Climate risks and adaptation in Asian coastal megacities: A synthesis

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Damage costs in 2050 are largelyattributable to land subsidenceLand subsidence as a result of groundwater utilizationis a major problem in Bangkok. While there isreason to worry about climate change, the impactsof land subsidence are even bigger. For example,if we look at the impacts of a 1-in-30-year flood inTable 4.2, with current (2008) climate conditions, thecosts are about THB 35 billion ($1 billion). However,this increases to THB 99 billion ($3 billion) in 2050,just from expected land subsidence (2050-LS). Thus,there is a nearly two-fold (181 percent) increase inflooding costs between 2050 and 2008 as a result ofland subsidence.If we add climate change to this projectedchange in land subsidence and estimate damagecosts in the context of a 2050-LS-SR-SS-A1FI scenario,the costs of a 1-in-30-year flood are THB 148billion ($4.5 billion). Climate change results in afurther 49 percent increase in flood damage costsin 2050 (relative to 2050-LS). However, the bulk ofthe increase (67 percent) in flooding costs in 2050is attributable to land subsidence. Thus, in order toreduce the costs of flooding in 2050, a top priority shouldbe policies to reduce land subsidence.Damage costs vary by sectors, with morethan 75 percent of the costs attributable tobuildingsDamage to buildings dominates flood-related costsin Bangkok. In the context of a 1-in-30-year flood,in each of the five climate and land scenarios consideredfor Bangkok, 76–77 percent of total damagecosts are attributable to damage to buildings. AsTable 4.2 shows, in 2008, a 1-in-30-year flood couldcause building damages to the extent of THB 27 billion($800 million) in Bangkok. A similar 1-in-30-yearflood could cost up to THB 75 billion ($2.3 billion) in2050 after taking into account land subsidence andeconomic development. If we add climate changeimpacts, the damage costs further increase by 51percent to THB 110 billion ($3.4 billion). 47 There is asteep increase in building costs between 2008 and2050 (177 percent) simply because of land subsidence(Table 4.2). The increase in damages from climatechange is also significant, but less steep.Damage costs to transport are likely to belimitedThe Bangkok study examined different types of infrastructureand sought to understand the impact offloods on public investments. In general, new publicinfrastructure in Bangkok has taken the possibilityof flooding into account. For example, because ofthe height at which highways and the metro rail arebuilt, transportation will generally be unaffected byflooding. This does not mean that small streets inBangkok will not be flooded, but the economic coststo transport infrastructure is expected to be limited.The Bangkok study was unable to estimate the trafficdelay costs associated with flooding, and thereforethis potentially important cost is not included.There are unlikely to be direct water and sanitationinfrastructure-related costs because of theirlocation at higher than flood levels. However, thereare likely to be revenue losses to water and sanitationagencies if flood waters rise above 2 meters.Under these conditions water supply may becomedysfunctional and the agencies will likely incur revenuelosses. 48 The revenue loss to water supply andsanitation utilities is expected to more than doubleto THB 13 million ($390, 235) in 2050, given climatechange (A1FI), sea level rise, storm surge, and landsubsidence. However, the bulk of this increase incosts is attributable to land subsidence.If flooding is higher than 1 meter, the MetropolitanElectricity Authority will lose revenues tothe extent of THB 1.1 billion ($33 million) in 2050(A1FI-SL-SR-SS-T30). The damages with climatechange are twice the damages that are likely to occurin a no-climate-change scenario (2050-LS-T30).However, infrastructural damages are limited becauseenergy to Bangkok is supplied by two powerplants that are either being retired or will be retiredby 2050. Future infrastructure is expected to be47These values are all in 2008 THB and reflect simply thephysical changes that would be wrought as a result of climatechange, economic development, and land subsidence.48The average losses are calculated by multiplying watercharges by the average water used per day and scaling thisup for the duration of floods and number people affected ifflood waters were higher than 2 meters. Similarly, sanitationcosts = No. of affected people x waste generation (solid andliquid) per capita per day x treatment cost x flood duration54 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
uilt outside the cities and are not expected to beimpacted by floods.The Bangkok study estimates that health carecosts could double with climate change (Table 4.2).The costs from a 1-in-30-year flood could be aboutTHB 2 billion ($60 million) in 2050 with climatechange (2050-LS-SS-SR-A1FI), sea level rise, stormsurge, and land subsidence. This is about twicethe cost that would occur in 2050 without climatechange and only land subsidence (2050-LS). Thisincrease in health costs is primarily triggered bythe larger number of people likely to be affectedby floods.Daily wage earners will see significantincreases in income lossesClimate change will affect the population of workersliving in condensed housing areas and deliversignificant income losses to daily wage earners. AsTable 4.3 shows, losses to daily wage earners arelikely to increase by 25 percent when we consideran A1FI climate change scenario (2050-LS-SR-SS-A1FI-T30) in 2050 relative to a scenario where thereis only land subsidence (2050-LS-T30).Table 4.3 ■ Changes in Income Lossesto Wage Earners,Commerce, and IndustryChanges in income losses* from extreme weather (1/30 flood)under different scenarios2050-LS-SR-SS-Scenarios 2008-T30 2050-LS-T30 (%) A1FI-T30 (%)Daily wage— 11 25earnerCommerce — 266 45Industry — 168 38*Each column represents the percentage change in income relative to the previouscolumn.However, as expected, the overall cost to lowincomeworkers is very small relative to the estimatedcosts to industry and commerce (Table 4.2).Commercial income losses come second only tobuilding damages as a source of losses from floods.For instance, in the case of a 1-in-30 -year flood in aclimate change scenario (2050-LS-SR-SS- A1FI-T30),income losses to commerce are estimated at 21 billionTHB ($630 million).Box 4.1 ■ Examining Building Damages, Income Losses, and Health Costs inBangkokIn order to estimate the damage to buildings, the Bangkok study developed GIS maps of areas likely to be flooded. Different categories of buildingslikely to be impacted—identified using National Housing Authority data (2004)—were overlaid on these maps. Of particular concern was condensedhousing, which refers to clusters of more than 15 houses in an area of 1 rai. These areas, where poverty is high, were separately identified.To value buildings, the Bangkok case study identified the book value of buildings of different types and then depreciated these values. Damagecosts were assessed as a percentage of total value based on the extent and duration of floods. Added to this was the value of assets that may bedamaged. Average asset values associated with residential buildings (obtained from census data) are THB 328,889 for Bangkok and THB 220,180 forSamut Prakarn. Building damages were estimated separately for residential, commercial, and industrial buildings.With extreme precipitation and flooding, income losses can be incurred in flooded and non-flooded areas. The Bangkok study estimated threetypes of income losses in flooded areas: (a) business income loss, (b) industrial income loss, and (c) losses to daily wage earners.To obtain business losses, the Bangkok study first identified the average income per day from commercial establishments based on businesssurveys. This was then adjusted to reduce operational expenses. The average net commercial income was estimated to be THB 4,930 per establishmentper day. A similar accounting was used to estimate average income to industrial establishments. These average values are multiplied by the number ofdays of flooding and the number of buildings affected by floods to estimate income losses from commerce and industry. Income losses to daily wageearners living in condensed housing areas were estimated based on the population in these areas affected by floods of different intensity.Disease outbreaks in the form of diarrhea, cholera, typhoid, and other diseases are possible during times of flood, depending on the durationand nature of the areas affected. But few estimates are available of the likelihood of these outbreaks and what populations may be affected. In theabsence of disease and cost information, the average cost of hospitalization in Bangkok and Samut Prakhan was used as a proxy for public healthcosts. These costs, which are THB 7,582 and THB 3,756 per person per admission in the two regions respectively, were multiplied by 50 percent of theaffected population to get health damages.Assessing Damage Costs and Prioritizing Adaptation Options | 55
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© 2010 The International Bank for
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Figure 4.6 Damage Costs Associated
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AcknowledgmentsThis synthesis repor
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Executive SummaryIntroduction and R
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For each city, complex hydrometeoro
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infrastructure but a high emission
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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 and 44: 3Estimating Flood Impactsand Vulner
Page 45 and 46: Table 3.2 ■ Bangkok Monthly Avera
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: Table 4.2 ■ Summary of Flood and
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
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Page 95 and 96: 5Conclusions andPolicy Implications
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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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