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1P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Hydrological Models for Flood Forecast
2P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
OverviewThis presentation deals with "flood forecasting" and
"hydrological modelling" with a specific angle
Hydrological modelling for flood forecasting : state of art, locks and challenges, regarding the whole forecasting system. Which gain for the whole system is expected from (hydrological) modelling ? Who is in charge of the global picture ?
3P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
THE FLOOD FORECASTING SYSTEM
• Météorological forecasting• Rainfall forecasting, nowcasting• Quantification and spatialization of rainfalls• Discharges/water stages forecasting• Flood plains forecasting• Message and delivery service/system• Evaluation of the system
4P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
FLOOD FORECASTING/WARNING SYSTEMS ARE NOT GIVEN RESEARCH OBJECTS
It probably makes no sense to study any hydrological or meteorological components (for real time purposes) out of the framework of the global organization of the forecasting/warning system itself,
How to go beyond the limits of hydrological and meteorological products recycling ?
It’s not about usual “academic/applied sciences” discussion, but about systemic approach.
5P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
The MINIMAX MODEL (1)There is a real danger in only minimizing the
“maximum” (extreme floods) without really improving the global system and the medium or moderate floods. However, and because of the media coverage, this is the actual trend,
To find a good compromise between Prevention and Prevision is a real challenge,
Flood forecasting and warning have to be incorporated within the global flood management scheme.
6P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
MINIMAX MODEL (2)
e
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3501971
1976
1981
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Années
Q (m3/s)
Intermediate Range
Structural Methods Range
Crisis management Range
DAILY FLOWS
Extreme events
7P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
FLOOD/WARNING SYSTEMS ARE USERS ORIENTED (1)
The USERS are both :
For the scientists, the users are technical Services and institutional bodies : They operate the networks, our models, … (all technical systems), and design and deliver appropriate messages to
End users (ie individuals, citizens, …, nothing to do with technical people) who are the recipients of the messages (dissemination response) and whose comfort, quality of life ,and sometime just life, depend of them.
8P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
FLOOD/WARNING SYSTEMS ARE USERS ORIENTED (2)
If the research and technical object to consider is the global warning system, who is in charge of the this global picture ?
If we consider only the hydrological/meteorological part of the system, what is the maximum possible benefit for the global system, due to improvements of these “hydromet” components, and who is in charge of the global evaluation, to draw future priorities for research and transfer ?
Hydromet components : Robustness or accuracy ?
9P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Forecasts at downstream site derived from :
Observations/measurements of water stages at downstream and upstream sites
Measurements of (catchments) and upstream reach flows
Observation of rainfall (snow melting)
Forecasts of rainfall
Nowcasting and forecasts from other basins
flood forecasts, lead time and time to peak
10P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
TENTATIVE S/T LOCKS AND CRITICAL COMPONENTS IDENTIFICATION
For the headwater catchments, the nowcasting, the rainfall observations and forecasts, the snow melting modelling are, at least, critical components,For the downstream forecasting sites, flow routing in main channels (including upstream reaches) are critical components,At basin scale, the improvement of runoff production(robust across scale) and water transfers controlled by topography and soil is important. All spatialized relevant information (geology, terrain, land use and land cover -DOT) is also important, and the incorporation of embedded meteorological information at different scales as well.
11P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
RAINFALL OBSERVATION AND MEASUREMENTS
12P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
RAINFALL OBSERVATION AND MEASUREMENTS
It’s now obvious that hydrological radar will be soon the most appropriate device in rainfall measurements, in cooperation with the ground systems,
The capability to feed hydrological models with quantified spatially consistent rainfall is critical, even for global rainfall-runoff models, and not only for distributed physically based models (robustness and uncertainty ?)
That doesn’t mean that only distributed physically based models are relevant modelling components
13P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
0.0
0.4
0.8
1.2
02 - DEC 03 - DEC01 - DEC
Rai
nfal
l ( m
m )
RAINFALL KNOWLEDGE
0
2468
1012
02 - DEC 03 - DEC01 - DEC
Flow
( m
3s-
1)
Observed
Forecast (known rainfall)
Forecast (rainfall stopped)
Forecast (same rainfall)
14P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
abcourbes des dˇbits prˇvus � 2 heurestraces des prˇvisions de dˇbits de 1 � 9 heures
WITH AND WITHOUT RAINFALL FORECASTSON A SMALL BASIN
J. Lavabre and Al
15P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
16P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Hydrological Model Choice?
Thanks to Bob Moore for the picture
17P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
LE MODELE HYDROLOGIQUE GR3H
figure 4 – Modèle GR3H
A
P
S = k.A
Ps = (1-k²).P Pr = k².P
Q = QR + Qp
0.1 Pr
C
3/CHU1
2C
3/2C
HU2
B RQp
QR = RDEB-RFIN
0.9 Pr
444111BRR DEBFIN
+=
C
lnA=5.3 fixé : lnB=5.43 ; lnC=-1.15 ; Nash=94
lnA=5.3 et lnB=4.4 fixés : lnC=1.01 ; Nash=83
a
bfigure 5 – Perte en calage (crue juin 2000).
18P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
RADAR NETWORK, NEW CONCEPTS
New (X-band) Radar are now available, with doppler and multi-polarization facilities
19P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
HYDROMET COUPLING ACROSS SCALE
24 hours precipitation forecastcomputed by ALADIN model
20P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Hypsometric curve
Elevation zones
Observed flowModelled flow
PACK Snowmelt ModelThanks to Bob Moore
Model simulation
21P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
ROUTING AND INUNDATION MODELLING
22P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
ROUTING and INUNDATION MODELLINGIn main rivers, the channel flow routing is critical to
improve the forecasts. One robust possibility is to use Kinematic wave based models (with lateral flows) as the CEH KW model for example
cuxqct
q =∂∂+∂
∂ 1 4 n-1320
21 43 n-1 n
2tu
The difficulty is in using the results of these models to draw the flood plains according to the inundation modelling needs. The hydrodynamics based models are more efficient, but less robust and, to a certain extend, data driven
23P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
The 1D hydrodynamics models are robust enough to be used as a component incorporated in operational systems. The main questions are about the needs in geometric data to feed the models, and the operational staff skills in operating them,
The flood plains mapping is much more easy from these models if, and only if, only one geometric database is used,
The geometric characteristics of the basins are more and more needed in hydrological modelling, generally speaking, the use of DOT is one way of improvements.
ROUTING and INUNDATION MODELLING
24P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
1D HYDRAULICS/GEOMATICS MODELLING
25P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Flood simulation maps
300 m3/s 500 m3/s 900 m3/s
Flooded area
26P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
27P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
28P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
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Dis charge [m3.s -1]
Wat
er le
vel [
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hydrometric measurementra ting curve before floodrating curve after flood
DISCHARGE MEASUREMENT IS STILL A CHALLENGE
29P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
RUNOFF PRODUCTION
30P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Improved process representation relevant to scales beyond the point : hillslope, grid, catchment, …, using with a better “yield” the available DTM and DEM,Water tracking on slopes, runoff-production is dominated by sub-horizontal water transfers controlled by topography and soil,Better use of spatial dataset support : terrain, soil, geology, land use, land cover, weather variables, …- Improved model transfer to ungauged catchments across
scales- Whole catchment models, linking rainfall-runoff and
hydrodynamic river models- Atmospheric/hydrological model coupling
RUNOFF PRODUCTION MODELLING IMPROVEMENTSvs ROUTING IMPROVEMENTS
31P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Many relevant parameters are derived from spatially consistent information
32P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
Soil humidity expressedby API index on 6 August
Soil humidity expressedby API index on 11 August
Soil moisture (API index) on August 6th
Soil moisture (API index) on August 11th
33P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
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SPACE AVERAGE of DAILY PRECIPITATION on BASIN and FLOW PEAK DOWNSTREAM
34P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
THE GROUND NETWORKS ARE CRITICAL COMPONENTS, and the RESEARCH BASINS,
DEVOTED TO FLOOD FORECASTING AS WELL
Real-Collobrier research basin
J. Lavabre
35P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
RISK ASSESSMENTAll the technical components have the unique
purpose to provide the Service in charge of public warning with relevant information.
Messages design and dissemination, and dissemination response, are the most important tasks of a flood forecasting system which must be first a flood warning system
The answer is not in hydrological modelling
36P. Givone, Cemagref - Direction Scientifique PREVISION DES CRUES
ARE YOU TALKIN’ TO ME ?
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