Mountain Torrent Disaster reduction in China

Mountain Torrent Disaster
reduction in China
HUANG, Jinchi
Chief Engineer
hjc@iwhr.com
Research Center on Flood & Drought
Disaster Reduction, MWR
CONTENS
 Status
of the mountain torrent flood
disasters in China
 Challenge
we are facing for mountain
torrent flood management
 What
we are doing
Characteristics of the flash flood
Forecasting is not
so easy
The damage caused
by flash flood is
impressive
Developing very fast
Normal situation
15 Minutes later
Damage induced by mountainous flood disaster (1)
most of the casualties caused by flood is owing to the
mountainous flood. Based on the statistical data from
1950∼2000,the death caused by flood is 263 thousands, of
which mountainous flood induced is 180 thousands,
68.4%. a more recent statistics on
the data from 2000-2010
shows the ratio of the
mountainous flood
induced death is still in
increase as in the fig..
Damage induced by mountainous flood disaster (2)
with the economical development, the damage
induced by mountainous flood is also increased in
recent years. Based on the statistical data from 1950
∼1990, the damaged cultivated land is about
3million ha. and collapsed house 800 thousands .But
from 1990∼2000 the damaged cultivated land
increased to 5.4 million ha.，and the collapsed
houses increased to 110 million. Two typical flash flood disasters occurred in China
June 10, 2005, Shalan
township, Helongjiang
province in China, a flash flood
induced over 100 casualties Aug. 7, 2010, intensive
rainfall induced debris flow
inundated the Zhouqu
county, Gansu Province
and induced over 1700
casualties.
Structure works for mountainous
flood disaster reduction
① 
② 
③ 
④ 
⑤ 
Reservoirs in up-streams: over 80,000, play a very
important role for mountainous flood disaster
reduction.
Dikes: based on the national standard to the downtown
area, some protection dikes had been built for the
protection of the concerned people and properties.
Check dam for debris flow in small river basin.
Forestation.
River training(it is a little different from large river
system, river channel stability, dike protection)
An efficient measure of soil erosion control
Check dam system for controlling of the soil erosion in the
loess plateau. In a relatively closed small watershed, the
soil erosion is keep equilibrium and the damages induced by
flash flood is effectively reduced
Flood control measure-leveesusually 20 years return period
cities development—water requirement--near the
river systems--tolerate flooding, or protection cities
from flooding. After much debate regarding levees
and other methods of flood protection, the policy
that led to the construction of levees for local
protection was developed.
Population density is very high!
Flood Control Methods-RESERVOIRS
 Over
80000 reservoirs are built in upstream of those
rivers with flash flood often occurred. All of those
reservoirs are playing very important role for the
water supply, recreation, irrigation, and other
comprehensive objectives
 Flood control: Storing flood water; reducing
peak flood discharge
Challenge 1: urbanization changes flood process
Economical
development
Old city area
50
Number of Cities(>1 million)
45
40
35
30
25
20
15
10
5
0
1950
Popul at i on i ncr eas e
45
40
rate of urbanization
1955
1960 1965
1970
1975 1980
1985 1990
1995
35
30
25
20
15
10
5
0
year
2000
number of cities with
population more than 1
million in 2000
Rate of urban population
(%)
50
results
urbanization
Economical development,
population increase
inducing urbanization
which will greatly change
the flood regime.
• Harden
• More
• Those
ground surface greatly changing the flow regime;
properties will concentrated into urbanized area;
people in the newly developed area can not adapted
to the new requirements for flood prevention;
• No
enough flood proof measures for infrastructures;
• City
extension makes more area vulnerable to flash flood.
Challenge 2 so many streams need to be trained
Environmental limitation; ecological limitation
Investment limitation
Challenge 3 reservoir safety is very
important for the flash disaster reduction
Challenge 4: hydrological theory is not so
adaptive to changed environment
1、ground vegetation cover greatly changed－
theoretical basement varied- data series can be
directly used for flood analysis? Rainfall-runoff
model ?
2、climate change-how to adapted to hydrological
analysis?
3、what is the flood protection standard- how to
select designing flood-acceptable risk.
Challenge 5: comprehensive
consideration-focus points of nonstructural investment
  Balance
between structure and nonstructure;
  Balance between multiple sections;
  Balance between efficiency and risks;
  Balance between flood defence and
environmental improvement(ecological
aspects).
Challenge 6：theory for flood management is still
in progress
How to improve the public knowledge is still a
Hard task for flash flood disaster reduction!
1、uncertainty of hydrological events, results of frequency analysis
and the analysis methods can not be understand by public
(designing flood, early warning methods);
2、how to understand the the acceptable risk;
3、risk characteristics of those structure works is not so clear;
4、comprehensive risk assessment methods (such as the overlaying
process from different area in a river basin)
Early warning of flash flood
国家级
管理平台
GSM/GPRS
Internet
Internet
县级平台
部署服
务器
Internet
网
站
Internet
无
安线
装预
在警
村设
备
)
GPRS/CDMA/SMS
短信发
自动雨
量站
电
视播
电广
台台
(
综合信
息服务器
省级管
理平台
GSM/GPRS
送设备
信 短机手
Assessment of the warning message: accuracy and
forecasting earliness
Contents of warning system against mountain torrent disasters: (1)observation system, (2)analysis and platform for the disaster , (3) emergency response planning, (4)institutional structure, (5)
training, and practice drill for emergency action.
Index for early warning
The most important index: threshold rainfall
rainfall
 
 
 
 
 
 
threshold
Frequency analysis on
disaster events and rainfall；
Intensity and last time
Basin characteristics
Geomorphologic
conditions；
geological conditions
Conveying capacity
in river channel。
Disaster events
Risk analysis for flash flood disaster
1．Identification: (dam break, dike break, rainfall induced
flood, debris flow?)
2. Risk calculation: a calculation method is developed
(integrated all the factors to gather form a comprehensive
result
3. Possible measures analysis (structure works, non-structure
works?)
4. Risk assessment: (cost-benefit analysis, social,
economical, environmental analysis)
Procedures for flash flood early warning(1)
Concerned
objectives
Monitoring
Warning
Response
Procedures for flash flood early warning(2)
山洪灾害人工上报
简
易
监
测
设
备
或
其
它
方
式
乡镇防汛机构值班室
Procedures for flash flood early warning(3)
县防汛机构值班室
事件分析
 基础信息查询
 水雨情监测查询
 气象国土信息服务
 水情预报服务
 预案建议
 基于地图的应急部署
 周边应急资源搜索
主要业务流程及各级防
 影响分析
部
所发挥的作用
Flash flood disaster prevention
Public acknowledge to flash flood disaster
Training to Administrative staff, managers, public
is very important. Every people need to be
mobilized to react to the flash flood emergency
response Mountain torrent flood disaster prevention
For the effectiveness
of a emergency
response planning,
some preparedness
excise and practice
tests need to be
carried out frequently
Flash flood disaster prevention
A website is setup for information dissemination
Some key technologies for
effective flash flood disaster early
warning
How to get a reasonable warning index is
still a very important research work
  How to get a reasonable risk area
  Institutional aspect is the key point for
the successful operation of a flash flood
early warning system
  How to get a good emergency response
planning
 
conclusions
Prac%ce in China illustrated that the early warning system is a very effec%ve measure for mountainous flood disaster reduc%on, only a;er you fully completed following several points:   Reasonable observa,on points distribu,on   Good risk analysis system which can get a rela,vely accurate risk analysis result   Timely warning signal dissemina,on mechanism   Reasonable ins,tu,onal structure, based on the administra,ve structure   Perfect emergency response system   Prac,cal evacua,on system based on community.
Thank you for your attention!