Seite - 292 - in Loss and Damage from Climate Change - Concepts, Methods and Policy Options

292 W.J.WouterBotzenet al. Thefinalsectionprovidesasynthesisof thedifferentapproachespresentedin the chapter, anddraws conclusions on the links between climate riskmanagement and theL&Dmechanism. 12.2 Climate RiskAssessment—CaseStudiesJakarta andHo ChiMinh City Thedecisionsonadaptationinterventionstominimisetheimpactsofclimatechange requirestheunderstandingofwhatistheamountofriskthatcanorcannotbereduced. Theamountsofrisk thatcannotbereduced(residual impacts)will tosomeextentbe relevant to theL&Dmechanism.For risk assessment, two activities are necessary: (1) to quantify the present and future risk in a riskmodel framework; and (2) to quantify theeffectivenessofpossiblemitigationoradaptationmeasures in reducing risk. Wepresenthere two recent case studies that apply suchassessments for Jakarta, Indonesia, and forHoChiMinhCity,Vietnam, twoAsianmegacities that display highvulnerability tonaturalhazards, inparticularfloods, and toclimatechange. In Jakartamultiple drivers compound the risk of flooding: the huge rate of land subsidence,due togroundwaterextraction,sea level riseandchangeinprecipitation patterns, both due to climate change. Following the definition of risk reported in Sect. 12.1. Budiyono et al. (2015) employed a hydrological and hydraulic model to produce maps of river flood.Moreover, they assembled specific exposure and vulnerability data for each landuse type, by tapping the expert judgement of local stakeholders.A framework for quantifyingflood riskwas then build, based on the DamagescannermodelofKlijnetal. (2007),whichproducedresults ingoodagree- mentwith reportedflooddamages, and estimated current expected annual damage in theorderofhundredsof thousandUSDperyear. Asuccessivestudyexpandedthismodellingframeworktoproject theriskassess- ment into the future until year 2050 (Budiyono et al. 2016). Thehazardmodelling incorporatedprecipitationchanges fromacombinationof fourRepresentativeCon- centrationPathways(RCP)emissionscenariosandfivedistinctclimatemodels,and a lowandahighscenarioof sea level rise toexplore theprobabilities andscenario- dependencyof changes inflooding. Furthermore, the effect of the severe land sub- sidence rates on hazard, and of land use changes on exposurewere included. The results showthat theprobabilitydensity functionof annualdamages shifts tomuch higher values in the absence of adaptation (seeFig. 12.2). This is primarily due to the effects of land subsidence, but also the result of sea level rise. Climate-change induced changes inmaximum rainfall, on the other hand, introduce a large uncer- tainty in thefuturedamages,assomemodelsandscenarios implyanincrease,while others a decrease in hazard. If land usewill change according to the government plans, it will have the potential of reducing risk by some 12%. Finally, Budiyono etal. (2017)calculatedtherisk-reducingpotentialofaplannedupgradeofthepolder