Lessons learned from Floods 2011 and what s next?

Transcription

1 Lessons learned from Floods 2011 and what s next? Sucharit Koontanakulvong Department of Water Resources Engineering Faculty of Engineering, Chulalongkorn University. March 17, 2012 Presented at the 10 th Kyoto University Southeast Asia Forum 2012, Thailand What happened issues Floods 2011 causes Lessons Learned Short and Long term Plan What is next? Conclusions Recommendations 2 1

2 Introduction Flood 2011 started in the north since July Four big summer monsoons occurred during July October 11 Big floods attacked many main cities in the central plain including Bangkok Huge impacts towards lives, socio economicsาง Water Balance analysis to investigate causes 3 Summer monsoon in 2011 พาย ไห ถาง (Haitang) September 2011 พาย เนสาด ( Nesat) 25 Sep. - 1 Oct พาย นาลแก ( Nalgae) a 28 Sep - 5 Oct

3 July: 2011 km 2 August: 4895 km 2 September: 8402 km 2 October: 13, km 2 November: 14,241 km 2 Source : GISTDA 5 Accumulated 2011 rainfall compared with 30 year average 30 year average 2011 rainfall during rainy season Difference in percentage 6 3

4 Accumulated rainfall during rainy season Monthly rainfall and its accumulated in 2011 May June July August September October 7 Discharge at Nakornsawan (station C.2) compared with 1995, 2002, 2006 and 20 source : daily discharge from RID 8 4

5 Bang Chom See Gate On Sep 14, 2011 overflow at Bang Chom See Gate about 700 cms Picture and data from RID, region 10 9 Upper Central Plain Inflow Bhumipol Dam Sirikit Dam Wang River (station W.4A) Yom River (station Y.16) Rainfall in the area Outflow Nokornsawan (station C.2) 10 5

6 Water Balance 2011 for Upper Chao Phraya Item/location Monthly Discharge (MCM) May June July Aug Sep Oct Accumu. Inflow from Bhumipol Dam , , Sirikit Dam , , , W.4A (Wang River) , , Y.16 (Yom River) , , , , , Total Inflow 1, , , , , , , Rain fall (mm) , Runoff from rainfall , , , , , , Runoff ratio Total inflow 2, , , , , , , Total Outflow (C.2) 2, , , , , , , Net acc water (in-out) , , , , Lower Central Plain Inflow Nakornsawan (Station C.2) Pasak Dam Tap Salao Dam Kra Sio Dam Rainfall in the area Outflow Discharge into Siam Gulf 12 6

7 Water Balance 2011 ( Lower Chao Phraya) Inflow discharge May June July August September October Nov Dec Total Nakornsawan (C2) 2,246 2,899 3,213 5,423 9,362 11,606 2,797-37,545 Tapsalao Dam Krasiew Dam Pasak Dam ,093 1, ,858 Rainfall in the area 789 1,557 2,990 2,988 4,486 3, ,924 Total Inflow 3,119 4,800 6,778 9,012 14,979 16,145 2,864-57,696 Lower Chao Phraya (east) , ,757 Lower Chao Phraya (west) ,799 Chao Phraya River (max) 3,098 4,606 6,036 6,993 7,774 8,018 1,799-38,324 Total Outflow 3,098 4,606 6,036 7,500 9,101 9,674 2,864-42,879 Net acc water (in-out) ,003 2,515 8,393 14,865 17,729-17,729 Remark : In November, Inflow is accumulated until 11 Nov Water volume that was distributed to Eastern and Western field of Lower Chao Phraya basin is not reported in the RID daily flood report during May to July Sources : Rainfall data from RID and TMD Streamflow data from RID Dam outflow data from EGAT Relationship of flood area and net accumulated water Upper Lower Flood Area (sq.km) Net accumulated water (MCM) 14 7

8 อ ตราการไหลรายว นส งส ด ย อนหล งป และป 2549, 2554 ข อม ลจากกรมชลประทาน Flood frequency curve for C.2 Blue dot: daily peak discharge ( , 2006, 2011) at Nakornsawan station Red dot: daily peak discharge ( excluded 2006 and 2011) Plotting position is based on Weibull s formula: p = m/(n+1) 8

9 100 year Floods at C.2 station 100 year floods (cms) ป ท ใช ในการว เคราะห จ านวนข อม ล (ป ) Gumbel distribution log Pearson Type III และ 2549, Haima Hairang Nargae Sirikit Dam Nokten Naesart 18 9

10 Causes Rainfall pattern and volume Water Management for Irrigation Damages of main structures Ineffective flood warning system Unsystematic rescue/communication system 19 Lessons learned Flood prediction system Flood warning system Flood fighting system Facilities maintenance Social and political involvement Self help volunteership 20 10

11 Long Term Plan Upstream plan (Reforestation and reservoir) Midstream plan( flood plain management) Downstream plan ( management of Land use and development, flood way) Administration (organization, compensation regulations, data base, prediction and warning) Social aspect (understanding, acceptance and participation) 21 11

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15 Prevention and Mitigation Principles (for short term planning) Make use of existing structures with the consideration of local lcharacteristics ti in each area Enhance storage and drainage capacity Prevent flood in community and economical zones Supportive measures (if needed) 12/23/2011 คณะท างานโครงสร างพ นฐานระยะเร งด วน-กยน

16 Short term plan Repair the main gates to protect overflow Establish control chart and points (C2 and Bangsai) Drainage capacity alignment and enhancement (dredging, pumping, dyking) Control flood water at C2 (upper area) Utilize storage capacity (middle area) Drainage zoning (lower area : east and west) Flood warning system and single command Sakae Krang River west 490 นา area 0.05 M ha 1.09 m depth. storage 619 MCM. 27 Dec นา Retention area in flood year (as normal) Chaophraya Diversion นา ,800 1,800 1, haya Chainart-Anyth Nakornsawan 250 นา Retention area in flood year (as normal) Monkey cheek 3,000 Siam Gulf 12/23/2011 คณะท างารงสร างพ นฐานระยะเร งด วน-กยน Water Distribution Chart and control volume with present capacity (cms) Rama VI Diversion 210 Monkey cheek east 315 Area 0.08 M ha 1.22 m depth storage 922 MCM Normal Control improve unit: cms 32 16

17 Sakrakrang River 700 West นา area 0.19 M ha 0.5 m depth. storage 978 MCM. area 0.05 M ha 1.5 m depth storage 839 MCM. 27 Dec นา Retention area in flood year (as normal) Chaophraya Diversion 940 นา 4,600 Nakornsawan 2,800 1,800 1, haya Chaihart-Ayuth นา Retention area in flood year (as normal) Monkey Cheek 3,000 Siam Gulf 12/23/2011 คณะท างานโครงสร างพ นฐานระยะเร งด วน-กยน Water Distribution Chart and Control volume for short term planning with 2011 volume Rama VI Diversion Monkey Cheek 210 East 315 Area 0.14 M ha 0.50 m depth storage 695 MCM. area 0.08 M ha 1.5 M depth. storage1128 MCM Normal Control Improve unit: cms 33 Experiences from the past What to do what not to do monitor water level and discharge know your location and nearby canal(s) listen to more than two medias do not be panic do not stay alone 34 17

18 what is next? New organization (single command) New Dam operational rule (45 % in May) Prepared retention area ( 2 M rai) Better water drainage capabilities (dredging and more pumping) Social acceptance talk Emergency waterway and flood way 35 Conclusions Flood 2011 causes Short term mitigation (to reduce flood as 2011) Long term mitigation ( to tackle future flood scenarios) Lessons learned What are next issues? 36 18

19 References Flood 2006 Assessment Report by Chulalongkorn University and Royal Irrigation Department, September 2007 (in Thai). Rainfall data from Thai Meteorology and Royal Irrigation Department River Discharge and Water Level from Royal Irrigation Department Bhimipol and Sirikit Dam data from EGAT Sattlelite Data from GISTDA Flood 2011 Situation, technical report, Faculty of Engineering, Chulalongkorn University, November 2011 (in Thai). SFCWRM, Immediate Term Flood Mitigation Report, Jan, 2012 (in Thai). SFCWRM, Long term Strategy for Flood Prevention and Mitigation in Chao Phraya Basin, Jan 14,