Chanchai Vitoolpanyakij Director Department of Drainage and Sewerage Bangkok Metropolitan Administration Coastal Cities and Adaptation to Climate Change: Bangkok Study

Climate forcing on Bangkok Temperature changes Rainfall changes (local & upper catchment) Sea level rise Altered frequency of extreme events (storm surge) Compounding factors –Flat topography –Land subsidence

Local and global temperature vertical axis – Bangkok mean temperature change horizontal axis - global mean temperature change SERS (Special Report on Emissions Scenarios) Red - A1B, blue - B1 solid black line - least-square fit to all data points There is a robust linear relationship between local temperature increase and global mean temperature increase Source: Study on Climate Impact Adaptation and Mitigation in Asian coastal mega cities: Interim Report, JBIC, 2008

Local temperature trends Annual mean ( ) minimum and maximum temperatures in Bangkok is rising Overall, Thailand’s temperature rise show similar trend during the same period

Sea level rise Sea level rise (Increased coastal erosion, inundation of coastal wetlands, Increased risk of flooding and storm damage) Upper Gulf of Thailand (includes Bangkok) - most vulnerable to sea-level rise in Thailand Source: Tidal record analysis by the consultant. Yearly averaged values are shown here

Extreme events Storm surges and typhoons are not uncommon Most recent - typhoon LINDA (1997) –caused strong winds and heavy rainfall –significant wave height of 3-4 m was measured Altered frequency of extreme weather events (Increased waves and surges, Altered cyclone zones) MaeKlo ng Thac hin Chao Phraya Bangp akong Storm surge

A gloomy future! IPCC SERS (Special Report on Emissions Scenarios) Case Source: Study on Climate Impact Adaptation and Mitigation in Asian coastal mega cities: Interim Report, JBIC, 2008 Strom surge: 61 cm SERS caseTemperature change ( 0 C) Rainfall change (%) Sea level rise (cm) A1 FI B

Altered flood risks.. Floods due to altered extreme precipitation from the upstream, and in the Bangkok area and tide are crucial for Bangkok

Future floods Max depth (30-yr return period) 2008 condition Max depth (30-yr return period) 2050 A1FI + Sea level rise + Land subsidence + Storm surge condition

Structural measures (1995 to present) Dike along both sides of the Chao Phraya River King’s Dike to protect BMA east side Dike to protect BMA west side Dike to protect BMA east side expansion (under construction) Dike to protect Suwanaphum International Airport Improve Pumping System to m.MSL m.MSL Bangkok Existing and planned flood protection systems will not have enough capacity to cope with the climate change of A1FI scenario at the return period higher than 10 years

Structural measures – earlier proposal Large storage dam in the upper basin Barrage at the river mouth Diversion channel Coastal erosion protection – the shoreline on the west of the Chao Phraya River has been eroded about 5 to 10 m per year

Dikes, pumps, and drainage canal improvement Dike crest elevations in the future – include land subsidence of 0.20 m and free board of 0.30 m Three new pumping stations at Klong Khun Rat Phinit Chai, Phasi Charoen and Sanam Chai (capacities of 100, 400 and 200 m3/sec for flood at 30-year return period) Improvement of drainage canals Structural measures – current proposal

Maximum future inundation Inundated area - reduced from to km2 or decreased 382 km2 or 51.35%. Without proposed structural adaptation With proposed structural adaptation

Pursue shoreline protection of the western area of the Chao Phraya River (along the shoreline of Bang Khun Thien) as proposed by BMA (2007) Shoreline of the eastern area of the Chao Phraya River, raise the crest of the proposed rock-pile embankments along all the length of the embankments. The total estimated costs are 35,228 million baht to protect the against a 30-yr return period flood of the future Non structural measures (next presentation) Coastal erosion protection – current proposal

Thank you