Presentation on theme: "Suphat Vongvisessomjai"— Presentation transcript:
1 Suphat Vongvisessomjai Flood Mitigation Master Plan for Chao Phraya DeltaINWEPF 2007Suphat VongvisessomjaiProfessor, Water and Environment ExpertTEAM Consulting Engineering and Management Co.,Ltd.
2 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 developedafter 1983 flood from the King’s initiation by King’s Dike toprotect rainwater from northern and eastern boundariesand the Chao Phraya river water from the westSecond master plan of flood mitigation for Chao Phraya Deltaafter 1995 flood, Initially developed by AIT,DHI and ACRESfor World Bank, further developed in details by JICA, andfinally developed in Thai by Crown Property Bureau. The proposed master plan of flood mitigation for Chao PhrayaDelta after 2006 flood, with new diversion using AIT rivernetwork model.
3 1.Introduction The Chao Phraya Delta,rice bowl of Thailand FAO study in 1948 recommended that Thailand’s economicstrength lay in exporting rice to alleviate world-widefood shortages due the war.1950,Thailand secured a World Bank loan1952,commenced work on the Greater Chao Phraya1957,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 andThailand is ranked first in rice export. AIT river network model was developed by Vongvisessomjai andSuppataratarn 1998 and used as tool for Chao Phraya floodmanagement review for World Bank and forecast future floodsespecially 2006 flood
4 Eastern Bangkok Polder 2. Literature Review2.1 The First Master Planfor BangkokThe King recommended King’sDike to protect Bangkok after4 months flood in 1983 dueto heavy rainfallFigure 1Eastern Bangkok Polder(JICA 1986)
5 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 Mitigationbased on recommended work plans of World Bank report Crown Property Bureau reported in Thai the framework of water resourcesmanagement which proposed 3 mitigation measures for water shortages,floods and pollutions
7 3. Methodology 3.1 Important Data of 2006 Flood The proposed master plan is developed from 2006 flood data3.1 Important Data of 2006 Flood(1) Severe floods occurred more frequently, i.e. in 1995,2002 and 2006due to invasion of upper catchments, and insufficient drainage of flood flowresulted in extensive damages at Singhburi,Angthong,Ayutthaya andBangsai which is a bottle-neck that limit the flow less than 3,500 m3/s resultedIn flooding upstream in all areas of Ayutthaya(2) Flood waves in 2006 from Chao Phraya Dam to Bangsai :At Chainat, 7 m. and peak at m.At Singburi, 6 m. and peak at m.At Angthong, 5 m. and peak at 8.19 m.At Ayutthaya, 2 m. and peak at 4.70 m.At Bangsai, 1.5 m. and peak at 3.60 m.
8 Figure 3 2006 Flood Hydrographs of the Daily Highest Water Level (m.MSL)Date from 16 September to 15 November16 Sep Sep Sep. 1 Oct Oct Oct Oct Oct Oct Oct. 5 Nov Nov. 15 Nov.Chao Phraya Dam (Present)Singhburi (Present)Angthong (Present)Ayutthaya (Present)Bangsai (Present)Chao Phraya Dam (-500 cms)Singhburi (-500 cms)Angthong (-500 cms)Ayutthaya (-500 cms)Bangsai (-500 cms)Chao Phraya Dam (-1,000 cms)Singhburi (-1,000 cms)Angthong (-1,000 cms)Ayutthaya (-1,000 cms)Bangsai (-1,000 cms)Figure 32006 Flood Hydrographs of theChao Phraya River from Chao Phraya Dam toBangsai and the Decreased Water Levelsdue to Diversion of 500 and 1,000 m3/s at Bangsai
10 (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 inundatedChao-chet,Pakhai and Sena,then flowed to theTha Chin and flooded Banglen to the mouth ofthe Tha Chin at Krathumban and Muang ofSamut Sakhon.
11 Flooded Area and Maximum Figure 5Flooded Area and MaximumWater Level in 1995
12 Figure 6 Satellite Image of 2006 Flooded Area in the Chao Phraya River (Contributed by GISTDA from SummaryReport on Satellite Imagery of Flooding in 2006)
13 3.2 The Proposed Master Plan (1) The leftover mitigation, the diversion, is very costly and not soeffective 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 ChaoPhraya Dam parallel to the Chao Phraya river. Its capacity is only10 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 sectionsare large enough for 1,500 m3/s(4) Therefore, a diversion canal in the upper Tha Chin is best mitigation
14 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)
15 with respect to distance and time. Water Level (m)Maha Sawat (89)Phra Pimon (121)River Mouth (0)Distance (km)Phraya Banlu (142)Date in January 2002Figure 7b. Three-dimensional plot of water surface fluctuation in the Tha Chin Riverwith respect to distance and time.
16 Figure 8a : Physical layout of the River (Vongvisessomjai,S. and Network Model(Vongvisessomjai,S. andSuppataratarn,P.1998)
17 Figure 8b : Schematization of the (Vongvisessomjai,S. and River Network Model(Vongvisessomjai,S. andSuppataratarn,P.1998)
18 Figure 9: 2006 Flood Hydrographs of the Daily Highest Water Level (m.MSL)Figure 9: 2006 Flood Hydrographs of theChao Phraya River from Chao Phraya Damto Bangsai and the Decreased Water Levels dueto Diversion of 500 and 1,000 m3/s to theTha Chin River
19 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 of3,000 m3/s in the river will not have overspillage. This diversion fromthe Chao Phraya Dam can flow to the river mouth without pumps dueto its high head. No more floodings from Banglen to the river mouth.
20 4. Conclusion(1) Floods in the Chao Phraya Delta were caused by the in sufficientdrainages to the sea which inundated the rice bowl of Thailand The eastern diversion could not be built due to its expensiveland cost and high pumping cost(2) The new diversion was found most effective to mitigate floodin the Chao Phraya Delta. It helped minimize floodings at Chainat,Singhburi,AngthongAyutthaya and Bangsai It also helped minimize floodings downstream of the Tha Chinfrom Banglen to the river mouth.(3) The new diversion costed less than the eastern diversion and hadless impact to the people since its course was along the existingriver which required less dredging and its merit of high head nearto the Chao Phraya Dam which required no pumping.