Climate risks and adaptation in Asian coastal megacities: A synthesis

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Importance of BMR to the regionaleconomyThe Bangkok Metropolitan Region (BMR) is theeconomic center of Thailand. It is the headquartersfor all of Thailand’s large commercial banks andfinancial institutions. The area to the east of Bangkokand Samut Prakarn is also an important industrialzone. In 2006, the gross domestic product (GDP) ofthe Bangkok Municipal Region was 3,352 billionbaht, or 43 percent of the country’s GDP (7,830 billionbaht). The annual average growth rate was 7.04 percent,and per capita GDP was 311,225 baht (Bangkokcase study report). The current official population ofBangkok is estimated to be about 10 million people(based on 2007 estimates) with an estimated growthrate of .64 percent between 2003–07. 30Nature of urban povertyAs stated in the Bangkok study, in 2007, 0.6 percentor 88,361 people in the BMR were poor (Table 3.1).The poverty line for the Bangkok municipal regionwas 1,638 baht ($49) per person per month in 2007. 31The number of poor is an official estimate and doesnot include unregistered people. Most of the poorlive in condensed housing and are unregistered.Statistics from the Office of National Economic andSocial Development Board (NESDB 2007) show768,220 people living in 133,317 housing units ofthe condensed housing area. Therefore in the assessmentof flood impacts on the poor, this housingunit and population was used as a base for the assessmentof income loss of the poor.Climate and precipitation in the ChaoPhraya River BasinBangkok has a tropical monsoon climate. The averageannual rainfall over the basin is 1,130 mm, and ishigher in the northeastern region of the basin (Table3.2). About 85 percent of the average annual rainfalloccurs between May and October (Panya Consultants2009). Tropical cyclones occur between Septemberand October. In this case, rainfall continuesfor a long period of time in a relatively wide area.The peak river discharge is registered in October atthe end of the rainy season. Severe flood damagemay arise with high tide in this period (ibid.). BMA’smaximum temperature is in April and its minimumtemperature is in December. The mean temperatureranges from 26 ° C to 31 ° C.Main climate-related drivers of floodingSevere flooding in Bangkok is associated withheavier than normal rainfall occurring over several30This figure does not include unregistered migrants.31Poverty incidence is measured at the household level bycomparing per capita household income against the povertyline, which is the income level that is sufficient for anindividual to enjoy society’s minimum standards of living.If an individual’s income falls below the poverty line, he orshe is classified as poor.Table 3.1 ■ Poverty Line and the Poor in the BMR 1Poverty Line (Baht/person/month) Proportion of the Poor (%) No. of the Poor (person)Province2006 2007 2006 2007 2006 2007BMA 2,020 2,065 0.51 1.14 28,692 64,422Samut Prakarn 1,647 1,712 — 0.78 — 9,961Samut Sakhon 1,511 1,564 0.76 0.42 4,313 2,436Nonthaburi 1,529 1,561 0.30 0.06 4,124 845Pathum Thani 1,409 1,458 0.56 0.20 5,376 1,939Nakhon Pathom 1,434 1,466 0.45 0.98 3,918 8,758BMR 1,592 1,638 0.43 0.60 46,422 88,361Source: The Office of National Economic and Social Development Board (NESDB), 2007 as cited in the Bangkok city study.1Most of the poor live in condensed housing and are unregistered. So the figure of 768,220 does not align with the number of poor in the table.24 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
Table 3.2 ■ Bangkok Monthly Average Temperature and PrecipitationMonth Temperature Average Low ( o C) Temperature Average High ( o C) Average precipitation (mm)January 23° 32° 7.2February 24° 33° 13.7March 26° 34° 32.5April 27° 35° 58.3May 27° 34° 170.8June 26° 33° 112.5July 26° 33° 118.1August 26° 33° 160.0September 25° 33° 262.5October 25° 32° 207.3November 24° 32° 32.4December 22° 32° 3.3Total 1,171.4Source: http://weather.uk.msn.com/monthly_averages.aspx?wealocations=wc:THXX0002months during the monsoon period over the ChaoPhraya watershed. The flooding can last severalweeks to over a month. Intense short-duration rainfallover the city can cause localized flooding thatnormally lasts for less than 24 hours. Bangkok isnot subject to direct hits from tropical typhoons orcyclones. Large floods have occurred in 1942, 1978,1980, 1983, 1995, 1996, 2002, and 2006. A numberof dams in the upper watershed—including theBhumibol Dam (1964) and Sirikit Dam (1971)—havehelped reduce flooding in Bangkok. In 1995 a seriousflood occurred due to a series of tropical stormsreaching the upper watershed from the end of Julyto September. The resultant runoff exceeded the storagecapacity of the Sirikit Dam, which had to release2,900 million m 3 of storm runoff. Despite efforts toattenuate the flood wave by allowing flooding ofagriculture lands upstream of Bangkok, the floodwave crest reached Bangkok at the same time as thehigh spring tide, flooding 65 percent of BMA withinundation depths up to 2 meters and left some areasflooded into December. The flood event of 1995 isestimated to have a return frequency of 1-in-30 years.Non-climate drivers of floodingIn addition to climate-related drivers, non-climatedrivers such as land subsidence, deforestation,urbanization, and removal of natural attenuationbasins (like wetlands) also contribute to flooding.Land subsidence is a critical factor in flooding andis discussed later in the section.Existing flood protection in Bangkok—diversion canals and flood dikes withpumped drainageIn response to the flooding, Bangkok has implementeda large-scale flood protection system thatincludes a flood embankment surrounding thecity and a pumped drainage system. In 2006 therewas another significant flood event in the upperChao Phraya watershed. Flood peaks were againattenuated by allowing the agricultural lands northof Bangkok to flood, and flood flows were also divertedto channels to the east of Bangkok. The floodembankment system and pumped drainage systemprotected the city. Nevertheless, areas surroundingBangkok continue to experience inundation duringpeak flood flow. The city and national plannershave plans to add further flood protection, whichhas been planned and budgeted through 2014. Thelong-term land use plan until 2057 for the greaterBangkok region provides for development areasand environmental zones that will be used to allowflood flows and drainage. Most of the flood controlEstimating Flood Impacts and Vulnerabilities in Coastal Cities | 25
Page 4 and 5: © 2010 The International Bank for
Page 7 and 8: Figure 4.6 Damage Costs Associated
Page 9: AcknowledgmentsThis synthesis repor
Page 13 and 14: Executive SummaryIntroduction and R
Page 15 and 16: For each city, complex hydrometeoro
Page 17 and 18: infrastructure but a high emission
Page 19: these include strategies that focus
Page 23 and 24: policy implications have broader re
Page 25: 2Methodologies forDownscaling, Hydr
Page 28 and 29: Table 2.1 ■ Climate Change Foreca
Page 30 and 31: Return periods considered 18In this
Page 32 and 33: Figure 2.2 ■ Manila Rainfall-Runo
Page 34 and 35: Figure 2.3 ■ Estimation of Damage
Page 36 and 37: sion and distribution lines, and en
Page 38 and 39: Figure 2.5 ■ Possible Relationshi
Page 40 and 41: prices and the same prices are appl
Page 43: 3Estimating Flood Impactsand Vulner
Page 47 and 48: Estimation of storm surge in the ca
Page 49 and 50: Climate Change Impact and Adaptatio
Page 51 and 52: Figure 3.5a ■ Affected Condensed
Page 53 and 54: Manila’s current climate—Tropic
Page 55 and 56: Table 3.6 ■ Manila Climate Change
Page 57 and 58: Figure 3.10 ■ Areas of High Popul
Page 59 and 60: is also a key economic and financia
Page 61 and 62: Box 3.3 ■ HCMC in 2050Future land
Page 63 and 64: original swamp land on which the ci
Page 65 and 66: from 68 percent to 71 percent; that
Page 67 and 68: Table 3.15 ■ Districts Affected b
Page 69 and 70: Table 3.16 ■ Effects of Flooding
Page 71 and 72: 4Assessing Damage Costsand Prioriti
Page 73 and 74: Table 4.2 ■ Summary of Flood and
Page 75 and 76: uilt outside the cities and are not
Page 77 and 78: ■■■■■■For the eastern p
Page 79 and 80: Table 4.6 ■ Flood Damage Costs Wi
Page 81 and 82: Table 4.8 ■ Flood Damage Costs in
Page 83 and 84: Figure 4.5 ■ Loss Exceedance Curv
Page 85 and 86: Box 4.3 ■ Increased Time Costs an
Page 87 and 88: Table 4.11 ■ Adaptation Investmen
Page 89 and 90: Marikina River areas through a dam,
Page 91 and 92: Table 4.14 ■ Present Value of the
Page 93 and 94: of reducing vulnerability of the po
Page 95 and 96:
5Conclusions andPolicy Implications
Page 97 and 98:
open land use is expected to be flo
Page 99 and 100:
hydrometeorological data, yielding
Page 101 and 102:
BibliographyAllen, M. R., and W. J.
Page 103:
Reduction: Inventory and Prospect.
Page 106 and 107:
a paper commissioned by JICA (Sugiy
Page 108 and 109:
mercial and industrial establishmen
Page 110 and 111:
ADB. The selection and prioritizati
Page 113 and 114:
AnnexCAdaptation to IncreasedFloodi
Page 115:
of people and institutions to manag
Page 120:
THE WORLD BANK1818 H Street, NWWash
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Climate risks and adaptation in Asian coastal megacities: A synthesis

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