Progress and Pilot Practice ofFlood Hazard Mapping in China
By Luo Xiaoqing
Engineer, Office of State Flood Controland Drought Relief Headquarters（OSFCDRH）
Beijing, China

China is undertaking strategic adjustment
in flood control and disaster mitigation¾ Preventing and controlling flood and waterlogging
disasters is a pressing task in China.
¾ The core of strategic adjustment is to implement
scientific flood management in accordance withthe concept of harmonious coexistence of man
and nature.
¾ The concept of ‘transfer from flood control to flood
management’ is widely accepted by floodmanagement administrations and the public.

How to analyze and evaluate flood risk forbetter avoiding and mitigating flood risk?
¾ In the “Eleventh Five-Year Development Plan for
the National Water Sector”, a comprehensive planfor FHM was firstly brought forward.
¾ The objective is to complete FHM of important
flood-prone areas, flood detention areas and cities
along main streams of seven major rivers.
¾ FHM is expected to play an directive role for flood
control plan, flood control works construction, land
exploitation and awaking public consciousness etc.

Contents
1.General introduction of pilot practice ofFHM in China
2.Outcome of pilot practice on FHM in HuaiheRiver
3.Problems encountered in process of FHM
4.Short-term Tasks and Suggestions on FHMProgress on FHM in China¾ In 2003, OSFCDRH sponsored a research project,
for the purpose of drafting the guideline.
¾ In July 2005, tentative guideline for FHM waspromulgated by OSFCDRH.
¾ 35 pilot regions from seven major rivers wereselected to make FHM for acquiring experience.
¾ China Institute of Water Resources andHydropower Research (IWHR) is responsible fortechnical support and training.

Pilot Regions for FHM in China¾ 35 regions fromseven major rivers
12 rivers, 8 cities, 6reservoirs and 9
flood detention
areas¾ Diverse types offlood control works
included.
¾ sufficient basic
information, explicit
boundary, moderatetask.

Objective of Pilot Regions for FHM¾ To clarify thoughts, estimate rationality and availabilityof the tentative guideline.
¾ Expected to complete pilot practice within 2 years, andexperience of pilot practice will be summarized.
¾ Hereafter FHM will be extended to seven major rivers
and it aims to establish flood risk management system
in China.

Briefing of Tentative Guideline for FHM¾ 4 chapters
general principle, flood riskmapping, flood risk
computer system platform,
outcome and supplementary
principle.

Content of Tentative Guideline for FHM（1）Definition
FHM is a series of special maps
to show flood risk information clearly
when a specific region is inundated
in terms of different presumed
scenarios.
It’s made by flood control
administrations based on the actual
need, categorized as digital andprinted flood hazard maps.

Content of Tentative Guideline for FHM（2）Information
Flood risk information comprises
inundation boundary, flood depth,
velocity, inundation duration andarriving time, etc of different floods
with return period of 5, 10, 20, 50 to
100 years.
Flood control scheme, evacuationroutes and refuge shelters should beembodied in flood management
information.

Content of Tentative Guideline for FHM（3） Classification
Flood hazard map is classified
into three categories
River and lake, flood detention
area and reservoir. Each type offlood hazard map shows the floodrisk of different flood control works
separately.

Content of Tentative Guideline for FHM（4） Flood Risk Analysis Methodology
3 types of methods and models offlood risk analysis.
Hydrological method is used toanalyze flood risk in the mountainousrivers.
Hydraulic method is used tocalculate flood evolution process in theplain when embankments andreservoirs broken.
For these regions where historicalflood datum and disasters can beobtained, historical flood disastermethod will do work.

Content of Tentative Guideline for FHM（5） Procedure
Collectabundantmaterials

1:10000
CombinebasemapSelectfloodrisk analysis
methodtopographical, hydrological,
social and economic materials,
flood control works and schemes,
etc.

Draw andPrint FHM

Develop
computersoftwareplatform

Make
flood
hazardmap

Content of Tentative Guideline for FHM（6） Breach Supposition of flood
control works
The breach spots ofembankment and reservoirs aresupposed according to experience.
In the condition of datum
unavailable, embankment breachexperiential formula in Korean
Guideline for FHM and dam breachexperiential formula summarized
by Mr. Lu Jikang are suggested toanalyze flood risk.

Contents
1.General introduction of pilot practice ofFHM in China
2.Outcome of pilot practice on FHM in HuaiheRiver
3.Problems encountered in process of FHM
4.Short-term Tasks and Suggestions on FHMPilot Regions for FHM in Huaihe River

Left bank of Yi River

Shilianghe Reservoir
Lianyungang
City

Huangdunhu Lake

Chengdonghu Lake

New Shu River¾6 pilot regions inHuaihe River
2 rivers, 1 city, 1reservoir and 2 flood
detention areas

Pilot Regions for FHM in Huaihe River

FenyiWat rushu
ercourse
Remote Sensing Map of Yi River¾480km2¾several severefloods occurred inyear 1730, 1957,1974 etc
Embankments havebeen reinforced inrecent years andcan withstand floods
with a return periodof 20 years.

iver
Shu
R

Yi River

2.1 Left Bank of Yi River¾

Embankment of Yi River2.1 Left Bank of Yi River¾

Zhujiamiao, where embankment will beTingzhikou

LinYi HydrologicalStation

exploded to divert floods into left bankiver

Tingzhikou, the weakest spot whereembankment broke during floods of1957 and 1974.

Yi R

¾ive
r

Embankment breach SpotsuR

plain of Yi River, for safeguarding

Shpeople’s life when flood peak of LingYi
Hydrological Station exceeds 13,000
m3/s (return period of 20 years) according
to flood control scheme.

FeZhujiamiao
nyirushuWaterc ourse2.1 Left Bank of Yi River
2-dimension unsteady hydraulic calculation method

Tingzhikou

Zhujiamiao

FHM of 100-year floods

Flow rate (m3/s)

Design flood hydrograph of 100-year flood in Zhujiamiao

Zhujiamiao

FHM of 100-year floodsTime (h)Zhujiamiao

Flow rate (m3/s)

Flood Diversion flow rate of 100-year flood in Zhujiamiao

Time (h)FHM of 100-year floods

Loss and impact of different flood

Zhujiamiao

FHM of 100-year floods

Legend and explanation

Zhujiamiao

FHM of 100-year floods

2.2 Shilianghe Reservoir
Storage capacity:
5.31×108 m3
Main dam
22.0 m high, 5.2 km long
Two auxiliary dams.
Southern auxiliary dam
Shilianghe Reservoir

New

200 m long, 8.5 m highNorthern auxiliary dam

ShuRiver120 m long, 31.5 mhigh.

2 scenarios of main dam and north auxiliary dam breachseparately are analyzed in FHM using two-dimensional
unsteady hydraulic evolution method.
Dam failure width and process can be calculated
according to dam breach experiential formula summarized
by Mr. Lu Jikang suggested in the tentative guideline.
Flood risk information, inundation boundary, maximum
water depth, arriving time and inundation duration etc, canbe indicated in FHM separately.

Maximum inundation depth

Maximum inundation depth

Distribution map of auxiliary dam breach Distribution map of main dam breach

Auxiliary Dam
Main Dam2.3 Huangdunhu Lake
¾335.8km2¾

14.7×108m3
capacity¾222,400 residents¾Floods will bedischarged into
Huangdunhu Lake
when water level ofLuomahu Lake rises
up to 25.5 m and will
exceed 26.0 m
predicted

Huangdunhu Lake
GrandCanal

Huangdunhu Lake
Luomahu Lake
Abandoned YellowRiver2.3 Huangdunhu Lake
Two ways of diverting
floods into Huangdunhu
Shuangheqiao Spot

Lake
Huangdunhu Sluice
Gate (design discharge is2000 m3/s)

Huangdunhu Sluice Gate

Caodian andShuangheqiao spotsCaodian Spot

exploded when necessary(design width is 300 m).

2.3 Huangdunhu LakeFHM of Huangdunhu Sluice
Gate diversion (scenario 1)

FHM of Huangdunhu Sluice Gate andtwo exploded spots diversion (scenario 4)

Contents
1.General introduction of pilot practice ofFHM in China
2.Outcome of pilot practice on FHM in HuaiheRiver
3.Problems encountered in process of FHM
4.Short-term Tasks and Suggestions on FHM

3.1 FHM really reflect the actual flood risk?
Some of flood control administrations are unfamiliar withflood hazard mapping, question of “why, how and for whom
to make FHM” exists commonly.
For a few simplifications and artificial suppositions are set
in the process of FHM, such as certain spots in embankment
and dams supposed to break, partition of finite element
meshes etc, FHM only shows flood risk of one scenario
supposed, actual flood risk status maybe differs from FHM.

3.2 Lack of laws support
Flood Control Law of People’s Republic ofChina came into force as of January, 1998, but
no such provisions about flood risk and hazard
maps were stipulated in the law.
It’s not an obligation for local governments
to make FHM. If local flood control
administrations are lack of enthusiasm orcapital, it’s hard to impel this work.

3.3 Incomplete basic datum, irregular data
format, lack of technical specification
Some datum are outdated with low accuracy. Mass time,energy and capital are devoted into basic datum analysis anddisposal.
The computer digital platforms to show flood hazard
mapping differ with communities, and uniform technicalcriterion is in great demand.

3.4 Flood management information isignored in FHM
Most work focus on two-dimensional unsteady hydrauliccalculation to analyze flood risk. On the contrary, flood
management information, such as evacuation routes, refugee
shelter etc, is seldom indicated in FHM.

3.5 Dynamic flood risk simulation analysis
systems haven’t established
Mostly flood hazard map only shows several specific floodrisk of supposed conditions, it’s static. Dynamic flood
simulation systems based on real conditions haven’t been
established.

3.6 Work of typhoon disaster risk mappinglags
Nearly Seven to eight typhoons land in China every year inaverage. Last year, 1522 people were killed by typhoon, 67%of death toll affected by flood and waterlogging disasters.
Typhoon can affect wide area and induce severe damage,it’s urgent to make typhoon hazard mapping. Nowadays,
corresponding research about how to make typhoon hazard
mapping lags behind demand.

Contents
1.General introduction of pilot practice ofFHM in China
2.Outcome of pilot practice on FHM in HuaiheRiver
3.Problems encountered in process of FHM
4.Short-term Tasks and Suggestions on FHM

4.1 To promote pilot FHM project unceasingly
It’s expected to finish the pilot project by the end of thisyear. Tentative guideline will be emended based on
experiences achieved, detailed criteria and specification will
be enacted, digital platform will be developed to show floodrisk mapping uniformly, for the purpose of improving
standardization level of flood hazard mapping.

4.2 To intensify early stage work of FHM

Proposal report for flood hazard mapping is being compiled
by OSFCDRH, and it’s hopeful to be approved by Ministry ofWater Resources. And it’s in the process of applying fornational investment of Eleventh Five-Year Period.

4.3 To summarize function of FHM

Through 1~2 years practice, verify roles of flood hazard
mapping in flood management.

4.4 To strengthen cooperation on typhoon
disaster mapping

East and Southeast Asian countries suffer from heavy
typhoons, and we hope to exchange information andexperience about typhoon and tsunami prevention.

Thank you for your attention！

iv er

2.2 New Shu River¾45 km long

¾Embankments along

ShuR

both banks canYellow Seawithstand floods
with a return period

Ganyu Countyof 20 years, design
flow velocity of 5000

NewShum3/s.
River
Lianyungang CityDonghai County

2.2 New Shu River¾

Fanhe sluice gate andMaoyuan weak spot
are supposed as levee
breach spots for floodrisk analysis.

¾

Based on twodimensional unsteady

Fanhe Sluice Gate

hydraulic method, 2scenarios of 50 years

Maoyuanfloods at left and right
Weak
ness

banks were calculated.

2.2 New Shu River
Maximum Flood Velocity

Maximum inundation depth

Distribution map

Distribution map

Fanhe Sluice Gate

Fanhe Sluice Gate

2.3 Lianyungang City

¾Xinpu district, urban
area of Lianyungang
City, 27.2 km2¾Dapu River, flowing
through Xinpu district,greatly influences
waterlogging in Xinpu
district.

¾The drainage capacityof Dapu River totals
108 m3/s ( 48 m3/s byLianyungang City

gravity drainage, 60
m3/s by pumpingstations)2.3 Lianyungang City
¾The pure precipitation and residual water quantity are calculatedusing hydrological method. As the topography is flat at equivalentelevation, waterlogging depth can be obtained in terms of residual
water quantity distributed even in the district.

¾8 scenarios of 20, 50, 100, 200-years floods can be obtained in FHM

2.3 Lianyungang City

Maximum inundation depth

Maximum inundation depth

Distribution map of 50-year flood

Distribution map of 100-year flood2.5 Chengdonghu Lake¾

It is a natural lake isolatedby Cross-lake Dam andChengdonghu Sluice Gate

Sluice Gatefrom Huaihe River, andhas a catchment area of
2170 km2¾

Low-level mountains anddepressions are encircled
around the lake.

¾Capacity 15.9×108 m3¾Area: 380 km2¾

total population of
132,600

¾According to highest flood level
sequence from year 1954 to 2003,
using hydrological probability
analysis method, flood levels ofvaried flood probability, such as 5,10, 20, 30, 50-year flood can beachieved. For flood level is evenin the lake, therefore inundation
area can be marked according towater level~capacity~area curvefrom topographical map

¾

In the meantime, scenarios of different flood diversion
quantity ranging from 0.5×108 m3 to 9×108m3 combinedwith the lake water level ranging from 22.3 m to 24.7 m areanalyzed in FHM.