Transcript Presentation

4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
U. Petry, Y. Hundecha, M. Pahlow, A. Schumann
Institute of Hydrology, Water Resources Management and Environmental Engineering,
Ruhr-University Bochum, Germany
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Contents
• introduction
• concepts of the different models
• the case study
• evaluation of hydrological risk
• conclusion
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Motivation
• objective: evaluation of efficiency of flood protection measures (reservoir)
• safety approach:
 one single parameter (peak probability) for hydrological risk assessment
 no detail information about conditions for system failure
 uncertainty in the applied level of protection
• risk based approach:
 considering different features of flood events (spatial distribution)
 conditional probabilities for system failure
 requires broad data base
• generating flood scenarios by stochastic rainfall in combination with a rainfall runoff model
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Approach of generating extreme flood events
1. Generation
2. Disaggregation
3. Simulation
stochastic
rainfall model
disaggregation
model
rainfall runoff
model
daily time series
of rainfall
hourly time
series of rainfall
hourly time
series of flow
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Contents
• introduction
• concepts
of the different models
• the case study
• evaluation of hydrological risk
• conclusion / discussion
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
The stochastic rainfall model
• combination of multivariate autoregressive model and mixture of Gamma / Pareto
distribution function (Hundecha et al., 2008)
• objectives:
 reproduction of the statistical properties of the historical rainfall at each site
 maintenance of the historical spatial correlation structure
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
The disaggregation models
• combination of an univariate and a multivariate rainfall model in a disaggregation
framework (Koutsoyiannis et al., 2003)
• univariate model (Hyetos):
 generating a synthetic rainfall series at one location
• multivariate model (MuDRain):
 considering the temporal statistics and the spatial correlation between the stations
• work flow of disaggregation:
generating daily
rainfall at multiple
locations
Hyetos
temporal
disaggregation at
reference station
MuDRain
spatial-temporal
disaggregation at
all other stations
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
The rainfall runoff model
• proven conceptual model NASIM (Hydrotec, Germany)
• allows short-, middle- and long-term simulations (flexible increment for in- / output)
• simulation of important hydrological processes (e.g. retention, snow melting, rainfall,
runoff formation, flood routing)
• implementation of a reservoir model (operation rules)
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Contents
• introduction
• concepts of the different models
• the
case study
• evaluation of hydrological risk
• conclusion / discussion
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
The Wupper catchment (813 km²)
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Results of rainfall disaggregation MuDRain (statistics based on hourly time steps)
sample station 2
0.60
0.70
0.50
0.60
mean precipitation [mm]
mean precipitation [mm]
sample station 1
0.40
0.30
0.20
0.10
0.50
0.40
mean
0.30
0.20
0.10
historical 1h
0.00
0.00
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m onth
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m onth
historical 3h
generated 1h
max/min
3.5
variance precipitation [mm²]
variance precipitation [mm²]
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
generated 3h
max/min
3.0
2.5
2.0
1.5
variance
1.0
0.5
0.0
1
2
3
4
5
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m onth
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1
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m onth
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Results of rainfall disaggregation MuDRain (maxima based on hourly time steps)
sample station 1
sample station 2
80.0
80.0
precipitation [mm]
70.0
60.0
kostra
50.0
generated
precipitation [mm]
historical
40.0
30.0
20.0
10.0
70.0
historical
60.0
kostra
50.0
generated
30.0
20.0
10.0
10
100
10
1000
0.0
100
1000
0.0
0
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2
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0
1
return period T [yrs] or y(T)= -ln ln(T/(T-1))
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3
4
5
6
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return period T [yrs] or y(T)= -ln ln(T/(T-1))
100.0
120.0
historical
90.0
historical
kostra
80.0
kostra
80.0
precipitation [mm]
100.0
precipitation [mm]
annual
1-hour-maxima
precipitation
40.0
generated
60.0
40.0
70.0
generated
60.0
annual
3-hour-maxima
precipitation
50.0
40.0
30.0
20.0
20.0
10
100
1000
0.0
10.0
10
100
1000
0.0
0
1
2
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return period T [yrs] or y(T)= -ln ln(T/(T-1))
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0
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return period T [yrs] or y(T)= -ln ln(T/(T-1))
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Results of rainfall runoff simulation (probabilities based on hourly time steps)
Annual maxima of discharge peaks at gauge Kluserbrücke with Wupper reservoir
300.0
historical (18 yrs)
simulation max (10x100 yrs)
250.0
discharge peak gauge Kluserbrücke [m³ s-1]
simulation min (10x100 yrs)
200.0
150.0
100.0
50.0
10
0.0
-2
-1
0
1
2
25
3
50
4
100
5
return period T [yrs] or y(T)= -ln ln(T/(T-1))
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Results of rainfall runoff simulation (probabilities based on hourly time steps)
Annual maxima of discharge peaks at gauge Kluserbrücke with Wupper reservoir
300.0
historical (18 yrs)
250.0
discharge peak gauge Kluserbrücke [m³ s-1]
simulation (1000 yrs)
200.0
150.0
100.0
50.0
25
0.0
-2
-1
0
1
2
3
50
4
100
200
5
500
6
1000
7
8
return period T [yrs] or y(T)= -ln ln(T/(T-1))
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Contents
• introduction
• concepts of the different models
• the case study
• evaluation
of hydrological risk
• conclusion / discussion
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
• evaluation of hydrological risk according to local stages of flood warning
(discharge at gauge Kluserbrücke)
 up to 80 m³ s-1
 no flood conditions
 80 to 150 m³ s-1
 severe flood conditions
 more than 150 m³ s-1
 critical flood conditions
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
simulated annual maxima discharge at gauge Kluserbrücke
0.25
simulated events (1000)
relative frequency
0.20
0.15
0.10
0.05
0.00
10
30
50
70
90
11
0
13
0
15
0
17
0
19
0
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0
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0
25
0
27
0
discharge peak at gauge Kluserbrücke [m³ s-1]
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
simulated annual maxima discharge at gauge Kluserbrücke
relative frequency
0.14
0.12
discharge without reservoir < 80
m³ s^-1 (339)
0.10
discharge without reservoir > 80
m³ s^-1 (661)
separating events with
peak < 80 m³ s-1 at
gauge
Kluserbrücke
without reservoir
0.08
0.06
0.04
0.02
0.00
10
30
50
70
90
0
11
0
13
0
15
0
17
0
19
0
21
0
23
0
25
0
27
discharge peak at gauge Kluserbrücke [m³ s-1]
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
• evaluation of hydrological risk according to local stages of flood warning
 up to 80 m³ s-1
 no flood conditions
 80 to 150 m³ s-1
 severe flood conditions
 more than 150 m³ s-1  critical flood conditions
• evaluation of the efficiency of the Wupper reservoir
 reduction of discharge peak at gauge Kluserbrücke
 up to 80 m³ s-1
 reservoir efficient
 80 to 150 m³ s-1
 reservoir less efficient
 more than 150 m³ s-1  reservoir inefficient
• reasons for different efficiency levels (flood conditions)
 available flood control storage, inflow to reservoir, spatial distribution of discharge
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk (available flood control storage, inflow to reservoir)
300.0
flood control storage filled up to 50 %
(463)
flood control storage filled more than 50 %
(198)
discharge peak at gauge Kluserbr. [m³ s-1]
250.0
reservoir
inefficient
200.0
150.0
reservoir
less efficient
100.0
reservoir
efficient
50.0
0.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
-1
inflow peak to Wupper reservoir [m³ s ]
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk (available flood control storage, inflow to reservoir)
0.25
discharge peak < 80 m³ s^-1
(161)
relative frequency
thresholds for
classification
discharge peak 80-150 m³ s^-1
(275)
discharge peak > 150 m³ s^-1
(27)
0.20
0.15
flood control storage
filled up to 50 %
0.10
 10 m³ s-1
 60 m³ s-1
 100 m³ s-1
0.05
0.00
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
inflow peak to Wupper reservoir [m³ s-1]
0.25
discharge peak < 80 m³ s^-1
(43)
discharge peak 80-150 m³ s^-1
(139)
discharge peak > 150 m³ s^-1
(16)
relative frequency
0.20
thresholds for
classification
0.15
flood control storage
filled more than 50 %
0.10
 40 m³ s-1
 60 m³ s-1
 100 m³ s-1
0.05
0.00
10
20
30
40
50
60
70
80
90 100 110 120 130 140 150
inflow peak to Wupper reservoir [m³ s-1]
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk (depth of runoff)
storage filled up to 50 %, inflow < 10 m³ s-1
relative frequency
0.35
0.30
discharge peak at gauge 80-150 m³ s^-1
(110)
0.25
discharge peak at gauge > 150 m³ s^-1
(20)
threshold for
classification
 200 mm
0.20
0.15
0.10
0.05
0.00
25
50
75 100 125 150 175 200 225 250 275 300 325 350 375 400
depth of runoff downstream reservoir [mm]
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk (total number of events)
discharge at gauge
unaffected by reservoir
filling of flood
control storage
inflow to
reservoir
depth of runoff
downstream
evaluation of
reservoir efficiency
< 200 mm
less efficient
 200 mm
inefficient
< 100 mm
efficient
 100 mm
less efficient
< 50 mm
efficient
 50 mm
less efficient
< 125 mm
less efficient
 125 mm
inefficient
110
< 10 m³ s-1
20
130
≤ 80 m³ s-1
up to 50 %
127
173
10-60 m³ s-1
46
339
147
463
34
simulated
runoff
60-100 m³ s-1
> 80 m³ s-1
113
661
13
198
6
> 100 m³
more than
50 %
s-1
7
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk (probabilities)
discharge at gauge
unaffected by reservoir
filling of flood
control storage
inflow to
reservoir
depth of runoff
downstream
< 10 m³ s-1
less efficient
 200 mm
inefficient
< 100 mm
efficient
 100 mm
less efficient
< 50 mm
efficient
 50 mm
less efficient
< 125 mm
less efficient
 125 mm
inefficient
0.15
0.28
up to 50 %
< 200 mm
0.85
starting
point
≤ 80 m³ s-1
evaluation of
reservoir efficiency
0.73
0.37
10-60 m³ s-1
(0.27)
0.27
0.34
0.32
0.70
0.23
simulated
runoff
60-100 m³ s-1
> 80 m³ s-1
(0.07)
0.77
0.66
0.03
0.30
0.46
> 100 m³
more than
50 %
s-1
0.54
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Conclusion
• objective: risk-based approach for evaluation of flood protection measures
• combination of stochastic rainfall model, disaggregation model and rainfall runoff model
 good agreement of historical and simulated rainfall and runoff
 broad data base of flood events
• allow consideration of (probabilities of) differentiated flood characteristic
• evaluation of risk (efficiency) for different conditions by conditional probabilities
• further steps:
 simulate longer time series to get better data base for extreme floods
 different criteria for evaluation of efficiency (e.g. reduction of flood damage)
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4th International Symposium on Flood Defence
Generation of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
Thanks to
• German
Ministry for Education and
Research (BMBF) / RIMAX
• the water board of the Wupper catchment
• the German Weather Service
... and the audience for its attention !!!
contact: [email protected]
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