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Flood Mitigation Master Plan for Chao Phraya Delta INWEPF 2007 Suphat Vongvisessomjai Professor, Water and Environment PowerPoint Presentation
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Flood Mitigation Master Plan for Chao Phraya Delta INWEPF 2007 Suphat Vongvisessomjai Professor, Water and Environment Expert TEAM Consulting Engineering and Management Co.,Ltd. e-mail : suphat@team.co.th. Abstract. Master plans of flood mitigation for Chao Phraya Delta,

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Flood Mitigation Master Plan for Chao Phraya Delta

INWEPF 2007

Suphat Vongvisessomjai

Professor, Water and Environment Expert

TEAM Consulting Engineering and Management Co.,Ltd.

e-mail : suphat@team.co.th

slide2

Abstract

  • Master plans of flood mitigation for Chao Phraya Delta,

rice bowl of Thailand, are as follows :

  • First master plan of flood mitigation for Bangkok developed

after 1983 flood from the King’s initiation by King’s Dike to

protect rainwater from northern and eastern boundaries

and the Chao Phraya river water from the west

  • Second master plan of flood mitigation for Chao Phraya Delta

after 1995 flood, Initially developed by AIT,DHI and ACRES

for World Bank, further developed in details by JICA, and

finally developed in Thai by Crown Property Bureau.

 The proposed master plan of flood mitigation for Chao Phraya

Delta after 2006 flood, with new diversion using AIT river

network model.

slide3

1.Introduction

The Chao Phraya Delta,rice bowl of Thailand

FAO study in 1948 recommended that Thailand’s economic

strength lay in exportingrice to alleviate world-wide

food shortages due the war.

1950,Thailand secured a World Bank loan

1952,commenced work on the Greater Chao Phraya

1957,first phase completion of Asia’s largest irrigation project.

1961,additional component : Bhumibol dam and irrigation canal.

1977,Sirikit dam finished for 25 year irrigation program and

Thailand is ranked first in rice export.

 AIT river network model was developed by Vongvisessomjai and

Suppataratarn 1998 and used as tool for Chao Phraya flood

management review for World Bank and forecast future floods

especially 2006 flood

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2. Literature Review

2.1 The First Master Plan

for Bangkok

  • The King recommended King’s

Dike to protect Bangkok after

4 months flood in 1983 due

to heavy rainfall

Figure 1

Eastern Bangkok Polder

(JICA 1986)

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2.2 The Second Master Plan for Chao Phraya Delta

 After 1995 flood with extensive damage, World Bank requested AIT,DHI,

and ACRES to conduct a Chao Phraya flood management review

 JICA provided assistance to develop an Integrated Plan for Flood Mitigation

based on recommended work plans of World Bank report

 Crown Property Bureau reported in Thai the framework of water resources

management which proposed 3 mitigation measures for water shortages,

floods and pollutions

slide7

3. Methodology

The proposed master plan is developed from 2006 flood data

3.1Important Data of 2006 Flood

(1) Severe floods occurred more frequently, i.e. in 1995,2002 and 2006

due to invasion of upper catchments, and insufficient drainage of flood flow

resulted in extensive damages at Singhburi,Angthong,Ayutthaya and

Bangsai which is a bottle-neck that limit the flow less than 3,500 m3/sresulted

In flooding upstream in all areas of Ayutthaya

(2) Flood waves in 2006 from Chao Phraya Dam to Bangsai:

AtChainat, 7 m. and peak at 17.50 m.

AtSingburi, 6 m. and peak at 13.14 m.

AtAngthong, 5 m. and peak at 8.19 m.

AtAyutthaya, 2 m. and peak at 4.70 m.

AtBangsai, 1.5 m. and peak at 3.60 m.

slide8

Chao Phraya Dam (Present)

Singhburi (Present)

Angthong (Present)

Ayutthaya (Present)

Bangsai (Present)

Chao Phraya Dam (-1,000 cms)

Singhburi (-1,000 cms)

Angthong (-1,000 cms)

Ayutthaya (-1,000 cms)

Bangsai (-1,000 cms)

Chao Phraya Dam (-500 cms)

Singhburi (-500 cms)

Angthong (-500 cms)

Ayutthaya (-500 cms)

Bangsai (-500 cms)

Daily Highest Water Level (m.MSL)

16 Sep. 21 Sep. 26 Sep. 1 Oct. 6 Oct. 11 Oct. 16 Oct. 21 Oct. 26 Oct. 31 Oct. 5 Nov. 10 Nov. 15 Nov.

Date from 16 September to 15 November

Figure 3

2006 Flood Hydrographs of the

Chao Phraya River from Chao Phraya Dam to

Bangsai and the Decreased Water Levels

due to Diversion of 500 and 1,000 m3/s at Bangsai

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(3) Satellite images of 1995 and 2006 in Figs 5&6

showed severe floodings in Chainat,Singhburi,

Angthong and Ayutthaya

 Undrained water’s at Bangsai inundated

Chao-chet,Pakhai and Sena,then flowed to the

Tha Chin and floodedBanglen to the mouth of

the Tha Chin at Krathumban and Muang of

Samut Sakhon.

slide11

Figure 5

Flooded Area and Maximum

Water Level in 1995

slide12

Figure 6 Satellite Image of 2006 Flooded Area

in the Chao Phraya River

(Contributed by GISTDA from Summary

Report on Satellite Imagery of Flooding in 2006)

slide13

3.2The Proposed Master Plan

(1) The leftover mitigation, the diversion, is very costly and not so

effective as shown in Fig.3

(2) The river diversion is the major factor to alleviate flooding

(3) It can be seen in Fig.4 that the Tha Chin river flows from Chao

Phraya Dam parallel to the Chao Phraya river. Its capacity is only

10 percent (350 m3/s) of the Chao Phraya river (3,500 m3/s)

because of 4 regulators (Pholathep,Thabote,Samchuk&Phophraya)

but downstream of Phophraya to the river month, the river sections

are large enough for 1,500 m3/s

(4) Therefore, a diversion canal in the upper Tha Chin is best mitigation

slide14

Figure 7 : Three-dimensional plot of the analytical model of water surface fluctuation with respect to distance and time. (Vongvisessomjai,S. and Chatanantavet,P. 2006)

slide15

Water Level (m)

Distance (km)

Phraya Banlu (142)

Phra Pimon (121)

Maha Sawat (89)

River Mouth (0)

Date in January 2002

Figure 7b. Three-dimensional plot of water surface fluctuation in the Tha Chin River

with respect to distance and time.

slide16

Figure 8a : Physical layout of the River

Network Model

(Vongvisessomjai,S. and

Suppataratarn,P.1998)

slide17

Figure 8b : Schematization of the

River Network Model

(Vongvisessomjai,S. and

Suppataratarn,P.1998)

slide18

Daily Highest Water Level (m.MSL)

Figure 9: 2006 Flood Hydrographs of the

Chao Phraya River from Chao Phraya Dam

to Bangsai and the Decreased Water Levels due

to Diversion of 500 and 1,000 m3/s to the

Tha Chin River

slide19

AIT river network model reveals that

  • At Chainat and Singhburi, flood depths drop 2 m.
  • At Angthong, drop 1.5 m.
  • At Ayutthaya, drop 1 m.
  • At Bangsai, drop 0.5 m.
  • No more floodings in the Chao Phraya Delta. The reduced flow of
  • 3,000 m3/s in the river will not have overspillage. This diversion from
  • the Chao Phraya Dam can flow to the river mouth without pumps due
  • to its high head. No more floodings from Banglen to the river mouth.
slide20

4. Conclusion

(1) Floods in the Chao Phraya Delta were caused by the in sufficient

drainages to the sea which inundated the rice bowl of Thailand

 The eastern diversion could not be built due to its expensive

land cost and high pumping cost

(2) The new diversion was found most effective to mitigate flood

in the Chao Phraya Delta.

 It helped minimize floodings at Chainat,Singhburi,Angthong

Ayutthaya and Bangsai

 It also helped minimize floodings downstream of the Tha Chin

from Banglen to the river mouth.

(3) The new diversion costed less than the eastern diversion and had

less impact to the people since its course was along the existing

river which required less dredging and its merit of high head near

to the Chao Phraya Dam which required no pumping.