hydraulic modelling of wetland flow data collection and problem solving prof. dr. ir. ronny...

Hydraulic Modelling of Hydraulic Modelling of wetland flowwetland flow

Data collection and problem solvingData collection and problem solving


Data collection and problem solvingData collection and problem solving

Prof. dr. ir. Ronny VerhoevenProf. dr. ir. Ronny Verhoeven

Hydraulics LaboratoryHydraulics Laboratory

Ghent UniversityGhent University

BelgiumBelgium

Prof. dr. ir. Ronny VerhoevenProf. dr. ir. Ronny Verhoeven

Hydraulics LaboratoryHydraulics Laboratory

Ghent UniversityGhent University

BelgiumBelgium

WETHYDRO WORKSHOP – 13 – 14 June 2003


• IntroductionIntroduction• Hydraulic modelling of open channel flow Hydraulic modelling of open channel flow • Extension to wetlandsExtension to wetlands• Data collection – problems, questions, solutionsData collection – problems, questions, solutions• Input data – problems, questions, solutionsInput data – problems, questions, solutions• Conclusions - questionsConclusions - questions

WETHYDRO WORKSHOP – 13 – 14 June 2003

IntroductionIntroduction

Engineer >>Engineer >>translates realitytranslates realityinto formulainto formula

Engineer >>Engineer >>translates realitytranslates realityinto formulainto formula

Deterministic approach is Deterministic approach is what he likes: p = what he likes: p = g h g h

Stochastic representation is Stochastic representation is what he needs to live withwhat he needs to live withStochastic representation is Stochastic representation is what he needs to live withwhat he needs to live with

IntroductionIntroduction

Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow

SupositionsSupositions

•Uniform velocity distribution: Q = A . UUniform velocity distribution: Q = A . U

•Prismatic bed – constant cross-sectionPrismatic bed – constant cross-section

•Hydrostatic cross sections Hydrostatic cross sections

•Constant bottom slopeConstant bottom slope

•Constant friction factorConstant friction factor


Steady stateSteady state

Continuity:Continuity:

Q = A . UQ = A . U

Motion – Bresse equation:Motion – Bresse equation:

Uniform flowUniform flow>> Manning <<>> Manning <<

U = 1/n.RU = 1/n.R2/32/3.S.S001/21/2

³²21

gABQSo

SfSoxh


Unsteady stateUnsteady state

Saint Venant equationsSaint Venant equations

Continuity:Continuity:

Motion:Motion:

0t

hB

x

Q

x

hSSAg

A

Q

xt

Qfo

...

2


Unsteady stateUnsteady state

Saint Venant equations – solved by implicit finite Saint Venant equations – solved by implicit finite

difference Preismann schemedifference Preismann scheme

>> choise of >> choise of is important > stability is important > stability

>> choise of >> choise of s and s and t also > accuracyt also > accuracy

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50

Time [h]

Q [

m3/

s]

Extension to wetlandsExtension to wetlands

Quasi 2D modellingQuasi 2D modelling

>> Network structure - flow>> Network structure - flow

>> Cells - exchange of volumes>> Cells - exchange of volumes

>> Combination - what to choose?>> Combination - what to choose?

Input data – what do we need?Input data – what do we need?

• Cross-sections of river and floodplainCross-sections of river and floodplain

• Longitudinal profile (Thalweg)Longitudinal profile (Thalweg)

• Water levels ( f(t) )Water levels ( f(t) )

• Discharge ( f(t) ) – lateral dischargesDischarge ( f(t) ) – lateral discharges

• Friction coefficientsFriction coefficients

• Sediment transport (bottom / suspended) Sediment transport (bottom / suspended)

TopographicalTopographical

HydraulicHydraulic

Data collectionData collection

TopographicalTopographical

• ? Distance between 2 cross-sections? Distance between 2 cross-sections• ? Boundaries of flood plains? Boundaries of flood plains• Altitude measurements should be the most accurate onesAltitude measurements should be the most accurate ones• Accuracy of measurements is influenced by:Accuracy of measurements is influenced by:

- mud- mud- vegetationvegetation- obstacles in cross-section- obstacles in cross-section- soft bottomsoft bottom


Hydraulic data – discharge measurementsHydraulic data – discharge measurements

• Integration of velocity field over cross-sectionIntegration of velocity field over cross-section• Propeller meter or electromagnetic, acoustic velocity meterPropeller meter or electromagnetic, acoustic velocity meter• From bridge or from boatFrom bridge or from boat


Hydraulic data – discharge measurementsHydraulic data – discharge measurements> Problems <> Problems <

• Velocity distribution – horizontal / verticalVelocity distribution – horizontal / vertical

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

0 5 10 15 20 25

Depth y (m) Mean velocity (m/s)

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0 0,1 0,2 0,3 0,4 0,5

velocity [m/s]D

epth

[m

]


Hydraulic data – discharge measurementsHydraulic data – discharge measurements> Problems <> Problems <

• VegetationVegetation- velocity fluctuation as a function of time- velocity fluctuation as a function of time- slowing down propeller- slowing down propeller- block the propeller- block the propeller- local influence on velocity meter- local influence on velocity meter

• Stones or rocksStones or rocks• Soft bottomSoft bottom• Wind while measuring from a boatWind while measuring from a boat• Measuring errorsMeasuring errors

Influence ofInfluence of

Oso

wie

c

Dol

isto

wo

Biebrza R.

Bie

brza

R.

Elk

R.

Aug

usto

wsk

i Ch.

Brozow

ka R.

Rud

zki C

h.

Sidra R.

Ost

row

ie

Gon

iadz

Lipsk

Jagl

owo

7.00

0.91

6.88

1.339.17

6.88

8.06

Karpowicze

Sztabin

Deb

owo

Przechody

Bialogrady

5.98

1.15

0.86

0.89

3.94

3.43

Measurement Campaigns: discharges in m3/s 2000

0.48

0.24

Oso

wie

c

Dol

isto

wo

Biebrza R.

Bie

brza

R.

Elk

R.

Aug

usto

wsk

i Ch.

Brozow

ka R.

Rud

zki C

h.

Sidra R.

Ost

row

ie

Gon

iadz

Lipsk

Jagl

owo

9.15

1.90

8.58

3.4818.10

7.18

16.57

Karpowicze

Sztabin

Deb

owo

Przechody

Bialogrady

13.63

3.04

2.36

1.79

10.77

6.14

Measurement Campaigns: discharges in m3/s 2003

0.52

0.85

2.67

Input dataInput data

How to determine the cross-section?How to determine the cross-section?


How to determine the cross-section?How to determine the cross-section?

????

-0,1

-0,05

0

0 0,5 1 1,5 2 2,5

width [m]

dep

th [

m]

-0,1

-0,05

0

0 0,5 1 1,5 2 2,5

width [m]

dep

th [

m]

-0,1

-0,05

0

0 0,5 1 1,5 2 2,5

width [m]

dept

h [m

]

Solution: define cross-section with A, P and R Solution: define cross-section with A, P and R equal to the average value of all cross-sectionsequal to the average value of all cross-sections

>> Calibration of friction coefficient becomes>> Calibration of friction coefficient becomes very important !!!very important !!!


How to determine the longitudinal profile?How to determine the longitudinal profile?

Effect of friction!Effect of friction!


How to determine the bottom slope?How to determine the bottom slope?


How to determine the friction coefficientHow to determine the friction coefficient

• n = f (bottom roughness, shape cross-section, vegetation, n = f (bottom roughness, shape cross-section, vegetation, obstacles, meandering, velocity distribution, …)obstacles, meandering, velocity distribution, …)• n = f (time, location, interaction of previous parameters)n = f (time, location, interaction of previous parameters)• n must be determined from measurementsn must be determined from measurements

hu

hd

Q Bresse n

Oso

wie

c

Dol

isto

wo

Biebrza R.

Bie

brza

R.

Elk

R.

Aug

usto

wsk

i Ch.

Brozow

ka R.

Rud

zki C

h.

Sidra R.

Ost

row

ie

Gon

iadz

Lipsk

Jagl

owo

0.0600.045

Karpowicze

Sztabin

Deb

owo

Przechody

Bialogrady

0.040

0.090 –0.369

0.069 –0.651

0.030 –0.2760.061

Manning n determination by calibration

Determination of n using:Determination of n using:• Uniform flow principle (Manning formula)Uniform flow principle (Manning formula)• Bresse equationBresse equation

115,0

115,5

116,0

116,5

117,0

117,5

118,0

118,5

119,0

32 37 42 47 52 57 62 67 72

distance along river [km]

wat

er le

vel [

m a

Bsl

.]

measurement 02.06.2002

n by Manning formula

n by calibration

BUT!!!BUT!!!

Discharge variation in Goniadz : B-14

27

32

37

42

47

52

57

0 5 10 15 20 25 30

time [days]

Q [

m3/

s]

UNETmeasurement


Conclusions and QuestionsConclusions and Questions

• Flood-routing theory is quite simpleFlood-routing theory is quite simple• Numerical solution methods are well developedNumerical solution methods are well developed• Practical application is confronted with many inaccuraciesPractical application is confronted with many inaccuracies• Good simulation results thanks to well considered calibrationGood simulation results thanks to well considered calibration

• ? Definition of cross-section?? Definition of cross-section?• ? Determination of longitudinal profile?? Determination of longitudinal profile?• ? Best way to determine the friction coefficient?? Best way to determine the friction coefficient?• ? Suggestions to improve measurements quality? ? Suggestions to improve measurements quality?

AcknowledgementsAcknowledgements

T. Okruszko, S. Ignar, R. Michalowski, J. Chormanski, T. Okruszko, S. Ignar, R. Michalowski, J. Chormanski, D. Swiatek, I. Kardel D. Swiatek, I. Kardel

SGGW, Warsaw SGGW, Warsaw

L. Van Poucke, M. Huygens, R. Banasiak L. Van Poucke, M. Huygens, R. Banasiak Hydraulics laboratory, Ghent UniversityHydraulics laboratory, Ghent University

Universities of Brussels and AntwerpUniversities of Brussels and Antwerp

Funding from Polish and Flemish government Funding from Polish and Flemish government bilateral cooperation projectsbilateral cooperation projects

Biebrza National Park AuthoritiesBiebrza National Park Authorities

19981998

20022002

hydraulic modelling of wetland flow data collection and problem solving prof. dr. ir. ronny...

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