Climate risks and adaptation in Asian coastal megacities: A synthesis

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aising dikes, and improved pumping capacity thatwould reduce and/or eliminate the impacts of floods.Manila targets adaptation options thatwould almost eliminate floods in the Pasig-Marikina River basinSeveral structural measures are examined in orderto analyze the economic implications of these investments.The Manila study focused on analyzingadaptation options that could eliminate floods to theextent possible. 53 These include:■■■■Pasig-Marikina River: In this area, in order toprevent overbanking and flooding from theriver, investments in raising the embankmentare considered. Embankment raising is consideredboth with the possibility of buildingthe Marikina Dam and without. The MarikinaDam was initially proposed as part of the 1990master plan and would be able to prevent a1-in-100-year flood.West of Mangahan and KAMANAVA area: Inthese areas, improved pumping capacity andstorm surge barriers are required to reducefloods. The investment required for installingpump capacity to control flooding under anallowable inundation depth of 30 cm is considered.For preventing overflows from Manila Baycaused by typhoons, the study looks at optionsfor increasing the height of storm surge barriersin coastal areas.The Manila study examines adaptation optionsamong a number of different scenarios involvingdifferent types of construction in different areas. Table4. 11 identifies the options that were consideredunder each scenario. Notably, while the Bangkokstudy looks at adaptation only in the context of anA1FI scenario, the Manila case study looks at adaptationoptions in the context of no-climate-change(SQ), B1 and A1FI scenarios. The Manila study alsoexplores scenarios in which a major investment inconstructing the Marikina dam is undertaken (wD)and cases where the dam is not constructed (nD).The costs of adaptation are also considered in thecontext of whether the existing master plan (MP) isimplemented or not (EX).Table 4.12 presents the estimated initial costs ofeach adaptation option considered. 54 In this analysis,the construction period considered is 5 years startingfrom 2010 and the project’s life is expected tolast until 2060. Investments after the completion ofthe master plan are assumed to start from 2014. Nomaintenance cost was included.The incremental benefits of moving fromthe current situation to full adaptation andfrom implementing the master plan andthen moving to full adaptation consideredThe investment costs (assumed to occur over a5-year period) are compared with the incrementalexpected annual benefits from flood reduction associatedwith a 1-in-10-year, 1-in-30-year, and 1-in-100-year flood protection projects. The incrementalbenefits emerge from adaptation investments thatwould take Metro Manila from its:■■■■existing infrastructure (EX) to full adaptationlevel (difference between EX and full adaptationin Figure)1990 master plan level (MP) to full adaptationlevel (difference between MP and full adaptationin Figure)The annual benefits are identified in Figure 4.9.The area between the existing infrastructure curveand full adaptation level are the annual benefitsfrom making investments in the current situationwhere the master plan has not been implemented.The area between the master plan curve and the fulladaptation level refers to the annual benefits fromgoing beyond the master plan.In the cost benefit analysis of the differentinvestments, flood control benefits are assumed togrow at an annual rate of 5 percent. The net presentvalue (NPV) of benefits was obtained using a dis-53For KAMANAVA and West of Mangahan areas, totalelimination is not possible because of their low height.Rather, pumping capacity improvement is considered tominimize the duration of the flooding.54For each scenario only certain types of adaptation investmentsare considered. For example, in a B1EXwD scenario,there is no investment considered for a 1/10 flood since thisscenario already includes a dam, which is expected provideprotection for a 1/10 flood.66 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report
Table 4.11 ■ Adaptation Investments Considered for Different Return Periods andClimate ScenariosClimateScenarioAdaptation Investment Options/Costs Considered1/10 flood 1/30 flood 1/100 floodSQ SQ EX wD Pasig Marikina River embankment + Marikina Dam Pasig Marikina River embankment+Marikina DamSQ EX nD Storm surge barrier Pasig Marikina River embankmentSQ MP wDMarikina Dam in addition to investments alreadyconsidered under the MPSQ MP nD0 costs because additional flood prevention investmentsare already incorporated under the MPB1 B1 EX wD Pasig Marikina River Embankment + Additionalembankment in Marikina River + Marikina Dam +storm surge barrierB1 EX nDStorm surge barrier + Pumpcapacity improvement (KA-MANAVA +West of Mangahan)Pasig Marikina River embankment +additional embankmentin Marikina River + storm surge barrierB1 MP wD Additional embankment in Marikina River +Marikina DamB1 MP nDAdditional embankment in Marikina riverA1FI A1FI-EX wD Pasig Marikina River embankment +additionalembankment in Marikina River + Marikina Dam +storm surge barrierA1FI-EX nDStorm surge barrier + Pumpcapacity improvement (KA-MANAVA +West of Mangahan)Pasig Marikina River embankment +additionalembankment in Pasig and Marikina River + stormsurge barrierA1FI MPwD Additional embankment in Marikina River +Marikina DamA1FI MP nDAdditional embankment in Pasig and Marikina River0 costs because flood prevention costs,including Marikina Dam, area alreadyincorporated into the MPPasig Marikina River embankment +Marikina Dam +additional embankmentin Pasig and Marikina River basinAdditional embankment in Pasig andMarikina River basinPasig Marikina River embankment +Marikina Dam +additional embankmentin Pasig and Marikina River basinAdditional embankment in Pasig andMarikina River basinTable 4.12 ■ Investment Costs and Net Present Value of Benefits Associated withDifferent Flood Control Projects in Manila (PHP) using a 15 percentdiscount rate1/10 Flood 1/30 Flood 1/100 FloodClimate Scenario Investment Cost NPV Investment Cost NPV Investment Cost NPVSQ SQ EX wD NA 14,121,102,133 809,000,801 13,501,553,721 3,763,340,285SQ EX nD 42,887,291 209,952,438 10,943,489,020 2,939,371,200 NASQ MP wD NA 3,177,613,113 1,199,401,356 0.00 4,755,005,784SQ MP nD NA 0.00 3,329,771,755 NAB1 B1 EX wD NA 14,232,087,722 5,634,294,466 13,604,450,310 10,150,493,344B1 EX nD 1,003,222,253 (349,951,115) 11,054,474,609 7,764,664,865 NAB1 MP wD NA 3,216,390,949 3,512,076,308 102,896,589 7,587,409,494B1 MP nD NA 38,777,837 5,642,446,707 NA(Continued to next page)Assessing Damage Costs and Prioritizing Adaptation Options | 67
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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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Page 43 and 44: 3Estimating Flood Impactsand Vulner
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Page 49 and 50: Climate Change Impact and Adaptatio
Page 51 and 52: Figure 3.5a ■ Affected Condensed
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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
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
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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
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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.
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Page 113 and 114: AnnexCAdaptation to IncreasedFloodi
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Climate risks and adaptation in Asian coastal megacities: A synthesis

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