Climate risks and adaptation in Asian coastal megacities: A synthesis

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RecommendationsCoastal cities in developing countries face enormouschallenges linked with current patternsof population and economic growth, associatedenvironmental externalities, urban expansion andexisting climate variability. Climate change willpose additional risks beyond those currently facingcoastal megacities. As the study shows, these riskswill also be associated with significant costs to localpopulations and infrastructure. Strong political willis thus needed to strengthen the capacity to addressboth existing climate variability and additional risksposed by climate change. Three main lessons standout from the study.Better management of urban environmentand infrastructure will help manage potentialclimate-related impactsAnalysis carried out in the city case studies showthat sound urban environmental management isalso good for climate adaptation. As the Bangkokstudy shows, land subsidence, if not arrested, wouldcontribute a greater share of damage costs fromfloods than a projected change in climate conditions.Thus, addressing land subsidence and factors contributingto it is important from the perspective ofurban adaptation. While the HCMC study has notestimated the damage costs due to other environment-developmentfactors—such as the presence ofsolid waste in the city’s drains and waterways, poordredging of canals, siltation of drains, deforestationin the upper watershed—it provides extensivequalitative evidence to demonstrate the role thesefactors play in contributing to urban flooding.Collectively, the studies highlight the importanceof addressing existing environment-developmentfactors as a critical part of urban adaptation. Theyalso show that given the high risks of continuingto urbanize according to current patterns, muchmore effort should be given to considering theenvironmental implications of urban growth andexpansion in the context of managing current andfuture climate risks.Climate-related risks should be considered asan integral part of city and regional planningWhile improved urban environmental managementis important, the studies also show that given theadditional costs linked with climate change, citiesneed to make a proactive effort to consider climaterelatedrisks as an integral part of urban planningand to do so now. First, city planners need to developstrategic urban adaptation frameworks formanaging climate risks involving a range of toolssuch as policy and regulatory reforms, investments,and capacity building. Such a strategy can providean overarching framework for actions taken withineach sector at the regional, delta, and city levels.Second, much more emphasis needs to be given toimproving the knowledge base regarding climaterisks and related socioeconomic and developmentfactors. Developing and updating scenarios andplanning for a range of potential outcomes will becritical for urban planners. This can be accomplishedby strengthening the collaboration between planningand sector agencies and research institutions,thus giving municipal agencies the tools to makedecisions regarding risk management over the longterm (Rosenzweig et al. 2007) Third, it is importantto strengthen the capacity of local urban governmentalinstitutions to adapt to climate change.Among other things, this involves strengthening thecapacity to prioritize different adaptation options,improving coordination between various urbansector agencies and sector plans, and incorporatingclimate change considerations into the earlieststages of decision making.Targeted, city-specific solutions combininginfrastructure investments, zoning, andecosystem-based strategies are requiredGiven that cities are characterized by distinct climatic,hydrological, and socioeconomic features—but also that the urban poor in general are morevulnerable to increased flooding due to climatechange—targeted, city-specific, and cutting edgeapproaches to urban adaptation are needed. First,xvi | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
these include strategies that focus on the morevulnerable areas of the city and the urban poor.Second, as the studies show, hard infrastructureinterventions can also be usefully combined withecosystem-based solutions. For instance, constructionof dykes can be matched with managementand rehabilitation of mangrove systems, reforestationof upper watersheds, river and canal bankprotection, and implementation of basin-wide flowmanagement strategies. Urban wetlands providea range of services, including flood resilience, allowinggroundwater recharge and infiltration, andproviding a buffer against fluctuations in sea leveland storm surges. Thus, rehabilitation of urbanwetlands is critical. Third, as the city case studiesshow, while a combination of climate-related factorscan contribute to urban flooding, some factors aremuch more important than others in different citiesdepending on location, elevation, and topographyof the city. For instance, in HCMC, storm surgesand sea level rise are important factors contributingto flooding. However, in Bangkok these factors arerelatively less important. The policy implication isthat adaptation measures need to be designed basedon the specific hydrological and climate characteristicsof each city. Fourth, damages to buildingsemerge as a dominant component of flood-relatedcosts, at least in Bangkok and Manila. Vulnerabilitymapping, land use planning and zoning could beused to restrict future development in hazardouslocations, ultimately retiring key infrastructureand vulnerable buildings in these areas. Similarly,building codes aimed at flood-proofing buildings(including the lowest habitable elevation in vulnerableareas) could dramatically reduce damage costs.Such targeted measures could go a long way inhelping coastal megacities to adapt to current andfuture climate risks.Executive Summary| xvii
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: infrastructure but a high emission
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
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Table 3.16 ■ Effects of Flooding
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4Assessing Damage Costsand Prioriti
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Table 4.2 ■ Summary of Flood and
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uilt outside the cities and are not
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■■■■■■For the eastern p
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Table 4.6 ■ Flood Damage Costs Wi
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Table 4.8 ■ Flood Damage Costs in
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Figure 4.5 ■ Loss Exceedance Curv
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Box 4.3 ■ Increased Time Costs an
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Table 4.11 ■ Adaptation Investmen
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Marikina River areas through a dam,
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Table 4.14 ■ Present Value of the
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of reducing vulnerability of the po
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5Conclusions andPolicy Implications
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open land use is expected to be flo
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hydrometeorological data, yielding
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BibliographyAllen, M. R., and W. J.
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Reduction: Inventory and Prospect.
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a paper commissioned by JICA (Sugiy
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mercial and industrial establishmen
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ADB. The selection and prioritizati
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AnnexCAdaptation to IncreasedFloodi
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of people and institutions to manag
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THE WORLD BANK1818 H Street, NWWash
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Climate risks and adaptation in Asian coastal megacities: A synthesis

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