Modeling of Flood Inundation in Urban Areas Including

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

Outline § Introduction § Model Description － Storm Sewer Surcharges － Dual Drainage Analysis － Underground Space Inundation § Application § Conclusions & Discussions Kyungpook National University, Korea 2

Recent Flood Damages in Korea Kyungpook National University, Korea 3

Flood Disaster in Urban Areas Kyungpook National University, Korea 4

Flood Disaster in Urban Areas Kyungpook National University, Korea 5

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. Kyungpook National University, Korea 6

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. Kyungpook National University, Korea 7

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. Kyungpook National University, Korea 8

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. Kyungpook National University, Korea 9

Concept of Inundation Analysis Excess of Drainage Capacity Inundation of surcharged flow with complex building arrangement and topography Kyungpook National University, Korea 10

Concept of Underground Inundation Kyungpook National University, Korea 11

Schematic Diagram of Urban Inundation Analysis Kyungpook National University, Korea 12

Basic Concept of Link-Node Method Kyungpook National University, Korea 13

Governing Equations • Mass Balance Equation – Stream Type • Mass Balance Equation – Weir Type : Free Weir : Submerged Weir Kyungpook National University, Korea 14

Governing Equations • Momentum Equation 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 Kyungpook National University, Korea 15

Comparison with Analytical Solution • Simulation Condition : <Stream Type> - Rainfall Intensity 30 mm/hr - Duration 10 min - Compare with Analytical Solution <Weir Type> Kyungpook National University, Korea 16

Model Application – Jangan Basin (a) land use condition Kyungpook National University, Korea (b) DEM (c) drainage system 17

Model Application – Jangan Basin (a) Building allocation Kyungpook National University, Korea (b) Ratio of building area 18

Model Validation – Jangan Basin § Comparison with flood trace map (a) flood trace map Kyungpook National University, Korea (b) simulation result 19

§ Comparisons of simulation results (Jangan basin) Classification Fitness Total grid Simulation time 15 m x 15 m 64% 18842 3 day 11 hr 10 min 25 m x 25 m 72% 6781 16 hr 44 min 50 m x 50 m 58% 1702 1 hr 18 min 100 m x 100 m 49% 422 7 min Fitness : where, : the area of flood trace map : the area of simulation result Kyungpook National University, Korea 20

Model Application – Dorim Basin (a) land use condition Kyungpook National University, Korea (b) DEM (c) drainage system 21

Model Application – Dorim Basin (a) Building allocation Kyungpook National University, Korea (b) Ratio of building area 22

Model Validation – Dorim Basin § Comparison with flood trace map (a) flood trace map Kyungpook National University, Korea (b) simulation result 23

§ Comparisons of simulation results (Dorim basin) Classification Fitness Total grid Simulation time 15 m x 15 m 69% 12032 3 day 3 hr 35 min 25 m x 25 m 71% 4338 15 hr 11 min 50 m x 50 m 64% 1083 29 min 100 m x 100 m 58% 271 6 min Fitness : where, : the area of flood trace map : the area of simulation result Kyungpook National University, Korea 24

Model Application – Banpo Basin (a) land use condition Kyungpook National University, Korea (b) DEM (c) drainage system 25

Model Application – Banpo Basin (a) Building allocation Kyungpook National University, Korea (b) Ratio of building area 26

Model Application – Banpo Basin § Flood inundation analysis (a) 5 hours Kyungpook National University, Korea (b) 7 hours (c) 9 hours 27

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 wallstructures. § Empirical discharge formulas were introduced to analyze weir-type flow for a underground shopping mall and channel-type flow for subway railroad respectively. Kyungpook National University, Korea 28

Application to Underground Space • Constitution of underground spaces - B 1 st floor : Shopping Street - B 2 nd floor : Ticket Office and Management Office -B 3 rd floor : Platform and Railway Kyungpook National University, Korea 29

Inflow into Underground Spaces Kyungpook National University, Korea 30

Inundation Analysis in B 1 st Floor Kyungpook National University, Korea 31

Inundation Analysis in B 2 nd Floor Kyungpook National University, Korea 32

Inundation Analysis in B 3 rd Floor Kyungpook National University, Korea 33

Model Validation – Banpo Basin § Comparison with flood trace map (a) flood trace map Kyungpook National University, Korea (b) simulation result 34

Inundation Analysis for Underground Kyungpook National University, Korea 35

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 linknode 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. Kyungpook National University, Korea 36

Thanks for Your Attention ! Kyungpook National University, Korea 37

Depth Variation due to Inundation Analysis Kyungpook National University, Korea 38