modeling of flood inundation in urban areas including underground space - 2008. 5. 6.- kun-yeun han,...
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Modeling of Flood Inundation in Urban Areas Including Underground Space
- 2008. 5. 6.-
Kun-Yeun Han, Gwangseob Kim,
Chang-Hee Lee, Wan-Hee Cho
Kyungpook National University, Daegu, Korea
2Kyungpook National University, Korea
Outline
Introduction
Model Description
－ Storm Sewer Surcharges
－ Dual Drainage Analysis
－ Underground Space Inundation
Application
Conclusions & Discussions
3Kyungpook National University, Korea
Recent Flood Damages in Korea
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Flood Disaster in Urban Areas
5Kyungpook National University, Korea
Underground Inundation
Pump station
Levee
Inunation by Levee Break
P
Inunadation by Surcharge Discharge
Ur
ba
n
St
re
am
Flood Disaster in Urban Areas
6Kyungpook National University, Korea
Purpose of the Study
Inundation in the urban area causes serious damage to people and assets because of the concentration of infrastructure and high population growth.
Especially, flood inundation in underground spaces
can be an important component in urban flood.
A numerical model developed in this study, which combines 1-dimensional drainage flow with 2-dimensional surface and underground inundation phenomena.
7Kyungpook National University, Korea
Methodology
1. Hydrologic rainfall-runoff analysis model
－ Using the SWMM model (RUNOFF Block), hydrologic
rainfall-runoff model computes flood discharge to estimate
manhole inflow for each basin.
2. Hydrodynamic flow analysis model for urban area
drainage system
－ For hydrodynamic flow analysis SWMM model
(EXTRAN Block) is employed to compute flow routing in
drainage system with surface overflow.
8Kyungpook National University, Korea
Methodology
3. Hydraulic flow analysis model for inundated area
－ DEM based hydraulic flow analysis model is developed to
determine inundated area and flow depth.
4. Inundation analysis model for underground spaces
－ Link-Node model (irregular cells based) is developed to
determine inundated area and flow depth.
9Kyungpook National University, Korea
Basic assumptions and limitations
The drainage system is established by main pipelines, and the runoff volume of each subwatershed inflows through the manhole located in the main pipelines.
During flood simulation it is assumed that the inundation process initiated when surcharged overflow occurs, then it propagates to the downstream outlet of the drainage area.
The effect of buildings has been accounted in the flood analysis by considering occupation area without such factors as incoming flows to buildings, directional, and density effects.
10Kyungpook National University, Korea
Surface Runoff
Sewerfin QQ
inc QQ
Sewer
fin QQ inc QQ
Surcharged Flow
sQExcess of Drainage Capacity
Inundation of surcharged flow with complex building arrangement and topography
Concept of Inundation Analysis
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Surface Inundation
Inflow to Underground Space
Link-Node Method
Inundation
Surface Areas
Underground Inundation
Concept of Underground Inundation
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Rainfall-Runoff Analysis
Hydrodynamic Flow Analysis in Drainage
Network
Hydraulic Flow Analysis of Surface Overflow
Estimate Surcharged Flow
Estimate Inundation Depth and Velocity
Overflow
Inflow of Inundated Discharge
Inundation to Underground
Spaces
Inflow
Schematic Diagram of Urban Inundation Analysis
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Stream Type
(Walkway,Rail Road)
Weir Type
(Shopping mall, Office)
Basic Concept of Link-Node Method
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• Mass Balance Equation – Stream Type
• Mass Balance Equation – Weir Type
ikkiikki HHHHHsignQ ,,
wkwi HHHH 3
2: Free Weir
2/31, 2 wkki HHgbQ
wkwi HHHH 3
2: Submerged Weir
2/12, 2 ikwkki HHHHgbQ
Governing Equations
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• Momentum Equation
k
kikiini
Si HHQQdt
dHA ,,
iH
kH
SiA
inQ
kiQ ,
Water Surface Line of Cell i
Water Surface Line of Cell k
Area of Cell i
Incoming flow to cell i
Discharge between Cell i and Cell k
Governing Equations
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50m Manning’s Roughness : 0.015
0.5m
0 5 10 15 20 25Tim e (m in )
0
0.0001
0.0002
0.0003
0.0004
0.0005
Q (
cms/
m)
Ana lytica l
Calcu lated
0 5 10 15 20 25Tim e (m in )
0
0.0001
0.0002
0.0003
0.0004
0.0005
Q (
cms/
m)
A na lytica l
C alcu lated
<Stream Type>
<Weir Type>
• Simulation Condition :
- Rainfall Intensity 30 mm/hr
- Duration 10 min
- Compare with Analytical Solution
Comparison with Analytical Solution
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Model Application – Jangan Basin
(a) land use condition (b) DEM (c) drainage system
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(a) Building allocation (b) Ratio of building area
Model Application – Jangan Basin
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Comparison with flood trace map
(a) flood trace map (b) simulation result
Model Validation – Jangan Basin
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Fitness :
100(%) calobs
calobs
AA
AAFit
where, : the area of flood trace map
: the area of simulation result
obsA
calA
(%)Fit
Classification Fitness Total grid Simulation time
15m x 15m 64% 18842 3day 11hr 10min
25m x 25m 72% 6781 16hr 44min
50m x 50m 58% 1702 1hr 18min
100m x 100m 49% 422 7min
Comparisons of simulation results (Jangan basin)
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Model Application – Dorim Basin
(a) land use condition (b) DEM (c) drainage system
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(a) Building allocation (b) Ratio of building area
Model Application – Dorim Basin
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Comparison with flood trace map
Model Validation – Dorim Basin
(a) flood trace map (b) simulation result
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Fitness :
100(%) calobs
calobs
AA
AAFit
where, : the area of flood trace map
: the area of simulation result
obsA
calA
(%)Fit
Classification Fitness Total grid Simulation time
15m x 15m 69% 12032 3day 3hr 35min
25m x 25m 71% 4338 15hr 11min
50m x 50m 64% 1083 29min
100m x 100m 58% 271 6min
Comparisons of simulation results (Dorim basin)
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Model Application – Banpo Basin
(a) land use condition (b) DEM (c) drainage system
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(a) Building allocation (b) Ratio of building area
Model Application – Banpo Basin
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Flood inundation analysis
Model Application – Banpo Basin
(a) 5 hours (b) 7 hours (c) 9 hours
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Application Strategies
Flow characteristics in underground space were computed by link-node system.
The suggested model can simulate the underground flood flow related to the influence of stairs and wall-structures.
Empirical discharge formulas were introduced to analyze weir-type flow for a underground shopping mall and channel-type flow for subway railroad respectively.
29Kyungpook National University, Korea
• Constitution of
underground spaces
- B1st floor :
Shopping Street
- B2nd floor :
Ticket Office and
Management Office
-B3rd floor :
Platform and Railway
Application to Underground Space
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Inflow Point
Inflow into Underground Spaces
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Inflow Point
B1 # 448
B1 # 594
B1 # 494 B1 # 501
B1 # 627 B1 # 634
B1 # 471
B1 # 601
Inundation Analysis in B1st Floor
0 4 8 12 16T ime (hr)
0
0.1
0.2
0.3D
ep
th (
m)
B 1 # 448
0 4 8 12 16T ime (hr)
0
0.1
0.2
0.3
De
pth
(m
)
B 1 # 471
0 4 8 12 16T ime (hr)
0
0.1
0.2
0.3
De
pth
(m
)
B 1 # 494
0 4 8 12 16T ime (hr)
0
0.1
0.2
0.3
De
pth
(m
)
B 1 # 501
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B2 # 379
B2 # 507
B2 # 402 B2 # 409
B2 # 545 B2 # 523
B2 # 426
B2 # 511
Inflow Point from 1st floor
Inflow Point from 1st floor
Inundation Analysis in B2nd Floor
0 4 8 12 16Tim e (hr)
0
0.04
0.08
0.12
0.16
De
pth
(m
)B2 # 379
0 4 8 12 16Tim e (hr)
0
0.04
0.08
0.12
0.16
De
pth
(m
)
B 2 # 409
0 4 8 12 16Tim e (hr)
0
0.04
0.08
0.12
0.16
De
pth
(m
)
B 2 # 545
0 4 8 12 16Tim e (hr)
0
0.04
0.08
0.12
0.16
De
pth
(m
)
B 2 # 426
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PatformRailroad
Railroad
Inflow Point from 2nd Floor
B3 # 366 B3 # 54
B3 # 763
B3 # 87
B3 # 386B3 # 820
B3 # 30
B3 # 787
Inflow Point from 2nd Floor
Inundation Analysis in B3rd Floor
0 4 8 12 16
T im e (hr)
0
0.04
0.08
0.12
0.16
0.2
De
pth
(m
)B 3 # 54
0 4 8 12 16
T im e (hr)
0
0.04
0.08
0.12
0.16
0 .2
De
pth
(m
)
B 3 # 366
0 4 8 12 16
T im e (hr)
0
0.04
0.08
0.12
0.16
0.2
De
pth
(m
)
B 3 # 763
0 4 8 12 16
T im e (hr)
0
0.04
0.08
0.12
0.16
0.2
De
pth
(m
)
B 3 # 787
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Comparison with flood trace map
(a) flood trace map (b) simulation result
Model Validation – Banpo Basin
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Inundation Analysis for Underground
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Conclusions
1-D and 2-D unsteady flow analysis was performed considering the flow rates through the surcharges from storm sewer networks.
Inundation in underground space was computed by link-node system. Empirical discharge formulas were introduced to analyze weir-type flow for a underground shopping mall and channel-type flow for subway railway, respectively.
The model was applied to Banpo subway station in Seoul. The simulated results agree well with observed data.
37Kyungpook National University, Korea
Thanks for Your Attention !
38Kyungpook National University, Korea
Depth Variation due to Inundation Analysis
- Subbasin runoff discharge from runoff block
- Time independent inflow discharge
- Time variable inflow discharge
- Inundated surface discharge
Hydrodynamic flow analysis in drainage pipelines (EXTRAN)
- Checking the status of inflow - Estimate inflow discharge - Idendifying overloaded flow condition - Estimate overflow discharge
Inundated Discharge
Inflow of inundation discharge
Surface runoff due to overflow discharge
2D inundation anlysis