Climate risks and adaptation in Asian coastal megacities: A synthesis

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Potential increase in drought in 2050 underlow emission scenarioAn initial analysis of the data collected for thestudy shows that “the frequency of dry seasondrought in 2050 is likely to increase by the order of10 percent under the low-emission scenario withlittle change under high-emission scenario” (ADB2010). Further, the incidence of drought is likely toFigure 3.17 ■ HCMC Droughts andSalinity Intrusion in2050Source: ADB (2010).increase under the low-emission scenario in both thedry and the wet season. These assessments requiremore in-depth analysis. However, they do providean indication of the order of magnitude of changeand illustrate which scenarios are more susceptibleto drought.ConclusionTo sum up, all three megacities face considerableclimate-related risks in terms of changes in temperatureand precipitation. These climate risksare compounded by risks posed by non-climatefactors (such as land subsidence, poor drainage,and deforestation in upper watersheds), thus increasingthe likelihood of urban flooding. Underdifferent scenarios, in all three cities, there is likelyto be an increase in the area exposed to floodingand an increase in the percentage of populationaffected by extreme events. Given that all threecities are megacities with high population growthrates, the results warrant serious consideration.Despite data limitations, it is apparent that bothclimate and non-climate factors are important andneed to be considered in future adaptation efforts.While flood protection infrastructures are eitherin place or planned, the analysis shows that in allthree megacities, while these are likely to reducethe impact of flooding, they are not sufficient toprovide the expected level of protection from futureclimate events.50 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
4Assessing Damage Costsand Prioritizing AdaptationOptionsChapter 3 described the scale of physicalimpacts in terms of area, population, andsectors that are likely to be affected underdifferent climate and infrastructure scenarios inthe coastal cities. In this chapter, we discuss (a) thenature of the damages and monetary costs borneas a result of these physical changes, and (b) adaptationoptions considered by the city studies. Theoverall approach to estimating costs was discussedin chapter 2 and is further elaborated in this chapter.Bangkok: Analysis of DamageCosts Related to Floodingin 2008 and 2050In Bangkok, climate-change-induced flooding willlikely result in physical damages to buildings andhousing, income losses to individuals and firms,revenue losses to public utilities, and might alsoadversely affect public health. In estimating costs,the Bangkok study examines direct and indirecttangible damages (Table 4.1) associated with potentialfloods under 16 scenarios. Damage costs areevaluated for the base year of 2008 and for 2050. Aspreviously described, the scenarios include threeclimate change scenarios (current climate, B1 andA1FI), three levels of flood intensity (1-in-10 year,1-in-30 year, and 1-in-100 year) and additional scenariosthat include land subsidence, sea-level rise,and storm surge. Estimates for area, depth, and durationof flooding derived from the hydrological analysis wereTable 4.1 ■ Summary of DamagesAssessed in the BangkokStudyDamage Type Sector Damage MechanismDirectResidential units Damage to buildings and assetsDamagesCommercial units Damage to buildings and assetsIndustrial units Damage to buildings and assetsIndirectDamagesTransportation,public health, energy,water supplyand sanitationPopulationCommercial unitsIndustrial unitsTransportationPublic healthEnergyWater supply andsanitationSource: Panya Consultants (2009).No direct damage to theseinfrastructures expected in thefutureLoss of incomeLoss of incomeLoss of incomeLoss of revenue (negligible)Additional costs of medical careLoss of net revenueLoss of net revenuekey inputs for the damage cost assessment. In addition,the damage cost assessment makes numerous assumptionsregarding prices, population growth,GDP, and the location of major infrastructure such asroads, electric utilities and so on related to Bangkokin 2050, as discussed in chapter 2. While assessingdamage costs, prices are held constant in real terms51
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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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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
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Page 43 and 44: 3Estimating Flood Impactsand Vulner
Page 45 and 46: Table 3.2 ■ Bangkok Monthly Avera
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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: Table 3.16 ■ Effects of Flooding
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
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Page 91 and 92: Table 4.14 ■ Present Value of the
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Page 101 and 102: BibliographyAllen, M. R., and W. J.
Page 103: Reduction: Inventory and Prospect.
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Page 108 and 109: mercial and industrial establishmen
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Page 113 and 114: AnnexCAdaptation to IncreasedFloodi
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