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

대형 지하공간 개발

Urbanization and

concentration of population

Riversides lowlands

development

Capacity deficit of

disaster prevention

facility

Impervious surface

increases

Capacity deficit of disaster prevention

facility

Construction of a

large underground space

Seoul city Busan city

Hourly rainfall of Seoul and Busan cities

Kind 1990s(average) 2000s(average) Remark

Max. rainfall

intensity 94.6㎜/hr 97.4㎜/hr ↑2.8㎜/hr

Max. daily rainfall 355.8㎜ 415.2㎜ ↑59.4㎜

Typhoon central

pressure 951hPa 944hPa Larger

Rainfall has increased and typhoon has become larger

(Torrential rain increases)

Development of riversides lowlands

Ground level lower than river plan flood elevation

Urbanization and concentration of population

Increase in casualties and property damage

Land use change

Impervious surface increases due to various urban development

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

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

Damage history

July 2009, Busan

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

Damage history

(Incheon city in 2010)

Flooded damage

굴포천 배수

14:00~18:00 장제로구간 통제

Damage causes

-Sewer capacity deficit,

-Insufficient capacity of internal drainage

-Drainage capacity decrease due to water level

increase out of levee

- Lowlands flooded

(at large underground space)

Sadang station Underground shopping mall

Yongsan subway station Building basement

Disaster Prevention Measures for

Future Urban Flood

(National countermeasures)

Strengthen the

participation of

local residents

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 prevention

based on IT , GIS

•Development of eco-friendly

flood prevention technology

• 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

Urban Flood

Prevention

River Flood

Prevention 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

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

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)

Integrated Disaster Prevention System

- River and Urban Area

- Structural, Non-structural

NDMI’s Measures & Strategy for

Urban Flood Mitigation

Experimental facility for infiltration gutter Development of recycled porous

infiltration gutter

2011 Gangnam Inundation 2011 Gangnam Landslide

CCTV Information Population,

Building information

Public Info

Monitoring of Inundation

Occurrence Areal Information

Internet

Dissemination Dissemination of forecasted results of

Inundation

Analysis of risk area and

past inundation events

Inundation Forecasting

and Risk analysis

Detailed Information

Dissemination

Expected Inundation Area Past Inundation Event

CCTV Population Buildings

NEMA

Local Province

Traffic

Non-

Structural

Analysis

Structural

Analysis

Link-

Analysis

Detailed

Information

Non-Structural Data

Structural Data

Twitter News Media

Blog Internet Wall Board

Real-time precipitation, hazard map,

Soil characteristics, River Basin etc.

Non-Structural Data

Structural Data +

Governmental Info

Combination with Radar-based rainfall forecasting system

<Urban Flood alert system based on radar measurements>

Rainfall-runoff simulation

Flood-expected area Inundation depth

Radar rainfall

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

2.Development of underground inundation

analysis model

3.Development of integrated inundation

analysis model

Concept of Integrated inundation analysis model

4.Development of integrated inundation

analysis system(based on GIS)

Sewer

Channel

Pumping station

Underground

space

Embankment road

Building

Surface flow

River Road

Underground entrance

Car entrance

Stairs

Connecting passage

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

Analysis model for

surface water movement

• 1-dimensional real time

model

• Analysis considering on

building, road, rail road,

underpass

Overflow

Inflow of

flooding

Prediction of flooding by the hour Prediction of inundation area

and height by the hour

Calculation of rainfall

• Extreme rainfall

• Design rainfall

• Short-term predicted rainfall Road

Embankment road

Channel

Building

Esta

blis

hm

ent o

f DB

for s

imula

tion

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

Case 1

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 2 Case 3

As a result, inundation depth of case 3 is the biggest

[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

[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