Weather Extremes

The Great Bangkok Flood

Posted by: Christopher C. Burt, 20:30 GMT le 29 octobre 2011

The Great Bangkok Flood

Bangkok, the capital of Thailand, is currently experiencing what is perhaps the greatest flood ever to swamp a city so large in world history. This dynamic Asian megalopolis has a population of around 10 million within the city limits and a metropolitan population of at least 20 million. The flood is affecting virtually every resident and many have evacuated to provinces outside the flood zones.

The worst of the flood was expected to occur on Saturday October 29th as the river that bisects the city, the Chao Praya, was expected to crest at its highest level ever recorded (some 8 feet above normal) and astronomical high tides were expected to peak, possibly causing the drainage of the cities canals and the Chao Praya to back up and push the flood waters into the heart of the city. Fortunately however, it appears that, so far, the dikes have held and the worst-case scenario is not playing out. This could change at a moments notice.

Here are a series of maps outlining the situation:

Above are two satellite views of the south-central Thailand region with Bangkok near the bottom of both images, just north of the Gulf of Siam into which the Chao Praya River flows. The top image shows a typical end of the rainy season flood situation with the flooded portions showing up in black (photo taken on November 13, 2008). The bottom image shows the same view as of October 25th this year.

This map is an overview of the greater Bangkok metropolitan area (about thirty miles by thirty miles square) and what the various flood risks are by district. The downtown Bangkok area is centered on the east side of the Chao Praya River between Nontha Buri and Bang Na. Map produced by Bangkok Post graphics.

Here is a close up of the central Bangkok area and where the flooding situation stands as of Oct. 29th. The color codes are the same as in the top map but the areas in bright yellow are where the flood has most recently expanded into.

This a ‘worst case scenario’ map illustrating the maximum possible depth of flood waters expected in the greater Bangkok area should the dikes fail. One foot is about 25 centimeters.

As of Saturday, much of the Bangkok is shut down and many residents have left the city.

Historical Perspective

It is likely that this flood will surpass the great flood of 1942 both in terms of depth of floodwaters and certainly in terms of economic costs. In recent times, the worst flood to affect the city was in May of 1986 when 15.79” of rain inundated the city in a 12 hour period on May 10-11th of that year. This, however, was a flash flood and although the water reached 3-5 feet deep in much of the downtown area, the waters receded quickly since it was the first rain of the season. Nevertheless, the disruption to city life was such that the mayor lost his job and a new massive sewage infrastructure project was undertaken, the results of which have to some degree alleviated floods in the city since. The system has never been so challenged as now.

A photo of Sanam Luang Park in front of the Grand Palace in Bangkok during the flood of October 1942. Photo source unknown.

Looking into the future, this photo and caption from the Asian Property Report may best sum it up!

Christopher C. Burt
Weather Historian

Categories: Flood

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1. BaltimoreBrian 02:33 GMT le 31 octobre 2011
Is Bangkok experiencing subsidence like New Orleans? Bangkok is south of the main typhoon belt, which may make them less attentive to sea defenses. I'd be interested to know how river dams and engineered modifications in the rivers to support agriculture have changed how rivers there respond to excessive rainfall. Member Since: 9 août 2011 Posts: 25 Comments: 3345

2. Patrap 03:04 GMT le 31 octobre 2011
Published on Oct 28, 2011 by itnnews Bangkok evacuation as the Chao Phraya river threatens to burst its banks. Report by Anna Drury. Like us on Facebook at http://www.facebook.com/itn and follow us on Twitter at http://twitter.com/itn Member Since: 3 juillet 2005 Posts: 371 Comments: 111503

3. Christopher C. Burt, Weather Historian 03:10 GMT le 31 octobre 2011
Quoting BaltimoreBrian: Is Bangkok experiencing subsidence like New Orleans? Bangkok is south of the main typhoon belt, which may make them less attentive to sea defenses. I'd be interested to know how river dams and engineered modifications in the rivers to support agriculture have changed how rivers there respond to excessive rainfall. Good question. The short answer is yes, Bangkok is subsiding and it's future is certainly in peril. I believe, the city has sunk about 1/2 meter in the past 20 years, but don't quote me on that figure. Perhaps no major city (sorry New Orleans is not a major city) has sunk like Bangkok has. One thing going for them is that it is a very rich city and as such has the resources to build a system of dikes to protect itself or take other measures for its survival. Watch out Dhaka! P.S. No, agriculture is probably not responsible for the subsidence of Bangkok. Construction and consequently population increase is. This city is literally sinking under its own weight and the sucking up of the aquifers that feed its water consumption are literally sucking it underwater. (NOTE: in terms of how agriculture might be playing a role in that, well, perhaps). Excessive rainfall isn't the problem in the long term. The city is sinking and nothing short of a massive levee project will save it from future flood events, whether those are because of tides or rainfall runoff. Member Since: 15 février 2006 Posts: 159 Comments: 161

4. Patrap 03:15 GMT le 31 octobre 2011
(sorry New Orleans is not a major city) Maybe re-think the obvious. New Orleans: A Geopolitical Prize By George Friedman New Orleans is not optional for the United States' commercial infrastructure. It is a terrible place for a city to be located, but exactly the place where a city must exist. With that as a given, a city will return there because the alternatives are too devastating. The harvest is coming, and that means that the port will have to be opened soon. As in Iraq, premiums will be paid to people prepared to endure the hardships of working in New Orleans. But in the end, the city will return because it has to. Geopolitics is the stuff of permanent geographical realities and the way they interact with political life. Geopolitics created New Orleans. Geopolitics caused American presidents to obsess over its safety. And geopolitics will force the city's resurrection, even if it is in the worst imaginable place. Also check the Author and date.. 4 comments and growing. ,but Im not a professional. Good info though,, Bangkok a Fine place. As here. Member Since: 3 juillet 2005 Posts: 371 Comments: 111503

5. Christopher C. Burt, Weather Historian 03:23 GMT le 31 octobre 2011
Quoting Patrap: (sorry New Orleans is not a major city) Maybe re-think the obvious. New Orleans: A Geopolitical Prize By George Friedman Also check the Author and date.. 4 comments and growing. Im not a professional though. Good info though,, Bangkok a Fine place. As here. Sorry if you interpreted what I said as a diss of my favorite city in the world, New Orleans. I just meant to say that a city of ten million doesn't compare in the 'major city' league' as New Orleans with a relatively small population and not a center of global commerce. Member Since: 15 février 2006 Posts: 159 Comments: 161

6. BaltimoreBrian 03:25 GMT le 31 octobre 2011
Thanks for your response Dr. Burt. Subsidence is not good for mega-cities like Bangkok. Hopefully this flood will inspire them to improve their flood defenses for the future. Member Since: 9 août 2011 Posts: 25 Comments: 3345

7. SpaceCoastGhost 12:21 GMT le 02 novembre 2011
Thanks for the info! Member Since: 3 août 2007 Posts: 0 Comments: 4

12. Christopher C. Burt, Weather Historian 18:50 GMT le 03 novembre 2011
Quoting capelookout: ok nola might be dangerous but u didn't have to be so mean about it. very inappropriate. DR. Burt. do you ever see Bangkok's situation improving? By saying "ever" seeing Bangkok's situation improving flood-wise, I suspect you mean in the long term. The city is certainly in a very precarious situation since it is slowly subsiding and the Gulf of Thailand is slowly rising (in the long term as a result of AGW). That combination certainly bodes ill for future flood events. However, the country of Thailand has considerable financial resources to work with in order to mitigate future flooding problems. Ultimately, a sophisticated series of dykes and drainage canals will have to be built to protect the urban heart of Bangkok. However another issue is how to protect the vast industrial estates that surround the city and have born the brunt of the flooding this year. I'm not sure how they can be protected in the future, relocating may be the only solution for them. Member Since: 15 février 2006 Posts: 159 Comments: 161

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About weatherhistorian

Christopher C. Burt is the author of 'Extreme Weather; A Guide and Record Book'. He studied meteorology at the Univ. of Wisconsin-Madison.

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