Proposal Report
OnFlood Hazard Mapping Projectin LiNan Polder

Prepared By
Liao Hongzhi
Changjiang Water Resources Commission
China

FLOOD HAZARD MAPPING TRAINING COURSE
JFY 2008

1. Background of the proposal
Flooding has caused enormous damage through its history on Changjiang River inChina. After 1998, China government made great efforts to implement the project
to prevent floods. The flood control systems in Changjiang River are composed ofstructural and non-structural measures. Combined two measures, the main goal offlood management are prevention of casualties and reduction of economic losses tothe least. Flood Hazard Map (FHM) is one of the very important non-structuralcountermeasures.
FHM is referred to a map that is prepared primarily to prevent human damage by
providing residents with inundation related information, such as levee braches andflood occurrences and evacuation information in an easy to understand way. TheFHM aim is to minimize the damage in case of foods by giving information to theresidents in advance.
In order to promote the execution of FHM, Guidelines for flood hazard mapping
were issued by the Office of State Flood Control and Drought Relief Headquartersin May, 2005. Then ， 36 pilot studies in seven major river basins have beenarranged, including some detention areas, cities, dike protected areas and dam
failure events. 6 areas which are chosen to make a FHM in Changjiang river basin.
In 2008, the FHM in 6 areas are compiled. Through the pilot study, we get someconclusions for feature stage:
9 The criterion for FHM should to be established immediately;
9 The basic information and date should to be collected more comprehensive,
specially the social and economic data should to be included;
9 The FHM compiled should to be published and disseminated to residents.
Therefore, based on the pilot study of FHM and applying the knowledge and ideas
acquired and discussed in the Flood Hazard Map Training Course, the target area
(LiNan Polder) is chosen to compile the FHM. Not only to compile the FHM, butalso to disseminate it to residents to make them aware of the danger caused byfoods and be prepared for them.

12. Outline of the LiNan Polder
Li River is among 4 rivers of DongTing Lake water system. LiNan polder is locatedat the lower reaches of Li River. LiNan Polder has 34.3 km2 in area and 24.2 km indike length. About 77% of the land area is plantation. In 2006 the estimatedpopulation of LiNan Polder was 28326. 22 companies, 5 schools, 2 cliniques and 150
convenient stores are located on the polder.
LiNan polder is among 24
flood detention areas in
Hunan Province. It ischarged with the flood
diversion role for excess
flood discharge of Li River.
Li
When the water level of theLi River reaches the flood
diversion water level, if theLinanupriverdischarge
will
increase according to theforecast and the lower
reach of the Li River needtomitigate
theflood
influence, the diversion
gate will be opened, and the flood water will flow into the polder. Before flood flowin the polder, the residents will be evacuated to the evacuation center. After theflood flow out from the polder, the government will evaluate the damage and give
residents compensating caused by flood diversion.
LiNan polder has open landform and complanate hypsography. The upriver of Li
River is the famous storm zone, and the lower reaches of Li River influenced by thejacking of DongTing Lake flood. The flood disaster occurs frequently and threatens
the local people severely. LiNan polder belong monsoon climate and locate on thesubtropical zone. The rainfall quantity is abundant in this area. The mean annual
precipitation is 1254.2 mm, the mean annual evaporation is 1242.9 mm and themean annual rainy day is 142 days.
The average annual discharge of Li River near the LiNan polder is 478 m3/s. The
maximum flood peak discharge is 15900 m3/s. The design flood discharge of 20-years2floods is 15000 m3/s on Jingshi hydrometric station when the Jiangya Reservoir
regulate flood. The average annual water level of Li River near the LiNan polder is
31.48 m; the maximum observation water level is 42.85 m.
1998，flood have been overtopping the dike of LiNan polder. The water lever of
Liujiahe water gauge station is 44.825 m. The width of the dike breach on LiNanpolder is as following: BaiZhiPeng 296 m; WangJiaZhou 228 m; LiuJiaCiTang 188m. The maximum overtopping discharge is 9800 m3/s, the maximum storage level is45.8 m, the total storage capacity is 2 hundred million m3, the inundated area is 36
km2, the flooded infield area is 26.4 km2. 28.3 thousand people are influenced bythis flood disaster. The flooding duration is 45 days. The water depth ofcharacteristics position is 8.5 m. The flood damage is 3 hundred million Yuan.
2003, flood have been overtopping the dike of LiNan polder again. The water leverof Liujiahe water gauge station is 47.1m. The width of the dike breach on LiNanpolder is as following: SongJiaDu 308m. The maximum overtopping discharge is7500 m3/s, the maximum storage level is 43.745m, the total storage capacity is 2
hundred million m3, the inundated area is 36 km2, the flooded infield area is 26.4
km2. 28.3 thousand people are influenced by this flood disaster. The flooding
duration is 29 days. The water depth of characteristics position is 8.5 m. The flood
damage is 40 million Yuan.
LiNan polder has three evacuation centers with total area is 255 million m2. These
three evacuation centers can allocation 28.3 thousand people. The information
about them is as follows:
The total area of QiaoJiaHe evacuation center is 150 million m2. It can allocation
21072 people. The altitude of QiaoJiaHe is 47.95m.
The total area of ZhangJiaTan evacuation center is 90 million m2. It can allocation
5664 people. The altitude of ZhangJiaTan is 50.95m.
The total area of YiaoPo candidate evacuation center is 15 million m2. It can
allocation 1590 people. The altitude of QiaoJiaHe is 51.95m.
The diversion gate is controlled by the flood control and drought relief headquartersof HuNan province. LiNan polder flood control and drought relief headquarters takecharge of the organization of residents evacuate to the evacuation center.
33. Schedule of implementation
According to the process for the execution FHM and the situation of the LiNan
Polder, the implementation schedule for the LiNan Polder is making as follows: Data collection and analysis (6 months)
Some basic information should be collected in this stage:
999999999History flood records and inundation area;
Base map;
Social and economic data;
Hydrological and meteorological data;
Flood damage data;
Flood control project information;
Evacuation site and route information;Land use information;
Flood dispatching plan (river, reservoir, detention area and sluice).

 Inundation area analysis (2 months)
Through hydrological and hydraulic calculation and simulation, analysis theinundation areas, such as extent of inundation, water depth, flow rate, arrival
timing and the inundation duration etc.
 Flood hazard mapping (2 months)
9 Investigation all stakeholders’ suggestion or opinion (resident, central
government, province administration and community);
9 Calculation the population required to evacuate, accommodation provided byshelters;
9 Formulation the evacuation plan;
9 Compilation the flood hazard map.
 Dissemination FHM (1 month)
9 Dissemination the FHM to each level administration;
9 Dissemination the FHM to each household in inundation area.

4 Flood hazard drill and exercise (1 month)
9 Flood hazard education course;
9 Flood hazard drill and exercise.

4. Estimated budget
Item

Cost (RMB)

1

Data collection and analysis

500,000

2

Inundation area analysis

150,000

3

Flood hazard mapping

150,000

4Dissemination FHM

100,000

5Flood hazard drill and exercise

100,000

Sum

1,000,0005. Expected effectiveness
LiNan Polder flood detention area is an extremely important part of DongTing Lakeflood control system which taking on the duty of cutting flood peak and storing
floodwater. From 1998, LiNan Polder flood detention area was utilized to storage
floodwater four times. It is very important for the residents living in the detention
areas to evacuate fast when the detention area is utilized. When we finish theLiNan Polder FHM, it will be published by the government. After that, all theresidents, companies and communities will get the FHM. At same time, they will be
required to participate in the flood hazard drill and exercise which will help themunderstand the risk caused by flood and how to evacuate to the safety area in time.

5

LiNan Polder Flood Hazard Map6