Chanchai VitoolpanyakijDirector
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
(1961-2007) 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
ThaChin
Chao Phraya
Mae Klong
Ranong
Krabi
Bang Pakong
Chan Thaburi
Si Chon
Narathivat
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)
-2
-1
0
1
2
3
0 100 200 300 400 500 600 700 800
Hours
Wter
level(
msl)
MaeKlong
Thachin
Chao Phraya
Bangpakong
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 case Temperature change
(0C)
Rainfall change
(%)
Sea level rise (cm)
A1 FI 1.9 3 29
B1 1.2 2 19
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 sideexpansion (under construction)
Dike to protect SuwanaphumInternational Airport
Improve Pumping System
+2.50 to +3.00 m.MSL
+3.60 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 744.34 to 362.14 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
