Modeling of Flood Inundation in Urban Areas Including Underground Space Kun-Yeun Han, Gwangseob Kim, Chang-Hee Lee, Wan-Hee Cho Kyungpook National University, Daegu, Korea

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

Kyungpook National University, Korea 3 Recent Flood Damages in Korea

Kyungpook National University, Korea 4 Flood Disaster in Urban Areas

Kyungpook National University, Korea 5 Flood Disaster in Urban Areas

Kyungpook National University, Korea 6 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 7 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 8 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 9 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 10 Excess of Drainage Capacity Inundation of surcharged flow with complex building arrangement and topography Concept of Inundation Analysis

Kyungpook National University, Korea 11 Concept of Underground Inundation

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

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

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

Kyungpook National University, Korea 15 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 Governing Equations

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

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

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

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

Kyungpook National University, Korea 20 Fitness : where, : the area of flood trace map : the area of simulation result ClassificationFitnessTotal gridSimulation time 15m x 15m64%188423day 11hr 10min 25m x 25m72%678116hr 44min 50m x 50m58%17021hr 18min 100m x 100m49%4227min  Comparisons of simulation results (Jangan basin)

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

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

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

Kyungpook National University, Korea 24 Fitness : where, : the area of flood trace map : the area of simulation result ClassificationFitnessTotal gridSimulation time 15m x 15m69%120323day 3hr 35min 25m x 25m71%433815hr 11min 50m x 50m64%108329min 100m x 100m58%2716min  Comparisons of simulation results (Dorim basin)

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

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

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

Kyungpook National University, Korea 28 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.

Kyungpook National University, Korea 29 Constitution of underground spaces - B1 st floor : Shopping Street - B2 nd floor : Ticket Office and Management Office -B3 rd floor : Platform and Railway Application to Underground Space

Kyungpook National University, Korea 30 Inflow into Underground Spaces

Kyungpook National University, Korea 31 Inundation Analysis in B1 st Floor

Kyungpook National University, Korea 32 Inundation Analysis in B2 nd Floor

Kyungpook National University, Korea 33 Inundation Analysis in B3 rd Floor

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

Kyungpook National University, Korea 35 Inundation Analysis for Underground

Kyungpook National University, Korea 36 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.

Kyungpook National University, Korea 37 Thanks for Your Attention !

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