East & Southeast Asia Regional Seminar on
Flood Hazard Mapping, 2009

Flood Hazard Mapping in Dujiatai andHonghu Flood Detention AreasLi aChina Institute of Water Resources and Hydropower Research(IWHR)
Feb.17, 2009

General method for mapping
Physical geographical condition

Objectives for mappingTechnique restriction

Hydrological & meteorological condition

Application of mapping

Data limitation

Flood control project

Function demand

Outlay limitation

Social and economic condition

Covered scope

Talent restriction

Historical disasters

Effects

Time limitation

Basic situation investigation

Demand analysis

Problem analysis

Select the method for mapping
Collect and process data
Identify the flood hazard

Flood analysis and simulation

Flood disaster loss assessment

Flood risk analysis
Mapping flood hazard maps
Develop the flood hazard map management system

1Flood risk analysis

Topography
analysis
Statistics andevaluationof flood disaster

Source analysis
of flood
Flood inundation
analysisFlood frequency
analysisFlood risk analysis• Topography analysis• Source analysis of flood• Rainstorm, flash flood, high tidal level, projec damage, etc.
• Flood frequency analysis• Stage, discharge and frequency, etc.
• Inundation analysis• Area, water depth, duration of flooding and velocity offlow, etc.
• Statistics and evaluation of flood disaster• Possible affected population, assets, loss, etc.

2Flood hazard mapping

Base map
processing
Create Floodhazard map

Create theinundating layer
Set upthe database

Assistant
information
processing

Flood hazard mapping• Base map processing• Topography map, district map, water conservancy project map, socioeconomic map• Create the inundating map• inundated area, water depth, duration of flooding and inundat
ed process, etc.
• Assistant information processing• Name of map, basic legend, inundating legend, scheme expla
nation, statistic and evaluation information of flood disaster,
north arrow, producer and date, etc.
• Create the flood risk map• Base map, inundating map layers and assistant information.

3

Flood hazard mappingin Dujiatai flood detention area

Basic situation of Dujiatai flood detention area
Hanjiang River
Huanglingji Gate
Dujiatai Gate

Yangtze River

4

Situation of polder area
• In Dujiatai flood detention area, there are 20 polder areas, 9polder areas in river beach. The population is 256,200 and thetotal cultivated area is 31,000 ha.
• The area of flood detention area is 613.98 km2. The total lengthof dike is 183.25 km.
• The storage capacity of the detention area below 28.00m is
3.861 billion m3, and 2.671 billion m3 below 26.00m.
• Intake gate: Dujiatai flood divertion gate with 4,000 m3/s ofdesign discharge and 5,300 m3/s of check discharge.
• Gate for retreating flood: Huanglingji gate with 1,535 m3/s ofdesign discharge and 2,008 m3/s of check discharge.

Function of the detention area

• The function of Dujiatai detention area is to discharge theexcessive floodwater in the lower reaches of Hanjiang Riverin order to ensure the safety of the lower reaches ofHanjiang River and Wuhan city.
• When a big flood happens in Yangtze River, it also needs tostore and adjust the excessive flood in the main reaches ofYangtze River.

5Use of Dujiatai detention area in history
The Dujiatai detention area has been used for 20 times since 1956.

um.

YearThemaximum
discharge ofintakeflood(m3/s)

The highest
storage volumeof flood(billion m3)

Durationfor flood
diversion
（h））

um.

YearThemaximum
discharge
of intakeflood(m3/s)

The highest
storage volumeof flood(billion m3)

Duration forflood
diversion（h））

1

1956

2,510

0.514

100

11

1964

2,060

1.028

169.7

2

1956

3,120

0.837

131.28

12

1964

4,350

1.52

148.34

3

1957

1,380

0.313

63.31

13

1964

5,600

2.509

172.4

4

1958

3,230

0.73

87.1

14

1974

1,790

0.283

53.6

5

1958

4,800

0.257

190.34

15

1975

3,300

0.324

49.48

6

1958

2,305

0.543

79.47

16

1975

3,980

0.682

72.18

719582,270

0.738

93.15

17

1983

5,100

2.306

182

8

1960

4,755

1.977

234.24

18

1983

2,860

0.596

81

10

1964

2,400

0.438

70.8

20

2005

1,648

0.368

85

Flood disaster losses of the flood diversion in historyame of districtYearumber oflocations wheredike breakhappened

Cultivated area
inundated (ha)Caidian district ofWuhan city

1958

1

2,400

Xiantao city

1960

Caidian district,
Xiantao City

1964

62,163

Xiantao city

1974

2

Caidian district,
Xiantao City

1975

Caidian district,
Xiantao Cit
Caidian district,
Xiantao Cit
Caidian district,
Xiantao CityInundated
building

Affected
population(person)

Death(person)

13

720

Loss(××104 yuan)

60

1,050

180.5

10,545

468.5

720

1,100

263.2

7

3,967

1,150

585.5

1983

13

3,053

6,360

45,564

1984

10

3,780

1,429

8,005

5,123

2005

2

108

7,381

4,848

Total

41

16,912641

8,430

74,795

1

14

9,175

20,703.7

6

Flood risk analysis
Continuity equation:∂H ∂M ∂++=q∂t∂x∂y
Momentum equations:∂M ∂ (uM ) ∂ (vM )∂Zn 2u u 2 + v 2+++ gH+g=0
∂t
∂x
∂y∂x
H13∂Z∂ ∂ (u ) ∂ (v )n 2v u 2 + v 2+++ gH+g=0∂t∂x∂y∂yH13

Flood risk analysis
The study area is divided into 3108 irregular meshes. Theroughness of river type mesh is 0.027 and others are from 0.04
to 0.07.

7

Calculation conditions• Upper boundary condition : flood discharged from Dujiatai Gate
• Lower boundary condition : flood discharged from Huanglingji Gate

黄陵矶闸下水位过程杜家台分洪流量过程
24.2
24.0
23.8

3500
3000

23.6

2500
2000

系列1

1500
1000

水 位 (m)

3流 量 (m /s)

4500
4000

23.4
23.223.0
22.8500

22.6
22.4

0050100时间(h)150Dujiatai Gate

200050100

150200250300350400450

时间(h)Huanglingji Gate

Calculation conditions• The gates and dikes inside the study area are the inner boundary
conditions of the model.
• The operation schemes of flood control projects in study area areconsidered in the calculation.

8

Calculation schemesum. ame of scheme

Description1

djt_4000

Typical flood diversion process whose flood peak discharge is equal to the design flood diversion
discharge (4000m3/s) of Dujiatai gate.
Huanglingji gate is closed because of the backwater effect of Yangtze River.

2

djt_5300

Typical flood diversion process whose flood peak discharge is equal to the check flood diversion
discharge (5300m3/s) of Dujiatai gate.
Huanglingji gate is closed because of the backwater effect of Yangtze River.

3

djt_4000_38

Typical flood diversion process whose flood peak discharge is equal to the design flood diversion
discharge (4000m3/s) of Dujiatai gate and the total flood diversion volume is 3.861 billion m3.
Huanglingji gate is closed because of the backwater effect of Yangtze River.

4

djt_5300_38

Typical flood diversion process whose flood peak discharge is equal to the check flood diversion
discharge (5300m3/s) of Dujiatai gate and the total flood diversion volume is 3.861 billion m3.
Huanglingji gate is closed because of the backwater effect of Yangtze River.

5

djt_4000-d

Typical flood diversion process whose flood peak discharge is equal to the design flood diversion
discharge (4000m3/s) of Dujiatai gate.
Typical downstream stage process of Huanglingji gate.

6

djt_5300-d

Typical flood diversion process whose flood peak discharge is equal to the check flood diversion
discharge (5300m3/s) of Dujiatai gate.
Typical downstream stage process of Huanglingji gate.

7

djt_4000_38-d

Typical flood diversion process whose flood peak discharge is equal to the design flood diversion
discharge (4000m3/s) of Dujiatai gate and the total flood diversion volume is 3.861 billion m3.
Typical downstream stage process of Huanglingji gate.

8

djt_5300_38-d

Typical flood diversion process whose flood peak discharge is equal to the check flood diversion
discharge (5300m3/s) of Dujiatai gate and the total flood diversion volume is 3.861 billion m3.
Typical downstream stage process of Huanglingji gate.

9

10

Statistics and evaluation method of flood disaster
Model calculation
Remote sensing analysis

Natural feature offlood disaster(intensity, frequencyand spatial distribution)

Typical investigation offlood disaster loss

Field investigation

Flood disaster loss ratio relation(type, magnitude and spatialdistribution)

Economic investigation data
Economic statistics data
Spatial data

Socioeconomic featureof inundated area
(type, value and spatialdistribution)

Economic loss of Flood disaster(magnitude and spatialdistribution)

Steps of flood disaster loss evaluation

11

Statistics results of flood disaster

Inundated area

Inundated
cultivated area

Affected persons

Main traffic line
affected

（km2）

（ha））

（person））（km））

djt_4000

265.76

16,40026,00861.78

djt_4000_38

520.1733,827

103,966

164.83

djt_4000_38_D

525.35

34,153

105,843174

djt_4000_D

316.72

20,51335,65873.35

djt_5300

505.7432,66098,079161.13

djt_5300_38

523.4634,033105,013172.29djt_5300_38_D

525.35

34,153

105,844173.99djt_5300_D

521.3933,840104,175

170.48ame of scheme

Evaluation results of flood disaster

Loss ofresidentialbuilding

Loss of family
property

Agriculturalloss（×104 yuan）（×104 yuan）（×104 yuan） （×104 yuan） （×104 yuan）

djt_4000

5,372

1,077

17,306579

24,334

djt_4000_38

21,185

4,327

25,8591,064

52,435

djt_4000_38_D

25,345

5,455

28,0591,385

60,244

djt_4000_D

6,407

1,281

19,283663

27,634

djt_5300

18,5603,648

23,818917

46,943

djt_5300_38

22,0484,534

26,415

1,129

54,126

djt_5300_38_D

25,345

5,455

28,057

1,380

60,237

djt_5300_D

21,064

4,262

25,784

1,100

52,210ame of scheme

Loss of roadTotal

12

Flood hazard mappingin Honghu flood detention area

Basic situation•Honghu flood detention area is located in the middle reaches of Yangtz River
Basin and in the administrative region of Honghu and Jianli county.

•The total area is 2,783km2，，•

Design flood stage: 30.51m; design flood storage capacity: 16billion m3，，•

Design intake flood discharge 10,000m3/s; design discharge of retreating flood
2,000m3/s。
。

13Flood hazard analysis

The study area is divided into 5177 irregularmeshes. The roughness of lake type mesh is0.027 and others are from 0.04 to 0.07
according to the characteristics of surface
land.

Calculation condition• Upper boundary condition: stage process of the breaches
where dike break happened in 1998.
• Discharge of flood diversion is calculated using broad crest
weir formula.
• The time when dike break happens is determined by flood
peak level.
• The shape of breach is rectangle with a width of 600m.
• Ground elevation near dikes is taken as the bottom elevationof breach.

14

Calculation condition
Stage process of Jianli, Luoshan and Hankou station
监利、螺山、汉口水位过程监利站螺山站
汉口站

40.0

水位(m)

35.0
30.0
25.0
20.0
15.0
0

200

400

600

800
1000
时间(h)

1200

1400

1600

Calculation schemesum.

ame of scheme

Description1

hh_scw_600

The type of flood in 1998 happens in Yangtze River;
Dike break happens at Chewan in the Honghu main dike in Jianli with a width of600m.

2

hh_ls_600

The type of flood in 1998 happens in Yangtze River;
Dike break happens at Luoshan in the Honghu main dike in Jianli with a width of600m.

3hh_tk_600

The type of flood in 1998 happens in Yangtze River;
Dike break happens at Taokou in the Honghu main dike in Jianli with a width of600m.

4

hh_tk_1630

The type of flood in 1998 happens in Yangtze River;
Dike break happens at Taokou in the Honghu main dike in Jianli with a width of1630m.

5hh_tk_480

The type of flood in 1998 happens in Yangtze River;
The width of Yangtze River flood diversion gate in Jianli Honghu is 480m.

6hh_yw_600The type of flood in 1998 happens in Yangtze River;
Dike break happens at Yanwo in the Honghu main dike in Jianli.

15

16

17

Statistics results of flood disaster

Inundatedarea

Inundated
cultivated area

Affected persons

Main traffic line
affected

（km2）

（ha）
）

（person））（km））

hh_ls_600_360

2,385.37

71,260448,200

519.22hh_yw_600_600

2,384.25

71,193448,060

518.61

hh_tk_1630_250

2,385.35

71,247448,230

519.26hh_tk_600_360

2,385.34

71,253448,230

519.27hh_scw_600_188

2,385.32

71,293448,230

519.22

hh_tk_480_210

937.3624,347139,090225.87ame of scheme

Evaluation results of flood disaster
Loss of building

Loss of family
property

Agriculturalloss

Loss of industrial
property（×104 yuan）（×104 yuan）（×104 yuan）（×104 yuan）

ame of scheme
hh_ls_600_360

94,976

20,761

132,531

16,004

hh_yw_600_600

87,602

18,709126,957

15,606hh_tk_1630_250

93,691

20,405131,057

15,918hh_tk_600_360

94,08020,499131,633

15,950hh_scw_600_188

94,667

20,685

132,784

16,07822,019hh_tk_480_210
ame of scheme

4,281

47,758Loss of industrial output value

Loss of road

Direct economic loss

3,578

（×104 yuan）（×104 yuan）（×104 yuan）

hh_ls_600_360

11,9935,545

281,810hh_yw_600_600

11,978

5,080

265,932

hh_tk_1630_250

11,8375,500

278,408

hh_tk_600_360

11,974

5,516

279,652

hh_scw_600_188

11,6636,059

281,936

hh_tk_480_210

2,124

1,440

81,20018

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