4 th 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 1
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4 th International Symposium on Flood Defence Generation of Severe Flood Scenarios by Stochastic Rainfall in Combination with a Rainfall Runoff Model U.
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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
U. Petry, Y. Hundecha, M. Pahlow, A. Schumann
Institute of Hydrology, Water Resources Management and Environmental Engineering, Ruhr-University Bochum, Germany
1
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
2
Contents
• introduction
• concepts of the different models
• the case study
• evaluation of hydrological risk
• conclusion
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
3
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
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
4
Approach of generating extreme flood events
stochastic rainfall model
1. Generation
daily time series of rainfall
disaggregation model
hourly time series of rainfall
rainfall runoff model
hourly time series of flow
2. Disaggregation 3. Simulation
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
5
Contents
• introduction
• concepts of the different models
• the case study
• evaluation of hydrological risk
• conclusion / discussion
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
6
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
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
7
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:
Hyetos
temporal
disaggregation at
reference station
spatial-temporal
disaggregation at
all other stations
generating daily
rainfall at multiple
locationsMuDRain
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
8
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)
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
9
Contents
• introduction
• concepts of the different models
• the case study
• evaluation of hydrological risk
• conclusion / discussion
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
10
The Wupper catchment (813 km²)
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
11
Results of rainfall disaggregation MuDRain (statistics based on hourly time steps)
sample station 1 sample station 2
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1 2 3 4 5 6 7 8 9 10 11 12
month
mea
n p
reci
pit
atio
n [
mm
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
1 2 3 4 5 6 7 8 9 10 11 12
month
vari
ance
pre
cip
itat
ion
[m
m²]
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 2 3 4 5 6 7 8 9 10 11 12
month
mea
n p
reci
pit
atio
n [
mm
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1 2 3 4 5 6 7 8 9 10 11 12
month
vari
ance
pre
cip
itat
ion
[m
m²]
historical 1h
historical 3h
generated 1hmax/min
generated 3hmax/min
mean
variance
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
12
Results of rainfall disaggregation MuDRain (maxima based on hourly time steps)
sample station 1 sample station 2
annual 1-hour-maxima precipitation
annual 3-hour-maxima precipitation
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
0 1 2 3 4 5 6 7
return period T [yrs] or y(T)= -ln ln(T/(T-1))
pre
cip
itat
ion
[m
m]
historical
kostra
generated
10 100 1000
0.0
20.0
40.0
60.0
80.0
100.0
120.0
0 1 2 3 4 5 6 7
return period T [yrs] or y(T)= -ln ln(T/(T-1))
pre
cip
itat
ion
[m
m]
historical
kostra
generated
10 100 1000
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
0 1 2 3 4 5 6 7
return period T [yrs] or y(T)= -ln ln(T/(T-1))p
reci
pit
atio
n [
mm
]
historical
kostra
generated
10 100 1000
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0 1 2 3 4 5 6 7
return period T [yrs] or y(T)= -ln ln(T/(T-1))
pre
cip
itat
ion
[m
m]
historical
kostra
generated
10 100 1000
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
13
Results of rainfall runoff simulation (probabilities based on hourly time steps)
Annual maxima of discharge peaks at gauge Kluserbrücke with Wupper reservoir
0.0
50.0
100.0
150.0
200.0
250.0
300.0
-2 -1 0 1 2 3 4 5
return period T [yrs] or y(T)= -ln ln(T/(T-1))
dis
char
ge
pea
k g
aug
e K
luse
rbrü
cke
[m³
s-1
]
historical (18 yrs)
simulation max (10x100 yrs)
simulation min (10x100 yrs)
25 50 10010
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
14
Results of rainfall runoff simulation (probabilities based on hourly time steps)
Annual maxima of discharge peaks at gauge Kluserbrücke with Wupper reservoir
0.0
50.0
100.0
150.0
200.0
250.0
300.0
-2 -1 0 1 2 3 4 5 6 7 8
return period T [yrs] or y(T)= -ln ln(T/(T-1))
dis
ch
arg
e p
ea
k g
au
ge
Klu
serb
rüc
ke
[m
³ s
-1]
historical (18 yrs)
simulation (1000 yrs)
25 50 100 200 500 1000
4th International Symposium on Flood DefenceGeneration 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
15
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
16
• 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
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
17
simulated annual maxima discharge at gauge Kluserbrücke
0.00
0.05
0.10
0.15
0.20
0.25
10 30 50 70 90 110
130
150
170
190
210
230
250
270
discharge peak at gauge Kluserbrücke [m³ s-1]
rela
tiv
e f
req
ue
nc
y
simulated events (1000)
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
18
separating events with peak < 80 m³ s-1 at gauge Kluserbrücke without reservoir
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
10 30 50 70 90 110
130
150
170
190
210
230
250
270
discharge peak at gauge Kluserbrücke [m³ s-1]
rela
tive
fre
qu
ency
discharge without reservoir < 80m³ s -̂1 (339)
discharge without reservoir > 80m³ s -̂1 (661)
simulated annual maxima discharge at gauge Kluserbrücke
4th International Symposium on Flood DefenceGeneration of Severe Flood Scenarios by Stochastic Rainfall
in Combination with a Rainfall Runoff Model
evaluation of hydrological risk
19
• 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
4th International Symposium on Flood DefenceGeneration 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)
20
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
inflow peak to Wupper reservoir [m³ s-1]
dis
ch
arg
e p
ea
k a
t g
au
ge
Klu
se
rbr.
[m
³ s
-1]
flood control storage filled up to 50 % (463)
flood control storage filled more than 50 %(198)
reservoir inefficient
reservoir less efficient
reservoir efficient
4th International Symposium on Flood DefenceGeneration 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)