL in standalone mode, or runoff fields available
from the reanalysis and forecast products. The present model configuration runs globally at
about 25 km resolution (although the basic unit is a catchment rather than grid-point). In an
initial phase the routing scheme was tested and calibrated by carrying out simulations forced
by the output of HTESSEL offline. In these simulations, HTESSEL was forced by the ERA-
Interim with rescaled GPCP precipitation. The calibration was a necessary step, and was
performed by perturbing two model parameters (river bank height and river width) and
evaluating the river discharge on a global scale using about 1000 observations. Although the
limitations, and uncertainty of the calibration processes, the new set of model parameters led
to improved predictions of river discharge. Using this new parameters dataset, the routing
scheme was forced by the original ERA-40 and ERA-Interim runoff fields, as well as a
standalone simulation of HTESSEL forced by the original ERA-Interim dataset (LSH). The
LSHGPCP simulations provide the best predictions of river discharge, as expected, while
LSH, ERAI and ERA4 show some problems associated to under/over estimation of
precipitation. A clear signal was also found due to changes in the land surface model that
generates the runoff fields. Simulations of the routing scheme forced by the ECMWF
deterministic forecasts since 1995 to present are discussed, where the different model
changes can be compared in terms of predicting river discharge.
SESSION: PROCESSES
15
A NEW MODELLING TOOL FOR DETERMINING THE CATCHMENT
HYDROLOGICAL RESPONSE (CASE STUDY: ISONZO RIVER)
Ferri, M., Monego, M., Norbiato, D. and Bauruffi, F.
Autorità di bacino dei Fiumi dell’Alto Adriatico, Dorsoduro 3593, 30123 Venezia, Italy
E-mail: [email protected]
The River Basin Authority Alto Adriatico is responsible for the management of rivers flowing
into the Northern Adriatic Sea. With the purpose of contributing to the general objective of
theme “Advanced models and methods to improve the understanding and mitigation of
hydrological extreme events”, the paper contributes the experiences that are becoming part
of the European project KULTURisk, that aims at developing a culture of risk prevention by
means of a comprehensive demonstration of the benefits of prevention measures.
KULTURisk first focuses on water-related hazards as the likelihood and adverse impacts of
water-related catastrophes might increase in the near future because of land use and/or
climate changes. To achieve the aims of the project an innovative catchment scale
hydrological model has been implemented.
The basin hydrological response is estimated using a semi-distributed, continuous,
hydrological model based on a Geomorphoclimatic theory, relating the shape and scale of
the catchment transfer function to stream network topology, channels characteristics and
climate. Snow accumulation and melt are represented by using a distributed version of the
UEB model, while the soil water balance is solved towards a realistic description of the
temporal dynamics of soil moisture, with a physically based parameterisation which allows
use of vegetation coverage, soil texture and local slope data. The model captures the
essential physics of the relevant processes, rather than merely reproducing a
correspondence between inputs and outputs within a finite set of observations. Predictive
capabilities and robustness of the model were tested comparing simulation results with 9
years (2000-2008) of quality-controlled hourly data.
SESSION: PROCESSES
16
ANALYSIS OF THE DEPENDENCE STRUCTURE OF SIMULATED FLOOD PEAK-
VOLUME DATA USING COPULAS
Gaál, L.1, Bacigál, T.1, Viglione, A.2, Szolgay, J.1
1 Faculty of Civil Engineering, Slovak University of Technology, Bratislava, Slovakia
2 Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Vienna, Austria
E-mail: [email protected], [email protected], [email protected], [email protected]
In frequency analysis of hydro-climatological extremes, one is generally interested in the
extremes corresponding to low probabilities of the fitted cumulative distribution functions
(CDFs). However, usually there is not enough flood data in the right tail of the empirical
CDFs to derive reliable statistical inferences on the behaviour of the extremes. The scarcity
of the data is even more striking in a multivariate frequency analysis of variables (such as
flood peaks, volumes and durations etc.) where beside the marginal distributions of the
individual variables, one also needs to consider their dependence structure.
To extend the amount of information for the statistical inference, different techniques are
used. For instance, temporal extension methods allow for making use of historical or
paleoflood data, or spatial extension methods such as regional approaches extend the scope
of the analysis by pooling data in an adequately defined pooling group or region. In this
study, a different approach was adopted to increase the amount of data in the right tail of the
CDFs: our methodology took the advantage of simulated flood data from rainfall-runoff
modelling. The artificial flood data were then examined in terms of annual maxima of flood
peaks and flood volumes, and their dependence structure was analyzed by means of
copulas.
In order to generate artificial runoff data (i.e. to simulate flood records of lengths of
approximately 104–105 years), a two-step procedure was used. (i) First, the stochastic rainfall
generator proposed by Sivapalan et al. (2005) was modified for our purpose. This model is
based on the assumption of discrete rainfall events whose arrival times, durations, mean
rainfall intensity and the within-storm intensity patterns are all random, and can be described
by specified distributions. The mean storm rainfall intensity is disaggregated further to 15 min
intensity patterns. (ii) Secondly, the simulated rainfall data entered a semi-distributed
conceptual rainfall-runoff model that consisted of a snow routine, a soil moisture routine and
a flow routing routine. The applicability of the proposed method was demonstrated on a
selected site in Austria (Stampfangerbach Creek, Tirol). The pairs of simulated flood volumes
and flood peaks were analysed in terms of their dependence structure and different families
of copulas (Gumbel, Clayton, Frank, Plackett, Normal) were fitted to the observed and
simulated data. The question to what extent measured data can be used to find the right
copula was discussed.
SESSION: PROCESSES
17
APPLICATION OF BAYESIAN MCMC METHODS FOR INCLUSION OF
HISTORICAL FLOODS IN A STATISTICAL ESTIMATION OF DESIGN MAXIMUM
FLOODS
Gaál, L., Kohnová, S. and Szolgay, J.
Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Bratislava, Slovakia
E-mail: [email protected], [email protected], [email protected]
The presented work deals with temporal data extension for the purposes of a local frequency
analysis. The method consists in inclusion of historical hydrological events into the procedure
of flood quantile estimation. The statistical modelling takes the advantage of Monte Carlo
Markov chain simulations, which, within a Bayesian framework, represent a flexible tool for
an inclusion of hydrological information of different origin.
The practical aspects of Bayesian MCMC simulations are demonstrated through a case
study that focuses on the Myjava River at the cross-section Myjava. Two considerably high
flood peaks that appeared in the local series of observations are considered as ‘historical’
events, and we examine the results of the frequency analysis depending on whether i) these
two exceptional events are fully excluded from the data sample; whether ii) the whole series
of observations is analyzed or iii) the two discussed flood peaks are regarded as historical
events. The study suggests that the most acceptable results of the frequency analysis (i.e.,
the narrowest confidence intervals of the 100-year flood quantiles) are related to the last
option, which adopts the concept of inclusion of historical events.
SESSION: PROCESSES
18
WHAT HAS BEEN LEARNED FROM THE POST FLASH FLOOD SURVEYS
RECENTLY CONDUCTED IN EUROPE?
Gaume, E.1, Borga, M.2 and Marchi, L.3
1 IFSTTAR, Bouguenais, France,
2 University of Padova, Italy,
3 CNR – IRPI, Padova, Italy,
E-mail: [email protected], [email protected], [email protected]
Post-event survey and investigation is one way to gain experience on natural hazards. The
importance of the systematisation and standardisation of such investigations and re-analysis
is progressively recognised in all the geophysical sciences as shown by the growing number
of scientific papers and programs on the subject. But how to proceed in the case of flash
floods often affecting ungauged basins, what type of data should be collected for what type
of analyses and which particular issues to explore? To give a first answer to these questions,
a methodology for post-flash flood field investigations has been developed under the EC
FLOODsite project and tested under the EC HYDRATE project. Their usefulness having
been clearly demonstrated during these previous research programs, post-flood surveys
have been included in the observation strategy proposed for the recently launched HYMEX
project (Hydrological cycle in Mediterranean experiment). The principles of the post-flood
survey methodology will be shortly presented and its possible outcomes will be illustrated on
the basis of some flash floods recently analysed within the EC HYDRATE project.
SESSION: PROCESSES
19
RETROSPECTIVE CASE STUDIES OF FLOOD SIMULATIONS TO ADDRESS
THE SOCIOPOLITICAL ISSUES
Hoes, O. and Tariq, M.A.U.R.
Faculty of Civil Engineering and Geosciences, Technical University Delft, Stevinweg 1 Delft, 2628CN,
the Netherlands
E-mail: [email protected], [email protected]
At the end of World War II nearly 120 000 German soldiers were surrounded by allied forces
on a peninsula in the West of the Netherlands. As an act of despair the German army blasted
the dike surrounding a low-lying area in order to prevent landings of paratroopers. As a result
this 20 000 hectare large polder flooded in 48 hours with a layer of 4 meters of water. Over
7000 people succeeded to flee at once from the three villages in the area to higher grounds.
Despite the damage, this flood was well archived compared to other floods in polder areas in
the Netherlands. This provides today enough information to make this flood to be one of the
few full-scale experiments.
The objective of this paper is to compare the flood simulation results with the actual flood
data since 1945. Both the context, the breach growth process and the flood are explained in
our paper. Furthermore, it will be shown that to reproduce the flood - in our case - not bottom
friction, but final breach size is the only suitable but sensitive calibration parameter. For the
majority of all other conducted flood simulations in the Netherlands, such comprehensive
data are not available. This retrospective case simulation enhances the reliability of
simulations carried by the modern software tools with the help of GIS data.
SESSION: PROCESSES
20
TOWARDS ADVANCED SOLUTIONS FOR THE CALIBRATION OF HEAVY
METAL DISPERSION CONTAMINATION MODELLING IN FLOODPLAIN
Hostache, R.1, Matgen, P.1, Hissler, C. 1, Kies, T.2, Tosheva, Z.2, Stille, P.3, David, E.2 and
Bates, P.3
1 Environment and Agro-biotechnologies department, CRP – Gabriel Lippmann, 41 rue du Brill 4422 Belvaux,
Luxembourg, 2 Radiation Physics Laboratory, University of Luxembourg, 162A avenue de la Faïencerie 1511 Luxembourg,
Luxembourg 3 LHyGeS - UMR 7517, CNRS/EOST / UdS, 1 rue Blessig 67084 Strasbourg Cedex, France
4 Water Resources and Environment Division, SOGREAH Consultants, 6 rue de Lorraine B.P. 218 38432
Echirolles Cedex, France 5 School of Geographical Sciences, University of Bristol, University Road Bristol BS8 1SS, United-Kingdom
E-mail: [email protected] [email protected] [email protected],
[email protected] [email protected], [email protected], [email protected], [email protected]
Recent years have seen a growing awareness of the wider environmental significance of the
sediment loads transported by rivers and streams. This includes the importance of
suspended sediment in transporting nutrients and contaminants, such as some Potential
Harmful Elements (PHE - Cr, Co, Ni, Cu, Zn, As, Cd, Sn, Sb, Hg, Pb) - which threaten the
water quality and can cause severe impacts in downstream areas like wetlands and
floodplains. Contemporary data on the sediment loads of rivers provide clear evidence of
significant recent changes in the sediment fluxes of several rivers in response to human
activities. Sediment transport models validated by in situ experimentations are the only
available tool to predict the consequences of natural as well as man-induced environmental
changes and impacts on sediment dynamics. Mathematical models can help our
understanding of important processes and interactions that affect the water quality of water
bodies. They are approximate representations of complex natural systems and the
evaluation of a model with respect to its ability to reproduce multiple criteria and behaviour of
a real system is still problematic. Discussions between modellers and experimentalists
improve significantly the interpretation of the modelling output. These interactions between
different scientific disciplines led to formulate more realistic assumptions on the behaviour of
natural systems. The geochemical information, which appeared to be non-correlated with the
hydrological standard parameters, provides new information and contributes to give an
“orthogonal view” on the hydrologic system behaviour. Therefore, the evaluation of models
by using additional information – or complementary data – may give new information to reject
the erroneous hypotheses made during the model development. This applies especially to
basins that are heavily contaminated by PHE. Regarding the recent development in
geochemical tracer applications in models, the multi-tracer approach (elemental
concentrations and ratios, stable isotopes, radionuclides) may be a necessity to decrease
significantly the uncertainties in hydraulic modelling.
This study focuses on these new approaches in order to propose advanced solutions for the
calibration of 2D and 3D hydrodynamic models. This multidisciplinary approach is required to
assess the risk of floodplain contamination due to river sediment deposition. An important set
of hydrological, sedimentological and geochemical data is used in order to reach a more
efficient calibration of the TELEMAC modelling system. In addition to standard techniques of
hydrochemistry, new approaches of in situ suspended sediment transport monitoring,
geochemical tracing and spectroscopic analyses (Near InfraRed Spectrometry) will help
getting new insights on the hydraulic system behaviour.
SESSION: PROCESSES
21
OPERATIVE EVALUATION OF PEAK OUTFLOW DURING FLASH FLOOD USING
ARTIFICIAL INTELLIGENCE METHODS
Janál, P.1 and Stary, M.2
1
Czech Hydrometeorological Institute, Regional Forecasting Department, Kroftova 43, 616 67 Brno, Czech
Republic 2
Brno University of Technology, Faculty of Civil Engineering, Institute of Landscape Water Management, Žižkova
17, 60200 Brno, Czech Republic
E-mail: [email protected], [email protected]
The torrential rainfall prediction should be followed by suitable hydrological model able to
estimate at least the resultant peak outflow. The hydrological model construction interferes
with high measure of uncertainty, inherent in the rainfall prediction, rainfall-runoff process
and its simulation. The way how to eliminate influence of uncertainty is using fuzzy logic and
other artificial intelligence methods. The article deals with the fuzzy model capable of
predicting peak outflow of water from the basin in the case of flash floods. The fuzzy model
was compiled through the Fuzzy Logic Toolbox in the developmental environment of
MATLAB. Inputs characterizing the causal rainfall and the affected basins morphology have
been chosen for construction of a model. The constructed model was tested by means of
operational simulation during the summer season 2009.
The work was supported by Central Europe Programme, INCA-CE project (co-financed by European
Regional Development Fund).
This article was written as a part of the GAČR project: 103/07/1620 “Prediction and simulation models
in the water resources control”.
SESSION: PROCESSES
22
URBAN FOOTPRINTS ON CATCHMENT STORM RUNOFF
Kjeldsen, T. R., Miller, J. D. and Packman, J. C.
Centre for Ecology & Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, UK.
E-mail: [email protected]
The effect of urban land-cover on catchment flood response is evaluated using a lumped
rainfall-runoff model to analyse flood events from selected catchments in the United
Kingdom. The present study proposes and evaluates three extensions to an existing lumped
rainfall-runoff model to enable it to represent the urban effects, namely an increase in runoff
volume, reduced response time and a decrease in baseflow (resulting from decreased
infiltration). Based on observed flood events from seven catchments, cross-validation
methods are used to compare the predictive ability of the model variants with that of the
original unmodified model. The results show that explicit inclusion of the urban effects
increases the predictive ability of the model across catchments, despite significant large
between-event variability of model predictive ability. More detailed investigations into the
relationship between model performance and event characteristics (antecedent soil moisture,
rainfall duration, depth and intensity) did not identify obvious patterns, suggesting that the
model structure is unbiased, and indicating the residual level of between-event variation of
storm generating processes.
SESSION: PROCESSES
23
ESTIMATING CATCHMENT SCALE RETENTION CAPACITY FROM
SCATTEROMETER SOIL MOISTURE DATA
Komma, J.1, Merz R.2, Blöschl, G.1 and Wagner, W. 3
1
Institute for Hydraulic and Water Resources, Engineering, Vienna University of Technology, Vienna, Austria. 2
Department for Catchment Hydrology, Helmholtz Centre for Environmental Research (UFZ), Halle, Germany. 3
Institute of Photogrammetry and Remote Sensing, Vienna University of Technology, Vienna, Austria.
E-mail: [email protected]
Accurate knowledge of soil moisture is critically important for many purposes in hydrology
and water resource management, in particular, in hydrological forecasting. The fraction of
rainfall that becomes runoff (and does not infiltrate) is closely related to the soil moisture
state. As the soil moisture increases so does runoff, and the relationship is highly non-linear.
In this study we investigate the potential of the Advanced Scatterometer (ASCAT) sensor
onboard of the Metop satellite for the assessment of antecedent soil moisture conditions in
diverse physiographic regions of Austria. In a hydrologic context, the main advantages of
using spaceborne sensors for soil moisture estimation is their global availability and that they
provide an integral value over a large area rather than point values. The remotely sensed soil
moisture data is used to estimate the antecedent wetness conditions at a catchment scale
considering the relationship between SWI and the soil potential maximum retention
parameter, S, of the Soil Conservation Service-Curve Number (SCS-CN) method. As a
reference or benchmark observed runoff and rainfall data is used to estimate event based
retention capacities S for a large number of various catchments in Austria. First results
indicate that ASCAT soil moisture estimates do have the potential to improve the results from
SCS-CN method in Austria.
SESSION: PROCESSES
24
3-DIMENSIONAL MODELING OF RUNOFF GENERATION OF A MOUNTAINOUS
RIVER
Kuchment, L.S. and Demidov, V.N.
Institute of Water Problems of the Russian Academy of Sciences
(IWP RAS), 119333, Gubkina 3, Moscow, Russia,
E-mail: [email protected]
A physically based 3-dimensional model of mixed snowmelt-rainfall runoff generation of
mountainous river is proposed. The model is based on the finite-element schematization of
catchment area and river channel network and includes description of snow accumulation
and melt with accounting their dependences on altitude and topography, soil moisture
dynamics, overland, subsurface and channel flow. A case study was carried out for the
Upper Kuban River basin situated in Northern Caucasus region (the catchment area is 16900
km2). The input air temperature and precipitation are interpolated on basis of the 11 available
meteorological station data. The mean values of topography, river channel and soil
characteristics are assigned for every area or channel finite element using available
topography and soil maps and channel measurements. Five parameters have been
calibrated against runoff measurements at five runoff gauges. The carried out estimations of
Nash-Sutcliffe efficiency measures for each used gauge for ten-year calibration and
verification periods has showed that the developed model gives acceptable accuracy of
calculation of the runoff hydrographs. As an additional attempt of verification of the
developed model, simulation of the catastrophic flood of June 2002 was carried out during
which the maximum water stages in the Kuban region observed at various gauges exceeded
the maximum stages for the entire observation period. The model has been applied for short-
term hydrological forecasting.
SESSION: PROCESSES
25
ON THE VALUE OF MULTIOBJECTIVE OPTIMISATION FOR PROFITING FROM
SOFT INFORMATION IN UNGAUGED BASINS
Lombardi, L., Montosi, E., Toth, E., Castellarin, A. and Montanari, A.
Faculty of Engineering, University of Bologna, Via del Risorgimento 2, I-40136 Bologna – Italy
E-mail: [email protected]
The performances of single-objective and multi-objective algorithms for the calibration of a
rainfall-runoff model are compared by referring to an ungauged framework. Regional
procedures are applied to derive river flow statistics to be optimised in order to calibrate a
rainfall-runoff model in absence of hydrometric observations. Different combinations of
several objective functions were tested in calibration and validation mode. The minimisation
of the set of objective functions is carried out by using the AMALGAM algorithm to identify
behavioural parameter sets. The analysis refers to a wide area located in central Italy, in a
region where detailed hydrological and geomorphoclimatic information is available. These
catchments are considered as gauged and ungauged in turn: a baseline for model
performances is first obtained under gauged conditions and it is then compared to what
would be obtained in absence of observed runoff data.
Alternative hydrological models and combinations of river flow statistics were tested. The
results confirm the potential of the multiobjective approach and its capability to take
advantage of different information sources in a context characterized by significant
uncertainty.
SESSION: PROCESSES
26
RECONSTRUCTION OF THE HYDRAULIC CONDITIONS OF THE 1951
INUNDATION OF THE POLESINE REGION, ITALY
Masoero, A.1, Claps P.1, Di Baldassarre, G.2 and Asselman, N.3
1 Dipartimento di Idraulica, Trasporti ed Infrastrutture Civili, Politecnico di Torino, Torino, Italy
2 Department of Hydroinformatics and Knowledge Management, UNESCO_IHE, Delft, The Netherlands
3 Deltares, Delft, The Netherlands
E-mail: [email protected], [email protected], [email protected]
Flood inundation models have become essential tools in flood risk management, due to the
capability to simulate the hydraulic behavior of rivers and floodplain areas during extreme
hydrologic events. In particular, 1D and 2D models can be used for the analysis of historical
flood events, which can clarify baseline configurations for a more reliable assessment of the
flood hazard. This study aims to reconstruct the 1951 inundation of the Polesine Region,
Italy. The 1951 flooding was a mayor natural catastrophe in the XXth century in Europe. It
caused an inundated area of 1,080 km2 and produced devastating social consequences,
such as the displacement of more than 180,000 people. The reconstruction of the 1951
hydraulic conditions is currently based on partial knowledge of discharges and water stages
at the Pontelagoscuro’s gauging station (downstream of the 1951 levee breach) using also
extrapolation of the rating curves beyond the measurement range, which is, even today,
something open to uncertainty. To get a more reliable reconstruction of this relevant
historical event, we carried out a numerical exercise by using state-of-the-art flood inundation
models. In particular, the simulation of the 1951 flooding was based on a hybrid decoupled
methodology: a 1D model (HEC-RAS) was used to simulate the flow into the river and to
compute the overflow through the levee breach; this result was then adopted as the inflow
condition for a 2D model (SOBEK) application on the inundated area. The cross-section
survey made in 1954 was used as the geometrical input. The 1D model was also used to
reconstruct the historical rating curves. A good agreement between the patterns of the
observed and reconstructed inundation areas was found, and the timing of the inundation
was also found to be close to the information derived from the historical chronicles. Lastly,
using the results of the flood inundation modeling exercise, some technical considerations
about the relation between water stages and discharges, were drawn. In particular, the
maximum discharge simulated in the lower portion of the Po River was found to be
significantly lower than the one estimated in the past.
SESSION: PROCESSES
27
2D HYDRODYNAMIC FLOOD MODELLING IN A GRAVEL BED BRAIDED RIVER
Molnar, P., Boehringer, D., Wanner, P. and Burlando, P.
Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland
E-mail: [email protected]
While numerical 2-dimensional flood simulation models have become standard tools in
engineering practice (e.g. flood risk mapping), their development and improvement continues
to be an important research topic. A particularly challenging scientific and practical problem
is the simulation of large gravel bed braided rivers where very detailed spatial information on
bed topography is required in order to accurately capture complex flow paths when the
inundation of the river and floodplain increases dramatically with a rise in discharge. Apart
from obvious risk floods in these environments pose to humans and infrastructure, there are
also other effects floods have on the natural riverine system (e.g. riparian vegetation,
sediment transport and morphology, aquatic habitat) that are relevant and need to be
considered. In this paper, we conduct a modelling exercise to investigate the effects of floods
on some selected processes in the natural riverine system.
The study area is a 4 km reach of the Maggia River, a gravel bed braided stream with one of
the last remaining sizable natural floodplain ecosystems in Switzerland. The 2D vertically
integrated hydrodynamic model BASEMENT was used to simulate a sequence of steady
state flows ranging from low flows to floods with return period 300 yrs. Spatially distributed
maps of flow depth, velocity, bed shear stress and Froude number were produced for all
flows. Aerial photographs were used to calibrate the model under low flow conditions, and to
map the riparian woodland distribution (shrubs and hardwood species) on the floodplain. The
simulation results were then analyzed with three main focus points: the effect of floods on
morphological adjustment, riparian vegetation and fish habitat.
First we show that only floods with return periods of 3 yrs or more have the capacity to
conduct major morphological work. The longitudinal distribution of the average excess bed
shear stress required for motion of representative grains on the bed is spatially very variable,
which indicates why sediment transport in braided rivers is intermittent and most sediment is
re-deposited rather than exported out of the reach. What is also very evident is the highly
nonlinear response of the system to flood magnitude driven by the complex 3-dimensional
floodplain topography. Second we show that the riparian vegetation distribution on gravel
bars and banks is to some degree organized by floods by processes of vegetation removal
by erosion and the formation of suitable germination sites where the presence of fine grains
(sand) are key. On this basis we discuss the potential impacts of streamflow regulation due
to hydropower system operation in the headwaters of the Maggia basin on riparian
vegetation in the valley. Third we show how river habitat can be characterized on the basis of
flow depth and velocity for a common species of fish in the river (Leuciscus souffia) and on
that basis we estimate the potential habitat loss due to streamflow regulation. Our modelling
shows that the main advancement of 2D flood modelling in gravel bed braided rivers, i.e. the
ability to capture spatial variability, allows us to better explain riverine processes and study
their connections.
SESSION: PROCESSES
28
EVALUATION AND MODELLING OF THE IMPACT OF LAND USE ON
DISCHARGE, NITRATE AND SUSPENDED SOLIDS CONCENTRATION BY
FLOOD EVENTS IN SMALL CATCHMENTS
Moravcova, J., Pavlicek, T., Ondr, P., Koupilova, M. and Kvitek, T.
University of South Bohemia, Faculty of Agriculture, Department of landscape management, Czech Republic
E-mail: [email protected]
The aim of this article is to evaluate the role of landscape structure on particular water quality
parameters by flood events. The partial aims were to assess the impact of other factors,
which may have the influence on the change of selected water quality parameters during
flood events, and to simulate the impact of landscape structure in the catchment on the
discharge, nitrate and suspended solids concentration progress by SWAT model. All the
experimental works were carried out in two catchments – Jenínský and Kopaninský streams
in the southern respectively central part of the Czech Republic. The important result of this
research was the confirmation of the theory about rainfall water infiltration by flood events by
preferential flow paths, which is proved by synchronic dilution of nitrate concentration and
increase of phosphate concentration with the raising runoff on the rising limb of rainfall-runoff
event hydrograph. On the other hand the measured data of suspended solids by flood events
show the rise of the concentrations; this coincides with water level rising. Very important is
also the confirmation of significant role of infiltration areas management by runoff and nitrate
concentration formation by the flood events. Model solution in SWAT interface proved the
significant reduction of runoff and nitrate concentration values by agricultural use exclusion in
infiltration localities, and their grassing and afforestation. The results clearly showed that
special attention should be paid to the infiltration localities with regard to runoff height and
water contamination. For reduction of suspended solids concentration by flood events very
satisfactory results were achieved very satisfactory results by all scenarios of land use
change (grassing and afforestation of particular parts of the catchment).
This article is based on results of grant of Ministry of Agriculture of the Czech Republic
QH92034 Recharge zones identification by water vegetation stress in chosen catchments.
SESSION: PROCESSES
29
ON THE USE OF THE DIFFUSIVE WAVE MODEL FOR MODELLING EXTREME
FLOOD EVENTS IN THE FLOODPLAIN: NATURAL vs ANTHROPOGENIC
CATCHMENTS
Moussa, R.1, Ghesquière, J.1 and Bocquillon, C.2
1 INRA, UMR LISAH, 2 Place Pierre Viala, 34060 Montpellier Cedex 1, France
2 Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France
E-mail: [email protected]
During the last two decades, extreme flood events which occurred in the Mediterranean zone
in Southern France are a major threat to human life and infrastructures (death of over 100
people and around a billion Euros of damage). Catastrophic flood events are frequently
chosen as reference events, for modelling the impact of scenarios of river bank remediation
to prevent inundations. However, these rare events are poorly understood due to the poor
hydrological knowledge available, and due to the lack of data. A model for routing flood
events adapted to few available data during historical extreme events was developed. The
model subdivides the floodplain into cells linked to the main channel, and the diffusive wave
model with overbank flow was used to route floods in the main channel and through the
inundation floodplain (Moussa and Bocquillon, 2009, Journal of Hydrology, 374: 116-135). As
input data, the model requires a Digital Elevation Model, geographical map and cross
sections in order to subdivide the channel network into cells. The model parameters are the
Manning’s roughness coefficients in the main channel and in the floodplain. The linearized
equations are resolved by an implicit numerical scheme to ensure stability and convergence.
A new multi-criteria analysis method, to assess the model performance at the flood event
scale, is proposed and applied (Moussa, 2010 Hydrological Science Journal, 55(6):1074-
1084). We discuss the significance of the well-known Nash-Sutcliffe efficiency criteria when
calculated separately on flood events and we propose a new simple quick-to-use method to
analyse model performance using multi-criteria functions, on the basis of a lag translation, or
a homothetic ratio of the calculated hydrograph.
Application cases were conducted on two catchments located in southern France: under
natural conditions in the case of the Herault basin (2540 km²) and on an anthropogenic
elementary catchment characterized by a dense channel network in the case of the Roujan
basin (1 km²) a subcatchment of the Herault. First, we studied the flood event of October
1958 which caused one of the largest inundations in Southern France during the XXth
century (410 mm of rainfall during 48h). The model was applied to simulate the flood event of
1958, and was validated on other flood events under similar hydro-meteorological conditions.
Then, the model was applied to quantify the impact of scenarios of river bank remediation.
On the Herault basin, fourteen scenarios of construction of dams, embankments, or coupling
both dams and embankments, were modelled. On the Roujan basin, three scenarios of land
use management, agricultural practices, and channel network spatial distribution were also
modelled. The model simulates hydrographs in the main channel, the water depth, the area
and the volume on both right and left banks of the floodplain cells. Results show that the
model developed herein, with relatively little hydraulic modelling, is well adapted to simulate
extreme flood events, and is useful for environmental managers to study the impact of river
bank remediation on inundations.
SESSION: PROCESSES
30
A COMPARISON OF DIFFERENT APPROACHES TO DESIGN FLOOD
ESTIMATION IN ALPINE CATCHMENTS
Rogger, M.1, Kohl, B.3, Merz, R.2, Viglione, A.1 and Blöschl, G.1
1Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Austria,
2 Department for Catchment Hydrology, Helmholtz Centre for Environmental Research UFZ, Germany,
3Department of Natural Hazards and Alpine Timberline, Federal Research and Training Centre for Forests,
Natural Hazards and Landscape, Austria,
E-mail: [email protected], [email protected], [email protected], [email protected],
Design floods in small alpine catchments are estimated by a variety of different methods. In
general bottom up and top down methods can be distinguished. Applied bottom up methods
are for instance, event based and continuous rainfall runoff models which, if detailed
information on the catchments is available, can describe local hydrological processes
precisely. The standard top down approach often applied is flood frequency statistics, where
the design flood is estimated by fitting a distribution to measured discharge data. Top down
approaches that can be used in case when no discharge measurements are available are
regionalisation methods. If the different methods are applied to the same catchment the
estimated design floods are in some cases consistent but may in other cases also be very
different.
This study presents a comparison of design flood estimates for ten small alpine catchments
in Tyrol (Western Austria), where the 100-year flood was estimated applying bottom up and
top down approaches. In all ten catchments a detailed analysis of the runoff processes was
performed applying two bottom up approaches, a deterministic approach with an event
based rainfall runoff model and a probabilistic approach including Monte Carlo simulations.
As top down approaches the design floods were estimated by flood frequency statistics
based on measured discharge data and in a second approach by the Top Kriging
regionalisation method where the catchments were assumed to be ungauged. The results of
the different approaches were analysed in detail and show that inconsistencies in the flood
estimates can be attributed to factors such as specific hydrological processes on a local
scale or different assumptions on which rainfall input to use. Furthermore the analysis
highlights the advantages and disadvantages of each method, which should be taken into
account in design flood estimation.
SESSION: PROCESSES
31
WOODY DEBRIS TRANSPORT DURING FLOODS: 2D HYDRODYNAMIC
MODELLING APPROACH
Ruiz Villanueva, V.1, Bladé Castellet, E.2, Sánchez Juny, M.2, Bodoque del Pozo, J.M.3 and
Díez Herrero, A.1
1
Geological Survey of Spain, Natural Hazards Division. Ríos Rosas Street, 23, 28003, Madrid, Spain. 2 Flumen Institute, Universitat Politècnica de Catalunya. Jordi Girona Street, 31, 08034 Barcelona, Spain.
3 Mining and Geological Engineering Department, University of Castilla La Mancha, Campus Fábrica de Armas,
Avda. Carlos III, 45071, Toledo, Spain.
E-mail: [email protected], [email protected], [email protected]. [email protected]
Woody material mobilization in rivers has been studied during the last decades. Most of the
research carried out so far has been focused on the morphological role of woody debris, the
recruitment processes, and its spatial distribution in the streams. In addition to the ecological
and hydro-geomorphic points of view, one of the most important topics is the potential hazard
in communities adjacent to streams, since wood dramatically increases the destructive power
of floods. However, very few studies have dealt with this phenomenon as a potential hazard
during floods.
Models that predict when and where wood will be entrained or deposited could prevent and
mitigate the risk of such destructive events, but to this purpose there are no models available
for it so far. In this work a numerical model has been developed in order to simulate the
hydrodynamics and other fluvial processes (turbulence, sediment transport, etc.) together
with the woody debris transport. This model has been integrated as a new module into the
IBER hydraulic bidimensional model.
IBER is a numerical model for simulating turbulent free surface unsteady flow and
environmental processes in river hydraulics. Nowadays, IBER has 3 main computational
modules: a hydrodynamic module, a turbulence module and a sediment transport module. All
of them work in a finite volume non-structured mesh made up of triangular or quadrilateral
elements. The hydrodynamic module solves the depth averaged Shallow Water Equations
(2D-SWE), also known as the two-dimensional St. Venant Equations.
Wood entrainment is considered in relation to a force balance model acting on wood in
streams. Furthermore, turbulence may affect the woody debris transport. To incorporate this
effect an additional resistance to fluid deformation resulting from the internal chaotic fluid
motions that characterize turbulent flow has been added. The interactions between logs and
channel configuration and between logs each other have been also taken into account in the
model. The influence of woody debris (deposits or individual logs) in hydrodynamics has
been solved with an additional drag. To verify the model presented here, flume experiments
were carried out. Thus, the behaviour of wood in rivers was simulated performing different
flume configurations with different flow conditions and using several types of dowels as LWD.
SESSION: PROCESSES
32
DISCHARGE HYDROGRAPH ESTIMATION USING 2D DIFFUSIVE MODEL AND
SYNCRONOUS WATER LEVEL MEASUREMENTS
Sinagra, M.1, Nasello, C.1, Moramarco, T.2 and Tucciarelli, T.1
1 Department of Civil, Environmental and Aerospace Engineering, University of Palermo, Viale delle Scienze
90128 Palermo, Italy 2 Institute for Hydrologic Research, National Research Council, Via Madonna Alta 126, 6100 Perugia, Italy
E-mail: [email protected],[email protected], [email protected] [email protected]
Discharge monitoring in rivers, especially during flood events, is very important for the
calibration of hydrological and hydraulic models. Recently, new techniques have been
developed that are based on 1D hydraulic modeling and unsteady-state water level data
analysis. The adopted hydraulic model has the capability to compute the routed wave in
terms of discharges q(x,t) and water levels h(x,t) given as input the approximated initial
condition (at t=0) along all the reach, the stage hydrograph measured in the upstream
section (at x=0) and a constant roughness coefficient. The upstream discharge hydrograph is
computed by the model as q(0,t). An optimization process is used to estimate the roughness
coefficient that minimizes the mean square error of the computed stages at the downstream
section (x=L), with respect to the measured ones, within the time interval of the rising limb.
This optimum roughness coefficient is adopted to compute the discharge hydrograph in the
upstream section.
Most of the discharge estimation methods that are based on velocity measurements along
the entire cross section are aimed to the construction of the rating curve that links the
measured water stage to the unknown discharge. The reliability of the rating curve strongly
decreases when the measured water stage is much above the experimental points that are
the couple of discharge/stage values simultaneously measured.
The proposed approach only requires the use of two water level sensors located in two
different sections far few kilometers from each other, does not require any direct velocity
measurement and also allows the simultaneous estimation of the mean roughness coefficient
along the reach between the two sections. One limit of the method is that, when extreme
floods occur, the 1D assumption becomes very weak especially in the most dangerous
sections, where the flood plain inundation implies consistent lateral velocity components. To
overcome this limitation, the diffusive MAST 2D model is applied, in the same framework of
the previous 1D approach. Because only one water level sensor is likely to be available for
each monitored section, a constant water level has to be assigned, at each computational
time, to all the nodes that are located along the upstream section. Similarly, the same water
level measured by the instrument located in the downstream section is assumed to hold for
all the nodes located along the downstream section. The methodology has been applied to
the case study of the Tiber River (Italy), where water levels were recorded during two flood
events. The topography of the main channel and flood plains was reconstructed using an
unstructured triangular mesh, based on a 2mx2m fine DEM. The results were compared with
the discharge hydrograph computed using the 1D model, as well as with the discharge
hydrograph obtained using a rating curve, previously constructed using direct velocity
measurements.
SESSION: PROCESSES
33
SNOWMELT RUNOFF PREDICTION IN THE UPPER EUPHRATES BASIN,
TURKEY
Sorman, A.A., Gozel, E. and Sensoy, A.
Anadolu University, Department of Civil Engineering, Eskişehir, Turkey
E-mail: [email protected]
Snowmelt runoff in the mountainous eastern part of Turkey is of great importance, as it
constitutes nearly 2/3 in volume of the total yearly runoff during spring and early summer
months. Therefore, keeping track of snow dynamics and forecasting the amount and timing
of snowmelt runoff in the headwaters of the trans-boundary Euphrates River, where large
dams are located, is an important task in order to plan dam regulations, control flooding and
optimize water resources.
Upper Euphrates Basin in Turkey with an area of 10 275 km2 and elevation ranging from
1125-3500 m is selected as the study area since it is one of the main branches feeding the
Keban Dam Reservoir (first dam in the series of large dams in Euphrates Basin). Automatic
snow-meteorological stations are installed at various locations and altitudes in the Upper
Euphrates Basin operating in real-time. Since ground based observations can only represent
a small part of the region of interest, spatially and temporally distributed snow cover data are
acquired through the use of Moderate Resolution Imaging Spectroradiometer (MODIS)
optical satellite. Daily 500 m resolution MODIS satellite images on Terra and Aqua platforms
are used to determine cloud free snow depletion curves using certain combination and
filtering techniques. Snowmelt Runoff Model (SRM) is applied in the basin to forecast runoff
with a 2-day lead time for 2011 snowmelt period. Meteorological input data of precipitation
and temperature are provided from numerical weather prediction models and snow extent
data is estimated through stochastic modeling using MODIS images. In conclusion,
promising results indicate the possible operational use of runoff forecasting in the Upper
Euphrates Basin for future flood events.
SESSION: PROCESSES
34
INFORMATION EXPANSION FOR UNDERSTANDING TRANS-BASIN FLOODS
Uhlemann, S.1, Thieken, A.2 and Merz, B.1
1
Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Section Hydrology, Potsdam,
Germany 2 Helmholtz Centre Geesthacht – Climate Service Center (CSC), Hamburg, Germany
E-mail: [email protected], [email protected], [email protected]
Flood risk assessment is at foremost a subject of high societal relevance. It is therefore
inherently a subject of governmental action with a large body of authorities concerned with
the management of this risk and the planning of measures for flood loss reduction on all state
levels. Consequently, besides the scientific body of literature, an even larger body of studies
is being produced through these authorities, often endowed with a higher degree of detail.
Yet, the scientific community largely ignores these sources of information and hydrologic
expertise.
To analyse the reasons and to assess their validity we present results of an extensive study
aiming at the expansion of information for an improved understanding of trans-basin floods in
Germany. Trans-basin floods are extreme events occurring on a regional scale and across
catchment boundaries. Recently, Uhlemann et al. (2010) have presented a complete and
consistent set of trans-basin floods in Germany for the period between 1952 and 2002 based
on an analysis of multiple series of mean daily discharge. Understanding theses floods
requires an integrated assessment of the whole process chain from the meteorological cause
via the runoff formation in the catchments, the flood routing in the rivers, the effect of flood
protection, to the negative consequences of hydrological extremes.
Our objectives are three-fold: First, to identify the existing body of literature available on
floods in Germany and to assess the main obstacles in their application for flood analysis.
By applying a systematic literature review that includes an intensive study on sources and
ways of information dissemination, we identify a total of 250 relevant reports and studies.
Secondly, we exploit the information contained in the material for the task: What are the
governing hydrometeorological processes that have caused trans-basin flood events in
Germany over the period 1952 to 2002 and what were the consequences of these floods?
Therefore, we introduce the conceptual hierarchical framework developed for data quality by
Wang and Strong (1996) and adopt it to the assessment of flood report quality. The
framework explicitly accounts for the context in which the report is being used and intrinsic,
representational and accessibility quality criteria. We extend the concept by a pedigree
scoring scheme to quantify the level of information within each of the individual quality criteria
and to quantify the overall report quality.
Thirdly, for the largest 30 trans-basin flood events we combine the extracted and quality-
labelled information with a data based analysis of the hydrometeorological causes of trans-
basin floods. We can demonstrate that the interdisciplinary combination of methods and
systematic analysis of information can contribute to an improved process understanding.
REFERENCES: Uhlemann, S., et al. (2010), A consistent set of trans-basin floods in Germany between 1952-2002, Hydrology
and Earth System Sciences, 14(7), 1277-1295.
Wang, R. Y., and D. M. Strong (1996), Beyond accuracy: what data quality means to data consumers, Journal of
Management Information Systems, 12(4), 5-33.
SESSION: PROCESSES
35
FLOOD INUNDATION MODELLING IN LARGE RIVERS UNDER UNCERTAINTY
USING GLOBALLY AND FREELY AVAILABLE REMOTE SENSING DATA
Yan, K.1, Di Baldassarre, G.1, Solomatine, D.1 and Dottori, F.2
1
Department of Hydroinformatics and Knowledge Management, UNESCO-IHE Institute for Water Education,
Delft, the Netherlands. 2
Università di Bologna, Dipartimento di Scienze Della Terra e Geologico-Ambientali, Via Zamboni 67, 40126
Bologna, Italy
E-mail: [email protected], [email protected], [email protected],
The extreme consequences of recent catastrophic events have highlighted that flood risk
prevention still needs to be improved to reduce human losses and economic damages, which
have considerably increased worldwide. Hydraulic modeling is proved to be a powerful tool
for supporting flood risk management and lowland development. However, the lack of
hydrological and topographical data often has often been the bottleneck of implementing
hydraulic modelling and producing flood hazard and/or risk maps. Thus, the current
proliferation of new space-borne data has a great potential. However, the practical value of
the globally and freely available remote sensing data for hydraulic modeling still needs to be
tested.
This research aims to contribute to the understanding of whether the current growth in
availability of globally and freely available remote sensing data may allow the production of
probabilistic flood maps for the entire globe, i.e. global floodplain mapping. In this study, the
SRTM DTM is used for hydraulic model building, while ENVISAT-ASAR satellite image is
used for model validation. To test the usefulness of these globally and freely available data, a
model based on the high resolution LiDAR DTM and ground data is used as benchmark. The
work is facilitated by the use of a data-rich test site: a 98km reach of the River Po in Northern
Italy. The results show that the hydraulic model based on globally and freely available data
provides a satisfactory performance for a high magnitude flood event. Lastly, this technology
is generalized and implemented in two case studies to produce probabilistic flood inundation
maps of two large rivers: Yellow River (China) and Blue Nile (Sudan).
37
EGU Leonardo Conference Series on the Hydrological Cycle
SESSION: PATTERNS
Conveners: A. Castellarin, P. Claps, T. Kjeldsen, R. Merz
The analysis of flood patterns may provide key elements for addressing a number of
topical issues in hydrology. In particular, the session focused on:
• How analysis of space-time patterns of floods may effectively support flood hazard
estimation through an improved process understanding;
• An enhanced assessment and interpretation of variability and change in space-time
patterns of flood data;
• Integration of remotely and locally sensed data for improving understanding of
flood patterns.
SESSION: PATTERNS
39
DESIGN FLOOD GENERATION FOR LOWLAND RIVER SECTIONS
ACCOUNTING THE UNCERTAINTY GENERATED BY SUPERPOSITION AND
COINCIDENCE OF FLOODS
Bálint, G.1, Lipták, G.1, Szilágyi, J.2 and Zempléni, A.3
1 VITUKI Enviromental Protection and Water Management Research Institute
2 Department of Hydraulic and Water Resources Engineering, Budapest University of Technology and
Economics 3 Department of Probability Theory and Statistics, Eötvös Loránd University, Budapest
E-mail: [email protected], [email protected]
Major floods in the Tisza River system are usually the results of the superposition of several
flood waves from upstream sections and also their coincidence with floods of the tributaries.
This phenomenon was the basis for simulation exercises which were carried out for a limited
number of scenarios generated from the combination of a few historical events. A more
complex approach using a hybrid, seasonal, Markov chain based model for daily streamflow
generation were also used combined with a flood routing tool for the upper Tisza (Szilagyi et
al 2006). Preliminary success brought the motivation for this study where probabilistic and
hydrological methods were further combined in order to achieve an accurate model for
possible flood scenarios in the future. The first step in model construction was to fit a non-
homogenous Poisson process to the flood occurrences in the given area. The reversible
jump Markov chain Monte Carlo technique, originating from Green (1995) was also applied.
Results received produce possible future scenarios of flood events. For practical execution
three types of hydrological stations compose the simulation scheme, with different data
needs, namely: (a) Upstream stations for Markov Chain Monte Carlo (MCMC) type of
simulations of daily discharge series: Long observed daily discharge series are required with
minimum length of 30-50 years. (b) Flood routing stations: Observed 2-10 years of discharge
and water level series, preferably covering the entire range of observed water levels,
discharges, i.e. high and low water years. Additionally, rating curve representing present day
or designed future conditions. In case of sufficient station density observed water level time
series can also be utilized to create “interpolated” rating curves and/or discharge series. (c)
Target stations, selected flood routing stations, which simulated discharge and/or water level
“design” hydrographs are used as input and boundary conditions for hydrodynamic models.
Data requirements are as at flood routing stations – minimum requirement. To check and
validate flood frequency estimates received for simulated series additional long observed
daily discharge series are beneficial (at least 30-50 years). In most cases monthly (or at least
annual) maxima are sufficient. This may help water managers to prepare for events that have
not yet been observed in the past but none the less can be expected in the future. Detailed
analysis of target station flood distributions also supply the measure of uncertainty resulting
from the coincidence and superposition of flood waves.
SESSION: PATTERNS
40
INDIRECT ESTIMATION OF DESIGN VALUES OF HEAVY RAINFALL IN THE
ALPINE REGION OF SLOVAKIA: A CASE STUDY
Bara, M.1, Látečková, J.2, Kohnová, S.2, Gaál, L.2, Szolgay, J.2 and Hlavčová, K.2
1 Institute of Hydrology, Slovak Academy of Sciences, Bratislava, Slovak Republic
2 Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Bratislava, Slovakia
E-mail:[email protected]. [email protected], [email protected], [email protected],
[email protected], [email protected]
Design values of heavy rainfall are of very great importance in engineering hydrology, such
as input data for hydrological modeling, for the prediction of flood events, or for planning and
design in water resources management. In this study, the possibility of using the simple
scaling method for an indirect estimation of design values of heavy rainfall in a mountainous
area of Slovakia was tested. For the analysis, the Alpine region was selected, which is
located in the northern part of the country.
In general, the simple scaling method allows for an estimation of the design values of rainfall
of selected recurrence intervals and durations (i.e. T-year quantiles) shorter than a day by
using only the daily data from the regular network of non-recording rain gauges. Thus, the
design values of 1-day rainfall amounts were assessed (both by local and regional estimation
methods), and the T-year quantiles of higher temporal resolution were derived by scaling of
the T-year quantiles of the 1-day rainfall amounts. For the case study, a number of
verification meteorological stations were selected, in which the scaling exponents were
estimated for particular months of the warm season and also for the whole warm season.
According to this, averaged monthly and seasonal regional scaling exponents were derived
for the whole selected area. Using the regionally averaged scaling exponents, the IDF curves
were estimated by downscaling the quantiles of daily precipitation totals. Finally, the IDF
curves were compared one to another and to those assessed locally in previous studies.
SESSION: PATTERNS
41
FLOOD POTENTIAL IN SMALL BASINS OF SLOVAKIA
Barka, I.1, Minár, J.2, Trizna, M.2 and Bonk, R.
1 National Forest Centre, Forest Research Institute, T. G. Masaryka 22, 960 92 Zvolen, Slovakia,
2 Faculty of Natural Sciences, Comenius University, Mlynská dolina, 845 15 Bratislava, Slovakia,
E-mail: [email protected], [email protected], [email protected]
Landscape potential for floods (flood potential) in Slovakia has been assessed at a scale of
1:500 000 using geographic approach in 2005. Two partial flood potential were modeled:
morphometric potential for floods and geoecological potential for floods. The basic spatial
operational units were based on morphological-morphometrical terrain type.
Current research is aimed at evaluation of flood potential in the more detailed scale. It uses
similar methodological approach, but it is based on more precise data (e.g. digital elevation
model - DEM with 10 m resolution, Corine Land Cover data, forestry inventory data). The
small basins with an average area of approximately 25 km2 were chosen as a basic
operational spatial unit.
Morphometric potential express spatial differentiation of runoff velocity and was computed
using slope angle and drainage density. Geoecological potential involves also soil properties
and land cover as well. Overall potential for floods was estimated as a combination of
geoecological potential and meteorological data (probability of maximum daily rainfall within
100 years time period). It was calibrated by hydrological data (floods frequency data and rate
of mean and maximal discharge). Resulting flood potential is presented in ordinal scale.
The results were interpreted separately for flash floods and large floodplain related seasonal
floods. The new map of flood potential showed similar pattern comparing to assessment from
2005 but with more detailed spatial segmentation.
SESSION: PATTERNS
42
THE SURFACE WATER OCEAN TOPOGRAPHY SATELLITE MISSION:
PROSPECTS FOR FLOOD SCIENCE
Bates, P.
School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
E-mail: [email protected]
In 2019 NASA and CNES will launch the Surface Water Ocean Topography satellite mission
(see swot.jpl.nasa.gov) which will measure surface water height to centimetric accuracy
every 10 days with complete global coverage at 1km resolution over the oceans and for all
rivers above 100m wide. Over land the SWOT mission will provide measurements of water
storage changes in terrestrial surface water bodies and will provide estimates of discharge in
large (50 m-100 m width) rivers, globally. These data sets will provide a quantum
improvement on our current understanding of surface water and flooding dynamics. Beyond
improved characterization of the water cycle, meeting these measurements will enable
numerous applications of great scientific, social, and political importance.
SESSION: PATTERNS
43
EUROPEAN FLOOD DATA AVAILABILITY AND PARENT DISTRIBUTION OF
ANNUAL FLOODS
Castellarin, A.1, Kohnová, S.2 and ES0901 – WG2 Team3
1
Department DICAM, School of Civil Engineering, University of Bologna, Bologna, Italy 2
Department of Land and Water Resources Management, Faculty of Civil Engineering, STU Bratislava, Slovakia 3 ES0901 – WG2 Team and affiliations are appended below the Abstract body
E-mail: [email protected], [email protected]
Flood frequency analysis is broadly used for estimating the design-flood at a given location
(i.e., flood magnitude associated with the recurrence interval T, T-year flood). The approach
can be implemented locally (At-Site Flood Frequency Analysis, SFFA), or regionally
(Regional Flood Frequency Analysis, RFFA). SFFA and RFFA are mature disciplines and
consolidated methodologies are available for many European regions. As a result, different
European countries (and sometimes even different regions within a country) adopt different
methodologies. Also, methodologies are often selected on the basis of traditional choices or
what is known to work well for a limited number of local catchments, rather than an objective
assessment of available methods. The main objective of COST Action ES0901 European
procedure for flood frequency estimation (FloodFreq, http://www.cost-floodfreq.eu/) is to
address this disconnected picture, promoting a pan-European and synergic approach to
flood frequency analysis as requested by European Flood Directive (2007/60/EC). In
particular, during the first year of implementation of FloodFreq, the Working Group focusing
on assessment of statistical methods for flood frequency estimation (WG2) compiled a
catalogue of flood data availability/unavailability across Europe, together with relevant
information (e.g., catchment descriptors) recommended for use in flood frequency studies.
This paper presents the results of this recompilation effort, together with the outcomes of
some preliminary analyses that aim at identifying in an L moment-based framework the most
suitable parent distributions for representing the frequency regime of annual maximum peak
discharges across Europe. Results refer to some 2000 sequences of annual floods observed
in 8 countries.
3 ES0901 – WG2 Team
Kjeldsen, T., Centre for Ecology & Hydrology, Wallingford, Oxfordshire, UK
Szolgay, J., Gaál, L., Department of Land and Water Resources Management, Faculty of Civil Engineering, SUT Bratislava,
Slovak Republic
Diez, J. J., PuertosyCostas Escuela de Ingenieros de Caminos Politecnica de Madrid, Ciudad Universitaria, Madrid, Spain
Fleig, A., Lawrence, D., Norwegian Water Resources and Energy Directorate, Oslo, Norway
Lang, M., Cemagref, Lyon, France
Loukas, A., Department of Civil Engineering, University of Thessaly, Pedion Areos, Volos, Greece
Macdonald, N., The University of Liverpool Department of Geography, Roxby Building, Liverpool, United Kingdom
Madsen, H., DHI, Horsholm, Denmark.
Mediereo, L., Département de Génie Civil: Hydraulique et Energie, Université Polytechnique de Madrid
Merz, B., Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Section Hydrology, Potsdam, Germany
Neykov, N., National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, Sofia, Bulgaria
Nicholson, O., IHP/ICID, Hydrology and Flood Response Section, Office of Public Works, Dublin, Ireland
Onuşluel Gül, G., Dokuz Eylul University DEU Insaat Muh. Bolumu, Izmir, Turkey
Ozga-Zielinski, B., Institute of Meteorology and Water Management, National Research Institute, Warszawa, Poland
Pistocchi, A., EURAC, Institute for applied remote sensing, European Academy of Bolzano, Bolzano, Italy
Salinas, J., Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Austria
Kriauciuniene, J., Sarauskiene, D., Laboratory of Hydrology, Lithuanian Energy Institute, Kaunas, Lithuania
Strupczewski, W., Department of Hydrology and Hydrodynamics, Institute of Geophysics, Polish Academy of Sciences
Toumazis, A., Dion Toumazis & Associates, Nicosia, Cyprus
Veijalainen, N., Finnish Environment Institute, Freshwater Centre, Helsinki, Finland
Willems, P., K.U.Leuven, Hydraulics Division, Leuven, Belgium
SESSION: PATTERNS
44
ACCOUNTING FOR EXTREME FLOODS OCCURRED AT UNGAUGED SITES IN
REGIONAL FLOOD FREQUENCY STUDIES
Cong, N.C., Payrastre, O. and Gaume, E.
IFSTTAR, Bouguenais, France
E-mail: [email protected]
Flood frequency analyses are often based on continuous series at gauging stations.
However, the length of the available data sets is usually too short to provide reliable
estimates of extreme design floods. Hence, hydrologists have tried to make use of alternative
sources of information to enrich the datasets used for their statistical inferences. Three main
approaches were therefore proposed. The first one consists of a "temporal extension" of
information based on the valuation of historical and paleoflood data. The second, "spatial
extension”, consists in merging statistically homogeneous data to build a large regional data
samples. Recently, a combination of the two techniques aiming at including regional
estimated extreme discharge values at ungauged sites in regional flood frequency analyses
has been proposed (Gaume et al., 2010).
This new approach necessitates the calibration of a function relating the characteristics of the
watersheds to a local index flood value and the calibration of a regional one. In the initially
proposed approach, the index flood relation was adjusted a priori and the uncertainties
associated with this calibrated relation were not considered.
An improvement of this method will be presented where both (i) the index flood relation and
(ii) the regional growth curve are calibrated in the same time using a Bayesian MCMC
framework and enabling an accurate estimation of the uncertainties associated to the
estimated peak discharge distributions (computation of credibility intervals). Two regional
samples from France (167 records at 5 gauges and 35 ungauged extremes) and central
Vietnam (212 records at 7 gauges and 3 ungauged extremes) are used to test and validate
the method. Three types of results will be presented.
1. Comparison of this new proposed approach with a standard regional flood frequency
method when applied to measured discharge series available at gauged sites only.
2. Evaluation of the added value of extremes estimated at ungauged sites, which can only be
incorporated in the statistical inference with the new proposed method
3. Evaluation of the accuracy of the credibility intervals for the adjusted distributions
computed by the MCMC Bayesian inference framework for the new and standard method
through Monte Carlo runs.
All these tests reveal the accuracy and robustness of the new proposed regional flood
frequency method.
REFERENCES: Gaume, E., Gaál, L., Viglione, A., Szolgay, J., Kohnová, S., Blöschl., G., 2010. Bayesian MCMC approach to
regional flood frequency analyses involving extraordinary flood events on ungauged sites. Journal of hydrology.
doi:10.1016/j.jhydrol.2010.01.008
SESSION: PATTERNS
45
INFLUENCE OF OCEANIC PHENOMENA ON FLOODS
Diez, J.J., Esteban, M.D., López-Gutiérrez, J.S. and Negro, V.
Universidad Politécnica de Madrid, Spain. FP7-SMARTEST Project Researcher
E-mail: [email protected]
Flood events are relatively frequent phenomena in coastal areas from the Iberian. This type
of flood affects not only to the Mediterranean area of the Iberian Peninsula, but also to other
ones, like Biscay Gulf. And not only to coastal areas in a strict way, but also to other interior
areas, out of the Iberian Peninsula borders. Although this can occur at any zone of the
Peninsula, even with extension to the whole of it, the main intensity usually runs on the
eastern and southeastern areas of the Peninsula, particularly on its Mediterranean
catchments and basins. Some flooding examples of this type are the following ones:
Valencia, 1957; Cataluña, 1962; Almeria, 1973; Tous or the Santa Irene event, 1982;
Valencia and Murcia, 1987 and 1997; Cordoba, 2010; etc.
The Santa Irene flood, happened at the end of October 1982, is one of the most disastrous
flood events in Spain. Its renown is mainly due to the rupture of the Tous dam, but its main
meaning is to be the paradigm of the incidence of the littoral weather and the sea level on the
coastal plains inland floods. The type of floods before mentioned is related to a
meteorological phenomenon known as the cold drop one, which will be explained here. This
phenomenon leads not only to inland floods caused by rains and fluvial currents, but also to
floods in coastal areas as consequence of a combination of rains, fluvial currents, oceanic
waters entrance and/or, at least, temporal increase of the sea level.
There are some circumstances that can easily unleash the cold drop there: cold and dry
polar air masses coming onto the Iberian Peninsula and Africa, high water temperatures and
low atmospheric pressure (cyclone) areas in the western Mediterranean basin; these
circumstances are characteristics of the autumn season in that region with a great space-
temporal yearly variability (similar to hurricanes on Caribbean and western North-Atlantic
areas). Therefore, these phenomena may have a different magnitude each time.
The Santa Irene flood is analyzed, being selected because of the existence of enough
information and data about it. It is tried to expose here the result of a detailed analysis and
reflection about this phenomenon as a whole, on the generation of its rains and on the
different natures and consequences of its flood, exposing overall the ways in which the
maritime weather and consequent sea level govern the flood on the lowest zone of the
hydrographical basin. Above all because this type of floods can be identified at a first view as
only inland, some of them happened in areas far the coast for example the Caribbean
Hurricanes and the Monsoons.
REFERENCES: AUDIENCIA TERRITORIAL DE VALENCIA. 1991. Sentencia en la causa penal 56/1982, por el desmoronamiento
de la presa de Tous. 23 de octubre de 1990, Valencia.
DIEZ, J.J., 1992. El fenómeno meteorológico de Santa Irene. Revista de Obras Públicas, n. 3315: 77-81.
SESSION: PATTERNS
46
INVESTIGATING RUNOFF GENERATION MECHANISMS IN A SWISS PRE
ALPINE CATCHMENT BY SPATIAL INTERCOMPARISON
Fischer Benjamin, M. C.1 and Seibert J.1, 2
1 University of Zurich, Department of Geography - Hydrology and Climate Winterthurerstrasse 190, 8057 Zürich,
Switzerland 2 Uppsala University, Department of Earth Sciences, Uppsala, Sweden
E-mail: [email protected], [email protected]
Long term detailed data in mountainous catchments are generally sparse and even when
they exist, internal data such as groundwater or isotopic data are usually lacking. This makes
difficult to identify runoff generation processes. Here we present first results from a new data
set collected in the Zwäckentobel, a 4.3 km2 Swiss pre-alpine catchment. The high annual
precipitation input, flashy character of streams and dominant wet conditions, make this
catchment an exciting study area for hydrologists. However the contribution and response of
streams to storm flow in space and time is largely unknown. This study tried to address this
issue by comparing several sub-catchments. The aim was to learn from differences,
similarities and to put each catchment into perspective at different scales. The basic question
was whether there is a difference in response to rainfall and if so are the runoff contribution
processes different? For the Zwäckentobel and six ungauged sub-catchment rainfall, runoff
and isotope concentrations were measured and compared with the one sub-catchment with
long-term observations as reference. Here we present first results of this study, which show
the difference in rainfall runoff response and stable isotopes within this relative small
catchment scale. Especially the comparative isotope hydrograph separations were found to
be informative.
SESSION: PATTERNS
47
SCENARIOS OF HEAVY, FLOOD-TRIGGERING PRECIPITATION IN THE
CARPATHIAN AREA, ON THE BASIS OF HIGH RESOLUTION REGIONAL
CLIMATE MODELS
Gaál, L.1,2, Beranová, R.2, Kyselý, J.2 and Hlavčová, K.1
1 Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Bratislava, Slovakia 2
Institute of Atmospheric Physics, Czech Academy of Sciences, Prague, Czech Republic
E-mail: [email protected], [email protected], [email protected], [email protected]
Heavy precipitation events are of great importance since they may cause soil erosion,
landslides and floods. The present study examines possible changes in the regime of heavy
precipitation, aggregated on two different time scales: 1 hour and 5 days. Both time scales
have significant role in hydrology: while the heavy 1-hour precipitation, predominantly from
localized convective systems, may be one of the triggering factors of flash floods, heavy 5-
day precipitation events, usually of frontal origin, may lead to devastating large scale floods.
We analyze simulated precipitation outputs from 12 regional climate models (RCMs) with
high spatial resolution 0.5° (~25 km) over Europe made available within the EU-FP6
ENSEMBLES project. The RCMs are driven by several global climate models; nevertheless,
all the simulations are based on the SRES A1B emission scenario. The study examines the
50-year return values of the seasonal 1-hour and 5-day precipitation maxima that are
expected to occur at the end of the 21th century (time slice 2070–2099) in comparison with
the same statistics estimated for the control period (time slice 1961–1990), both for the
summer (June–August) and the winter (December–February) seasons.
The high quantiles of heavy precipitation are assessed by means of (i) local (at-site)
frequency analysis in individual grid boxes, and (ii) regional frequency analysis based on the
region-of-influence methodology as modified by Kyselý et al. (2011). In the latter method, a
set of similar grid boxes (a ‘region-of-influence’) is formed for each grid box, from which
information on extreme precipitation is taken when estimating extreme value distribution at
the target grid box.
Although the grids of the RCMs cover the entire Europe and all the frequency modelling is
carried out for the whole set of grid boxes for each RCM, the study focuses on a narrower
geographical area encompassing the Carpathian mountain range (17°–28°E and 44.5°–
50.5°N). The selected area has a complex orography and includes the whole territory of
Slovakia and Hungary as well as major parts of Romania and Ukraine. Slovakia is of a
particular interest of the study since as far as we are concerned, (i) no climate-change
scenarios of precipitation regime were based on such a dense network of grid boxes, and (ii)
no studies concerning the expected changes in precipitation at sub-daily scales appeared in
the regional scientific literature.
REFERENCES: Kyselý, J., Gaál, L., Beranová, R., Plavcová, E., 2011. Climate change scenarios of precipitation extremes in
Central Europe from ENSEMBLES regional climate models. Theoretical and Applied Climatology 104: 529–542.
doi:10.1007/s00704-010-0362-z.
SESSION: PATTERNS
48
CLIMATOLOGICAL AND GEOLOGICAL CONTROLS OF REGIONAL PATTERNS
OF FLOOD TIME SCALES IN AUSTRIA
Gaál, L.1, Szolgay, J.1, Kohnová, S.1, Parajka, J.2, Merz, R.3 and Blöschl, G.2
1 Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of
Technology, Bratislava, Slovakia 2 Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Vienna,
Austria 3 Department of Catchment Hydrology, Helmholtz Zentrum für Umweltforschung UFZ, Halle, Germany
E-mail:[email protected], [email protected], [email protected], [email protected],
[email protected], [email protected]
In this study, the dependence structure of two characteristics of extreme rainfall-runoff
events, i.e., flood peaks and flood volumes are examined. Unlike the common practice where
the dependence between two variables is usually described by means of linear or rank
correlation coefficients, here we focus on process based analysis of residual similarity of
dependence between these two variables that is expressed by the flood time scale defined
as the ratio of the flood volume to the flood peak. The case study is based on approximately
400 catchments in Austria.
In order to compare the variability of the flood time scales between and within the regions,
several smaller groups of pilot basins are used, within each one having homogeneous
geological background. The flood time scales of these are compared in terms of their
cumulative distributions functions. The hydrological and climatological driving factors of flood
generation are taken into consideration through a stratification of the time scales according to
the seasons of flood occurrence and flood types defined by Merz and Blöschl (2003).
Pronounced regional differences in the similarity of hydrological response were found, which
can be explained by different hydrological processes. For example, in Weinviertel (NE of
Austria), short duration flash floods play an important role with median time scale of ~10
hours. On the other hand, in the Alpine region, the rain-on-snow process dominates, leading
to large time scales exceeding 80–100 hours. In some areas, the time scales are consistent
between years as the majority of the flood events belong to a given flood type, such as long
rain floods, while in other ones (e.g., Innviertel and Mühlviertel), there is a mix of long
duration rain-on-snow and short duration frontal floods leading to a large variance of the time
scale.
REFERENCES: Merz, R., Blöschl, G., 2003. A process typology of regional floods. Water Resources Research, 39(12), 1340.
doi:10.1029/2002WR001952.
SESSION: PATTERNS
49
USING PROXIMITY ALONG THE RIVER NETWORK TO IMPROVE DESIGN
FLOOD ESTIMATION AT UNGAUGED SITES
Ganora, D., Laio, F. and Claps P.
Dipartimento di Idraulica, Trasporti ed Infrastrutture Civili, Politecnico di Torino, Torino, Italy
E-mail: [email protected]
Standard regional approaches for flood estimation at ungauged sites normally do not
preserve the information related to the hierarchy among gauged stations, which derives from
their location along the river network. However, this information is particularly important when
estimating runoff at a site located immediately upstream or downstream a gauging station.
We propose here a novel approach, referred to as Along-Stream Estimation (ASE) method,
to estimate a flood statistics at an ungauged site (target site), as a function of regional
estimates of the same variable (at the donor and target site) and of ancillary information
about the physical characteristics of both basins. A criterion to define the domain of
application of the ASE approach is proposed, and the uncertainty inherent with the obtained
estimates is evaluated. This allows one to compare the variance of the along-stream
estimates to that of other models eventually available for application (e.g. regional models),
and thus to choose the most accurate method (or to combine different estimates). This
approach is particularly useful in areas where many gauged stations with short record are
available.
The ASE model has been applied in the northwestern part of Italy in connection to an
existing regional model for flood frequency analysis. The analysed variables are the first L-
moments of the annual discharge maxima. The application demonstrates that the ASE
approach can be effectively used to improve the regional estimates for the L-moment of
order one (the index flood), particularly when the area-ratio of a pair of donor-target basins is
less or equal to ten. On the other hand, the method does not provide significant
improvements to the estimation of higher-order L-moments.
SESSION: PATTERNS
50
IMPROVING SIMULATIONS OF INUNDATION PATTERNS BY AIRBORNE LASER
SCANNING ANALYSES – A CASE STUDY IN A DANUBE WETLAND
Gschöpf, C.1, 2, Vetter, M.1, 3 and Blöschl, G. 1, 2
1 The Centre for Water Resource Systems, Vienna University of Technology, Karlsplatz 13, A-1040 Wien
2 Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology,
Karlsplatz 13/222, A-1040 Wien 3 Institute of Photogrammetry and Remote Sensing, Vienna University of Technology, Gusshausstraße 27-29, A-
1040 Wien
E-mail: [email protected] , [email protected], [email protected]
This study presents an analysis of inundation patterns covering both the extent of the
inundated area and the dynamics of a flood event. The frequency and duration of flooding at
partial areas of the flood plain is included. The flow regime is simulated by hydrodynamic
modelling. The aim of this study is to describe hydrological habitat characteristics that limit
the performance of ecosystems. This particularly applies to the flood regimes which are part
of the morphological equilibrium of riverine systems. Open-channel hydraulics, therefore, are
important to microbial and ecological research. This integrated interdisciplinary approach
raise river-basin management to a new scientific level.
Two-dimensional modelling, which is used for non-parallel overbank flow, requires a great
amount of input data from areas that are often poorly monitored relative to their size. To
satisfactorily represent the heterogeneous topographic surface in hydraulic models, the
commonly used parameterisation of the topographic elevation is derived from highly accurate
airborne laser scanning (ALS) data. To this end, digital terrain models (DTMs) are used;
however, in many cases the available accuracy of terrain information cannot be implemented
due to computer performance. Flow resistance, generally known as surface roughness, is
represented by Manning’s n. The surface roughness is traditionally estimated from land
cover maps which are a result of time consuming field campaigns and aerial images. A
further aim of this study is to present the estimation of surface roughness based on the same
data set as that used for the creation of the DTM. This new method provides an automatic
classification of the vertical structure of the ALS point cloud. This could be very important
when terrestrial field campaigns for land cover mapping cannot be realised at all, or not to a
sufficient degree. Currently used land cover maps could also have become obsolete due to
morphological changes that caused an alteration in the vegetation cover. These
morphological changes are due to the floods that took place in the interim since the date of
mapping.
This study is focused on an urban flood plain, the Lobau, which is part of the Danube riverine
landscape within the city limits of Vienna. The complex transient flow regime arises from the
back flooding of the river Danube through an opening at the downstream end of the flood
protection levee. This occurs after a certain threshold water level has been exceeded and the
flood spreads out over the flood plain.
SESSION: PATTERNS
51
CAN WE ATTRIBUTE FLOOD TRENDS?
Merz, B., Delgado, J., Hundecha, Y., Nguyen, D., Uhlemann, S. and Vorogushyn, S.
Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Section Hydrology, Potsdam,
Germany
E-mail: [email protected], [email protected], [email protected],
[email protected], [email protected], [email protected]
Over the last decade, the number of studies on trend detection in series of flood flows is ever
increasing. Frequently, when significant trends are detected, explanations on the causes of
the detected changes are given. This attribution step, i.e. establishing the most likely causes
for the detected changes, is very important in order to put the identified changes into context
and to evaluate the implications for flood risk management. We review the state-of-the-art of
flood trend attribution and assess to which extent attribution conclusions of recent studies are
credible. A classification for attribution studies is proposed, and we argue that approaches
are needed that integrate both a critical and broad usage of available statistical approaches
for trend detection as well as an attribution that extends beyond the confirmation of a single
hypothesis towards an in-depth analysis of a variety of physical and human induced
explanatory causes.
SESSION: PATTERNS
52
CROSS-CALIBRATION AT REGIONAL SCALE FOR RAINFALL-RUNOFF
MODELING IN UNGAUGED CATCHMENTS
Montosi, E.1, Montanari, A.1, Toth, E.1, Parajka, J.2 and Blöschl, G.2
1.University of Bologna, DICAM, Bologna, Italy
2 Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Vienna, Austria
E-mail: [email protected]
The objective of this study is to explore one possible solution to the question whether it is
possible to satisfactorily parameterize hydrological models in case of lack of runoff
measures. In ungauged or scarcely gauged basins it is impossible to turn to the classical
calibration of rainfall-runoff (R-R) models. Therefore it is common to transfer the parameters
from gauged catchments that are hydrologically similar, to the ungauged catchment with a
regionalization technique.
We propose a cross-calibration procedure based on the adoption, for all the gauged donor
catchments, of a unique, space- invariant parameter set. Therefore the proposed scheme
implies that the same parameters can be directly applied to the ungauged basin.
A basin in turn, for whom we pretend the local runoff data are missing, is selected and
identified as target catchment. We will refer to all the remaining catchments of the study area
as the donors. In detail, if there are n watersheds in the region of the ungauged catchment,
the process will need (n-1) steps. Firstly, the R-R model is calibrated on the most similar
donor, chosen according to a catchment distance measure. With a second step the process
develops calibrating the R-R model on the two most similar donors, and so on adding a new
donor at each step. For each set of donors we consider, as stated above, always a unique
parameter set, and the calibration is based on the simultaneous optimization of the simulated
streamflow over all the gauged catchments for the same calibration period. The parameter
set identified at each step is then applied, as it is, to the ungauged catchment, without any
further transfer technique.
With the identified cross-calibration we want to analyze the trade-off between the
disadvantage of assuming the parameters homogeneous in space and the benefit of adding
precious new information as the cross-calibration evolves, investigating if involving an
increasing number of catchments in the simultaneous cross-calibration leads to more robust
parameters estimation.
SESSION: PATTERNS
53
ANTICIPATORY FLOOD RISK ASSESSMENT - CASE STUDIES FROM AUSTRIA
Neuhold, C.
Universitaet fuer Bodenkultur Department fuer Wasser - Atmosphaere - Umwelt Institut fuer Wasserwirtschaft,
Hydrologie und konstruktiven Wasserbau
E-mail: [email protected]
The assessment of flood risk comprises hazard assessment and vulnerability assessment.
Flood hazard varies due to hydrological characteristics, land use change and climate
change. Flood vulnerability strongly depends on human behaviour, flood mitigation and flood
protection as well as susceptibility and exposure. The exposure to floods increased
substantially during the past decades due to change in land use from agricultural to industrial
and residential areas in former flood plains, leading to a significant increase in physical and
human exposure and consequently higher damage potential.
This paper aims at developing new approaches and methodologies to assess anticipatory
flood risk to enable strategic regional development within flood prone areas. Therefore, state
of the art approaches – assessing the current state of development – are extended by future
development scenarios based on several data sources referring to demography, land use,
building types, settlement characteristics, historic data, etc. Based on this information the
scenarios (1) “status quo”, (2) “extrapolation of previous development” and (3) “realistic
maximum development” are assessed based on various hydrologic scenarios (HQ30,
HQ100, HQ300 and extreme events). New approaches are developed, tested and validated
based on two case studies in Austria. Both case study sites are characterised by rural
settlements exposed to medium sized rivers (Mattig and Große Rodl) whereas the
municipality of Pfaffstätt/Mattig (case study 1) is not protected against floods at all, and the
municipalities Scharzgrub, Rodl and Höflein/Großen Rodl (case study 2) are protected
against a 100-year flood. Therefore, aspects of risk and residual risk are discussed by this
paper and are incorporated in the presented flood risk assessment methodologies.
Both case study sites show remarkable increase of flood risk (discounted on 2010) – for case
study 1 an increase of the expected annual losses is estimated at roughly 40% until 2100
(2010: 180000€/a; 2100: 250000€/a); for case study 2 tremendous increases are expected
as areas without protection are highly likely to be adapted (filling up to HQ100 level) and
settled. Nevertheless, an increase of the expected annual losses by a minimum of five times
the current values has to be expected (2010: 5000€/a; 2100: 28000€/a). The results clearly
indicate that the consideration of prospective development scenarios is needed to enable
comprehensive and anticipatory flood risk assessment providing a reliable basis for adequate
flood risk management strategies.
SESSION: PATTERNS
54
ELBE 3D – A SPATIO-TEMPORAL ANALYSIS OF SOIL MOISTURE PATTERNS
LINKED TO EXTREME FLOODS IN THE ELBE RIVER BASIN
Nied, M., Hundecha, Y. and Merz, B.
Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam,
Germany
E-mail: [email protected], [email protected], [email protected]
Large scale flood disasters, such as the Elbe / Danube flood in August 2002, are the result of
a complex interaction between meteorological event characteristics and catchment
conditions. This work is, therefore, aimed at developing a framework for flood risk
assessment that considers the interaction between meteorological and hydrological initial
conditions explicitly. The methodology is based on identifying extreme flood flows and
classifying important hydrological state variables (e.g. soil moisture) corresponding to the
identified events. The state variables are simulated using a semi-distributed conceptual
rainfall-runoff model that is calibrated using a Monte Carlo scheme with an objective function
that emphasizes high flows. Daily soil moisture index (soil water content standardized by field
capacity) at the subbasin scale is used as an indicator of the current catchment state. A
principal component analysis is applied to identify patterns of soil moisture index that explain
most of the variability of the soil moisture dynamics within the catchment. A cluster analysis
is applied to the leading principal components to identify days of similar soil moisture
patterns. The study was applied to the Elbe catchment, which was subdivided into 2268
subbasins with a mean size of 65 km², using daily hydrological and meteorological data over
the period 1951-2003.
Our analysis shows that the first three principal components explain the soil moisture spatio-
temporal variability related to flooding within the Elbe catchment. Cluster analysis applied to
these principal components identifies flood prone clusters. The relative frequency of flood
days within a cluster ranges between 0.0 and 0.32. The probability of discharge within each
cluster is computed to provide a quantitative probabilistic statement on high flows within a
cluster and thus on a soil moisture pattern.
In a subsequent step, precipitation patterns will be identified and conditional probability
distributions of discharge within each cluster of soil moisture and precipitation pattern will be
computed. This will enable us to quantify the effect of interaction of catchment state and
event precipitation characteristics on flood risk.
SESSION: PATTERNS
55
THE GRADEX-KC AND GRADEX-ZN METHODS FOR COMPUTING MAXIMUM
FLOODS WITH T-YEAR RETURN PERIOD WHERE DISCHARGE
MEASUREMENT SERIES ARE INCOMPLETE
Ozga-Zieliński B.
Institute of Meteorology and Water Management (IMGW-PIB), National Research Institute, Podleśna 61, 01-673
Warsaw, Poland
E-mail: [email protected]
The Gradex-KC method enables estimation of annual maximum floods with T-year return
period on the basis of short, say 10 to 15 years, series of annual maximum river discharge
and long i.e. 40 or more years annual maximum precipitation series. The method can be
used for relatively small basin areas i.e. up to 500 km2. In case of small catchments,
particular rainfall incident can cover whole basin area, what leads to assumption of its
uniform distribution on entire basin. Also small catchments can be characterized relatively
small variability of physiographical conditions, which allows to assume that direct runoff is
similar on entire basin area.
Two main assumptions are underlying the Gradex-KC method. Firstly, the rainfall is assumed
to yield an exponential, i.e. EV I distribution and secondly, the rainfall over certain threshold
Po is totally transformed into direct runoff. Accepting these both assumptions, the maximum
floods distribution function, above a value of discharge corresponding to a value of
precipitation Po, can be approximated by the maximum rainfalls distribution function. This
approximation is possible thanks to two parameters and Po, which are estimated in the
Gradex-KC method. Parameter a called GRADEX (GRADient EXtremes), as a parameter of
rainfalls distribution function, is evaluated on the basis of maximum precipitation series. But
parameter Po is calculated on the basis of the relationship between short series of river
discharge observations and corresponding to them rainfall observations.
The second problem, which is discussed, concerns estimation of maximum floods with T-
year return period in cases of ungauged watersheds due to proposed regional relationships
i.e. extended Gradex-ZN method. The Gradex-ZN method is based on theoretical
assumptions adopted in the Gradex-KC method introducing changes in parameters
estimation taking into account requirements of ungauged watershed. The parameter is
estimated for all rainfall stations situated on the area of ungauged watershed. Then on the
basis of particular gradex parameter of each rainfall station, isolines of gradex are drawn and
then they are used to evaluate a parameter for ungauged watershed. Whereas Po parameter
for ungauged watershed is proposed to be calculated on the basis of relationship between
river discharges and rainfalls for controlled basin on which ungauged watershed area is
situated.
SESSION: PATTERNS
56
DECADES OF FLOOD SEASONALITY ACROSS THE ALPINE–CARPATHIAN
RANGE
Parajka, J.1, Kohnová, S.2, Szolgay, J.2, Merz, R.3, Hlavčová, K.2 and Blöschl, G.1
1 Vienna University of Technology, Vienna, Austria, www.hydro.tuwien.ac.at,
2 Slovak University of Technology, Bratislava, Slovakia
3 Helmholtz Zentrum für Umweltforschung UFZ, Halle, Germany
E-mail: [email protected]
The aim of this contribution is to analyze the differences in the long-term regimes of extreme
precipitation and floods across the Alpine–Carpathian range, which includes the
southeastern part of France, Switzerland, the northern part of Italy, Austria, the southern part
of Germany, Slovakia, Romania and a small region along the Ukraine–Hungarian border.
This region represents diverse climatologic conditions between the Atlantic, the
Mediterranean and the continental part of Europe. The assessment is based on data
collected in the HYDRATE project (Gaume et al., 2009) and includes the time series of
annual maximum runoff at 577 stream gauges and annual maximum daily precipitation at
1945 climate stations with at least 20 years of measurements in the period 1961– 2000.
The seasonality assessment is based on directional statistics, which represents an effective
method for defining similarity measures on the basis of the timing of hydrological extreme
events with a year. We used the Burn index vector to analyze the mean date and variability
of occurrence of the extreme events. In order to investigate the change of the seasonality
with time period and magnitude of extreme events, the seasonality index is separately
estimated for different decades and for different number of the largest annual maximum
values.
The results will present similarities and differences in flood regime seasonality across study
region and discuss the shift in flood generating processes within different decades.
REFERENCES: Gaume, E., Bain, V., Bernardara, P., Newinger, O., Barbuc, M., Bateman, A., Blaškovicová, L., Blöschl, G.,
Borga, M., Dumitrescu, A., Daliakopoulos, I.,Garcia, J., Irimescu, A., Kohnova, S., Koutroulis, A., Marchi, L.,
Matreata, S.,Medina, V., Preciso, E., Sempere-Torres, D., Stancalie, G., Szolgay, J., Tsanis, J.,Velasco, D.,
Viglione, A., 2009. A collation of data on European flash floods. Journal of Hydrology 367, 70–78.
doi:10.1016/j.jhydrol.2008.12.028.
SESSION: PATTERNS
57
AN ANALYSIS OF CHANGE IN ALPINE ANNUAL MAXIMUM DISCHARGES:
IMPLICATIONS FOR THE SELECTION OF DESIGN DISCHARGES
Pistocchi, A.1, 2 and Castellarin, A.3
1 GECOsistema srl Rimini/Cesena, Cesena, Italy
2 Romagna Rivers Regional Basin Authority, Forlì, Italy
3 Department DICAM, School of Civil Engineering, University of Bologna, Bologna, Italy
E-mail: [email protected]
The contribution presents an analysis of 17 long annual maximum series (AMS) of flood
flows for Swiss Alpine basins, aimed at checking the presence of changes in the frequency
regime of annual maxima. We apply Pettit´s change-point test, the nonparametric sign test
and Sen´s test on trends. We also apply a parametric goodness-of-fit test for assessing the
suitability of distributions estimated on the basis of annual maxima collected up to a certain
year for describing the frequency regime of later observations. For a number of series the
tests yield consistent indications for significant changes in the frequency regime of annual
maxima and increasing trends in the intensity of annual maximum discharges. In most cases,
these changes cannot be explained by anthropogenic causes only (e.g., streamflow
regulation, construction of dams). Instead, we observe a statistically significant relationship
between the year of change and the elevation of the catchment outlet. This evidence is
consistent with the findings of recent studies that explain increasing discharges in alpine
catchments with an increase in the temperature controlling the portion of mountain
catchments above the freezing point. Finally, we analyze the differences in return periods
(RP’s) estimated for a given flood-flow on the basis of recent and past observations. For a
large number of the study AMS we observe that, on average, the 100-year flood for past
observations corresponds to a RP of approximately 10 to 30 years on the basis of more
recent observation. From a complementary perspective, we also notice that estimated RP-
year flood (i.e., flood quantile associated with RP) increases on average by approximately
20% for the study area, irrespectively of the return period RP. Practical implications of the
observed changes are illustrated and discussed.
SESSION: PATTERNS
58
T-YEAR MAXIMUM DISCHARGES ON WATER COURSES IN SLOVAKIA
Podolinská, J.1, Šipikalová, H.1 and Kohnová, S.2
1
Slovak Hydrometeorological Institute, Regional Centre Banská Bystrica, Zelená 5, 974 04 Banská Bystrica,
Slovak Republic 2
Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinskeho 11, 813 68 Bratislava,
Slovak Republic
E-mail: [email protected], [email protected], [email protected]
The T-year maximum discharges estimation is one of the most difficult tasks in hydrology. To
choose the method for design discharge calculation is also complicated and depends on the
catchment size and data availability. The Slovak Hydrometeorological Institute (SHMI)
processes and provides these data according technical standards. It is a tradition that the
whole territory of Slovakia is processed and the system of river network is considered. This
way was also applied for data updating with new methods and technologies (GIS).
Background materials were time series of hydrological data obtained from surface water
stream-gauging stations during the whole observation period (minimum 20 years). T-year
maximum discharges in 340 stream-gauging stations were calculated using mathematical-
statistic methods. Pooling scheme of 100-year maximum specific discharge (q100.max) was
used in the profiles without observation. The cluster analysis was applied for regional types
and relative estimate deviation q100.max determined using non-linear regression formula
expressing dependence of this value on specific physical-geographical characteristics. Input
data were time series from 197 selected stations with a catchment area from 20 to 300 km2
and minimum impact of anthropogenic activities.
SESSION: PATTERNS
59
FLOOD PREDICTION IN UNGAUGED CATCHMENTS: REDUCING
UNCERTAINTY WITH AN OPTIMUM USE OF REGIONAL INFORMATION
Randrianasolo, A., Ramos, M-H. and Andréassian, V.
Cemagref, Hydrology Research Group, UR HBAN, Antony, France
E-mail: [email protected]
The most commonly used tools in applied hydrology are essentially data-driven, which poses
a problem for several drainage basins in the world that are ungauged or poorly gauged.
These basins are characterized by the absence of discharge measurements or by
incomplete data series, with several gaps and a lack of information content for hydrological
applications. In flood forecasting, one of the main challenges when dealing with ungauged
basins concerns the need of data for, on one hand, the calibration of model parameters and,
on the other hand, the updating of initial conditions at the onset of the forecasts. Information
has to be retrieved from other hydrologically similar gauged catchments, which usually
correspond to neighbouring catchments within a homogeneous region, and transposed to the
ungauged site. The uncertainty associated with such procedure is considerable and
strategies to reduce the predictive uncertainty need to be implemented to produce reliable
forecasts that can be useful to decision-makers. The objective of this study is to investigate
different strategies to reduce the predictive uncertainty in ungauged catchments, with the
help of the geographical neighbourhood. Different scenarios are considered, combining both
the transfer of model parameters from neighbour catchments ("donors") for rainfall-runoff
simulation, and the transfer of observed discharges for updating the initial conditions at the
time of forecast. In search of an optimal use of the information coming from neighbours, the
assumption that using different donors to infer model parameters and to derive initial
conditions for updating will improve forecast performance is also tested. A leave-one-out
cross validation approach is applied for 211 catchments in France, considering each
catchment as ungauged at a time. Daily forecasts are issued by a lumped soil-moisture
accounting type rainfall-runoff model, using observed rainfalls as input, as well as ensemble
precipitation forecasts from the French meteorological centre (Météo-France) available for a
4-year period. Flow forecasts are evaluated using skill scores and the performances of the
different tests are compared. The results show that the main contribution of neighbouring
gauged catchments is in the transfer of model parameters. The transfer of specific
discharges for updating requires a more meticulous search for donors. The added value of
having at least local data available at the time of the forecast to perform the real-time
updating is illustrated. Key issues on alternative strategies to apply when no local updating is
possible are discussed.
SESSION: PATTERNS
60
STOCHASTIC MODELING OF LARGE FLOODS – SPATIAL DEPENDENCE
BETWEEN LOCAL RUNOFFS
Raschke, M.
Fa.M.Raschke, Gustav-Frextag-Str.24, 04277 Leipzig, Germany
E-mail: [email protected]
A stochastic model for floods in a large region has to include a model for the spatial
dependence between different runoffs beside the frequency functions for the local runoffs.
These dependencies are considered already in some approaches, for example by the
application of copulas. A disadvantage of such individual models is the large number of
parameters. Beside this, a possible relation between dependency and geographic
parameters of the catchment areas is not considered. Last but not least, the definition of a
locale, discrete flood event by a continuous local runoff variable is difficult and can influence
the entire model.
The concepts of random fields and max-stable random fields are the basic for a general
formulation for the spatial dependency between local runoffs. The concept of the parameter
estimation for a max-stable random field, the statistical analysis of block maxima, can
overcome the problem of event definition. This is shown by the data analysis of Thuringia.
Limits of the existing stochastic models and the issues of parameter estimation are also
discussed.
SESSION: PATTERNS
61
A NEW QUALITATIVE FIELD METHOD TO CAPTURE SHALLOW SOIL
MOISTURE PATTERNS IN WET ENVIRONMENTS
Rinderer, M., Kollegger, A., Fischer, B. and Seibert, J.
Department of Geography, Hydrology and Climate, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich,
Switzerland
E-mail: [email protected]
Soil moisture patterns and their spatio-temporal dynamics are of central interest in catchment
hydrology. It has been demonstrated, that information about these can give insightful
information on dominant runoff processes. Common measuring techniques are time
consuming and/or destructive (e.g., gravimetric method) or need sometimes expensive
instruments (Time Domain Reflectometry, TDR). Furthermore in very wet soils with a high
organic content TDR often does not provide reliable results. Here we present a qualitative
field method, which has been developed to offer a supplement to common quantitative
measuring techniques as it allows a quick and inexpensive mapping of soil moisture
conditions. This soil wetness classification scheme is based on qualitative but well-defined
topsoil indicators which can easily be mapped in the field. The scheme consists of seven
wetness classes from ‘very wet’, when water is visible at the soil surface to ‘very dry’, when a
person could sit at that spot for a longer time period without getting wet trousers. A test of the
new method with in total 18 people showed that soil wetness classes could be reasonably
well assigned to all 52 sampling points. The test persons, who did not have any prior expert
knowledge of soil moisture mapping, could classify all 52 points within 20 to 30 minutes.
Analysis of the test data set showed a small number of classification errors compared to a
reference classification mapped by an ‘expert’ when assigning the driest or wettest class.
Slightly higher variability could be seen for the classification of intermediate sampling points.
Overall, the test showed the potential of the new qualitative method. Further tests were
performed to link the qualitative classes to quantitative values of soil water content. This
promising qualitative method does not intent to replace common quantitative methods but
offers a potential to supplement them with the capability of covering a large number of
spatially distributed sampling points. These spatial soil moisture datasets offer a potential to
constrain model parameters and to study hydrological processes and their spatial
organization.
SESSION: PATTERNS
62
COMPARISON AND COMBINATION OF FLOOD REGIONALIZATION METHODS
IN SAXONY, GERMANY
Salinas, J.L.1, Merz, R.2, Laaha, G.3, Walther, J.4 and Büttner, U.5
1 Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Vienna,
Austria 2 Helmholtz Centre for Environmental Research, Halle, Germany
3 University of Natural Resources and Life Sciences, Vienna, Austria
4 DHI-WASY, Dresden, Germany
5 Saxonian Ministry of Environment and Agriculture, Dresden, Germany
E-mail: [email protected]
The spatial extension of flood frequency estimations is of vital importance in practical
engineering purposes, particularly in the case of prediction in ungauged catchments. From a
theoretical point of view there have been many different approaches, which could be
classified in two main groups: pooling and interpolation/regression methods. In this case
study in Saxony (Germany), the performance of different approaches was first separately
compared: Index-Flood method belonging to the first group; georegression and Top-kriging
to the second. On a second step, different combinations of the methods were analyzed with
different goodness-of-fit metrics, obtaining in some cases better results than with the original
methods.
SESSION: PATTERNS
63
COUPLING TOPOLOGICAL AND CANONICAL KRIGING FOR DESIGN-FLOOD
PREDICTION IN UNGAUGED BASINS IN THE SOUTHEASTERN UNITED
STATES
Stacey A. Archfield1, Castellarin, A.2, Jon O. Skøien3 and Julie E. Kiang4
1 Massachusetts-Rhode Island Water Science Center, U.S. Geological Survey, Northborough, MA,US
2 Department DICAM, School of Civil Engineering, University of Bologna, Bologna, Italy
3 Institute for Environment and Sustainability, Joint Research Centre, European Commission, Italy
4 Office of Surface Water, U.S. Geological Survey, Reston VA
E-mail: [email protected]
Spatial interpolation techniques of point data have been shown to be effectively applicable
for predicting streamflow statistics (i.e. flood flows and low-flow indices) in ungauged basins.
Literature reports successful applications of two techniques, Canonical kriging (or
physiographical-space based interpolation, PSBI) and Topological kriging (or Top-kriging).
PSBI performs the spatial interpolation of the streamflow statistics of interest in the two-
dimensional space of catchment descriptors. Top-kriging predicts the index along river
networks taking both the catchment area and nested nature of catchments into account. A
recent comparative analysis shows that PSBI and Top-kriging have complementary
performance, that is Top-kriging outperforms PSBI at larger river branches, and vice-versa
for headwater catchments. We focus on the possibility to couple PSBI and Topological
kriging for enhancing the prediction of 10-, 50-, 100- and 500-year floods in ungauged
conditions using a set of gages located across the southeastern US, which we simulate
through a leave-one-out cross-validation procedure. In particular, the analysis is twofold and
symmetric: (a) Top-kriging is initially used to estimate the flood-frequency statistics and PSBI
is then applied to the residuals and used to adjust the Top-kriging estimates; (b) PSBI is
initially used to estimate the flood-frequency statistics and Top-kriging is then applied to the
residuals and used to adjust the PSBI estimates. Our preliminary analysis aims at assessing
whether or not coupling PSBI and Top-kriging improves the performance of each
methodology applied as a standalone technique and, if so, providing users with some
indications on how most effectively to couple them.
SESSION: PATTERNS
64
POTENTIAL OF HIGH RESOLUTION MODELLING OF RUNOFF GENERATION
PROCESSES
Steinbrich, A. and Weiler, M.
Institute of Hydrology, University Freiburg, Germany
E-mail: [email protected]
The Distributed RunOff Generation (DROGen) model was developed with the aim to quantify
runoff formation processes with respect to floods at a height temporal and spatial resolution
(up to 1m²). The model is GIS based and not calibrated at all. All required parameters are
derived from geo data sets and experience, obtained from many experimental studies carried
out worldwide with respect to runoff generation processes. One benefit of the model is that
important runoff generation processes, as infiltration and the subsurface flow via macropores
and preferential flow pathways that often are neglected in models, are implemented based
on land-use and soil properties. A further advantage of the model is its GIS based
architecture that enables the modeller to visualize and analyse all model states at every time
step in very height spatial resolution. Since the model is adapted to the unique conditions of
its spatial environment by the information incorporated with the geo data, it is expected to
reproduce runoff generation and accumulation correct without a priori information about
precipitation - runoff relationship as commonly used when models are calibrated.
The potential of the new model was tested with several applications. Its capability to
reproduce observed flood hydrographs was tested in eight meso-scale catchments situated
in different regions (geology, soils, land-use) of the state on Baden-Württemberg. Short with
height intensity and long-lasting rain events with moderate intensities and different
antecedent moisture conditions were used to test the models ability to reproduce different
runoff generation mechanisms. It was found that especially the dynamics of the observed
flood hydrographs was well reproduced highlighting the eligibility of the model to correctly
account for the flood formation processes. An important potential of the uncalibrated model
when applying to catchments in different regions was the ability to test the correctness of the
modelling concepts and representation of processes when the model was not reproducing
the observed hydrographs correctly under certain antecedent and event conditions. Example
given the occurrence of tile drainage or impermeable soil horizons in podsolic soils, what was
not represented by the used geo data.
The model was also applied to the whole area of the state of Baden-Württemberg (~ 36,000
km²) at a resolution of 5*5m² using several scenarios representing different types of rainfall
events and antecedent soil moisture conditions. The results were visualised for the typical
pattern of runoff generation processes and also the dominant processes responsible in a
catchment for floods under various events and antecedent conditions.
SESSION: PATTERNS
65
A THREE STEP APPROACH TO ANALYSIS OF FLOOD HAZARDS IN COASTAL
BASINS: CASE SAR-ULLA RIVER, GALICIA-SPAIN
Vegas, E.1, García, E.2, Álvarez, C.1,2 and Listen, M.1
1 University of Cantabria,
2 Environmental Hydraulics Institute IH Cantabria, Avenida de los Castros s/n, 39005 Santander, Cantabria,
Spain.
E-mail: [email protected]
Flood events in Galicia (northern Spain) are associated with long duration rainfall episodes.
The confluence of Sar and Ulla rivers has a long record of catastrophic floods. The study
area is characterized by the proximity of the sea, scarce stream gauge data, complex terrain
and a variety of land uses. Due to these characteristics, a three step approach is proposed to
analyze flood hazards. The first step consists in a frequency analysis of rainfall to derive the
Intensity-Duration-Frequency curves. These curves are used to obtain a particular rainfall
event (project rainfall) and simulated discharge data using a distributed hydrological model
previously calibrated and validated. In the second step, the primary outputs become the input
for a dynamic 2D hydraulic model which simulates the effects of the flood in the confluence
between the rivers Sar and Ulla, i.e. flow levels velocities and large-scale patterns.
The third step consists in a flood hazard assessment based on several criteria, some
proposed by the authors, and some others suggested by different water management
organizations, as the Australian Commonwealth Scientific and Research Organisation
(CSIRO). Hazard maps have been evaluated for both steady and unsteady hydraulic
simulations, and the results vary notably due to dynamic effects.
The main conclusions are that the flood hazard results are very sensitive to the formula
applied, and also depend largely on the variability of velocities and water levels during the
flood event. In summary, this three-level integrated approach, with an especial focus on
hazard evaluation, facilitates the assessment of flood risks in complex and scarce gauged
basins.
SESSION: PATTERNS
66
EXTREME RAINSTORMS: TESTING REGIONAL ENVELOPE CURVES AGAINST
STOCHASTICALLY GENERATED EVENTS
Viglione, A.1, Castellarin, A.2, Rogger, M.1, Merz, R.3 and Blöschl, G.1
1 Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Vienna,
Austria 2 DISTART, School of Civil Engineering, University of Bologna, Bologna, Italy
3 Helmholtz Centre for Environmental Research, Halle, Germany
E-mail: [email protected]
The Depth-Duration Envelope Curves (DDEC) are regional upper bounds on observed
rainfall maxima for several durations. Recently, a probabilistic interpretation has been
proposed in the literature in order to associate a recurrence interval T to the DDEC's and,
consequently, to retrieve point rainfall quantiles for ungauged sites. Alternatively, extreme
rainfall quantiles can be retrieved from long synthetic rainfall series obtained with stochastic
rainfall generators calibrated to local time series of rainfall events. While DDEC's are
sensitive to outliers and data errors, the stochastic rainfall generator performance is affected
by the limited record lengths used for calibration. The objective of this study is to assess the
reliability of the two alternative methods by verifying if they give consistent results for a wide
study region in Austria. Relative to previous studies, we propose some generalisations of the
DDEC procedure in order to better represent the Austrian data. The comparison of rainfall
quantiles estimated with the two methods for large T shows an excellent agreement for
intermediate durations (from 1 h to 6 h), while the agreement worsens for very short (15 min)
and long (24 h) durations. The results are scrupulously analyzed and discussed in light of the
exceptionality of rainfall events that set the regional envelopes and the characteristics of the
stochastic generator used. Our study points out that the combined use of these regional and
local methods can be very useful for estimating reliable point rainfall quantiles associated
with large T within regions where many rain gauges are available, but with limited record
lengths.
SESSION: PATTERNS
67
MECHANISMS OF CLIMATE CHANGE EFFECTS ON FLOODS
Viglione, A.1, Salinas, J.L.1, Merz, R.2 and Blöschl, G.1
1
Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Vienna,
Austria 2
Helmholtz Centre for Environmental Research, Halle, Germany
E-mail: [email protected]
Understanding climate impacts on floods is essential for developing climate adaptation
strategies. The traditional scenario method of climate impact studies is problematic due to
the large uncertainties which are difficult to estimate. Moreover, it is rarely clear how the
uncertainties in the assumptions propagate to the results. The focus of this work is on the
mechanism to allow a more nuanced and transparent assessment of cause-effect than is
possible by scenarios alone. This allows us to separate changes that are likely to occur (hard
facts) from changes that are possible but not supported by data evidence (soft facts). For
instance, we found that some mechanisms allow us to suggest likely changes of floods with
some confidence, i.e., the increase of winter floods due to higher temperatures (rising snow
fall lines) and the decreasing summer floods due to earlier snow melt. Other mechanisms,
like future changes in convective precipitation, remain elusive.
SESSION: PATTERNS
68
BIVARIATE FLOOD ESTIMATION BY DIFFERENT THRESHOLD MODELS
Zempléni, A.1 and Bálint, G.2
1 Department of Probability Theory and Statistics, Eötvös Loránd University, Budapest
2 VITUKI Enviromental Protection and Water Management Research Institute
E-mail: [email protected], [email protected]
Univariate modelling of floods is a well-understood question, with sound theoretical
background. One may choose either the method of annual maxima and the extreme value
distributions or the peaks-over-threshold models and the corresponding Generalised Pareto
Distribution (GPD). However, in practice the joint investigation of two different gauges is also
important (because of the more difficult defence or the dangerous downstream floods caused
by such simultaneous events). There are different approaches for solving the above problem
of bivariate modelling. The annual maxima approach is not advisable here, most of all
because of the completely different time points of the two maxima. The peaks-over threshold
(MGPD) models are more promising. One of these approaches defines an observation
extreme only, if both components exceed the threshold (MGPD type I), while the other
considers all observations that are extreme in at least one component (MGPD type II). In the
talk I shall introduce parametric models for both cases and illustrate their potential by
applying them to Hungarian flood data from the Danube.
SESSION: PATTERNS
69
ON THE RELATIVE ROLES OF HILLSLOPE PROCESSES AND RIVER
NETWORK IN THE HYDROLOGIC RESPONSE TO SPACE-TIME VARIABLE
RAINFALL FIELDS
Zoccatelli, D. and Borga, M.
Department of Land and Agroforest Environment, University of Padova, Legnaro, Italy.
Email: [email protected]
This paper develops a new framework to analyze the relevance of hillslope with respect to
channel processes in the generation of the hydrologic response to space-time
heterogeneous rainfall fields. The dependence between rainfall spatial organisation, the
geomorphic features of channels and hillslopes, and the basin response, is examined by
suitably extending the concept of ‘Spatial moments of catchment rainfall’. The moments
describe the spatial rainfall organisation in terms of concentration and dispersion statistics as
a function of the distance measured along the flow routing coordinate. The introduction of
these statistics permits derivation of a simple relationship for the quantification of storm
velocity at the catchment scale. The first order moment controls the timing of the flood
hydrograph, whereas the second order moment and the storm velocity statistics both control
the temporal dispersion of the runoff hydrograph (i.e., the amplitude). The different processes
taking place in hillslopes and channel network are represented by using two different values
of celerity in hillslopes and channels. The effects of hillslope processes on the hydrologic
response to space-time heterogeneous rainfall fields is examined by varying the ratio
between the two runoff celerities. Applications are reported to five extreme flash floods
occurred in various European regions in the period 2002-2007. High resolution radar rainfall
fields and a distributed hydrologic model are employed to examine how effective are the
derived statistics in describing the degree of spatial rainfall organisation which is important
for runoff modeling with varying the role of hillslope contribution. Results are obtained
concerning the influence of hillslope contribution on the first two moments and on the storm
velocity statistics. It is shown that, with increasing the influence of the hillslope contribution to
the catchment response, the influence of the space-time rainfall variability on flood response
is progressively smoothed. The main controls of this influence are identified, quantified and
discussed.
71
EGU Leonardo Conference Series on the Hydrological Cycle
SESSION: PREDICTIONS
Conveners: G.T. Aronica, H. Madsen, B. Merz, R.J. Moore Flood risk predictions are characterized by considerable uncertainty that needs to be evaluated and clearly communicated to decision-makers. For that reason the session dealt with: • Estimation of uncertainty in extremes of rainfall, discharge, overbank flow and inundation extent for flood risk predictions and the characterisation of their uncertainty; • Predictions in catchments for which little or no measured data are available, with a particular focus on reduction and characterisation of uncertainty in those predictions; • Communication of flood risk and uncertainty to community and national decision-makers.
SESSION: PREDICTIONS
73
TOWARDS A SEAMLESS FLOOD EARLY WARNING SYSTEM: FROM FLASH
FLOODS TO GLOBAL FORECASTING
Alfieri, L.1, Salamon, P.1, Pappenberger, F.2, Burek, P.1, Krzeminski, B.2,
Muraro, D.1, Thielen, J.1 and de Roo, A.1
1 European Commission - Joint Research Centre, Institute for Environment and Sustainability, via E. Fermi, 2749,
21027 Ispra (VA), Italy 2 European Centre for Medium Range Weather Forecasts, Shinfield Park, Reading RG2 9AX, UK
E-mail: [email protected]
Ongoing changing climate has raised the attention towards weather driven natural hazards.
Flash floods and debris flows following exceptional downpours often come without any
adequate warning and cause heavy tolls to the human society. Also, recent large-scale
meteorological events have shown the catastrophic impact of floods in large river basins,
often affecting developing countries with scarce infrastructures for flood prevention and
mitigation. Current Numerical Weather Predictions (NWP) can skillfully forecast extreme
meteorological events, several days in advance. Yet, operational flood early warning systems
based on hydro-meteorological simulation often do not make use of the full capabilities of
state-of-the-art NWP. Besides, their coverage is mostly limited to country-wide extents, even
within trans-national river basins, leading to very heterogeneous level of preparedness to
extreme flood events.
Focus of this work is to give an overview of operational and experimental flood warning
systems currently being developed at the Joint Research Centre of the European
Commission, which tackle different flood processes through similar approaches, though at
different space-time scales and geographic extents.
An experimental system for extreme precipitation events and flash flood early warning is run
on a daily basis using 5-day limited-area ensemble forecasts covering most of Central and
Southern Europe. It is based on the detection of extreme precipitation events of short
duration, through comparison with a 20-year reforecast climatology, consistent with the input
forecasts. The European Flood Alert System is running pre-operationally since 2003 and
focuses on riverine floods in mid-size to large river basins in Europe. Streamflow simulations
are produced through distributed hydrological modeling of 120 ensemble weather forecasts
every day. In addition, a prototype of a Global Flood Alert System was set up in 2011 aimed
at detecting large river floods with lead time as long as one month. This system has been run
continuously on global coverage with ensemble hindcasts from January 2010 provided by the
European Centre for Medium-Range Weather Forecasts (ECMWF).
A number of case studies are shown to demonstrate strengths and weaknesses of the
different systems. Although the three systems have limited requirements in terms of local
measurements, a major challenge is faced in the scarce availability of observed discharge
data for comparison, particularly in remote unsettled regions and in ungauged catchments.
Finally, we make use of the acquired experience to comment on ongoing and future
challenges of operational warning systems.
KultuRISK and IMPRINTS FP7 projects are gratefully acknowledged for the financial support to the
research work.
SESSION: PREDICTIONS
74
THE MULTIVARIATE STATISTICAL ANALYSIS OF THE EXTREME
HYDROLOGICAL EVENTS
Bačová Mitková, V.
Institute of Hydrology SAS, Račianska 75, 818 11 Bratislava, Slovak Republic
E-mail: [email protected]
One-dimensional analyses of flood characteristics are now mainly used in studies of
hydrological extreme events. It means that the peak flow of flood wave or volume of flood
wave is statistically analyzed separately. A drawback of this approach is that the same family
of marginal distributions is assumed for all flood characteristics, while analysed variables
could show different margins. Hydrological phenomena are often multidimensional and
hence they require the joint modeling of several random variables. Therefore, for more
comprehensive analysis of the flood wave it is necessary to know and understand
relationship and dependence between the characteristics of the flood wave, what requires a
multidimensional statistical approach. For the multidimensional distribution copula functions
are usually used. The concept of copulas relaxes the restriction of traditional flood frequency
analysis and connects one-dimensional marginal distribution of random variables with their
joint distribution. The aim of this paper is to analyze and evaluate statistically the occurrence
of hydrological variables such as flow and volume of the phenomenon. In our work we focus
on the use of copula function in multidimensional statistical analysis of maximum annual
discharges and their assigned volumes of the flood waves on the Bodrog River in Streda nad
Bodrogom gauging station during the period 1950-2009. Some of three Archimedean
copulas were used for the analysis: Clayton copula, Gumbel copula and Frank copula. The
parameter theta of the each Archimedean copulas can be obtained by considering the
mathematical relationship between Kendall`s coefficient of correlation and generating
function. The simulations of the 1000 pairs of points from copulas were analyzed.
Results obtained by the multidimensional analysis of the variables, which characterize the
hydrological waves (flow, volume, time) can contribute to more reliable assessment of flood
risks. They give an overview of the flood event as a whole and practical use of these results
can be in water management and in the design of flood protective systems.
SESSION: PREDICTIONS
75
ON THE JOINT ESTIMATION OF FLOOD FREQUENCY DISTRIBUTIONS AT
SEASONAL AND ANNUAL TIME SCALE
Baratti, E.1, Montanari, A.1, Castellarin, A.1, Bezzi, A.2, Di Giulio, A.2 and Ruzzante, E.2
1 Department DICAM, University of Bologna, Via del Risorgimento 2, I-40136 Bologna, Italy
2 Studio ing. G. Pietrangeli Srl, Via Cicerone 28, I-00193 Rome, Italy
E-mail: [email protected], [email protected], [email protected]
Flood frequency distribution is usually estimated at annual time scale, by fitting observations
of annual maximum peak lows or peak flows exceeding a given threshold. However, in many
cases one is also interested in inferring the seasonal behaviour of the flood frequency
distribution, for instance when one needs to estimate the risk of flood in different periods of
the year. Seasonal flood frequency analysis has been rarely investigated. A key issue is to
ensure the compatibility between seasonal and annual flood frequencies. We propose an
approach to jointly estimate the parameters of intra-annual and annual probability distribution
of floods. The approach is based on the preliminary identification of an optimal number of
seasons within the year, which depends on the climatic and hydrological behaviours of the
investigated watershed. Then, parameters of intra-annual and annual flood distributions are
jointly estimated by using (a) an approximate optimization techniques and (b) a formal
maximum likelihood approach. The proposed methodology is applied to the case study of the
Blue Nile River, for which extended hydrological information is available at annual and
seasonal scale.
SESSION: PREDICTIONS
76
MODELLING OF CLIMATE CHANGE IMPACTS ON FLOODS BY CONTINUOUS
SIMULATION WITH UNCERTAINTY
Blazkova, S.1, Beven, K.2 and Martinkova, M.1
1 T.G. Masaryk Water Research Institute, Hydrology, Prague 6, Czech Republic
2 LancasterEnvironment Centre, Lancaster, UK
E-mail: [email protected]
The climate change is supposed to affect the occurrence of climate extremes. The presented
study is focused on estimation of climate change impacts on floods while using the outputs
from regional climate models of ENSEMBLES data set (http://ensemblesrt3.dmi.dk/).
The methodology used in this study is continuous simulation (i.e. the input is a series from a
precipitation simulator) within the uncertainty framework (many behavioural simulations are
taken into account). With the behavioural parametersets computed in the study, 100
thousand year series are modelled and hydrographs of large floods are extracted from them.
A special attention is paid to the initial conditions before extremely heavy rains. The problem
to whatdegree the volume and shape of the flood hydrograph is affected by a drought of
various depths on a catchment inessentially wet Central European climate is analyzed.
This research is supported by the Czech Grant Agency (P209/11/2045) and by the Czech
Ministry of Education (OC10024 and 7A08036).
The present study is a follows up of the paper of Blazkova and Beven (2009).
Blazkova, S., and K. Beven (2009), A limits of acceptability approach to model evaluation and
uncertainty estimation in flood frequency estimation by continuous simulation: Skalka catchment,
Czech Republic, Water Resour. Res., 45, W00B16, doi:10.1029/2007WR006726.
SESSION: PREDICTIONS
77
PERSISTENCE AS A FACTOR OF FLOOD HAZARD FOR EMBANKED RIVERS
Bogdanowicz, E.1 , Strupczewski, W.G.2 and Kochanek, K.2
1 Institute of Meteorology and Water Management, Podlesna 61, 01-673 Warsaw, Poland.
2 Department of Hydrology and Hydrodynamics, Institute of Geophysics, Polish Academy of Sciences, Ksiecia
Janusza 64, 01-452 Warsaw, Poland.
E-mail: [email protected], [email protected], [email protected]
Sense of security in floodplains of embanked rivers results from the belief that levees protect
against flood magnitude on which they were designed. So, if the actual forecasted flood peak
does not exceed the safety levels related to Levee designed value one can assume that the
risk that flood water will overtop the dike crest is negligible and so is the risk of flooding in the
protected area. The history of floods shows this is not true. An important factor to be taken
into consideration is the duration of high water levels. Long-lasting high stages may weaken
the levee structure (soaking) and cause dangerous leaks, blurs and breaks that threaten their
destruction. The break usually happens during the falling phase of flood hydrograph. That’s
why the classical FFA concerning only the frequency of the maximum flows is not suitable in
this case and ought be extended to the analysis of the duration of flows and corresponding
states over the given threshold. In Poland, as in many countries in the world, for each
hydrological station two benchmark water levels, called the warning stage and the alarm
stage, have been specified. The frequency of annual maximum uninterrupted duration, D (in
days), of flows over the flood alarm stage can be regarded as the measure of the risk of
flooding due to waning of the levees' strength. This study introduces formal aspects of the
Duration–flow–Frequency (DqF) modeling in stationary and non-stationary conditions. To
cater for the conventional FFA, the flow discharge corresponding to the alarm stage is used
here, i.e. the upper limb of the rating curve is regarded as time invariant. In the presented
statistical model, the duration (D) is considered as a random variable while the alarm flow
discharge is the fixed value.
SESSION: PREDICTIONS
78
DESIGN FLOOD PROFILES ESTIMATION: FREEBOARD VERSUS
UNCERTAINTY BOUNDS
Brandimarte, L. and Di Baldassarre, G.
UNESCO-IHE, Institute for Water Education, Delft, The Netherlands
E-mail: [email protected], [email protected]
The prediction of flood defence design profiles has always been associated with some
degree of uncertainty. The traditional deterministic approach takes uncertainty into account
by adding a freeboard to the simulated flood profile; the more recent probabilistic approaches
have provided sophisticated techniques for taking into account different sources of
uncertainty in hydraulic modelling and flood frequency analysis. Nevertheless, in engineering
practice, the deterministic approach, based on the outcomes of a well-calibrated model, is
still preferred to the probabilistic one. This might be due to the unfriendliness of the
implementations of methods to quantify uncertainties from different sources. However,
although easier to apply, the freeboard is often arbitrarily defined and may lead to a false
perception of additional safety level.
This paper proposes a pragmatic methodology to estimate design flood profiles and the
associated uncertainty, which is based on the use of uncertain flood profiles: the most
significant sources of uncertainty are explicitly analyzed by using a simple to apply approach.
An application to the Po river reach between Cremona and Borgoforte (Italy) is used to
illustrate the proposed framework and compare it to the traditional freeboard approach.
SESSION: PREDICTIONS
79
PROBABILISTIC FORECASTING OF ANTECEDENT SOIL MOISTURE
CONDITION AS FLASH FLOOD PRECURSOR VARIABLES
Brigandì, G.1, Aronica, G.T.1, Loukas, A.2, Vasiliades, L.2 and Papaioannou, G. 2
1 Department of Civil Engineering, University of Messina, Messina, Italy
2 Department of Civil Engineering, University of Thessaly, Volos, Greece
E-mail: [email protected]
Flood forecasting is a rather complicated task, particularly in those catchments which are
prone to flash flood formation or which the response time is of the order of few hours and,
even brief anticipation are important and welcomed. In this context, some kind of hydrological
precursors can be considered to improve the effectiveness of the emergency actions (i.e.
early flood warning). Now, in literature has been widely recognized how soil moisture is an
important factor in flood formation, because the runoff generation is strongly influenced by
the antecedent soil moisture conditions of the catchment. The basic idea of the work here
presented is to use soil moisture conditions in a probabilistic framework to define a first alert
phase in a flash flood forecasting chain. For the soil moisture conditions modelling, the
IHACRES model which is a spatially lumped rainfall-runoff model that can be employed to
reproduce the continuous daily response of the catchment was used to derive a series of
wetness indexes. Soil moisture conditions are defined using an Antecedent Moisture
Conditions index (AMC) similar to this widely used for the implementation of the Soil
Conservation Service – Curve Number methodology. Instead, for the soil moisture conditions
forecasting a Markov chain model has been implemented and tested. Application of the
proposed methodology has been carried out with reference to a river basin in Cyprus.
SESSION: PREDICTIONS
80
FLOOD PROTECTION OF THE CITY OF LJUBLJANA AND EXPERIENCES
GAINED DURING THE SEPTEMBER 2010 FLOOD
Brilly, M., Vidmar, A. and Rusjan, S.
University of Ljubljana, Faculty of Civil and Geodetic Engineering, Chair of Hydrology and Hydraulic Engineering
E-mail: [email protected]
In the contribution the flood protection problematic of the capital of the Republic of Slovenia,
the Ljubljana city, will be presented. Ljubljana lies in the southern part of the Ljubljana basin,
crossing the moor on the south and the north of Ljubljana field. The tectonic subsidence of
the area in the geological past has made it an important confluence of the rivers. The area of
the City of Ljubljana has a long history of various flood protection measures (e.g. first
waterworks in the Ljubljanica River channel by the Romans, Grubar flood canal excavation in
1780 for diversion of Ljubljanica moor floodwaters away from the city center, weir
construction on the Ljubljanica River in 1950s for floodwater manipulation and extended
widening of the Mali graben channel in the 1970s). However, despite the abovementioned
flood protection efforts, many parts of the urban area of the City of Ljubljana is presently
heavily threatened by the floods as the one experienced in September 2010. The southern
part of the city, particularly in the Ljubljana moor, is exposed to a risk of catastrophic,
medium and even small flood events. In the northern part of Ljubljana, at the Sava River
area, there is a risk of catastrophic medium flood events. Most heavily endangered is the
southern part of the city in the vicinity of the Ljubljanica River and its tributaries. The western
part between Podutik and Rožna dolina is endangered by Glinščica stream high waters and
its tributaries, south western part of the city (the whole Vič area) by Gradaščica with Horjulka,
southern part of the Rudnik suburbs with moor floodwaters and the central and northern part
of the Rudnik by tributaries from Golovec and inland waters. The main reasons for the
present insufficient flood protection of the City of Ljubljana lies especially in the
discontinuities and mutual exclusion of flood protection measures planning and overall
spatial development of the urbanized areas. As a consequence, some of the past flood
protection measures could no longer function properly due to intensive urbanization of some
areas (e.g. the Mali graben channel). On the other hand, some of the urbanized Ljubljanica
moor areas are becoming increasingly flood vulnerable due to past long-term intensive moor
area drainage and consequent slow decreasing of the overall ground levels. In the past
twenty years, as environmentally friendly maintenance, riverbank transformed in bush, that
also tremendously decrease flood discharge and increase flood in urban area.
SESSION: PREDICTIONS
81
NEW METHODS OF FLASH FLOOD FORECASTING AT THE CZECH
HYDROMETEOROLOGICAL INSTITUTE
Březková, L., Novák, P., Jonov, M., Kyznarová, H., Šálek, M., Frolík, P. and Janál, P.
Czech Hydrometeorological Institute, Regional Forecasting Department, Kroftova 43, 616 67 Brno, Czech
Republic
E-mail: [email protected]
The Czech Hydrometeorological Institute is the primary agency responsible for the
monitoring and forecasting of river stages at national level. For prediction of large scale
floods the hydrological models using the data from NWP models are used in daily routine.
However, the flash floods caused by heavy precipitation, which hit small catchmets in
summer season, still remain almost unpredictable phenomena due to their rapid rise.
In recent years, the precipitation estimates and nowcasting tools derived from the radar data
were established. Together with the hydrological models these tools were tested for the flash
flood forecasting. The high uncertainty of the predicting of such a type of phenomena leads
to using the various nowcasting methods for estimation of predicted rainfall sum. This
“variant-approach“ was successfully tested on case studies and was set up in testing
operation for pilot catchments. In the paper the first experience with the new flash flood
forecasting system is presented.
The work was supported by Central Europe Programme, INCA-CE project (co-financed by European
Regional Developement Fund).
SESSION: PREDICTIONS
82
EFFECTS OF UNCERTAINTY IN BOUNDARY CONDITIONS ON FLOOD HAZARD
ASSESSMENT
Domeneghetti, A.1, Vorogushyn, S.2, Castellarin, A.1, Merz, B. 2 and Brath, A.1
1 Department DICAM, School of Civil Engineering, University of Bologna, Bologna, Italy
2 Section 5.4: Hydrology, Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany
E-mail: [email protected]
Comprehensive flood-risk assessment studies should quantify the global uncertainty in flood
hazard estimation, for instance by mapping inundation extents together with their confidence
intervals. This appears of utmost importance, especially in the case of flood hazard
assessments along dike-protected reaches, where dike failures have to be considered. This
paper focuses on a 50km reach of River Po (Italy) and three major sources of uncertainty in
inundation mapping: uncertainties in the (i) upstream and (ii) downstream boundary
conditions, and (iii) uncertainties in the dike-failure location and breach morphology. We
derive confidence bounds for flood hazard maps by means of the Inundation Hazard
Assessment Model (IHAM) – a hybrid probabilistic-deterministic model. IHAM couples in a
dynamic way a 1D hydrodynamic model and a 2D raster-based hydraulic model through a
probabilistic dike-breaching analysis that considers three different failure mechanisms:
overtopping, piping and micro-instability due to seepage. To address the randomness
resulting from the variability in boundary conditions and dike-failures the system is run in a
Monte Carlo framework. Uncertainties in the definition of upstream boundary conditions (i.e.
design-hydrographs) are assessed by applying different bivariate copula families to model
the frequency of flood peaks and volumes. Uncertainties in the definition of downstream
boundary conditions are characterized by associating the rating-curve used as boundary
condition with confidence intervals which reflect discharge measurement errors and
interpolation errors. The results of the study are presented in terms of the Monte Carlo-based
flood hazard mapping for different flood-intensity indicators (e.g., inundation depth, flow
velocity, inundation duration, etc.) together with the corresponding uncertainty bounds. We
conclude on the influence of uncertainty in boundary conditions and provide decision makers
with an important piece of information for devising and implementing flood-risk mitigation
strategies.
SESSION: PREDICTIONS
83
THE VALUE OF URBAN FLOOD MAPPING: APPLICATION TO THE CASE
STUDY OF BARCELONNETTE (FRANCE)
Dottori, F.1, Di Baldassarre, G.2 and Alfonso, L.2
1 University of Bologna
2 Unesco-IHE, Delft
E-mail: [email protected]
Let us consider an urban settlement near a river, for which a flood alert system is installed. In
case of a flood alarm, it is evident that people living close to the river should be evacuated
anyhow, while people leaving very far away will not be affected by the inundation. In these
two opposite situations, any additional information to make a decision (evacuate / not
evacuate) has no value. However, in the flood prone areas between these two extremes,
urban flood mapping has a value, providing information on the dynamics of the flood event
and its consequences and therefore reducing the uncertainty associated to the event. In this
context, the goal of this study is to analyze the value of urban flood mapping, using the Value
of Information (VOI) concept. In particular, VOI is evaluated in terms of prevented damage
with probabilistic flood inundation maps. Such maps are ensemble-based, for which a
recently developed inundation model, based on cellular automata approach, is used. The
methodology is applied to a specific case study: The Ubaye River at Barcelonnette (France
Alps).
SESSION: PREDICTIONS
84
OPEN SOURCE GIS TOOLS FOR FLOOD HAZARD MAPPING WITHIN THE
DANUBE FLOOD RISK PROJECT
Franceschi, S.1, Monacelli, G.1 and Rigon, R.2
1
ISPRA Italy (Higher Institute for Environmental Protection and Research) 2 University of Trento, Department of Civil and Environmental Engineering, Italy
E-mail: [email protected]
The Danube River is one of the most important natural axes in South-East-Europe. It links
most of the countries in the SEE area. The DANUBE FLOODRISK project focuses on the
most cost-effective measures for flood risk reduction: risk assessment, risk mapping,
involvement of stakeholders and risk reduction by adequate spatial planning. 19 institutions
all along the Danube countries, central public bodies, universities, research institutes and
operational agencies, NGOs are involved in the project. ISPRA (Higher Institute for
Environmental Protection and Research in Italy) will give its contribution to the Danube Flood
Risk Project focusing on a set of studies and analyses on small Alpine catchments of the
study area of the Drau basin closed in Lienz. The attention will be focused on the influence
that planning and water management in small basins can have on the floods in the main
Danube River.
For this purpose some algorithms and methodologies have been integrated into the new GIS
library JGrassTools to be used in the project for hazard mapping, with particular attention to
the evaluation of the maximum discharge for floods with high content of transported
sediments and debris flow, as recommended by the European Flood Directive 2007/60CE.
The main reason for choosing the Drau basin as study area is to compare different
approaches and tools for hazard mapping. Therefore during the project specific tools will be
developed and the achieved results will be compared with those obtained with other
proprietary software. The development of GIS tools is a good starting point for data
harmonization and integration between different countries and also for stakeholders’
involvement because of the use of maps and colours for the presentation of results to the
public and because technicians and administrations can use the same tools for their
analysis. These tools are in fact used also in some academic and post academic courses on
hydro-geological risk evaluation.
The final purpose of the work is to have a set of well working Open Source tools that can be
used for planning, data management and integration and stakeholders’ involvement. These
tools will make the exchange of data and knowledge between neighbouring countries easier
and, on the other hand, they will be a guarantee of the quality of the work done by
professionals for the public administrations.
SESSION: PREDICTIONS
85
UNCERTAINTY ESTIMATION OF SIMULATED WATER LEVELS FOR THE MITCH
FLOOD EVENT IN TEGUCIGALPA
Fuentes, D. C.1,2, Halldin, S.1, Xu, C-Y.1,3 and Lundin, L-C. 1
1
Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden 2 Earth Science Institute, Universidad Nacional Autónoma de Honduras, Blv. Suyapa, Ciudad Universitaria,
Tegucigalpa, Honduras 3 Department of Geoscience, University of Oslo, P O Box 1047, Blindern, NO-0316, Oslo, Norway
E-mail: [email protected]
Hurricane Mitch in 1998 left a devastating flood in Tegucigalpa, the capital city of Honduras.
Simulation of elevated water surface provides a better way to understand the hydraulic
mechanism of large flood events. In this study the one-dimensional HEC-RAS model for
steady flow conditions was used to estimate the water level for the Mitch event in the river
reaches at Tegucigalpa. Parameters uncertainty of the model was investigated using the
generalized likelihood uncertainty estimation (GLUE) framework. Because of the extremely
large magnitude of the Mitch flood, no hydrometric measurements could be taken during the
event. However, post-event indirect measurements of the discharge and observed water
level were obtained in some previous studies. To overcome the problem of lacking direct
hydrometric measurement data, uncertainty in the discharge was considered by sampling the
value from a beta distribution function. Furthermore, the fuzzy set theory was used to provide
the model with flexibility in selecting behavioral parameter sets by considering an uncertainty
range in the post-event observed water level. If behavioral parameter sets can reproduce
water surface levels well for past events such as Mitch, more reliable predictions for future
events can be expected. The results acquired in this research will provide guidelines to deal
with the problem of modeling past floods when no direct data was measured during the
event, and to predict future large events taking uncertainty into account. The obtained range
of the uncertain flood extension will be an outcome useful for decision makers.
SESSION: PREDICTIONS
86
INTEGRARTION OF TIME SERIES MANAGEMENT SYSTEM AND DATA
SERVING FOR MODELLING APPLICATIONS
Gál, R.
KISTERS AG, Charlottenburger Allee 5, 52068 Aachen, Germany
E-mail: [email protected]
The core technology, which provides the backbone of key services for water management
data processing is called KISTERS Time Series Management (KiTSM). KiTSM is developed
in JAVA and is designed to organize, compute and share time series mass data in local
networks but as well in the Internet. KiTSM is combining interdisciplinary demands on time
series processing with regard to mass data capabilities, scalability, modular design and
flexibility to work in diverse specialist areas, high level of automation, reliability, security,
integration potential, broad platform independence, redundancy and resilience.
Standard time series data structure contains time stamp, value, quality and interpolation
type. Time interval of time series can be regular or flexible, with possibility to add time offset.
Between two points is clearly defined the interpolation type, which could be changed over the
time.
All calculations and auto validation routines comprise the organic part of execution system.
Data operations as algorithms, called Agents, are operating on time series data and their
main purpose is to either auto validate time series or derive other time series. Agents are
generally triggered on data change events and executed automatically each time the data is
accessed (such as by reports, graphs, exports, calculations); with KiTSM time series are also
automatically updated in the background.
WISKI as a client application desktop tool is connected to all metadata and time series data.
Key lists and basic data are organised in different hierarchies. Environment of graphical view
allows providing various types of data corrections, arranging graphical layout and elements
as well as print, copy or save the graph.
Extreme events and exceptional situations are controlled by AlarmManager. It handles
incoming event messages, classifies them, and reacts accordingly. Alarm messages are
created based on templates, then filled with additional information, and are distributed to
recipients via several media types.
Relevant hydrological data are available online in a web browser using WISKI Web Public
which disseminates data for general public covering peak accesses during flood situation.
Requirements of specific expert groups are fulfilled by WISKI Web Pro which is highly
interactive and works with dynamic filtering, mapping, lists and graphs.
The KISTERS Web Interoperability Solution KIWIS has been developed as a contribution to
interoperability experiments at Open Geospatial Consortium (OGC). KIWIS offers combined
services such as SOS, WOF, WMS and WFS for different data sources in one instance.
As a standard requirement the KISTERS archives have to serve data to a range of modelling
applications. In the majority of cases this data transfer is scheduled in time and is based
upon a variation of model specific ASCII file formats. To ease this process and to provide the
advantage of linking models to our customers the KISTERS time series server became
OpenMI compliant by the end of 2010. With the KISTERS OpenMI wrapper, local and/or
remote modelling users can establish the communication to a KISTERS time series server,
search and identify the appropriate input time series and retrieve data through the internet
directly into a chain of integrated modelling applications.
SESSION: PREDICTIONS
87
ASSESSMENT OF PROJECTED CHANGES IN PRECIPITATION EXTREMES IN
THE CZECH REPUBLIC USING A NON-STATIONARY INDEX FLOOD MODEL
Hanel, M., Vizina, A. and Martínková, M.
T. G. Masaryk Water Research Institute, p.r.i., Prague, Czech Republic
E-mail: [email protected]
Fourteen transient simulations of regional climate models (RCMs) are used to assess the
possible future changes in seasonal precipitation extremes of durations 1 to 30 days for the
Czech Republic. The statistical model used for analysis assumes that these precipitation
maxima follow a generalized extreme value (GEV) distribution with time-varying parameters.
In addition, spatial pooling of the maxima at various grid boxes is applied to reduce the
uncertainty of the parameters of the GEV model. The ensemble mean changes in the
quantiles are positive for all durations, return periods and seasons considered. Large
quantiles of the distribution of summer precipitation extremes increase more than moderate
quantiles and this increase is relatively large at short durations. The dependence of the
changes on duration and return period is much weaker in the other seasons, in particular in
winter and spring. Although the spread in the RCM ensemble is considerable, most of the
RCM simulations agree on the sign of the changes. The value of RCM projections of hourly
precipitation extremes is also briefly addressed.
SESSION: PREDICTIONS
88
SAFEFTY CRITERIA FOR FLOOD PROTECTION STRUCTURES IN SLOVENIA
Humar, N.1, Kryžanowski2, A., Brilly, M.2, Schnabl, S.2
1 Hidrotehnik d.d. Ljubljana, Slovenčeva 97, SI-1000, Ljubljana, Slovenia
2 Chair of Hydrology and Hydraulic Engineering, Faculty of Civil and Geodetic Engineering, University of
Ljubljana, Jamova 2, Si-1000 Ljubljana, Slovenia
E-mail: [email protected], [email protected], [email protected],
In Slovenia, several structures (e.g., dams, levees, floodwalls, etc.) which intend to protect
the affected flood prone areas have been built recently. Most of these structures have been
built in areas where failure would potentially results in massive damage or great loss of lives.
As a result, all these structures have to be designed, constructed, maintained, and inspected
appropriately. Thus, in this paper, design/safety criteria and practices used in relation to
these structures are reviewed and critically compared to other national standards applicable
to similar structures. Finally, based on this comparison, some improvements of the safety
criteria/standards adopted in Slovenia will be suggested.
SESSION: PREDICTIONS
89
SPRING FLOOD FREQUENCY ANALYSIS OF LITHUANIAN RIVERS
Kriaučiūnienė, J. and Šarauskienė, D.
Laboratory of Hydrology, Lithuanian Energy Institute, Breslaujos 3, LT-44403 Kaunas, Lithuania
E-mail: [email protected]
Flood frequency analysis is useful in forecasting flood magnitude and behavior. Statistical
prediction of design flood is very important for management of extreme flood control,
prevention of present and planned hydro technical structures, hydropower stations and
dams. Statistical methods of flood frequency analysis could be applied for dam safety
analysis (flood-hazard mapping). Since small rivers often have short series of observation
data or no data at all, there is a possibility to use available flood characteristics of other rivers
of the same homogenous region, applying flood frequency distribution as well.
The probabilistic behavior of floods has been studied for the Lithuanian rivers. Analysis of
different flood frequency distributions (Gumbel, Pearson Type III, General Normal, Log
Normal, Generalised Extreme Value) using long-term data of 32 hydrological gauging
stations was performed in order to estimate the best fit distributions for Lithuanian conditions.
The water measurement stations (WMS) were distributed in three hydrological regions of
Lithuania: 1 – Western Lithuania, 2 – Central Lithuania, 3 – Southeastern Lithuania.
Additionally the hydrological data from 5 WMS which are on the biggest rivers of Lithuania
(the Nemunas and the Neris) were investigated.
The results revealed that in 1961-1990 Log-Pearson type 3 probability distribution best fitted
actual data of spring flood in the Western region (where precipitation is the main river feeding
source) and GEV – for the Central region (that has mixed river feeding type) and
Southeastern region (where groundwater feeding prevails); in the period of 1991-2008 GEV
was the probability distribution that received the highest ranks in all regions.
Recently, in the period of significant climatic changes (1991-2008), GEV probability
distribution is the most suitable distribution for flood frequency analysis and could be used to
predict of flood maximum discharges in Lithuanian rivers. This probability distribution could
also be used for simulating flood frequency distribution in engaged rivers.
LN and EV1 probability distributions seemed to be the least suitable (out of the five studied)
for the modeling of the analyzed spring flood data.
SESSION: PREDICTIONS
90
ESTIMATION OF FLOOD FREQUENCY CURVES IN POORLY GAUGED
MEDITERRANEAN WATERSHEDS USING A DERIVED DISTRIBUTION
PROCEDURE
Loukas, A.1, Vasiliades, L.1, Papaioannou, G.1 and Aronica, G.T.2
1 Department of Civil Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece
2 Department of Civil Engineering, University of Messina , Via Nuova Panoramica dello Stretto, 98166 Villaggio S.
Agata - Messina, Italy
E-mail: [email protected], [email protected]
For engineering applications of hydrology, the estimation of the peak discharge for a given
return period at basin outlet is important because the planning and design of water resources
projects and floodplain design depend on the frequency and magnitude of peak discharges.
In ungauged and poorly gauged watersheds, it is not possible to apply statistical analysis of
flood data or using a calibrated rainfall-runoff model of varying degrees of complexity. A way
to circumvent the lack of data is to model the flood formation processes using simplified
descriptions of the hydrological processes characterized by a reduced number of robust
parameters in order to ensure a reduced uncertainty in model predictions. Such a modelling
procedure is the derived distribution approach, which uses a rainfall generator and a simple
rainfall-runoff model. In this work, an event rainfall-runoff simulation procedure based on the
derived distributions method is proposed for the estimation of flood frequency in ungauged or
poorly gauged watersheds in the Mediterranean. The procedure uses a stochastic generation
rainfall generation model and a rainfall-runoff model. The results of previous research on
rainfall characteristics and watershed response have been incorporated into the two models.
The rainfall characteristics are storm depth, storm duration and the storm spatial and
temporal distribution. The rainfall-runoff model is a simple model which describes the
hydrological processes with a reduced number of parameters. Some of the parameters of the
rainfall generation and hydrological model parameters are stochastic in nature and they are
generated using the Monte Carlo method simulating the flood hydrographs. The proposed
procedure has been applied in a watershed in Cyprus, and the results have been validated
against the observed flood frequency.
SESSION: PREDICTIONS
91
CLIMATE CHANGE IMPACT ASSESSMENT OF FLOOD RISK. CASE STUDY:
VIDAA RIVER BASIN
Madsen, H., Larsen, J. and Madsen, M.N.
DHI, Agern Allé 5, DK-2970 Horsholm, Denmark
E-mail: [email protected]
A methodology is presented for flood risk assessment under climate change. The
methodology is demonstrated for analysing changes in flood risk and dike safety in the Vidaa
River basin, a cross-border catchment located in the southern part of Jutland, Denmark and
northern Germany. The river discharges to the Wadden Sea through a tidal sluice, and
extreme water level conditions in the river system occur in periods of high sea water levels
where the sluice is closed and increased catchment runoff take place. To assess the impacts
of future climate change both changes in the meteorological forcing (precipitation,
temperature and potential evapotranspiration) and changes in sea water level are
considered. Changes in meteorological forcing data are based on an ensemble estimate of
downscaled regional climate model projections from the ENSEMBLES data archive. Future
sea water levels are estimated from current projections of the mean sea level rise in the
area, estimated isostatic changes, and changes in storm surge statistics predicted from a
hydrodynamic model simulation forced with a regional climate model.
To estimate the changes in flood risk in the Vidaa River basin an integrated hydrological and
hydraulic model has been set up and calibrated. This model forms the basis for simulation of
water levels in the river system using meteorological forcing and sea water level data for
current (using observed records) and future climate (using projected records), considering
two projection horizons, 2050 and 2100. Extreme value analysis is applied to estimate the
risk of dike overtopping.
More extreme precipitation events are expected in future, which result in an increase of the
extreme runoff in the river basin of about 8% in 2050 and 14% in 2100 (ensemble averages).
Hydrodynamic model results show increases in extreme storm surge levels at the Vidaa
sluice of up to 0.8 m in 2100. However, durations of extreme water levels are not seen to
increase. Currently, there is a relatively low risk of dike overtopping with annual exceedance
probabilities of 0.1% or less in most parts of the river system. For the worst-case scenario in
2100, pronounced changes in flood risk are seen with flood risks of 5% or more in the
downstream part of the river.
SESSION: PREDICTIONS
92
FLOOD RISK MAPPING UNDER UNCERTAINTY: APPLICATION TO SUNGAI
JOHOR BASIN, MALAYSIA
Md. Ali, A., Di Baldassarre, G. and Solomatine, D.
UNESCO-IHE Institute of Water Education, Department of Hydroinformatics and Knowledge Management,
Westvest 7, 2601 DA, Delft, The Netherlands
E-mail: [email protected]
Flood risk can be defined as a combination of flood hazard, vulnerability and exposure. In
particular, while flood hazard is usually derived by elaborating the outcomes of hydraulic
models, flood vulnerability and exposure are commonly evaluated via socio-economic
analyses, land use studies, and assessment of the capability of the population to deal with
flood disasters (e.g. evacuation plans).
Currently, flood risk mapping is often implemented without a serious consideration of the
large number of uncertainty sources affecting the risk assessment. A slight uncertainty in
estimating hydrologic flow can cause uncertainty in estimating the water surface elevation in
a channel, which in turn can cause uncertainty in mapping the flood inundation.
Choices of performance measures and observation sets could significantly influence the
estimation of flood hazard. Given the current state of uncertainty and recent advances in
various individual components, an integrated framework for flood inundation mapping is
needed. Advances in technology, data collection techniques, and modelling approaches
have led to improvements in overall simulation of hydrologic and hydraulic processes.
The goal of this research is to identify and quantify the main sources of uncertainty
associated with flood risk mapping and develop an efficient methodology to deal with them.
SESSION: PREDICTIONS
93
FLOOD IN TOWN – DECISION SUPPORT TOOL (VESNA)
Mišík, M., Kučera, M., Fridrich Tegelhoffová, M. and Mrnčo, I.
DHI SLOVAKIA, s.r.o, Hattalova 12, 831 03 Bratislava, Slovakia
E-mail: [email protected], [email protected], [email protected], [email protected]
Main idea and ambition of the VESNA project was to create a powerful tool, determined to
simplify decision-making in crisis flood situations for responsible personnel, on a local town
level – town Levice in central Slovakia (35 thousand inhabitants). Levice town is endangered
by small river Podlužianka, typical with fast flood response after heavy rainfall, flowing from
hilly catchment to a flat populated area. The River Podlužianka in Levice has mean
discharge 0,5 m3.s-1, flood discharge with 100 year return period is 65 m3.s-1.
The main scope of the project was creating a tool for decision-making support, which will use
standard meteorological and hydrological forecasts and operational data of SHMI (Slovak
Hydrometeorological Institute), published for public use on Internet.
On the basis of predicted (or even actual) meteorological and hydrological situation, the user
chooses one category, which matches the current prediction or situation best.
Several categories are defined in the system, covering a whole range of possible
meteorological and consequently also hydrological situations in the area. Each
meteorological and hydrological category is represented by one representative flood
scenario, which was simulated in detail. Representative scenarios also include a possibility of
breaking the flood protection lines. The system is oriented on single event heavy rainfall and
consequent floods with typical delay of flood 8 – 12 hours after rainfall.
Simulations of flood scenarios are not calculated in real time during actual flood, but were
calculated and mapped in advance, for the particular defined model area during project. To
its user the system offers a description of flood situation, its consequences, extend and time
advancement of flood in the text part. In the graphical part of the tool, the user has a chance
to view maps of water surface elevation, water depth, flow velocity and direction, as well as
dangerous zones in a detailed scale.
The results are complied with animations and 3D visualisation of the flooded area together
with a photo documentation of past floods.
Decision-making part of the system includes also other subsequent steps, which were
defined and formulated during the project in cooperation with its future users (town mayor,
flood commissions, river basin authority, rescue...). It is expected that after a testing and
practical use of the tool, it will be further supplemented by other useful recommendations for
action in urgent situations (announcing of flood level activity, evacuation of people, rescue
works, necessary material and technique...). Information on result uncertainty is also at one’s
disposal. The tool contains also contacts to involved organs and a complete flood plan of the
town.
It is possible to launch the VESNA system from flash memory stick (or HDD) on any PC
equipped with standard Internet browser. System does not require any additional installation
or licensed specialised software. Controlling of the system by the user is intuitive and
requires only a minimal training. Created system is open, which means that it will be possible
to input any necessary information according to current needs, to modify it, or add any other
steps required for decision-making.
SESSION: PREDICTIONS
94
UNCERTAINTY IN 1D HYDRAULIC MODELLING CAUSED BY
PARAMETERIZATION AND INFLOW INACCURACY
Mukolwe, M.M., Di Baldassarre, G., Werner, M. and Solomatine, D.
UNESCO-IHE, Institute for Water Education, PO Box 3015, 2601 DA Delft, the Netherlands
Email: [email protected]
It is widely acknowledged that the use of accurate techniques to predict the effects of water
related disasters, such as floods, forms a basis for the mitigation of the effects of such
occurrences. Consequently, emphasis is placed on the better understanding of the methods
and tools, including their associated uncertainty, that are applied in flood risk management.
This paper presents the analysis of uncertainty in hydraulic modelling, with focus on the
inaccuracy caused by inflow errors and parameter uncertainty. In particular, the study
develops a method to propagate the uncertainty induced by: (1) the application of a stage-
discharge rating curve (i.e. parameterisation of the power function), and (2) the calibration of
the channel roughness coefficients (i.e. Manning's roughness coefficient) through a 1D
hydraulic model (i.e. HEC-RAS). The methodology is applied and tested for a 98Km reach of
the River Po (Italy), between Cremona and Borgoforte. In particular, the hydraulic model was
evaluated by using two independent sets of hydrometric data (along the river reach), i.e.
observed water levels, within a GLUE (Generalised Likelihood Uncertainty Estimation)
framework. Independent calibration and validation, as well as the uncertainty analysis,
showed a good performance of the model. In fact, when conditioned on a flood event, the
model provided satisfactory results on predicting flood levels for another (independent) event
as the observations were found within 95% confidence interval of the ensemble simulation.
However, it should be noted that poor results were obtained when the model was conditioned
on a data type different from the one used to evaluate model predictions.
SESSION: PREDICTIONS
95
UNCERTAINTY ASSESSMENT OF STREAMFLOW SIMULATION ON
UNGAUGED CATCHMENTS USING A DISTRIBUTED MODEL AND THE KALMAN
FILTER BASED MISP ALGORITHM
Múnera, J.C.1, Francés, F.1 and Todini, E.2
1
Instituto de Ingeniería del Agua y el Medio Ambiente, Universidad Politécnica de Valencia. Camino de Vera, s/n
C.P. 46022, Valencia - España. Email: 2
DIPARTIMENTO di SCIENZE della TERRA e GEOLOGICO-AMBIENTALI, Università di Bologna. Piazza di
Porta San Donato, 1 – 40126, Bologna - Italia.
Email: [email protected], [email protected], [email protected]
In this work, an approach based on the MISP technique (Todini, 1978) is presented, which
make use of two interacting Kalman filters coupled in parallel seeking to improve the
historical hourly stream flow predictions made with a hydrologic distributed model in some
ungauged catchments. On the other hand, the Kalman filter approach allows assessing the
uncertainty associated to these predictions. The two coupled filters allow representing the
dynamic behavior of a discrete lineal system; the first filter is responsible for the minimum
variance estimation of the system state given a set of parameters, and the second one deals
with updating the parameters of the state transition matrix of the first filter, also with minimum
variance. Each moment is taken into account, the interaction between the two filters to get
the best estimate of the system state and parameters, which essentially is equivalent to solve
a non-linear problem (Todini, 1978).
In the configuration of the state vector measurable quantities must be related at discrete time
intervals. The state variables included in the state vector are the observed and simulated
stream flows in a gauging station at the basin outlet, which is used as a pivot point to transfer
information to an ungauged sub-catchment within it, as well as the stream flows simulated
with the model in the latter. Additionally, we have also included these variables at previous
time step, to account for autocorrelation in the process. Prior to execution of the filter, we
made a logarithmic transformation of data, seeking a better approximation of the hypothesis
of white noise, both in system and measurement errors. Finally, we have incorporated in the
covariance matrix of the measurement errors a cross covariance term, to take into account
the spatial correlation of errors between both stations.
This approximation of the MISP approach was applied to some gauging stations located on
the Illinois River basin, that were included in the second phase of the Distributed Model
Intercomparison Project (DMIP 2) of NOAA/NWS. The hydrological model used in this case
study is TETIS model (Vélez et al, 2002; Francés et al, 2009). In order to test the
effectiveness of the algorithm, every ungauged point of simulation has been matched with an
existing gauging station, in which observed data are used only for comparison purposes.
The obtained results suggest that the proposed methodology is a robust and very useful tool
for the uncertainty estimation related to streamflow predictions made with a hydrological
model on ungauged catchments, and in some cases allow to improve such estimates.
SESSION: PREDICTIONS
96
TOWARDS SPATIALLY DISTRIBUTED FLOOD FORECASTS IN FLASH FLOOD
PRONE AREAS: RESULTS OF A FIRST TEST IN THE SOUTH OF FRANCE
Naulin, J-P. 1, Payrastre, O.1, Gaume, E.1, Delrieu, G.2, Arnaud, P.3, Lutoff, C.4 and
Vincendon, B.5
1 IFSTTAR, Bouguenais, France,
2 CNRS - LTHE, Grenoble, France
3 Cemagref, Aix en Provence, France
4 CNRS – UMR Pactes, Grenoble, France
5 GAME/CNRM (Meteo France, CNRS), Toulouse France
E-mail: [email protected]
Accurate flood forecasts are crucial for an efficient flood event management. Until now,
hydro-meteorological forecasts have been mainly used for early-warnings in France
(Meteorological and flood vigilance maps) or over the world (Flash-flood guidances).
Forecasts are generally limited to the main streams covered by the flood forecasting services
or to specific watersheds with particular assets like hydropower dams which are in most
cases well gauge river sections, leaving aside large parts of the territory
Distributed hydro-meteorological forecasting models, able to take advantage of the now
available high spatial and temporal resolution rainfall measurements, are promising tools for
anticipating and quantifying the consequences at the ground of storm events all over a
region. They would be very useful, especially in regions frequently affected by severe storms
with complex spatio-temporal patterns. They would provide the necessary information for
flood event management services to identify the areas at risk and to take the appropriate
safety and rescue measures: prepositioning of rescue means, stopping traffic on exposed
roads, determination of safe accesses or evacuation routes.
Some preliminary tests conducted by the LCPC within the European project FLOODsite have
shown encouraging results of a distributed hydro-meteorological forecasting model. It seems
possible, despite the limits of the available rainfall measurements and the shortcomings of
the rainfall-runoff models, to deliver distributed forecasts of possible local flood
consequences – road submersion risk rating at 2500 different locations of the Gard
department in the tested case - with an acceptable level of accuracy. The PreDiFlood project
(http://heberge.lcpc.fr/prediflood/) aims at consolidating and extending these first results with
the objective to conduct pre-operational tests with possible end-users at the end of the
project.
Such a tool will not replace, but complement existing flood forecasting approaches in time
and space domains, short term forecasting at a regional scale, that have not been covered
until now. It will produce a completely new type of forecasts and the usefulness of such data
for the emergency services for their real-time decision making will be assessed within the
project. Beyond the direct operational objectives, this project aims at demonstrating, on a
specific application – the now-casting of road submersions, the possibilities and also the
limits and hence the needed improvements of tools that are still underused: high spatial and
temporal resolution rainfall measurements including radar quantitative precipitation estimates
but also precipitation now-castings, rainfall-runoff models and the recent knowledge acquired
on flash-floods consequence evaluation as well as event management.
SESSION: PREDICTIONS
97
PROBABILISTIC FLOOD RISK MAPPING INCLUDING SPATIAL DEPENDENCE
Neal, J.1, Keef, C.2, Bates, P.1, Beven, K.3 and Leedal, D.3
1 School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK.
2 JBA Consulting, South Barn, Broughton Hall, Skipton, N Yorkshire, BD23 3AE, UK.
3 Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
E-mail: [email protected]
Effective flood risk management depends on methods for estimating flood hazard and an
appraisal of the dominant uncertainties in the analysis. Typically hydraulic models are used
to simulate the extent of flooding for an estimate of the flow in a particular reach for a chosen
return probability. However, this definition causes problems at river confluences where flows
derive from multiple sources. Here a model-based approach was adopted to describe the
multisite joint distribution of river flows for three rivers that converge on the city of Carlisle
(UK). Monte-Carlo methods were used to generate a best estimate of the set of flood events
with realistic spatial dependence between tributaries which would occur over a 100 year
period. Each event was then simulated with a new computationally efficient two-dimensional
hydraulic model of the whole city. Simulations from the hydraulic model were used to map
inundation frequency, with the largest event in the event set assumed to represent the 1 in
100 year flood. To estimate uncertainty in the statistical model used to create the event set
block bootstrapping was used to produce a further 100 runs of the event generator. Each of
the ~47000 dynamic flood events created by this process was then simulated using the
hydraulic model. Flood risk was calculated for each of the 100 event generator runs based
on a depth damage curve. The 90th percentile of the resulting damage distribution was 55
times greater than the 10th percentile, indicating significant uncertainty in the flood damage
and the limitations of typical discharge records.
SESSION: PREDICTIONS
98
ENSEMBLE PREDICTION OF FLOODS – PROCESS CONTROLS
Nester, T. and Blöschl, G.
Vienna University of Technology, Austria, Institute for Hydraulic and Water Resources Engineering
E-mail: [email protected]
The runoff forecasting model for the Danube tributaries in Upper Austria and Lower Austria
has been in operational use since 2006. The model is based on a conceptual semi-
distributed water balance model with catchment sizes ranging from 25 to 25.000 km². The
aim of this study is to examine how the spread in ensemble runoff forecasts and the
differences between observed runoff and deterministic runoff forecasts are related. We are
also interested in the contributions of the model and precipitation errors to the total forecast
errors. Assuming that all ensemble members are equally likely, the statistical analyses
indicate that the ensemble spread of the flood forecasts is always narrower than the
distribution of the forecast errors. For shorter lead times, the contribution of the model error is
larger than the contribution of the precipitation error while for longer lead times the
contribution of the precipitation is the dominant factor.
SESSION: PREDICTIONS
99
FLOOD HAZARD UNDER CLIMATE CHANGE IN THE MEKONG DELTA
Nguyen, V.D.1,3, Delgado, J.M.1, Merz, B.1, Bárdossy, A.2 and Apel, H.1
1 GFZ German Research Centre for Geosciences, Section 5.4 Hydrology, Potsdam, Germany
2 Institute of Hydraulic Engineering, University of Stuttgart, Stuttgart 70569, Germany
3 Southern Institute of Water Resources Research SIWRR, Ho Chi Minh City, Vietnam
E-mail: [email protected]
Flood hazard analysis is an indispensable input for flood risk assessment. An essential part
is the determination of probabilities of occurrence of floods of different magnitudes. The
methods applied for the determination are mostly based on the stationary assumption.
However, this assumption does not hold for most of the observed discharge time series in
general, and in particular not for future climate conditions. It is now commonly agreed that
climate change leads to changing flood hazards. Therefore, this study aims at developing a
novel approach for flood hazard mapping considering the change in climate variability with
the Mekong Delta as an example. We explicitly take non-stationarity and dependence in the
discharge time series into consideration, for both annual maximum flood peak discharge and
flood volume. The dependency in the marginal distribution of flood peak discharge and
volume is modeled by copulas, while characteristic flood hydrograph shapes are identified
through a cluster analysis. We further analyzed the dependency of the statistical distributions
of flood peak and volume on the variance in monsoon indexes, which yielded a reliable proxy
for flood intensity in the Mekong Delta, avoiding time consuming and error prone
downscaling of GCM results and hydrological modeling. Future development of the flood
intensity and frequency was consequently estimated by the identified non-stationarity in the
extreme value statistics, the dependency of the frequency distributions to monsoon intensity,
and the monsoon variability simulated by 7 different GCM’s. The changes in the frequency of
flood peak and duration were mapped into probabilistic inundation maps by driving a large
scale hydrodynamic model for the Mekong Delta in a Monte Carlo framework. A comparison
of these maps for the projection year 2050 with the reference year 2000 illustrates the
changes in flood hazard spatially explicit for the whole delta.
SESSION: PREDICTIONS
100
FLOOD PRONE AREAS MAPPING THROUGH GIS AND MULTI-CRITERIA
ANALYSIS
Papaioannou, G.1, Loukas, A.1, Vasiliades, L.1 and Aronica, G.T.2
1Department of Civil Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece,
2Department of Civil Engineering, University of Messina , Via Nuova Panoramica dello Stretto, 98166 Villaggio S.
Agata - Messina, Italy,
E-mail: [email protected], [email protected]
Flood risk mapping is a basic component of the European natural disaster management
policy, directly connected to water resources management with the European Directive
(2007/60). This study presents a methodology for flood prone areas mapping using
geographical information systems (GIS) and multi-criteria evaluation techniques. Factors are
divided in different groups which do not have the same level of trade off. These groups are
related to geophysical, morphological, climatological/meteorological and hydrological
characteristics of the basin as well as to human activities. GIS are used for geographic data
acquisition and processing. The analytical hierarchy process (AHP) is the multicriteria
evaluation technique used, enhanced with different standardization methods. The method
has been applied to the watershed and the floodplain of Xerias River in the region of
Thessaly, Greece. In this work, a methodology which combines a risk based analysis and
geographical information systems is proposed for the mapping of flood prone areas. Xerias
river was repeatedly flooded in the last few years. These floods had major impacts on
agricultural areas, road networks and other technical infrastructures. Historical flood
inundation data in the study area have been used for the validation of the methodology.
SESSION: PREDICTIONS
101
VISUALISING PROBABILISTIC FLOOD FORECAST INFORMATION: EXPERT
PREFERENCES AND PERCEPTIONS OF BEST PRACTICE IN UNCERTAINTY
COMMUNICATION
Pappenberger, F.1, Stephens, E.2, Thielen, J.5, Salamon, P.5, Demeritt, D.3, van Andel, S.J.4,
Wetterhall, F.1 and Alfieri, L.5
1
European Centre For Medium Range Weather Forecasts, Reading, UK 2
University of Bristol, Bristol, UK 3 King’s College London, London, UK
4 Unesco IHE, Delft, The Netherlands
5 Joint Research Centre of the European Commission, JRC, Ispra
E-mail: [email protected]
The aim of this paper is to understand and to contribute to improved communication of the
probabilistic flood forecasts generated by Hydrological Ensemble Prediction Systems (HEPS)
with particular focus on the inter expert communication. Different users are likely to require
different kinds of information from HEPS and thus different visualizations. The perceptions of
this expert group are important both because they are the designers and primary users of
existing HEPS. Nevertheless, they have sometimes resisted the release of uncertainty
information to the general public because of doubts about whether it can be successfully
communicated in ways that would be readily understood to non-experts. In this paper we
explore the strengths and weaknesses of existing HEPS visualization methods and thereby
formulate some wider recommendations about best practice for HEPS visualization and
communication. We suggest that specific training on probabilistic forecasting would foster
use of probabilistic forecasts with a wider range of applications. The result of a case study
exercise showed that there is no overarching agreement between experts on how to display
probabilistic forecasts and what they consider essential information that should accompany
plots and diagrams. In this paper we propose a list of minimum properties that, if consistently
displayed with probabilistic forecasts, would make the products more easily understandable.
SESSION: PREDICTIONS
102
DEVELOPMENT OF DECISION SUPPORT SYSTEMS FOR FLASH FLOOD
FORECASTING IN SMALL CATCHMENTS
Poma, S.1, Brigandì, G.2, Aronica, G.T.2 and Candela, A.1
1
Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, University of Palermo, Italy 2 Dipartimento di Ingegneria Civile, University of Messina, Italy
E-mail: [email protected]
In the recent past throughout the Mediterranean area, many extreme events such as floods,
debris flows and landslides occurred. The use of a reliable flood forecasting model can play
an important role in managing land and water resources. The purpose of this work is the
development of a Decision Support System (DSS) for flash flood forecasting. A system of
alerts, based on the use of rainfall thresholds and structured in three phases, has been
implemented in order to achieve an integrated system of support for the prediction of
hydraulic and hydro-geological instability. Starting from precipitation and temperature air
data, the first phase of the DSS deals with the implementation of a procedure to model the
soil moisture conditions (saturation degree) using API index in order to generate a first
warning based on the antecedent moisture condition of the soil. In the second phase the
comparison between rainfall events and rainfall thresholds calculated for a given river section
of the catchment are displayed. Finally, the third phase concerns the imminence of a
possible hydrogeological risk by comparing the time when cumulative rainfall and rainfall
thresholds meet each other. The output of the first phase gives the probability of producing a
flood event if the catchment has a certain degree of saturation. To activate the other two
alarm phases it is necessary to derive, for a given river section where the critical discharge
has been fixed, rainfall thresholds as a function of the antecedent soil moisture conditions
and the temporal evolution of the rain storm. The implementation of the DSS allows to build a
user interface for the operator of the flood risk easy to understand. The system has been
successfully applied to the Giampilieri catchment, located in the north-east of Sicily. Actually,
the system could help to program a precise system of civil protection in order to put in place
all necessary emergency actions to reducing the loss of lives and damage to property.
SESSION: PREDICTIONS
103
AN ENTROPY APPROACH FOR THE OPTIMIZATION OF RIVER
CROSS-SECTIONAL SPACING
Ridolfi, E.1, Alfonso, L.2, Di Baldassarre, G.2, Dottori, F.3, Russo, F.1 and Napolitano, F.1
1
Dipartimento di Ingegneria Civile, Edile e Ambientale, Sapienza Università di Roma, Rome, Italy. 2
Department of Hydroinformatics and Knowledge Management, UNESCO-IHE Institute for Water Education,
Delft, the Netherlands. 3
Università di Bologna, Dipartimento di Scienze Della Terra e Geologico-Ambientali, Via Zamboni 67, 40126
Bologna, Italy.
E-mail: [email protected], [email protected], g.dibaldassarre@unesco-
ihe.org, [email protected], [email protected], [email protected]
Accurate definition of rivers geometry is a relevant task in the preparation of one-dimensional
hydraulic models. In particular, the selection of river cross section spacing is the key for
accurately describing the river hydraulics. In this work an entropy approach that allows
evaluating the optimum number of river cross sections and their location on the river
geometry is presented.
Given a redundant collection of pre-established cross section locations, the aim is to select a
subset of locations such that together provide the least redundant information and,
simultaneously, the highest information content. The problem can be posed as a
MultiObjective Optimization Problem (MOOP), in which two objectives are compromised:
minimising total correlation (as a measure of redundancy) and maximising joint entropy (as a
measure of information content). The MOOP is solved using the non-sorted genetic algorithm
NSGA-II and a Pareto front of optimal sets of cross section locations is obtained. The Pareto
front is then analysed and the most appropriate solution is chosen.
The proposed method is applied to an existing hydraulic model for the Po river between
Cremona and Borgoforte, built with an important number of redundant cross sections. In
order to accurately describe the profile of the watermarks of a flood event, the MOOP is
applied to find the optimal number and locations of cross sections. It is demonstrated that the
proposed approach matches very well with a previous methodology already presented in
literature.
SESSION: PREDICTIONS
104
FLOOD-RISK MAPPING – A NEW INSIGHT INTO A MAJOR ENVIRONMENTAL
PROBLEM
Romanowicz, R., Kiczko, A. and Osuch, M.
Institute of Geophysics Polish Academy of Science, Księcia Janusza 64, 01-452 Warsaw, Poland
E-mail: [email protected]
Derivation of flood risk maps requires estimation of maximum flood inundation extent with
assumed probability of exceedance, e.g. 100 or 500 year flood. The results of numerical
simulation of flood wave propagation are used to overcome the lack of relevant observations.
In practice, deterministic 1-D models are used for flow routing, giving a simplified image of a
flood wave propagation process. The solution of a 1-D model depends on the initial and
boundary conditions and estimates of model parameters which are usually identified using
the inverse problem based on the available noisy observations. Therefore, there is a large
uncertainty involved in the derivation of flood risk maps. This work is an attempt to quantify
this uncertainty. We compare the flood risk maps obtained using standard deterministic
methods with the maps that take into account some aspects of the uncertainty related to a
design flood input, observation errors and simplifications of the model structure. We apply
the Bayesian conditioning to assess the uncertainties of observations used for the calibration
of model parameters. The methods are compared using the Upper Narew catchment as a
case study. The results indicate that the uncertainties have a substantial influence on the
flood risk assessment. In this paper, we present a simplified methodology allowing the
influence of that uncertainty to be assessed.
SESSION: PREDICTIONS
105
BAYESIAN UNCERTAINTY ASSESSMENT OF FLOOD PREDICTIONS IN
UNGAUGED URBAN BASIS FOR CONCEPTUAL RAINFALL-RUNOFF MODELS
Sikorska, A.1,2, Scheidegger, A.1, Banasik, K.2 and Rieckermann, J.1
1 Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
2 Warsaw University of Life Sciences - SGGW, Faculty of Civil and Environmental Engineering, Dept. of Hydraulic
Engineering, Warsaw, Poland
E-mail: [email protected], [email protected], [email protected],
[email protected], [email protected]
Urbanization and the resulting land-use change strongly affect a watershed’s water cycle.
Especially with regard to precipitation, the slow natural response in discharge drastically
changes into a rapid and fast response of the urbanized catchment due to the additional
impervious area. Particularly in Eastern European cities, many urbanized areas experienced
rapid growth in recent years, resulting in more frequent urban flooding events.
However, often it is not trivial to predict the magnitude of a flood event, because catchment
data and hydrological measurements are not generally available. This usually prohibits the
use of detailed process-based rainfall-runoff models. On the one hand, it is difficult to inform
the parameters, e.g. soil moisture or hydraulic conductivity. On the other hand, most small
urban catchments are ungauged and therefore suffer from a lack of monitoring data.
Because of that, to predict the consequences of future urbanization, we are bound to using
simpler models. Our goal of the present study is two-fold: First, we investigate how far we
can use conceptual hydrological models to characterize runoff from ungauged urbanized
catchments. Second, we wanted to provide urban planners with a reliable measure of
uncertainty of the model predictions, which explicitly considers uncertainty from the simple
model structure as well as input uncertainty, e.g. from inaccurate rainfall measurements or
outdated GIS catchment data.
To this aim, we applied a methodology to assess the reliability of predicted discharges which
takes into account uncertainty in the model input, the model parameters, measurement
errors and uncertainty stemming from the simple model structure. A key feature of the
method is that it avoids common unrealistic assumptions on independently and identically
(normally) distributed residuals. Instead, the likelihood function is constructed by combining a
Box–Cox data transformation with a continuous-time autoregressive error model, which is
then used for Bayesian parameter estimation. To the best of our knowledge, this has not
been previously applied to assess conceptual models of ungauged urbanized catchments.
We demonstrate the potential of our approach on a case study from Sluzew creek, which
drains an urbanized catchment within Warsaw, PL. Specifically, we identified three potentially
suitable conceptual models from literature and investigated their predicted performance
based on several years of rainfall and streamflow measurements.
Our first results show a promising agreement between modelled and observed hydrographs
as well as a satisfactory prediction performance. However, prediction uncertainty is
dominated by the error due to the simple model structure and less by uncertainty in model
parameters. Therefore, the “manual” derivation of the parameters does not introduce
significantly more uncertainty. So far, we can conclude that conceptual models can deliver
reasonable predictions of the response from small ungauged urban catchments and – in
combination with Bayesian techniques – a sound description of the uncertainties is possible.
SESSION: PREDICTIONS
106
DEVELOPMENT OF EXPECTED ANNUAL DAMAGE CURVES AND MAPS AS A
BASIC TOOL FOR THE RISK-BASED DESIGNING OF STRUCTURAL AND NON-
STRUCTURAL MEASURES
Tariq, M.A.U.R., Van de Giesen, N.C. and Hoes, O.
Faculty of Civil Engineering and Geosciences, Technical University Delft, Stevinweg 1 Delft, 2628CN, the
Netherlands
E-mail: [email protected]
At present, probabilistic design standards for the flood protection measures are being
practiced in most parts of the word. These probability-based methods cannot be used to
design a non-structural measures and are unable provide an optimal design of structural
measures. Risk-based designs of flood management measures are getting more attention
due to their ability to optimize both the structural and non-structural measures. A flood
measure that is designed against a specific flood frequency may produce an under protection
design or a cost-inefficient solutions at its both extremes. Flood damages are probabilistic
events and flood intensity also greatly varies over the floodplain. Floods impacts are also
distributed variantly over spatial and temporal frames. It is important to consider the probable
floods and their possible damages while designing a measure.
In early 1990’s, US Army Corps of Engineers used the relationships of damage, frequency,
discharge, and stage for a floodplain to estimate expected annual damages (EAD) using a
hydroeconomic model. The problem with hydroeconomic model is that it estimates losses
using pre-established relationship between flood frequency and damages. Whereas, flow
regime may be changed significantly once a structural measure is introduced. Thence, this
method cannot provide accurate estimates of expected losses in such cases. Calculation of
losses on the bases of GIS data and hydraulic modeling is proposed in our research. The
proposed methodology recommends the calculation of EAD based on (modified) actual flow
regime.
These indicators can also be used for any development project or non-structural measure in
a floodplain. Each of these indicators has its specific use. Categorically speaking, EAD value
can be used as a deciding tool while choosing between the flood management options or
strategies. Any flood management plan will correspond to a single EAD value; which can be
used to conclude a decision. It is obvious that the strategy having lowest EAD is more
acceptable in general. EAD curves and EAD maps provide a detailed illustration of risk
distributions. EAD Maps are also known as risk maps. At present, these maps are mostly
used to develop flood zoning. These maps combine the hazard and vulnerability. Flood risk
maps can be developed to estimate and alleviate the potential flood damages. EAD curve
depicts the trend of damages against probable floods. Whereas, EAD map helps in
determining flood impacts over both time and space frames. EAD map is also helpful for
land-use planners.
EAD curves, maps, and values were calculated in our case study areas of the Chenab and
Swan rivers in Pakistan. These basic indicators were used in further development of
structural and non-structural measures as a part of our project.
On the basis of their design philosophy, their capabilities and convenient usability, the use of
EAD is highly recommended for the design almost all kind of flood management measures.
SESSION: PREDICTIONS
107
FLOOD FORECASTING WITH CONSTRAINED DOWNSTREAM CONDITION IN
YUVACIK BASIN, TURKEY
Uysal, G.1, Yavuz, Ö.1, Şensoy, A.1, Şorman, A.A.1, Akgün, T.2 and Gezgin, T.2
1 Anadolu University, Iki Eylul Campus, Department of Civil Eng., 26555, Eskisehir, Turkey,
2 Akifer Su Hizmetleri Ltd. Sti., Izmit Icme Suyu Aritma Tesisleri, Basiskele, Kocaeli, Turkey
E-mail: [email protected], [email protected], [email protected], [email protected],
[email protected], [email protected]
Yuvacık Dam Basin, located in the Marmara region of Turkey with a 248 km2 drainage area,
has high flood potential due to its steep topography, mild and rainy climate. The basin shows
fast flow response, especially to early spring and fall precipitation events. Moreover, the
basin’s elevation ranges between 80 – 1548 m, allowing considerable snowmelt contribution
to the streamflow during melt season.
The dam reservoir, having a total volume of 56 million m3, is designed to provide 142 million
m3 of domestic and industrial water annually for the city of Kocaeli with a population of 1.5
million people, despite the relatively small capacity of its reservoir.
The 12 km length downstream reach of the stream passes initially from a narrow valley near
a rural district and thereafter flows into the Marmara Sea after sharp curvature by a
manmade channel next to industrial and urban areas. Hence, the maximum amount of water
to be released is set as 100 m3/s by the regional water authority taking the drainage
discharge condition into consideration although the spillway capacity is 1560 m3/s. The
reservoir spillway is operated by radial gates behind which excess water is stored especially
during the flood season (late February to June) and operations require release regulation
through downstream.
A hydrological model with an embedded snow module is used to establish relationship
between the rainfall and runoff to calculate the inflow into the dam reservoir. The basin is
divided into four sub-basins, along with the three elevation zones for each basin. Hydro-
meteorological data are collected via 11 automated stations in and around the basin and a
semi-distributed rainfall runoff model, the HEC-HMS, is calibrated for sub-basins that drain
into the reservoir lake.
Daily total precipitation and daily average temperature forecast data that constitute the
hydrological model input are provided from the Mesoscale Model 5 (MM5) numerical weather
prediction data. Predicted precipitation and temperature data are compared with ground
observations to examine consistency. Thereafter, the representative MM5 data pixels are
assigned to rain gages. A kind of lapse rate is applied to remove temperature difference due
to the topography.
The study is carried out to test reservoir operation discharges especially during flood events
in conditions of using different reservoir level scenarios. Predicted inflows are used as main
inputs in HEC-ResSim for the hourly and daily reservoir simulation of flood events.
In this case study, Yuvacık Dam reservoir operation for the 6 – 11 April 2010 flood event,
during which spillway has been operated, is selected and simulated with different reservoir
level scenarios. The operations and release decisions are analyzed to propose an
improvement in its decision support system. Model parameters calibrated for several flood
events are used in real time forecasting of reservoir inflows and several scenarios are tested
to improve management of the reservoir.
SESSION: PREDICTIONS
108
UNCERTAINTY ANALYSIS OF HEAVY RAINFALL EVENTS REPRESENTED BY
A HYDROMETEOROLOGICAL MODEL AND SATELLITE RAINFALL
ALGORITHM FOR FLOOD FORECASTING
Yucel, I.1 and Mert, I.2
1Middle East Technical University, Civil Engineering Department, Water, Resources Lab, 06800 Ankara Turkey
2Turkish State Meteorological Service, Kalaba 06120 Ankara Turkey
E-mail: [email protected], [email protected]
Evidence is showing that global warming or climate change has a direct influence on
changes in precipitation and the hydrological cycle. Extreme weather events such as heavy
rainfall and flooding are projected to become much more frequent as climate warms. On the
other hand, hydrologic predictions are critical for decision-making related to flood mitigation
and water resources. In data sparse regions, alternative products such as atmospheric
model forecasts and remotely sensed data should be used for flood forecasting and warning
issues as they provide more continuous monitoring of precipitation data both spatially and
temporally over large extent of coverage. Hydrologic model simulations depend heavily on
the availability of reliable precipitation estimates. Difficulties in estimating precipitation in data
sparse regions impose an important limitation on the possibility and reliability of hydrologic
forecasting and early warning systems. Therefore, as supplement to rain gauge and radar
rainfall data the use of remotely sensed and numerical model-based precipitation products
becomes critical in hydrological simulations. This study investigates the performance of the
rainfall products obtained from the Multi Precipitation Estimates (MPE) and Weather
Research and Forecasting (WRF) model and provide an uncertainty analysis among them by
comparing with gauge rainfall measurements. The precipitation estimates obtained by using
the three-dimensional variational (3D-VAR) data assimilation scheme within WRF system are
also used in uncertainty analysis. Uncertainty analysis is performed for the selected number
of heavy rainfall events and associated flooding conditions over the mountainous West Black
Sea Basin in Turkey. The MPE and WRF-estimated rainfall showed capabilities in capturing
the timing of the flood events and in some extent spatial distribution and magnitude of the
heavy rainfall events. WRF with assimilation improved area-averaged precipitation forecasts
by 9 percent and at some points there exists quantitative match for heavy rainfall events,
which are critical for hydrological forecast.
SESSION: PREDICTIONS
109
UNCERTAINTY ASSESSMENT OF CLIMATE CHANGE ADAPTATION OPTIONS
IN URBAN FLASH FLOODS
Zhou, Q. and Arnbjerg-Nielsen, K.
Technical University of Denmark
E-mail: [email protected]
Adaptation is necessary to cope with the increasing flood risk in cities due to anthropogenic
climate change in many regions of the world. The choice of adaptation strategies can and
should be based on a comprehensive risk-based economic analysis to indicate the net
benefits of proposed options. However, the analysis is complicated by irreducible
uncertainties about present and future hydrologic conditions as well as the present and future
vulnerability of the area in question. Further, modeling of the actual hazards given the
hydrologic conditions also entails substantial uncertainty.
The work presented is based on a flood risk framework that is in accordance with the EU
flood directive, but adapted and extended to incorporate anticipated future changes due to
city development and hydrologic extremes. The framework is used to study the importance of
inherent uncertainties in order to find robust adaptation options. The case study is a small
urban catchment where no significant city development is anticipated. Therefore the main
focus is on estimation of impact of uncertainties related to present and future hydrological
conditions, impacts on assets, and costing of the damages. The uncertainties are calculated
using Monte Carlo simulations and thus the resulting uncertainties are described by
probability density functions.
Two different adaptation options are studied to reduce the increase in risk of flooding, namely
increasing the pipe capacity and the use of local infiltration measures to hold water back from
flood prone areas. The two options represent classical engineering solutions and water
sensitive urban design, respectively. These options are compared to a business-as-usual
scenario, where no adaptation is foreseen in the area. The results indicate that infiltration is
less cost-effective regardless of the uncertainties from climate change impacts and /or
damage estimation procedure when considering the ability to reduce the risk of flooding. The
description of the correlation structure between the key inputs proved to be important in order
to obtain a correct description of the resulting uncertainties.
The study shows that uncertainties associated with climate adaptation benefits are large, but
still it is possible to choose no-regret adaptation options. The introduced procedure provides
an important tool for achieving an explicit and thorough uncertainty analysis of the risk-based
economic evaluation.