世界銀行-萊索托道路國家氣候風(fēng)險(xiǎn)和脆弱性評估：萊索托道路脆弱性評估工具的開發(fā)和選定集水區(qū)的脆弱性評估（英）

PublicDisclosureAuthorizedThisworkwassupportedwithfundingfromPROGREEN(/en/programs/progreen),anxxxxLesothoisalreadyexperiencingthenegativeimpactsofclimatechange,includingincreasedfrequencyofextremeweatherevents,floods,droughts,increasedratesofsoilerosionandcatchmentdegradationthatalsothreatentheroadnetwork.In2022,thecountryexperiencedheavyrainfallandfloodsthatleftmanypartsofLesothoimpassableanddisconnected.Theimpactsofheavyrainsweremoreapparentinruralareasthaninurbanareas.Someruralareashavebecomeinaccessibleduetolandslides,rockfalls,anddamageddrainagesystemscausingfloodingofroadsandbridges.Inaddition,Lesotho’stopographyinfluencesitsclimaticconditionsandfurtherexacerbatesthecountry'svulnerabilitytoclimatevariabilityandlong-termclimatechange.InformationfromtheLesothoRoadsManagementSystem(LRMS)indicatesthattherearecurrentlyinexcessof7,500kmofroadsunderthemanagemetnoftheRoadsDirectorate(RD)includingmajorroadways(i.e.,“A”and“B”roads)whichamountto5,844kmofthisnetwork,ofwhichonly1,527kmispaved,andtherestaregravel(3,015km),earth(1,170km),andtracks(132km).TheMinistryofLocalGovernmentandChieftainship(MLGC)managessecondaryroads(i.e.,“C”and“D”roads)totalling1,636km,whicharelargelyunpaved.DatafromtheLRMSsuggeststhatmostpavedroadsareinfairtopoorcondition,withveryfewroadsingoodcondition,whilemostunpavedroadsarepoortoverypoor.TheLesothoExtremeClimateIndicesReport1predictsincreasingtemperaturesacrossthewholecountryandincreasingrainfallfrequencyandseverity,particularlyinthelowlands.Lesothoisthereforelikelytoexperiencesignificantimpactsofclimatechangewhichwillimpacttheconditionoftheexistingroadsinfrastructureandcatchmentareas,particularlyintheformofincreasingtemperaturesandrainfallintensity.ThisreportsummarisesthemethodologyandoutcomeofaClimateRiskVulnerabilityAssessment(CRVA)forroadsinLesothobasedonexistingriskframeworksandpolicies.Thiswasdoneusingarisk-basedspatialapproach,assummarisedbelow.=?Rainfallimpacts(ΔmaxPrecip)?Temperatureimpacts(ΔmaxTemp)?Conditionoftheroads(pavedandunpaved)?Conditionofthebridges?Conditionoftheculverts?Wherethehazardsandroads,bridges,andculvertsoverlapspatiallyTheinputstothenational-levelCRVAinclude:bThecurrentstateandlocationofroads,bridgesandculvertsobtainedfromtheLRMS.bExpectedchangesinmaximumtemperatureandmaximumone-dayrainfallby2070acrossallofLesothoandderivedfromtheLesothoExtremeClimateIndicesReport.Theoutcomewasaclimatehazard,vulnerability,andriskratingforeachsectionofroadextractedfromtheLRMS.ThisspatialtoolisbasedonLRMSandclimatechangedata,andcaneasilybeincorporatedintotheLRMStoassessfuturerisksandprioritisehotspots.Itisrecommendedthatthisframeworkbeusedtoidentifynationalpriorityroadinfrastructure.Thisframeworkshouldbeusedincollaborationwithexistingframeworksforclimaterelatedplanning.Forthepriorityroadsegments,theseadditionalframeworkscouldconsiderissuessuchas:i)costtotheeconomyofinaction;ii)distributionaleffectsofdifferentinvestments;iii)potentialgainsindifferenteconomicsectorsfrominvestingincatchmentandfloodmanagement;andiv)fundingandfinancingstrategybehindaportfolioofinterventions.1TheanalysisisbasedonthedatafromtheCoupledModelinter-comparisonProjectPhase5(CMIP5)setofglobalclimatemodels(GCMs)anddownscaledundertheCoordinatedRegionalClimateDownscalingExperiment(CORDEX)forAfrica.No.of1kmroadsegmentsNo.No.of1kmroadsegmentsNo.of1kmroadsegments00TheresultsofthenationallevelCRVAforroadsinLesotho(shownbelow)sugestthatmostpavedroadsarelikelytobesubjecttoahighlevelofclimate-relatedrisk.Inaddition,mostunpavedroadsarelikelytoexperiencehightoveryhighlevelsofclimaterisk.Whiletheassessmentattributessomeoftheseobservationstotheexpectedincreaseinextremerainfallandmaximumtemperatures,themostsignificantcontributortotheoverallriskisthecurrentpoorconditionoftheroads.Addedtothisaretheadditional“riskamplifiers”relatedtocatchmentdegradation.DistrictDistrictWhileclimatechangewillundoubtablyhaveasignificantimpactonrainfallandtemperaturepatternsinLesothoandplaceincreasingstrainontransport-relatedinfrastructure,mostofthecurrentroad-relatedchallenges/hazardsarenotcausedbychangingweatherpatterns.Insteadclimatechangewillaggravatethesehazards.Therefore,inmostcases,implementingthecurrentdesignstandardswillhelpimprovetheclimateresilienceofcriticaltransportinfrastructure.AreviewofthecurrentdesignstandardsandguidelinesforroadsinLesothorevealedthatthesecanbeupdatedrelativelyeasilytoaccountforthelikelyimpactsofclimatechangebutthatthiswillrequirefurtheranalysisofparticularclimatescenariosandagreementontheacceptablelevelorriskgiventhelevelofuncertaintyoffutureclimatechangescenarios.Therearealreadexamplesofwhereclimatechagneisbeingincludedinthedesignofnewroads.However,onecasestudyrevealedthatthecapacityofexistingroaddrainagestructuresneedstobeincreasedtomeetexistingdesignstandards,letaloneanincreaseofaround12%toaccountfortheexpectedimpactsofclimatechange.Thereviewofguidelinesalsorevealedthatoftentheconcernisnotthedesignguidelinesthemselvesbutrathertheimplementationofthese.Duetoalackoffunds,theGovernmentofLesothocanonlymeettheminimumstandards,significantlyincreasingtheoverallclimate-relatedrisks.Forexample,roadsidedrainsareoftenunlinedandthereisnopavingoftheshouldersoftheroadway.Inmanycases,whilethedrainagestructureitselfmaybeadequate,thebridgeapproachesareoftenunprotectedorinsufficienttodealwithexpectedchangesinextremerainfall.ThereportmakesthefollowinggeneralrecommendationsregardingthepotentialforimprovingtheclimateresilienceofcriticalroadinfrastructureandupdatingthedesignguidelinesinLesotho:bPrioritiseinvestmentsthatimprovetheclimateresilienceofroadswithahighoverallclimate-relatedriskorwhicharedeterminedtobemostcriticalforconnectivity.bConsideraddingpavedshoulderstoallmajorroads(AandBroads)toprotectthemainsectionoftheroadfromerosionandtoimproveconnectivityoftheroadwithdrainagestructures.bConsiderincreasingdesignfloodrequirementsforallnewdrainagestructuresbasedonareviewofthelatestclimatechangescenariosfromtheWorldBankClimateChangeKnowledgePortal.bApplyaminimumof900mmculvertstomakeiteasierformaintenanceandclearing.bFactortheimpactsofincreasingrainfallintensitiesandtemperaturesduetoclimatechangeintoallnewroaddesignsandrehabilitationprojects.bReducetheerosionofminorconnectingroadsandthesubsequentimpactonintersectingmajorroadsbypavingthefirst25moftheminorroadwhereitconnectswithamajorroad(AandB)andensuringtheprovisionofadequatedrainage.bUndertakeareviewoftheconditionsofallmajorbridgestodeterminetheirabilitytomanageincreasedfloodfrequencies,includingareviewoftheapproachesandembankments.Theapproachesandembarkmentsareparticularlyvulnerable.Additionally,considerfloodprotectionacrosstheentirefloodplainandnotjustatthelocationofthecurrentriverchannel.bEngagewithlocalcommunitiestosupporttheclearingofculvertsandidentificationofpriorityinterventionstoreducetherisktoroadsaspartofacatchmentmanagementplanandwithsupportfromthelocalcouncilandtechnicalsupportfromtheRoadsDirectorate.Inadditiontothisreportonthenationallevelclimateriskandvulnerabilityassessmentandreviewofexistingdesignstandardsandguidelines,aseparatereportdetailstheapplicationoftheclimateriskandvulnerabilityassessmentframeworkfortwopilotcatchmentsinLesotho:theMakhalengandUpperMohokarecatchments.ExecutiveSummary ii1Introduction 11.1BackgroundandContext 11.2ClimateChangeRisksforLesotho 31.3ClimateChangeRisksforRoadsandBridges 51.4FundingOpportunitiesforImprovedClimateResilience 51.5CatchmentDegradationasaClimateRiskAmplifier 71.6StudyAimandObjectives 81.7PurposeofthisReport 92ReviewofExistingFrameworksandPlans 112.1ReviewofExistingRiskAssessmentFrameworks 112.2ReviewofExistingNationalPolicies 142.3OverviewofClimateChangeRiskandVulnerability 142.4AdaptedCRVAFrameworkforRoadsinLesotho 153NationalClimateChangeRiskandVulnerabilityAssessment(CRVA)forRoadsinLesotho. 183.1CurrentStateofRoads,BridgesandCulverts 183.2OverviewoftheApproachandMethodology 203.3ClimateRelatedHazardsforLesothoRoads 243.3.1Overviewofavailableclimatechangeindicesandscenarios 243.3.2Selectedclimatechangescenarios 273.3.3Selectedclimatehazards 283.4CurrentConditionandVulnerabilityofRoads 363.5OverallClimateChangeRiskforRoadsinLesotho 453.6ConsiderationforAdditionalRiskAmplifiers 473.6.1SoilErodibilityRisk 473.6.2CatchmentDegradation 493.6.3IncreasingLandslideSusceptibility 503.7SummaryConclusionsandRecommendations 513.8UpdatingClimateRiskInformationintheLRMS 524CatchmentLevelClimateRiskAssessment 534.1AimandObjectives 534.2SummaryFeedbackfromCommunities 544.3Summaryofspecifichazardsidentified 574.4ConclusionsandRecommendations 665IncorporatingClimateChangeintoCurrentRoadDesignStandardsandDesignGuidelines 675.1ReviewofExistingRoadDesignGuidelines 675.1.1Volume1:DesignStandardsforGeometricDesign 675.1.2Volume2:DesignStandardsandExplanatoryNotesforBridges,Culverts,andLow-LevelStructures 685.1.3Volume3:DesignStandardsandGuidelinesforPavementMaterialsDesign 685.1.4Volume4:DesignGuidelinesandExplanatoryNotesforHydrologyandDrainageoftheRoadwayPrism 695.1.5Volume9:GuidelinesforEnvironmentalControl 705.1.6SummaryReviewofUpdatingRoadDesignGuidelines 705.2IncorporatingClimateChangeintoDesignGuidelines 715.2.1TemperatureImpacts 715.2.2PrecipitationImpacts 745.2.3FreezeThawCycles 755.2.4RunoffImpacts(floodinganddrainage) 775.2.5ClimateChangeImpactsonRIDesignFloodDetermination 795.2.6GeologicalandGeotechnicalRisksforRoadsinLesotho 815.2.7ClimateChangeRiskScreeningTools 815.3GuidelinesforSustainableRoadsinRuralAreas 836ConclusionsandRecommendations 897References 92FiguresFigure1-1:PopulationdensityofLesotho(datatakenfromWorldPop)Figure1-2:RainfallinLesothoFigure1-3:Expectedimpactofclimatechangeonmeantemperature(left)andmaximumdailytemperature(right)forLesotho.(Source:WorldBankClimatePortal)Figure1-4:Expectedimpactofclimatechangeonmeanannualprecipitation(left)and1-daymaximumrainfall(right)forLesotho.(Source:WorldBankClimatePortal).Figure1-5:Climaterelatedrisksforcriticalinfrastructure.Figure1-6:SourcesofAdaptationFinance(Burmeisteretal.,2019)Figure1-7:Examplesofprojectelementsthatqualifyasadaptationactivities(AfDB,2013)Figure1-8:BridgedamagedduetofloodingnearMohale’sHoekFigure1-9:MapofPriorityCatchmentAreasinLesotho.Figure1-10:KeydeliverablesofthisprojectFigure2-1:SummaryoftheReCAPFramework'sguidelinesandsupportingdocumentsFigure2-2:Summaryofclimatechangeexposure,risk&vulnerability(IPCC,2007)Figure2-3:SummaryoftheClimateResilienceandSustainableDevelopmentFrameworkforLesothoRoadsandIntendedOutcomesFigure3-1:Visualconditionmapofpavedroadssurveyin2021aspartoftheLRMSupdateprojectFigure3-2:Visualconditionmapofunpavedroadssurveyin2021aspartoftheLRMSupdateprojectFigure3-3:Visualconditionmapofbridgessurveyin2021aspartoftheLRMSupdateprojectFigure3-4:Visualconditionmapofculvertssurveyin2021aspartoftheLRMSupdateprojectFigure3-5:FormulausedforassessingtherisksofLesotho’sroadsnetworkFigure3-6:Methodologyusedtocalculateclimaterelatedhazardsandroadinfrastructurevulnerability.Figure3-7:SummaryofthemethodologyusedtocalculateclimaterelatedrisksFigure3-8:Spatialpatternoftrendsintotalprecipitation(PRCPTOT),fortheemissionscenariosRCP4.5andRCP8.5fortheperiods:2011-2040,2041-2070,2071-2100(Source:CORDEXData,LMS,2018)Figure3-9:ProjectedtemperaturechangeoverLesotho.Source:ThirdNationalCommunicationFigure3-10:Historical(1972-2000)hottestday(monthlymaximumvalueofdailymaxtemperature)Figure3-11:Predictedchangeinhottestdayfromhistoricaltopresent(2011-2040)Figure3-12:Predictedchangeinhottestdayfromhistoricaltonearfuture(2040-2070)Figure3-13:Historical(1972-2000)monthlymaximum1-dayprecipitationFigure3-14:Predictedchangeinmonthlymaximum1-dayprecipitationfromhistoricaltopresent(2011-2040)Figure3-15:Predictedchangeinmonthlymaximum1-dayprecipitationfromhistoricaltonearfuture(2040-2070)Figure3-16:Historical(1972-2000)coldestday(monthlyminimumvalueofdailymaxtemperature)Figure3-17:Predictedchangeincoldestdayfromhistoricaltopresent(2011-2040)Figure3-18:Predictedchangeincoldestdayfromhistoricaltonearfuture(2040-2070)Figure3-19:Rainfall,temperature,andclimatehazardsfortheLRMSroadsnetworkFigure3-20:Rainfall,temperatureandclimatehazardsfortheLRMSroadsnetwork,summarisedperdistrictFigure3-21:Distributionofsurfacedroadsdistressandothercharacteristicratingsbypercentageofroadlength(2021surveyedroadnetwork)(RoadsDirectorate,2022)Figure3-22:Distressesandcharacteristicsforgravelroadsbypercentageofroadlength(2021surveyednetwork)(RoadsDirectorate,2022)Figure3-23:Distressesandcharacteristicsforearthandtrackroadsbypercentageofroadlength(2021surveyedroadnetwork)(RoadsDirectorate,2022)Figure3-24:Pavedroads:OverallhistoricalVCI(2010-2021)(%roadperconditioncategory)(RoadsDirectorate,2022)Figure3-25:Unpavedroads:OverallhistoricalVGI(2010-2021)(%roadperconditioncategory)(RoadsDirectorate,2022)Figure3-26:PavedandunpavedroadsoverallconditionperdistrictFigure3-27:SummaryofroadsconditionandvulnerabilityforallofroadsinLesotho.Figure3-28:OverallconditionsofbridgesandculvertsinLRMSFigure3-29:CurrentcapacityofdrainagestructuresontheThabaTsekatoKatseRoad,requiredcapacity,andfuturedeficitbasedona12%increasetoaccountforclimatechange.Figure3-30:Temperature,rainfall,andclimateriskcategoriesforpavedandunpavedroadsFigure3-31:Totallengthofroadsineachcategoryofclimaterelatedrisk(i.e.combinationofhazard,vulnerability,andexposure)forpaved(top)andunpavedroads(bottom)ineachdistrictFigure3-32:MapshowingsoilerodibilityriskforLesotho(Source:LeRoux,2008)Figure3-33:Erodibilityindexofroads(pavedandunpaved),bridgesandculvertsinLesothoFigure3-34:Erosionriskperdistrict,forpavedandunpavedroadsFigure3-35:Landdegradationperdistrict,usingLandCoverChangeasakeyindicator(WFP,2015)Figure3-36:ExtensiveerosionscarsinMohale’sHoekdistrict,Makhalengcatchment.ThisareahasexperiencedsomeoftheworstlanddegradationinLesotho.Figure3-37:LandslidesusceptibilitymapforSouthAfricathatcouldbedevelopedforLesotho(Source:Singhetal,2011)Figure4-1:Meetingswith4CommunityWatershedTeamsinthenorthernMohokareandMakhalengcatchmentsFigure4-2:ApoorlymaintainedsidedrainagechannelintheMakhalengcatchmenthasresultedinerosionofboththeroadandtheadjacentfarmland.Figure4-3:ExampleofahandmadeconcretetamperFigure4-4:Acommunity-builtroadintheMakhalengcatchmentthatisresurfacedonanannualbasisafterextremerainfallevents.TheerodedsoilisdepositedintheMakhalengriver.Figure4-5:Anunprotectedcommunity-builtsidedrainwhichhasresultedinerosionFigure4-6:Culvertpossiblyblockedbycommunity(left)andfieldimmediatelydownstreamoftheculvertoutlet(right).Mohokarecatchment.Figure4-7:AlienvegetationgrowinginariparianareaintheNorthernMohokarecatchmentFigure4-8:Erodedsidedrain(left)whichhasresultedinfurtherdegradationdownstream(right)Figure4-9:SmallcheckdamsusedtopreventerosionofsidedrainsintheMakhalengcatchmentFigure5-1:7-dayaveragemaximumasphalttemperaturesforSouthAfricaFigure5-2:MinimumasphalttemperaturesforSouthAfricaFigure5-3:Climatezonesforconsiderationinroadpavementdesign(afterWeinert,1980)Figure5-4:ExampleofGraphShowingFreezingandThawingIndexes(NorthernHemisphere)Figure5-5:LesothoFreeze/Thawinfluencelines(Source:GovernmentofLesotho)Figure5-6:SCS-SArainfallintensitydistributiontypesforSouthernAfrica(Left)UnitHydrographVeldZonesforSouthernAfrica(Right)Figure5-7:ProcedureforIncorporatingClimateChangeAllowancesinDetailedEngineeringDesignFigure5-8:ConceptualframeworkoftheWorldbankClimateScreeningtool(/)Figure5-9:Issueidentificationforintegratedcatchmentmanagement(Braid,2019)Figure5-10:ExampleofaproblemtreeforlanddegradationfromtheSouthAfricanCatchmentManagementGuidelines(Braid,2019)Figure5-11:Sustainablelandmanagementimplementationoptions(Braid,2019)Figure5-12:ErosionmanagementalongroadsidepartI(Braid,2019)Figure5-13:ErosionmanagementalongroadsidepartII(Braid,2019)Figure5-14:ErosionmanagementalongroadsidepartIII(Braid,2019)Figure6-1:Overviewofapproachfordeterminetheimpactofenvironmentalconditionsonroaddegradationwhichcanthenbeusedtodetermineoverallmaintenancecostsandimpactsofclimatechange.TablesTable1-1:NSDPStrategicobjectivesandinterventionsregardingsustainabletransportnetworkTable1-2:Summaryofclimatechangerelatedrisksfortransportglobally(Thibault,2015).Table1-3:Summaryoffinancinginstrumentsforadaptationfunding(Burmeisteretal.,2019)Table2-1:Summaryofthereviewofclimateriskandvulnerabilityassessmentframeworksforroads.Table2-2:CRVAframeworkforroadsinLesothoTable3-1:ClimateChangeExtremeIndicesandtheirexplanation(redfillfortemperaturerelatedindicesandbluefillforprecipitation)(takenfromLMS,2018)Table3-2:ClimatemodelsusedfortheLesothoThirdNationalCommunicationTable3-3:Climatedrivers,theimpactinLesothoandthecorrespondingCORDEXdatausedTable3-4:Ratingscalesforpavedroads(binderconditionandsidedrainagecondition)Table3-5:Ratingscalesforunpavedroads(sidedrainageconditionandadequacy)Table3-6:OverallRoadcondition-VCIandVGIvaluesTable3-7:OverallconditionratingsforbridgesandculvertsTable5-1:ListofexistingroadsdesignstandardsandguidelinesforLesothoTable5-2:RoaddrainagemanualTable5-3:Applicationandlimitationsoffloodcalculationsmethods(SANRAL,2013)Table5-4:ChangeinReturnPeriodfortheLargest1DayPrecipitationforLesotho(2035-2064)Table5-5:SummaryofclimaterelatedgeotechnicalrisksforroadsTable5-6:IndicatorsconsideredwithintheWorldBankClimateScreeningtoolsTable6-1:Primaryroadshazards,andtheimpactsofclimatechangeontheseListofAcronymsAFAdaptationFundAfDBAfricanDevelopmentBankADBAsianDevelopmentBankAfCAPAfricaCommunityAccessPartnershipCMPCatchmentManagementPlanCORDEXCoordinatedRegionalClimateChangeDownscalingExperimentCRVAClimateRiskandVulnerabilityAssessmentCMIP5CoupledModelInter-ComparisonProjectPhase5CSIRCouncilforScientificandIndustrialResearchCWTCommunityWatershedTeamDRRDepartmentofRuralRoadsEIAsEnvironmentalImpactAssessmentsETCCDIExpertTeamonClimateChangeDetectionandIndicesGCF