Hydraulic Modelling of wetland flow Data collection and problem solving Prof. dr. ir. Ronny...
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Hydraulic Modelling of Hydraulic Modelling of wetland flowwetland flow
Data collection and problem solvingData collection and problem solving
Hydraulic Modelling of Hydraulic Modelling of wetland flowwetland flow
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
Hydraulic Modelling of Hydraulic Modelling of wetland flowwetland flow
• 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
Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow
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
Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow
Unsteady stateUnsteady state
Saint Venant equationsSaint Venant equations
Continuity:Continuity:
Motion:Motion:
0t
hB
x
Q
x
hSSAg
A
Q
xt
Qfo
...
2
Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow
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- vegetation- vegetation- obstacles in cross-section- obstacles in cross-section- soft bottom- soft bottom
Data collectionData collection
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
Data collectionData collection
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
]
Data collectionData collection
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?
Input dataInput data
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 !!!
Input dataInput data
How to determine the longitudinal profile?How to determine the longitudinal profile?
Effect of friction!Effect of friction!
Input dataInput data
How to determine the bottom slope?How to determine the bottom slope?
Input dataInput data
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!!!
Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow
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
Hydraulic Modelling of Hydraulic Modelling of open Channel Flowopen Channel Flow
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