National Disaster Management Institute

National Disaster Management Institute

CONTENTS one Cause of Urban Flood Disaster two Urban Flood Damage Case three Disaster Prevention Measures for Future Urban Flood four NDMI s Measures & Strategy for Urban Flood Mitigation

Cause of Urban Flood Disaster

Torrential rain increases Caused by climate change Capacity deficit of disaster prevention facility Riversides lowlands development Construction of a large underground space Impervious surface increases Urbanization and concentration of population Capacity deficit of 대형 지하공간 disaster prevention 개발 facility

(Torrential rain increases) Hourly rainfall of Seoul and Busan cities Seoul city Busan city Rainfall has increased and typhoon has become larger Kind 1990s(average) 2000s(average) Remark Max. rainfall intensity 94.6mm/hr 97.4mm/hr 2.8mm/hr Max. daily rainfall 355.8mm 415.2mm 59.4mm Typhoon central pressure 951hPa 944hPa Larger

Development of riversides lowlands Ground level lower than river plan flood elevation Land use change Impervious surface increases due to various urban development Urbanization and concentration of population Increase in casualties and property damage Capacity deficit of disaster prevention facility Urban drainage facility design criterion : Trunk ; 10years, Branch ; 5 years Urban river design criterion : small and medium streams ; 50 or 100 years Construction of a large underground space Construction of large underground space such as shopping mall and subway

Urban flood damage case

July 2001, Seoul Damage history Casualties Death 35, Injury 104 Flooded Buildings 94,375 Major causes Sewer capacity deficit Insufficient capacity of internal drainage Lowland flooding Insufficient capacity of pumping station and detention pond Poorly drainage due to sediment spill July 2009, Busan Damage history Casualties Death 2, Injury 3 Flooded Buildings 1,428 Major causes Sewer capacity deficit Insufficient capacity of internal drainage Lowland flooding Insufficient capacity of pumping station and detention pond Poorly drainage due to sediment spill River flooding

(Incheon city in 2010) Damage causes -Sewer capacity deficit, -Insufficient capacity of internal drainage -Drainage capacity decrease due to water level increase out of levee - Lowlands flooded 굴포천 배수 14:00~18:00 장제로구간 통제 Flooded damage

(at large underground space) Yongsan subway station Building basement Sadang station Underground shopping mall

Disaster Prevention Measures for Future Urban Flood

(National countermeasures) Strengthen the participation of local residents Institutionalization of citizen participation for flood defense alternative decision Release of the flood hazards maps and flood situation Strengthening of the institutions and budget of central government Strengthening of the connection for flood countermeasures between each governmental departments Strengthening of field control ability in local government Institutionalization of precaution in local government Roles assignment of central and local governments Strengthen the practical and scientific research capabilities Flood prediction and alert in small river Rational criteria for flood prevention Development of high technology for disaster preventio based on IT, GIS Development of eco-friendly flood prevention technology

Integrated Disaster Prevention System - River and Urban Area - Structural, Non-structural Strengthening of criteria for disaster prevention facilities Legislation of inundation prevention facilities for basement houses Establishment of disaster prevention strategies for large-size basement Expansion of rainfall detention and basement detention facilities Urban Flood Prevention River Flood Prevention Review of design criteria by water control safety Development of river design criteria considering on urban inundation Restoration of natural river (flood plain, flood field) Non-structural Prevention Development of integrated prediction-alert system for river and urban area Development of flood map and inundation map Strengthening of law, system, guideline, criteria Development of manual for private properties inundation Strengthening of education and training program

NDMI s Measures & Strategy for Urban Flood Mitigation

2011 Gangnam Inundation 2011 Gangnam Landslide Experimental facility for infiltration gutter Development of recycled porous infiltration gutter

Non- Structural Analysis Non-Structural Data Twitter News Media Blog Internet Wall Board Monitoring of Inundation Occurrence Internet Areal Information Structural Analysis Structural Data Real-time precipitation, hazard map, Soil characteristics, River Basin etc. Analysis of risk area and past inundation events Expected Inundation Area Past Inundation Event Link- Analysis Non-Structural Data + Structural Data Inundation Forecasting and Risk analysis Detailed Information Governmental Info CCTV Information Public Info Population, Building information Detailed Information CCTV Population Buildings Traffic Dissemination Dissemination of forecasted results of Inundation Dissemination NEMA Local Province

Combination with Radar-based rainfall forecasting system Radar rainfall Rainfall-runoff simulation Inundation depth Flood-expected area <Urban Flood alert system based on radar measurements>

SWMM is a distributed, dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas.

Design and sizing of drainage system components including detention facilities Flood plain mapping of natural channel systems Control of combined and sanitary sewer overflows Generating non-point source pollutant loadings for wasteload allocation studies Evaluating BMPs and LIDs for sustainability goals

Not applicable to large-scale, non-urban watersheds Cannot be used with highly aggregated (e.g., daily) rainfall data Its an analysis tool, not an automated design tool Unable to analyze the integration of ground and underground space It s not free, so, we have to pay huge costs when we buy and update the program(about US $ 25,000)

1.Development of ground inundation analysis model Surface flow 2.Development of underground inundation analysis model Embankment road Channel Sewer Building Pumping station 3.Development of integrated inundation analysis model Road Underground space River Underground entrance 4.Development of integrated inundation analysis system(based on GIS) Stairs Car entrance Connecting passage Concept of Integrated inundation analysis model

Calculation of rainfall Extreme rainfall Building Design rainfall Short-term predicted rainfall Channel Road Embankment road Analysis model for rainfall runoff in storm sewage Module for analyzing rainfall collecting facilities (i.e. drip box) Module for designing Safety space for detention basin and drainage pumping plant Overflow Inflow of flooding Analysis model for surface water movement 1-dimensional real time model Analysis considering on building, road, rail road, underpass Prediction of flooding by the hour Prediction of inundation area and height by the hour

Establishment of DB for simulation

Simulation conditions 30-year frequency rainfall, Cell size :30m, computation time step:10sec, Total computation time:80sec As a result, simulation result is good agreement with observed inundation area

Construction of various flooding scenarios Case 1 : Normal condition(all prevention facilities work properly) Case 2 : Dysfunction of sewer network(other prevention facilities work properly) Case 3 : Dysfunction of pumping station(other prevention facilities work properly) Simulations were performed for each scenario Case 1 Case 2 Case 3 As a result, inundation depth of case 3 is the biggest

[Expected effects] - Integrated system for large-size urban area inundation - Reduction of computation time by using 1-dimensional model Able to real-time prediction-alert system [Application] - Real-time alert system for antecedent precipitation in large-size urban area - Real-time inundation alert system in central and local government - Disaster disaster risk reduction for the public Strengthening of National Disaster Prevention Ability