Climate risks and adaptation in Asian coastal megacities: A synthesis

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Table 4.15 ■ Summary of Present Valueof Climate Change Costsin HCMC (USD)Regular Flooding Extreme Flooding TotalLand (linear) 22,658,038,001 6,850,465,427 29,508,503,427Land6,156,082,749 423,561,165 6,579,643,914(quadratic)GDP 49,492,036,285 489,388,337 49,981,424,623Source: ADB (2010). Some differences due to exchange rate variations.1 USD=16302.25to market prices for land) undervalue land in thecity. On this basis alone, had market prices for landvalues been used instead of administratively determinedland prices (which were effectively used), theestimated cost of climate change using land valueswould have been higher than presented earlier.Second, GDP per capita figures at the district levelwere unavailable. This may overestimate the GDPloss across the city as rural districts in the southsuch as Can Gio and Nha Be are responsible forvery little GDP production, and yet which may bemore vulnerable to climate change. Further detailedinvestigations and data collection would be requiredto refine these figures.Box 4.4 ■ Rough Estimate ofViability of Proposed Flood ControlMeasuresHCMC has already proposed to build a system of flood defensesthat will significantly alter the pattern of flooding and the hydrologyof the city. This project has an estimated capital cost of $750million and is expected to be completed by 2025. The effects of theproposed flood control measures on regular flooding would seemto be significant in reducing the population exposed to flooding in2050 from an estimated 10.2 million to 6.7 million, a reduction of 35percent. Based on the GDP method of estimation, the project wouldproportionately decrease damage costs by 35 percent, making thisan economically viable project. However, further economic analysesof this project needs to be carefully undertaken.Source: ADB (2010).Analysis of Adaptation inHCMCUnlike the Bangkok and Manila studies, the HCMCstudy did not undertake a detailed cost benefitanalysis to prioritize adaptation options. Whileit did provide an estimate of the viability of thegovernment’s flood protection project (Box 4.4), themain focus was to identify institutional mandateswith respect to urban planning, flood protection,and adaptation and propose a range of adaptationoptions that need to be undertaken in coordinationwith different sectors.Broadly, adaptation measures in the context ofmanaging floods can be categorized as those thatinvolve (a) protection against predicted climatechange, (b) accommodation to improve resilience,(c) retreat to reduce exposure, and (d) improvedmanagement (see Annex C). 58 For instance, infrastructuralmeasures such as construction of floodembankments, polders, sea walls, and pumpeddrainage are common engineering solutions andare being implemented in all three cities discussedin this report. “Accommodation” measures thatseek to minimize vulnerability include measuressuch as raising houses on stilts, adjusting croppingpatterns, and revising building codes for housingand industry. In some cases, where the risks of lossof life or assets is severe, “retreat” as a planning optioncan reduce exposure to extreme events. Usedin conjunction with restoring natural ecosystemsthat provide flood protection benefits, it can be auseful planning tool. Finally, flooding needs to beconsidered in the context of overall water basinmanagement and the institutional capacity to managethe resource.Developing sector specific adaptationoptions with focus on the poorIn the HCMC study, a combination of these measuresis proposed. Specifically, the study argues fordevelopment of sector specific adaptation optionswith a focus on the poor. For instance, in terms58Drawn from IPCC, AR4, chapter 6, Coastal systems andlow-lying areas, Figure 6.11 Evolution of planned coastaladaptation measures, pg. 342, 2007.72 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
of reducing vulnerability of the poor, the studyrecommends livelihood protection and livelihooddiversification schemes, improved early warningsystems, improved building construction requirements,land use planning and use of open spacefor flood management, zoning controls to ensurethat low income housing is located outside offlood prone zones. HCMC already has a plannedprogram of resettlement away from rivers anddrains and this may require expansion to includevulnerable areas (Can Gio and Nha Be districts)identified by the HCMC analysis. Priority adaptationactions in the transport sector include reviewand revision of design standards for roads, bridges,and embankments so they are consistent with expectedflooding and climate conditions. Further,in light of the findings of the study, new transportinfrastructure needs to be reassessed. Given thatmost industrial zones and clusters in HCMC willbe at direct risk of flooding with or without theproposed flood control plan, a number of adaptationmeasures—such as locating industrial zonesoutside of vulnerable areas and retrofitting existinginfrastructure—are proposed.Combining infrastructure based solutionswith eco-system based adaptation measuresAn important recommendation of the HCMC studyis to combine infrastructure-based solutions withthe use of ecosystem-based adaptation measures,which provide a buffer against climate risks. Themangrove forests to the south of HCMC providesignificant protection against storm surges, but areunder severe pressure due to land use change andencroachment. Natural systems of the Dong NaiRiver basin provide a range of ecosystem servicessuch as regulation of hydrological flows, freshwaterstorage, erosion control, and water purification.These too are under threat due to land use changeand urban development. Adaptation approachessuggested by the study include reforestation ofthe Dong Nai River basin watershed, restorationof wetlands, rehabilitation of canals and rivers,strengthening zoning regulations to protect ecosystemresilience, and planting of buffer zones alongdykes and riverbanks, including dykes proposedby the planned flood control system.Strengthening institutional capacity toadapt to climate related risksThe HCMC study argues that comprehensive adaptationplanning is needed to provide the overallframework and direction for adaptation at the citylevel, in line with national level goals and targets.A key institutional recommendation arising fromthe study is the development of an HCMC ClimateChange Adaptation Plan. The HCMC Peoples Committee(PC), the study argues, can take a proactiveleadership role in this context and in driving climatechange adaptation in the city. Further, there are severalkey agencies that shape overall land use, spatialzoning, environmental quality, and natural disasterresponse management in the city, each of whichcan pursue a range of actions within their sectoraldomain (Table 4.16). Since one sector or area’s planhas implications on activities carried out by othersectors, coordination between different adaptationplans and planning processes is critical.ConclusionGiven the magnitude of climate change costs, adaptationto climate change clearly needs to be a seriousconsideration. As discussed, adaptation investmentsare already under way in all three cities. Eachof the cities will be better protected against climatechange with the flood control measures that areeither already planned or are slowly being implemented.However, additional policy, institutional,and ecosystem-based measures also need to be putin place and prioritized by the city governments.The analysis undertaken in the three casestudies needs to be viewed as an initial attempt atestimating the impacts and damage costs relatedto climate change. As discussed in chapter 2, thereare a number of uncertainties associated with eachlevel of analysis. The climate downscaling and thehydrological models provide results that are by nomeans certain. The economic analysis overlays alarge number of assumptions related to prices, GDP,population distribution, growth, the structure ofcities and so on, over and above these uncertainties.Therefore, they should be viewed as a preliminaryattempt to be followed by improved studies.Assessing Damage Costs and Prioritizing Adaptation Options | 73
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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
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policy implications have broader re
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2Methodologies forDownscaling, Hydr
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Table 2.1 ■ Climate Change Foreca
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Return periods considered 18In this
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Figure 2.2 ■ Manila Rainfall-Runo
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Figure 2.3 ■ Estimation of Damage
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sion and distribution lines, and en
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Figure 2.5 ■ Possible Relationshi
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prices and the same prices are appl
Page 43 and 44: 3Estimating Flood Impactsand Vulner
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Page 49 and 50: Climate Change Impact and Adaptatio
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Page 55 and 56: Table 3.6 ■ Manila Climate Change
Page 57 and 58: Figure 3.10 ■ Areas of High Popul
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Page 61 and 62: Box 3.3 ■ HCMC in 2050Future land
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Page 67 and 68: Table 3.15 ■ Districts Affected b
Page 69 and 70: Table 3.16 ■ Effects of Flooding
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Page 83 and 84: Figure 4.5 ■ Loss Exceedance Curv
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Page 91: 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 113 and 114: AnnexCAdaptation to IncreasedFloodi
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