countermeasures against urban flood in beijing - gfdrr.orgsession_5)_yang_fen_wang_jing... ·...

Countermeasures against

urban flood in Beijing

Fen Yang

Beijing Institute of Water (BIW), China

Urban flood inundation warning and flood

hazard mapping in China

29th May, Korea

Wang Jing

China Institute of Water Resources and Hydropower Research

(IWHR), China

Flood control system in Beijing

Information of Beijing

16400 km2

About 20 million people

2 important reservoirs

5 main rivers

Mountain 61%

Guangting

Reservoir

Miyun Reservoir


Centrol Town

The Central Town

1085 km2(7%)

About 12 million

people(60%)

Yongding River in the

west is for flood control

Beiyun River in the east

is for drainage


Flood Control Project

Reservoir

total 9.4billion m3, control the

flow generated by 70% mountain

area.

Rivers

425 Rivers with 6400 km long

in the city.

143 Rivers with 2004 km long

in plain, 32% regulated.

40 Rivers with 380 km long in

central town, 72% regulated.

controlled natural


3645

5056

113 115

128.9

0

20

40

60

80

100

120

140

1年 2年 3年 5年 20040710 20060731 20110623

小时雨量(mm)

Food Control Project

Rainwater Pipeline

2000 km long covered 95%

area of central town.

most design standard is 36mm

(1year), or 56mm(5year) in

some important place.

Rainwater Pump station

Total 130 pump stations in

the city, most designed suitable

for 2~3 year return period.

Design standard distribution of

pump station in Central Town

Urban flood events

Recent years, urban flood happened suddenly and

frequently because of extreme weather and local sudden

rainstorm, which replaced the past flood most came from

the Yongding River.

Extreme weather events have occurred 41 times since 2004.

http://photo.blog.sina.com.cn/showpic.html

“2012.7.21” Flood Event

7.21 Flood Detail

Rainfall

average rain is 170 mm in the

city, which is the maximum

rainfall since 1949(63year).

average rain is 215 mm in

Central Town, which is the

maximum rainfall since

1963(49year).

the rainstorm center is in

Fangshan, 541 mm rainfall is the

maximum recorded rainfall.

Effect of Current Flood Control System

Reservoir & Sluice

The city's large and medium-

sized reservoirs and sluice running

normal, while effectively held

flood, cutting flood peak, increase

water storage.

Chongqing

Reservoir

Dingjiawa

Reservoir

flood diversion and

storage

Safe discharging

Source reduction

monitoring forecast

regulation

Department linkage, social

participation


River & Embankment

The Yongding river

200year flood control

standard), Chaobai river,

Beiyun river ( 50year flood

control standard) and other

Small and medium-sized

rivers regulation (20year

drainage standard) make

flood through the central

town normally，and ensure

the urban safety.

Beiguan Sluice open for flood discharge in Beiyun River

Chiwei river for flood discharge in Fangshan

flood diversion and

storage

Safe discharging

Source reduction

monitoring forecast

regulation


participation


Stormwater utilization

these structural measures

are useful for increasing

infiltration ,storing water and

reducing downstream pressure.

flood diversion and

storage

Safe discharging

Source reduction

monitoring forecast

regulation


participation

Artificial lake

Sand and gravel pit

Small watershed governance

Flood volume and flood peak decreased

by 36% ~ 58%,

Runoff coefficient changed from 0.6~0.7

to 0.3~0.4.


Monitoring forecast Regulation

According to rain forecast and

upstream real-time monitoring, 5

hours in advance notice of people

evacuated.

flood diversion and

storage

Safe discharging

Source reduction

monitoring forecast

regulation


participation

Mountain disaster monitoring and early

warning system broadcast 728 times,

warning of more than 10,000 text

messages, keep contact and well

regulation when public communication

interrupt, make the loss to a minimum.


Department linkage, social participation

flood diversion and

storage

Safe discharging

Source reduction

monitoring forecast

regulation


participation

The Next Focus

Basic Principle

Keep human safety primarily

Overall plan, systemic management

Integrated structural and non-structural measures

coordinate the relation between the near future

and the forward future

The Next Focus

Take 4 years

river governance 1460

km long

Reduce water

accumulation in flyover,

lower elevation etc.

(Low standard, human construction in river etc.)

The Next Focus

flood detention facilities

storage : use Sand and gravel pit, rivers, make sure under 100-

year flood do not flow through the central town.

reduction: in small watershed drainage unit, enforce construction

of lower elevation greenbelt, permeable pavement, provide source

control, slow down flow.

Detention: Use of low-lying land, park green land, as storage to

cut flood peak.

storage

lower

elevation permeable

The Next Focus

Flood simulating

In important rivers and key areas,

figure out flood submerged area ,

depth, duration, etc.

Flood risk grading

Define urban flood risk

management area

The Next Focus

Establish and improve early warning mechanism

build linkage mechanism with television and other media and

communications operators, expand coverage of early warning.

Improve safe work mechanism for flood in key areas

no entry to dangerous mountain road, go around the city roads and

flyovers with water, strengthen security warning in danger zone etc.

Build command platform for flood control

include rainfall and flow monitoring, early warning, emergency

rescue, flood dispatching, flood disaster reporting etc.

The Next Focus

Universal education about flood prevention, risk escape, self-

aid and mutual-aid, disaster mitigation etc.

popular science readings,

lectures, safety drills,

television, radio,

newspapers, network,

phone message, etc.

Urban flood inundation warning and flood

hazard mapping in China

29th May, Korea

Wang Jing

Department of Water Hazard Research

China Institute of Water Resources and Hydropower Research

(IWHR)

Contents

3 Urban Flood Simulation model

1 Urban inundation events in China

2 Characteristics of urban inundation

6 Conclusions

5 Flood hazard mapping in China

4 Urban Flood inundation warning


June 2005, Wuzhou

July 2007, Jinan and Chongqing

August 2008, Shanghai

August 2009, Wenzhou

May 2010, Guangzhou

July 2004, June 2011,

July 2012, Beijing

August 2010, Zhouqu


“2004.07.10” Rainfall in Beijing

Serious inundation on street and

under overpass seriously, traffic tied

up in city


“2012.07.21” Rainfall in Beijing

Serious inundation on street,

highway in low-lying area and

under overpass seriously, traffic tied

up in city


Flood from Xijiang River affected Wuzhou city

on 22nd June,2005

Inundation hazard from outside flood

Heavy rain in Jinan on 18th July, 2007

flood spreading along streets , inundation under railway overpass

and inundation in underground square


Streets were changed to rivers


Heavy rain in Chongqing on 17th July, 2007

Mountain city


Typhoon Morakot in August, 2009


The death toll was 1463, and 302 missing

Flash flood and debris flow in Zhouqu county

in August, 2010

2 Characteristics of urban inundation disaster

The types of disasters which would cause urban inundation are multiple

1

Including heavy rainfall, outside flood, typhoon, flash flood, debris flow, and so

on

Many new features of urban inundation appear as the rapid development of cities

2

Such as: inundation under road overpass and railway overpass is serious

flood spreading along the street

flood flows into underground space

flood hazard of urban area in the lower reaches increases as

the flood control standard improved in the upper reaches.

2 Characteristics of urban inundation disaster

Secondary disasters are severe 5

Urban flood and waterlogging disasters would affect the lifeline system of a

city seriously, such as traffic, water supply, power supply and gas supply, etc.

The statistical flood and waterlogging disaster loss data of cities in Zhejiang

province in 1998 and 1999 shows that the waterlogging loss occupies about

40% of total loss.

For some cities, the waterlogging loss is severe 3

The main reason for death in mountain cities are flash flood and debris flow

4

In 1991, 1293 persons died caused by flash flood and debris flow in

Yunnan and Sichuan province ;

In 1997, 1680 persons died caused by flash flood and debris flow in China;

In 2004, the flash flood and debris flow caused by Rainne typhoon leaded

to 44 persons died which is 24.2% of total death toll.

3 Simulation technology: Urban

Flood Simulation model

Can’t reflect the spatial distribution and change process of

hydraulic factors for everywhere, such as flood depth,

velocity and inundation duration, etc.

Hard to reflect the function of flood control projects, such as

pumps, gates, drainage system

Flood simulation methods

Hydrological

model

Hydraulic

model

Digital terrain analysis

method based on GIS

technology

The basic principle is that water moves from high to

low. The simulation result can only reflect the eventual

state instead of the real movement process of flood.

Dimension description Available software

1D Solution of the one-dimensional

St Venant equations Infoworks RS(ISIS), Mike 11, HEC-RAS

1D+

1D plus a flood storage cell

approach to the simulation of

floodplain flow

Infoworks RS(ISIS), Mike 11, HEC-RAS

2D-

2D minus the law of

conservation of momentum for

the floodplain flow

LISFLOOD-FP

2D Solution of the two-dimensional

shallow wave equations

TUFLOW, MIKE21, TELEMAC

Urban flood numerical simulation model (UFSM)

developed by IWHR

2D+ 2D plus a solution for vertical

velocities using continuity only TELEMAC 3D

3D CFX, FLUENT, PHEONIX

3 Urban flood simulation model

Urban flood numerical simulation model (UFSM)

developed by IWHR

Urban flood numerical simulation model

(UFSM)——basic principle

The study area is dispersed by unstructured

irregular meshes

h M Nq

t x y

2 2 2

1/3

( ) ( )0

N uN vN Z n v u vgh g

t x y y h

Continuity

equation：

Momentum

equation：

2 2 2

1/3

( ) ( )0

M uM vM Z n u u vgh g

t x y x h

Basic

equations

×

×

× ×

× ×

× ×

× ×

× × Water level is calculated on the centroid of mesh

Flow is calculated on the passages of mesh

Finite volume method is used to solve the equations


Terrain

Building

Dikes

Rivers

Gates

Pumps

Drainage system

Underground space


Rainfall

River flood

Storm surge

Dike break

Combinations


Rainfall


Combination of

rainfall and storm surge


The different running way of the UFSM


Running ways of the model

Before disaster During disaster After disaster

Real-time

calculation

Forecasting

calculation Design scheme

calculation

Testing &adjusting

calculation ＋

4 Urban flood inundation warning

Urban area of Foshan city: 79.7km2

1km˟1km


QPF and QPE data

Every 6 minutes：

QPF(quantitative precipitation forecasting)—grid

precipitation for the 1st, 2nd and 3rd hour in future

QPE(quantitative precipitation estimation)—grid

precipitation for the last one hour, validated


Blue：0.15~0.30m

Yellow：0.30~0.50m

Orange：0.50~1.00m

Red：>1.00m

5 Flood hazard mapping

Practices of flood hazard mapping in China

Flood mapping research started in 1986

Practices of flood hazard mapping in 1997

From 2003 to 2008: compile guidelines, pilot projects (36)

New stage of flood hazard mapping from 2008 (21million RMB)

project of 1st phase national flood hazard mapping commenced


project of 2nd phase national flood hazard mapping commenced


Achievements Details

1. Report on flood hazard mapping in

China and abroad

2. Establish standards and

regulations for flood hazard mapping

Guidelines

Technical Rules

Administrative Regulation

Cost

3. Technical platform and template

Flood analysis system

Flood disaster impacts and loss

assessment system

Flood hazard mapping system

Flood risk map management

system

Achievements Details

4. 20 pilot areas

9 flood protection areas

6 flood detention areas

1 flooded area

2 cities (shanghai)

2 Reservoirs

5. Technical training course Three times



Practices of flood hazard mapping in China

Flood mapping research started in 1986

Practices of flood hazard mapping in 1997

From 2003 to 2008: compile guidelines, pilot projects (36)


project of 1st phase national flood hazard mapping commenced


project of 2nd phase national flood hazard mapping commenced


Tasks

1. Revise the standards and regulations for flood hazard mapping

2. Improve the technical platforms

3. Flood risk analysis technology development for mountain area and pilot

study

4. Flood risk analysis technology development for storm surge and pilot

study

5. Real–time flood risk analysis and flood hazard mapping study

6. Flood insurance system scheme study and pilot study

7. Flood hazard mapping in pilot areas

8. Pilot study on application of flood hazard maps

9. Development of flood hazard map management and application platform


The purpose of flood hazard mapping in China

In China, we hope flood hazard maps can be used in many fields

Serve for the flood

control and flood

fighting decision-

making at all

levels of FCH

Enhance the

consciousness of

flood hazard

mitigation of the

nation

Direct the

constructions of the

safety facilities for

the flood detention

areas, and to chose

reasonable way

and place for

evacuating people

in emergency Offer basic data

for assessing

flood losses, and

so on

Provide support for

working out flood

control planning,

drainage planning

Provide support

for working out

Flood defense

emergency plan

Historical rainfall Design rainfall

Dike break Inundation distribution on roads

Sea wall overflow

Sea wall break

Combination of

rainfall and Sea wall

break


Flood hazard mapping in urban area in China

661 cities

4 municipalities

283 prefecture-level cities

374 county-level cities

5 Conclusions

The urban type flood disasters are very serious in China. As

Cities of China are in a stage of rapid development, the urban areas

will expand continually. In future, the flood disaster risk will rise and

the types will be multiple.

In order to reduce the flood risk in urban area, flood simulation

technology is an important non-structural measures which can

provide support to flood hazard mapping, flood prevention warning

and decision-making. In fact, this technology have been applied in

many cities in China.

The urban inundation can not be avoided completely. But we

need to try our best to decrease the losses not only by improving

and reconstructing our drainage system, but also considering the

storage, detention, infiltration and utilization of rain water in process

of infrastructure construction.

countermeasures against urban flood in beijing - gfdrr.orgsession_5)_yang_fen_wang_jing... ·...

Documents