Thailand's flood gradually subsiding; climate change increasing Thai flood risk

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1987

Posted by: JeffMasters, 2:56 PM GMT on November 14, 2011

Unprecedented flood waters continue to besiege Thailand and its capital city of Bangkok this November. Heavy monsoon and tropical cyclone rains from July through October, enhanced by La Niña conditions, have led to extreme flooding that has killed 506 people and caused that nation's most expensive natural disaster in history, with a cost now estimated at $9.8 billion by re-insurance company AON Benfield. Thailand's previous most expensive natural disaster was the $1.3 billion price tag of the November 27, 1993 flood, according to the Centre for Research on the Epidemiology of Disasters (CRED). The floodwaters this year have hit 83% of Thailand's provinces, affected 9.8 million people, and damaged approximately 25% of the nation's rice crop. Thailand is the world's largest exporter of rice, accounting for 30% of the global total, and the flood has helped trigger an increase in world rice prices in recent months. Fortunately, the Food and Agriculture Organization of the U.N. reports that overall global food prices have been steadily falling since June, thanks in part to increases in wheat and corn production elsewhere in the world. Food prices had reached their highest levels since the late 1970s early in 2011.

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Forecast for the remainder of the 21st century: more mega-floods for Bangkok
Bangkok lies in the Chao Phraya River basin, which covers about 35% of the country, and has an average elevation just 1 - 2 meters above sea level. Obviously, sea level rise, which averaged 7 inches world-wide during the 20th century, and is predicted to be at least that high during the 21st century, is a huge concern for Thailand. Loss of land due to a sea-level rise of .5 m and 1.0 m could decrease national GDP by 0.36% and 0.69% (US$300 to 600 million) per year, respectively (Ohno, 2001). Higher sea levels also block the flow of flood waters out of the Chao Phraya River, backing up these waters into the city, putting stress on levees and raising flood heights. Another major concern of climate change is the increase in rainfall expected in a warmer world. A 2010 study by the World Bank found that a global temperature rise of 1.2 - 1.9°C would likely increase precipitation over Thailand by 2 - 3%. This extra rainfall, when combined with predicted levels of sea level rise and land subsidence due to groundwater pumping, would likely make a 1-in-50 year flood occur once every fifteen years by the end of the century. Since the flood control system in Bangkok is "generally designed to protect against 1-in-30-year floods", the report concluded that "people living in Bangkok will be facing more frequent events that significantly disrupt daily life." This study assumed that sea level rise by 2100 would be what the IPCC predicted in 2007: 0.6 - 1.9 feet. A number of studies published since that report are predicting much higher levels of sea level increase: 3 - 6 feet (1 - 2 meters) by 2100. If these higher sea level rise estimates prove correct, mega-floods like the 2011 flood will occur several times per decade in Bangkok by the end of the century--unless the Thais can engineer a massive sea wall to keep the ocean at bay.

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