POLICY BRIEF

Cost of Coastal Environmental Degradation, Multi Hazard Risk Assessment and Cost Benefit Analysis

Key Messages

• CoastalenvironmentaldegradationasaresultoferosionandfloodingposesasignificantthreattotheWestAfricancoastalenvironment,itspeopleanditsassets;thethreatwillincreaseincomingyearsduetotheimpactofclimatechange.

• TheknowledgebaseoncausesandconsequencesofcoastalenvironmentaldegradationinWest-Africaneedstobebroadenedandremediationsolutionsmustbeproposedandassessed.

• Inorder tosupport informedandultimatelysustainabledecision-making,amethodologyenabling thecalculationofthecostofenvironmentaldegradationandtheevaluationofthecost-efficiencyofDRRandCCAmeasuresisproposed.

• Thegeneralvalidityandutilityofthemethodologyhasbeendemonstrated.Itoffersanoperationalframe-workthatcanbefurtherimprovedbyintegratingbetterdataorinformationasitbecomesavailable.

• ThemethodologyhasbeenappliedtopilotsitesinBenin,Côted’Ivoire,GhanaandTogo.Resultssuggest thatcost-effectivemeasuresorcombinationsofmeasurescanbefoundtolimitthedamagesduetocoast-al erosionandfloodingat these locationsThefirstquick-scananalysis indicates that thebenefits (i.e.riskreduction)ofplannedretreatandaccommodationmeasuresoutweighitscostsandthatearlyaction (i.e.limitingdevelopmentinareasatrisk)willfurtherimprovethebenefit-costratio.

• Furtherapplicationofthemethodologyshallbepromotedinordertooptimizeresourcesspentoncoastalriskmanagement.

• Theintegrationofotherhazards,suchasriverflooding,inthemethodologywouldleadtoanimprovedselectionofDRRandCCAmeasures,suitingtheneedsofthepopulationwithincreasedadequacy.

• Coastal zone management requires an ‘all-of-society’ approach. The inclusion of stakeholders in the processwillensurethatthelocalknowledgeisvaluedasacomplementtoscientificknowledgeandwillguaranteethatselectedCCAandDRRmeasuressuittheneeds.

• Coastalprocessessuchaserosionandfloodingdonotstopatnationalborders.TheWestAfricancoastal zone can be seen as a unique system. Therefore, a regional approach to coastal management and implementationofDRRandCCAmeasureswillberequired.

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Coastal environmental degradation in Benin, Côte d’Ivoire, Ghana and TogoTheWestAfricancoastalareahosts large infrastructure,major industries, tourism,agricultureandfishing activitiesaswellashumansettlementsandcommunicationroutes.Theserapidlyurbanisingareasdrivena-tionaleconomicgrowthandprovidethelivelihoodstomany.

However,demographicpressuresandincreasingexploitationofcoastalresourceshaveledtorapidcoastalen-vironmentaldegradation.CoastalecosystemsinWestAfricanowfacearangeofchallenges,includingcoastalerosionandflooding,overexploitationofnaturalresources,marineandcoastalpollution,lossofbiodiversityandofecosystemservices,rapidurbanizationandunsustainablelanduse,andoverallpoorenvironmentalgovernance.

Inordertoaddressthesechallenges,theknowledgebaseoncausesandconsequencesofcoastalenviron-mentaldegradationinWest-Africaneedstobebroadenedandremediationsolutionsmustbeproposedandassessed.

Thepresentstudyaimsatcontributingtoinformedandultimatelysustainabledecision-makinginthefieldofDRRandCCAmeasures,byproposingamethodologyenablingthecalculationofthecostofenvironmentaldegradationandtheevaluationofthecost-efficiencyofDRRandCCAmeasures.Thismethodologyhasbeentestedononepilotineachoftheparticipatingcountries:Benin,Côted’Ivoire,GhanaandTogo.

ThemethodologyTheproposedmethodologyisinspiredbytheCoastalRiskAssessmentFrameworkwhichhasbeendevelopedanapplied tocoastalzones inEurope,andhasbeenadapted tocoastalerosionandflooding in theWest Africancontext.Itcanbedecomposedin2phases,aimingatansweringthe2followingquestions:

• Wheretoinvestfirst?–Phase1

• Whichmeasurestobepreferred?–Phase2

Phase 1: Identification and ranking of the hotspots (“What’s the priority? Where to invest first?”)

Thisstephelpsprioritizingtheactionbyrankinghotspotsalongthecoastintermsoftheirvulnerability.Thisisdonethroughthecalculationandrankingofcoastalindicesofpre-identifiedcoastalsectors.Coastalindicesreflectboththeseverityofthehazards(coastalerosionandflooding)andtheextentoftheexposure(popula-tionandassetsinthearea).

BOX 1 : Coastal indices

Coastalindicesaretheresultofthemultiplicationofqualitativehazardsindicatorsand social/environmental/naturalexposureindicators.

Coastalindicesmaps (e.g.EasternGhanaiancoastline

sectors)helpvisualizing thesituation.

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Coordinate System: GCS WGS 1984

Cost of Coastal Environmental Degradation,Multi Hazard Risk Assessment

and Cost Benefit Analysis

Coastal Index Multi-HazardsPresent Conditions

D2: Definition of the pilot sites

12148_010_161221_GH_Multihazard_PC Date: 21/12/16

Report no. xx.xxx Map 02

Revision Date DescriptionRev01 16/12/16 Initial

Van Immerseelstraat 66 B-2018 AntwerpenTel +32 3 270 92 20Fax +32 3 235 67 11 E-mail: info@imdc.be

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BOX 2 : Coastal erosion and coastal flooding

Coastal erosion corresponds to the wearingaway of land and removal of beaches or sanddunes due towaves, currents and tides and alackofsediments.Therepetitiveactionofwavescombined with strong storms leads to land retreats of several meters and sometimes more than10metersperyearinthestudyarea.

Coastal flooding corresponds to inundation ofdry landbyseawaterduetodirect inundation,overtoppingofcrestsorduneordykebreaches. It is due to storms and especially in the caseofstormsoccurringduringperiodsofhighsea waterlevels.

Theresultsofthisfirststephavebeenusedtosupporttheselectionofthepilotsitesbytherespectivenationalauthorities

Phase 2: Detailed study of the COCED and CBA of adaptation measures at selected sites (“which measures to be preferred?”)

Oncethesitestobefurtherinvestigatedhavebeenselected,amoredetailedstudycanbeperformedtoselectthemostappropriateDRRandCCAoption.

Thisstepisfurthersubdividedinsuccessivestepsaimedatcharacterizingthehazards,assessingtheexposure,calculatingthecostofdegradation,andevaluatingthecost-efficiencyofremediationmeasures.

Step 2.1 Characterization of coastal erosion and flooding (i.e. “what is causing the problem?”)

First,thethreattothecoastalenvironmentmustbecharacterized.ThiscanbedoneusingverysimpletoolssuchaGIS-basedfloodmapsorthroughmorecomplexmethodsusinghydrodynamicandhydromorphologicalmodellingsoftware.

In the latter case,probabilistic approaches, taking intoaccount the impactsof extremeeventsalongwiththeirprobabilityofoccurrenceareused.Climatechangeimpacts,includingsealevelrise,arealsotakenintoaccount.

Theendproductsofthissteparefloodmapscomprisingatleastinundationdepthsanderosionmapsquanti-fyingtheprogressiveretreatofthecoastline.

Step 2.2: Characterization of the people, assets and ecosystems exposed (i.e. “who and what can potentially be affected?”)

Inthefollowingstep,thepeopleandassetspotentiallyexposedarecharacterized.Asintheprevioussteps,thischaracterizationcanbedonewithvariouslevelsofdetails.Usefuldatacanbegatheredthroughanalysisofpreviousstudies,availabledataandmaps,sitevisits,etc.

Theendproductofthissubtasksarelandusemapsbasedonlanduseclassesthatareadaptedtothelocal context. The land uses are defined based on population density, the presence of social assets (schools, hospitals,placesofworship,monuments,etc.),oftransportinfrastructure(roads,railways,etc.),ofspecific economicactivities(industry,services,ports,quarries,etc.)orofhighnaturalvalue.

Foreachoftheland-uses,avalue(inUS$perhectare)isdefined.Thisvaluerepresentsthetotalcostofthelanduseformshoulditbecompletelylosttoerosionorflooding.Fornaturalareas,anoverallvalueforeco-systemsserviceshasbeenestimated.Forimpactsonhumanhealth(fatalities),valueofstatisticallife(VSL)hasbeenused.

Anadditionalfeatureisdevelopedinordertotakeintoaccountthefactthat lossesareinmostcasesonly partial(dependingforinstance,onthedurationanddepthofagiveninundation):thedamagefunctions.

BOX 3 : Damage functions

Definition:adamagefunctionisafunctionrelatingthedamagedonetoanasset(generallyasapercentofitstotalvalue)tocertaincharacteristicsofaneventaffectingit.

Damagefunctionshavebeendevelopedintheframeofe.g.riverfloodingprojectsinEuropeandhavebeenappliedthroughouttheworld.Thedamagecurvesusedinthisstudybuildonaworld-widereviewofexistingcurve.TheyhavebeenadaptedtotheWestAfricancontext.

Insomespecificcases (e.g.floodingimpactsonnaturalareasoronhumanhealth),newsimplifiedcurveshavebeendevelopedasnoexistingcurvescouldbefound.

Example:land-use“Rural1”definedforthisprojectandcorrespondingto“areaswith0-1inhabitantsperhectare,agricultureasonlyeconomicactivityandnootherspecificassetorinfrastructure”hasato-talvalueperhectareestimatedat480US$.Itstotalvalueisconsideredlostforfloodingdepthsofmorethan6meters.Forflooddepthsof1.5meters,roughlyhalfofitsvalueislost(254.40US$).

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Step 2.3: Calculation of the expected damage

In this step, hazards and land usemaps are combinedwith damage functions to obtain damagemaps. Technically,thisiscarriedoutthrough(raster)multiplicationofmapsofsimilarpixelsizes.

Hazerd(waterdepth) Damage

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Step 2.4: Cost benefit analysis of solutions (i.e. “what is the most cost-efficient solution to the problem?)

Thenextstepaimsatselectingthemostcost-efficientremediationmeasures.Thisisdoneusingcost-benefitanalysismethods.

PossibleCCAandDRRmeasuresinclude:

• Protection,

• Retreat,

• Accommodation(floodproofingofassets),

• Combinationoftheabove,inspaceandtime.

BOX 4 : DRR and CCA measures

Protection:examplesare“hardsolutions”:construction of dykes, seawalls, groins, revetments, armour units, breakwaters,storm surge barriers, land reclamation,etc. and “soft solutions”: beach nourish-ment, dune construction and rehabili-tation, mangrove restoration, “buildingwithnatureconcept”,etc.

Retreat:examplesaremanagedretreat,dike realignment,dike (re)opening,de-embankmentandde-polderisation,coastalsetbacks,etc

Accommodation:examplesarecoastalecosystemsreinforcement,wetlandrestoration,flood-proofing,floatingagriculturalsystems,floodhazardmap-ping,floodwarnings,etc.agriculturalsystems,floodhazardmapping,floodwarnings,etc.

Combination of different measures in space and time. Flexible planscombining a series of short termactionswithperiodicdecisionpointsover time, to address longer termobjectives.

Thecost-benefitanalysisof thesesolutionsinvolvesthecalculationofeconomicindicatorssuchasthenetpresentvalue(NPV).ThecalculationoftheNPVofmeasuresrequiresthefollowingactualizedinputs:

• Costs:investmentandmaintenancecostofmeasures(constructionofdykes,beachnourishmentworks,relocationofassets,floodproofingofbuildings,etc.).

• Benefits:valueofrisksavoidedifthemeasureweretobeimplemented.

Avoideddamagesarecalculatedasdescribedinpreviousstep.Protectionmeasureshaveanimpactonthehazardswhile retreatandaccommodationmeasureshavean impactonexposure.Bothultimately lead toreduceddamage.

Application of the methodology to the 4 pilot sites in Benin, Côte d’Ivoire, Ghana and TogoThe methodology has been applied to 4 pilot sites which have been selected by national authorities of participatingcountries.Theselectionprocesswassupportedbythepresentationoftheresultsof“Phase1:Identificationandrankingofthehotspots”

BOX 5 : The pilot sites

4pilotsiteshavebeenselected incollaborationwithnational authorities

Togo:

SectorincludingcitiesofTogoville,AgbodrafoandAneho

Ghana:

Sectorfrom NewNingoto Lekpoguna

Côted’Ivoire:

Sectorfrom Abidjanto Port-Bouët

Benin:

Sectorfrom TogobordertoGrand-Popo

Main outcomes

Atallfourpilotsitesandbasedonavailabledata,scenarioscombiningplannedretreatandaccommodationofbuildings/housesshowthebestbenefit/costratiocomparedtoothermeasures.Theycanindeedofferalargeshareofthebenefits(50%to90%)offullprotectionatamuchlowercost.Theircostswillbeearnedbackwithinafewdecadesbyreductionoftherisks.

Earlyimplementationofplannedretreatandaccommodation(e.g.limitingfutureeconomicdevelopmentinareasatriskafter2050)canlimitfuturecostsandimprovetheefficiencyofthescenarios.

Itmustbenotedthatthereliabilityoftheselectionofmeasuresdependsontheaccuracyofthecostandben-efitestimatesandthatforpolicy-supportingapplicationofthemethod,itisadvisable,giventheimportantissuesatstakeandthescaleoftheinterventions,thatmoredetaileddataandparametersareused.

Itisalsoimportanttonotethatsomecostsandimpactscannotbemonetizedandthereforecannotbecapturedbythecost-benefitanalysis.Thisisparticularlythecaseofsocialimpacts(e.g.destructionofcemeteries,ofplacesofworship,etc.).Theselectionofmeasuresthereforerequirestakingadditionalcriteriaintoaccount.Suchcriteriaare,forinstance:thefinancial,technicalandpoliticalfeasibility,thesocialacceptabilityandtheenvironmentalsustainabilityofmeasures.

Ways forward

1. Reuse the methodology, for various purposes, with better data, in other places, at other times, etc.

Thisframeworkwasdevelopedinordertonotonlystudyandquantifythecoastalerosionandfloodriskbasedontheavailabledata,butalsotoquantify thecostofcoastalenvironmentaldegradation,andidentifyandcomparepossibleDRRandCCAmeasuresineconomicterms.

Theresultsobtainedbythistypeofanalysishelptofurtherdevelopstrategicinvestmentplans,byindicatingthesiteswhereinvestmentsshouldcomefirst,andbyhighlightingtheDRRandCCAmeasuresthatshouldbepreferred.

Thisflexibleandrobustmethodologyoffersanoperationalframeworkthathasseveraladvantages:

• itcanbeappliedondifferentspatialscales:regionallevelorpilotsitelevel;

• itcanmakeuseofverydetaileddataorgenerallyavailabledatasets;

• it canbeappliedwithdifferent sorts of tools: frombasic applications (GISbasedapproaches) to very detailedmodels(e.g.hazardassessmentswithdetailednumericalmodels);

• itcanserveatdifferentstagesofastudyorprojectcycle:pre-feasibility,feasibility,predesign,detaileddesign,sinceitcancopewithdifferentdatatypesanddifferentlevelsofdetail.

Themethodologyshouldalsobereusedatdifferenttimestomakesurethatmeasuresremainadaptedtotherisksasthelattermayevolvewithtimeforvariousreasons(e.g.climatechange,economicordemographicgrowths,changeinlanduse,etc.).

Asdescribedintheintroduction,theproblemslinkedtocoastalerosionandfloodinginthestudyareaarehuge.Theeconomic,environmentalandsocial costsof the remediationoptionswill likelybeof thesame nature, thus requiring very well informed decision making. The present methodology represents a very efficienttooltoservethispurpose.

2. Improve the quality of data in the West African coastal zone

Themethodisrobustandcanworkwithverylimitedmetocean,morphological,physicaloreconomicdata.TheapplicationofthemethodologytothefourpilotssitesofBenin,Côted’Ivoire,GhanaandTogo,hasyieldedresultsbuthasalsohighlightedthelackofdatathatwillbeusefulforfurther,moredetailed,applicationsofthemethodology

Examplesofcriticallymissingdataare:

• Beachprofileandcrestelevation,whichisofcrucialimportancefortheevaluationofcoastalerosionandtheovertoppingofseawaterduringstorms;

• Localdemographicandeconomicdata,astheusageofnationaldataisoftenmisrepresentingtherealityofthe(much)moreurbanizedanddevelopedcoastalzone.

Future landusemaps thatpredict hownational economicordemographicgrowthwill affect landuse incoastalareas,aswellaslocalclimatechangeimpactscenarioswillalsohelpimprovetheevaluationofthefuturesituation.

Furtherimprovementsshouldalsofocusonavailabilityofdataindigitalformatandavailabilityofspatialdatawithreasonableresolution.

3. Integrate other hazards (e.g. river flooding)

Withinthepresentproject,directandindirectimpactsoftwodifferenthazards,coastalerosionandcoastal flooding, have been analyzed independently and jointly. Understanding where and how these multiple hazardswilllikelyaffectsocialandeconomicsystemsandinfrastructureincoastalareasenablesamoreintel-ligentandcost-effectiveselectionofDRRandCCAmeasures.Animpact-basedapproachisthereforecrucialtoriskreductiondecision-making.Addingdifferenthazards,suchasriverflooding,intothisanalysisispossible,andwouldgiveanevenbroaderandmorecompleteinsightintothelandandpeopleatrisk.

4. Involve stakeholders

Stakeholders,notonlyexpertsbutalsoordinarycitizensplayanimportantroleasprovidersandrecipientsofinformationoncoastalriskandapproachestodefineandselectDRRandCCAmeasures.Localresidentsareunderstoodasgatekeepersofimportanthistoricalandculturalknowledge,whooftenholdthekeytoun-derstandingbehavioursandattitudesinrelationtocoastalriskandDRRapproachesandmeasures.Effectivedisasterriskreductionrequiresan‘all-of-society’engagementandpartnership.

Anactiveinvolvementofdifferentstakeholderswasencouragedandfacilitatedbyperformingamulti-criteriaanalysis(MCA)ofthedifferentproposedDRRandCCAmeasuresduringthefinalworkshopforthepresenta-tionanddiscussionoftheresultsofthestudy.FirsttheMCAallowedtotakeintoaccountenvironmental,socialandpoliticalaspectsinselectingthepreferredDRRandCCAmeasures,nexttothetechnicalandeconomicinformationobtainedfromthepresentstudy.Second,theMCApromotedinteractionanddiscussionbetweenthedifferentstakeholdersduringtheworkshop,whichmightresultinnewandbettercontactsthatwillalsolastafterwards.

5. Promote regional cooperation

Throughin-depthanalysisofthefourdifferentcountriesandtheselectedpilotsites,theprojecthasrevealedsome interesting challenges for DRRmanagement inWest-Africa. Despite the differences in between the countries,somecommonchallengeshavebecomeevident.

Theserelateprimarilytotheneedforclarityingovernancestructuresandproceduresaswellastheimpor-tanceofcitizenengagement,bothintermsofprovidinglocalknowledgeandintermsofawareness-raisingforeffectivecoastalDRRandCCAresponses.

Also, the coastal erosion hazard inWest-Africa is a regional phenomenon,which can only be tackled byregional,cross-boundaryoperationandmanagement.DRRmeasureswithapositiveimpactinonecountrycouldheavilydeterioratethesituationintheneighbouringcountry.

FOR MORE INFORMATION

InternationalMarineandDredgingConsultants(IMDC)–www.imdc.be

AnneliesBolle-annelies.bolle@imdc.be-+322709295