europe’s coastal floods in a changing climate · 2019-06-14 · tectonic uplift, or more, due to...

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Europe’scoastalfloods

inachangingclimate

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Whatdeterminescoastalfloodrisk?Floodrisk=probabilityXconsequences•  Floodprobabilitychangesduetoclimatechange•  Floodconsequenceschangeduetosocio-economicdevelopments

Whatdeterminesfloodprobability?Climatechangeaffectsfloodprobabilitybecauseof•  Sea-levelrise,and•  Changesinstormsurgesandextremewaves

CoastalfloodsCoastalfloodrisk


Driversthatcontributetosealevelrisearethermalexpansionofoceanwater,meltingglaciers,masslossoftheGreenlandandAntarcticicesheets,andchangesinwatervolumesstoredonland(reservoirsbehinddamsandgroundwater).

Attheglobalscale,rateofsealevelriseisaccelerating:•  Tidegaugedata1901-1990:global

meansealevelrise1.1±0.3mm/year•  Satellitedata1993-2012:globalmean

sealevelrise3.1±1.4mm/yearHowever:atthelocalscale,instudiesforspecificpartsofEurope,nosignificantaccelerationintherateofsealevelrisehasbeendetectedduringthe20thcentury.

Sealevelrisehas‘twofaces’•  Absolutesea-levelriseand•  Relativesea-levelrise:sea-levelriserelativetothelandsurface

Becauseoflandsubsidence/landupliftrelativesea-levelrisecanbehigher/lowerthanabsolutesea-levelrise.Verticallandmovementsoccurduetotheon-goingadjustmentoftheEarth’scrusttothedeglaciationattheendofthelasticeage,tectonicactivityandlocalizedsedimentconsolidation.

Absolute Relative

Coastalfloodriskchangesbecauseof:relativesea-levelrise+changesinstormsurge+changesinextremewaves

CoastalfloodsSea-levelrise


NorthernEuropewascoveredwithanicesheetduringthelastglacialmaximum.Verticallandmovementsoccurduetotheon-goingadjustmentoftheEarth’scrusttothedeglaciation.InNorthernEurope,sealevelrisewithrespecttotheland(relativesealevelrise)isthecombinationofabsolutesea-levelriseandpostglaciallanduplift.Atotherlocations,verticallandmovementsmayresultfromtectonicactivityandlocalizedsedimentconsolidation.

Landuplift:Relativesealevelriseissmallerthanabsolutesealevelrise

Landupliftandrelativesea-levelrise

Coastalfloods

Landuplift

Landuplift


Anexample:IntenseandextendedgroundwaterextractionintheindustrialareaofThessalonikihasresultedinadramaticsubsidencesincethe1960s,upto2.8-5cm/yearandreachingupto3mfrom1955to1980.Thisstronglyimpactedfloodrisksincetheaverageheightabovesealevelofthisareaisa+2.5to+3.0minthenorthand0minthesouth.Seabarriersthatprotectthedeltaicplainweredestroyedandcatastrophicfloodshaveoccurredseveraltimes.

Landsubsidence:Relativesealevelriseislargerthanabsolutesealevelrise

Landsubsidenceandrelativesea-levelrise

Coastalfloods


Venice:2.5±0.2mmperyear

Scheldtestuary:15mmperyear

BlackSea:2.5mm/year

Turkishcoast:1-2mm/year

Croatiancoast:-0.8mm/yearto+1mm/year

Reykjavik:3.4mm/year

Polishcoast:1-2.5mm/year

SouthwestDenmark:1mmperyear

NorthernandeasternDenmark:0mm/yearNorthofIreland:

sea-leveldrops

SouthofIreland:0.23mm/year

Finland:sea-leveldrops

Estonia:0mm/year

CentralandSouthernEurope:

InotherpartsofEuroperelativesea-levelisrising.Inmanypartsrelativesea-levelriseexceedsabsolutesea-levelriseduetolandsubsidence:atseveralspotslandissinking,mostlyasaresultofgroundwaterwithdrawalorcompactionofthesoil.

NorthernEurope:

Postglaciallandupliftisgreaterthanabsolutesea-levelrise.Relativetothelandsurfacesea-levelisdropping

ForpartsoftheEuropeancoast,landupliftisroughlyinlinewithsea-levelrise.

Relativesea-leveldrops

Nochange

Relativesea-levelrises

Changerelativesea-level

Relativesea-levelrise:Afewnumbers

Coastalfloods

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IntheScheldtestuary,effectivesealevelriseisupto15mmperyearsince1930,amuchhigherratethanatthecoast:wetlandembankmenthastriggeredextrasealevelrise,becausestorageareaforfloodwatersislost,causingwaterlevelstorisefasterintheremainingchannelsoftheestuary.

AbsolutemeansealevelriseinthesouthernGermanBightinthelast100yearswas11-17cm;forthisperiod,alandsubsidenceofaround4to16cmwasquantified,beingspreadveryunevenlyfromoneplacetoanother.Forthisarea,nosignificantaccelerationofsealevelrisecanbedemonstratedyet.

CurrentrateofabsolutesealevelriseatthenortherncoastsofthewesternMediterranean(MarseilleandGenoa)andatthenortherncoastsoftheAdriaticSea(Trieste)is1.1-1.3mm/year,thuslowerthantheglobalvalue.Overtheperiod1871-2014,theaveragesubsidenceofVeniceanditssurroundinglandwas1.5±0.3mmperyear.AveragerelativesealevelriseinVenicewas2.5±0.2mmperyearoverthisperiod.

IntheeasternPoplaininthenorthofItaly,landsubsidenceasaresultofhumanactivitiesislarge;aclear-cutcorrelationbetweenfloodfrequencyandrapidsubsidencehasbeendemonstrated.

Since1900sealevelriseoftheNorthSeaneartheDutchcoasthasbeen19cm,whichiscomparablewiththeglobalaverage.Inaddition,thereislandsubsidenceoflargepartsoftheDutchsoilupto8mm/year.

ResearchsuggeststhatseasurfacelevelsintheBlackSeahaveincreasedby2.5mm/yearoverthelast60yearsandthisisattributedlargelytofreshwaterflux,althoughlandmovementsmayhaveplayedarole.ThereisprobablyaninflowofMediterraneanwater.

AttheCroatiancoastrelativesealevelisfallingatsomeparts(-0.5to-0.8mm/year)andrisingatothers(+0.53to+1mm/year);thesedifferencesareprobablytheresultofdifferentiallocalupliftandsubsidenceofthecoastinthistectonicallyactiveregion.

Sea-levelrisesby1-2mm/yearalongmostoftheTurkishcoast.Insomepartsrelativesea-levelriseisless,duetotectonicuplift,ormore,duetosubsidenceofespeciallythelargerriverdeltas.

Absolutesea-levelriseinthesouthernBalticSeawas3.2mmperyearbetween1992and2016.PostglaciallandupliftofthePolishcoastis0.4-0.5mm/year.Thisupliftispartofthereasonwhyrelativesea-levelrisevariesalongthePolishcoastline:from1mm/yearinthewestto2.5mm/yearintheeastduring1886-2006.

ThesouthoftheUKwassituatedontheforebulgeattheedgeoftheicesheet.SoutheastEnglandnowissinkingby-2mm/year.

Relativesea-levelriseinReykjavikduring1997-2007wasabout3.4mm/year,closetoglobalsea-levelrise.

Untilnow,postglaciallandupliftaroundthecoastsofFinlandhasbeengreaterthansea-levelrise.

TherateofpostglaciallandupliftalongtheNorwegiancoastis1-5mm/year.

Relativesea-levelrise:Thestorybehindthenumbers

Coastalfloods


Now(1986–2005)

2050(2046–2065)

Lowendlowscenario:17cm

Highendhighscenario:38cmLowendlowscenario:26cm

Highendhighscenario:82cm2100(2081–2100)

Globalmeansea-levelriseaccordingtotheIPCC(2013):Projectionsfor2046–2065and2081–2100relativeto1986–2005

NewinsightspointatfutureinstabilityoftheAntarcticicesheet.ThismayacceleratesealevelriseuptoonemeterhigherthantheIPCCestimatesfor2100.Anupperhigh-endprojectionupto292cmsealevelrisein2100hasevenbeenreported.

Globalmeansea-levelrise:Projections2050and2100

Coastalfloods


2200


Highendhighscenario:203cm



2100(2081–2100)

2500



2300



Globalmeansea-levelriseaccordingtotheIPCC(2014):Projectionsfor2200onwards

Globalmeansea-levelrise:Projectionsbeyond2100

Coastalfloods


Now(2000)

2050

Mediumscenario:21cmHigh-end:24cm

Mediumscenario:53cm

High-endscenario:77cm2100

Averagerelativesea-levelrise(Vousdoukasetal.2017):Projectionsformediumandhigh-endscenariosofclimatechange

ThedominantuncertaintyinsealevelriseisassociatedwiththefateofAntarctica,followedbyexpansionofoceanwatersduetowarminganduncertaintiesinglacialisostaticadjustment.

ProjectedsealevelriseishighestalongtheNorthSeaandAtlanticcoasts,followedbytheBlackSea,andsmallestfortheBalticSeaduetolandupliftinthisarea.

Relativesea-levelriseinEurope:Projections2050and2100

Coastalfloods

InanassessmentcarriedoutfortheDutchDeltaProgramme,Dutchscientistsconcludedthatunderaworst-casescenariosea-levelriseontheNorthSeamightbeupto2-3metresin2100,andupto5-8min2200.


AttheCroatiancoastprojectedrelativesealevelriseis+38±14cm.

InDenmark'sadaptationstrategiesasealevelriseof0.1-0.5mby2050isassumed.Thisispartlycompensatedforbyalandriseof0-0.1m.

LandsubsidenceinWalesis2-14cm/century.Estimatedrelativesealevelriseby2050relativeto1961-1990levelsis26.5-35.5cm(medium-highscenario)upto79cm(highscenario).

SealevelintheGulfofFinlandwillremainroughlyatthepresentleveluntiltheendofthecentury:theacceleratingriseinthemeansealevelwillbalancethelanduplift.Uncertaintiesarelarge,however:projectedrelativesealevelchangevariesfromastillfallingmeansealevelto50cmsea-levelriseintheeasternpartoftheGulfofFinland.

NorthernEurope:

Postglaciallandupliftnolongerexceedsabsolutesea-levelriseinlargepartsoftheNorth.Fortheseparts,landupliftisroughlyinlinewithsea-levelrise.


InotherpartsofEuropesea-levelisrisingrelativetothelandsurface.

Relativesea-levelrise:Afewnumbers

Coastalfloods


AttheCroatiancoastprojectedrelativesea-levelriseis+65±35cm.

InDenmark'sadaptationstrategiesasealevelriseof0.2-1.4mby2100isassumed.Thisispartlycompensatedforbyalandriseof0-0.2mby2100.

Maximumrelativesea-levelriseinEstoniaisestimatedtovaryfrom0.9minsouthwestEstoniato0.7monthenorthwesterncoastduetodifferentvelocitiesoflanduplift.

AccordingtothemostrecentscenariosoftheRoyalNetherlandsMeteorologicalInstitute,sealevelontheSouthernNorthSeawillbe25to80cmhigherin2085thanin1981-2010.For2100anupperlevelofsealevelriseisprojectedof100cm.Inaddition,landsubsidenceoftheDutchsoilwillcontinueupto4mm/year,dependingonthelocationinTheNetherlands.

ProjectedrelativesealevelchangesinNorwayfortheperiod2090-2099relativeto1980-1999varybetween-0.2to0.3m.Forahigh-endscenarioof6°CglobalwarmingandanemergingcollapseforsomeareasoftheAntarcticicesheetsrelativesealevelriseforNorwayvariesbetween0.25and0.85m.

Projectionsofsea-levelriseforthePolishcoastare28,53and98cmby2100relativeto1986-2005levelsunderalow-end,moderateandhigh-endscenarioofclimatechange,respectively.

Overtheperiod2000-2100,anetsea-levelriseisprojectedof60-80cm(Kaliningradarea)and40-60cmalongtheRussiancoastlinesoftheGulfofFinland.

Takingintoaccountpostglaciallanduplift,globalabsolutesealevelof88cmtranslatesintorelativesealevelriseby2100ofabout80cminsouthernSweden,50cminthecentralregionand20cminthenorthernregion.Intheuppernorth,landupliftandanyriseinsealevelsessentiallycountereachother.

Bythe2080srelativesealevelmaybe26-86 cmabovethecurrentlevelinsoutheastEnglandcomparedwith2-58 cmabovethecurrentlevelinsouthwestScotland.

Anupperend,thoughveryunlikely,scenarioforsea-levelriseandstormsurgeisestimatedfortheUKof93cmto1.9mby2100.

AllalongEurope’scoastline(exceptfortheuppernorth)relativesea-levelisrising.

Coastalfloods Relativesea-levelrise:Afewnumbers



InotherpartsofEuroperelativesea-levelisrising.Inmanypartsrelativesea-levelriseexceedsabsolutesea-levelriseduetolandsubsidence:atseveralspotslandissinking,mostlyasaresultofgroundwaterwithdrawalorcompactionofthesoil.

NorthernEurope:

Postglaciallandupliftisgreaterthanabsolutesea-levelrise.Relativetothelandsurfacesea-levelisdropping

SouthernScandinaviaandBalticStates:

Landupliftisroughlyinlinewithsea-levelrise.

Relativesea-leveldrops

Nochange

Relativesea-levelrises

NorthernEurope:

Postglaciallandupliftnolongerexceedsabsolutesea-levelriseinlargepartsoftheNorth.Fortheseparts,landupliftisroughlyinlinewithsea-levelrise.


InotherpartsofEuropesea-levelisrisingrelativetothelandsurface.

AllalongEurope’scoastline(exceptfortheuppernorth)relativesea-levelisrising.

Changerelativesea-level

Relativesea-levelrise:Thebigpicture

Coastalfloods


Whatcausesextremelyhighwaterlevels:Coastalfloodingisoftentheresultofextremelyhighwaterleveleventsduetothecombinedcontributionsoflargewaves,stormsurge,hightides,andmeansea-levelanomalies.Waves,stormsurges,andtidesinturnareinfluencedbythemorphologyofthecoastalzone.Theimpactofsea-levelriseontheriskofcoastalfloodingmustbeassessedaspartofallthesecontributingfactors.Itisdifficult,therefore,topredicttheeffectofsealevelriseonepisodicfloodingeventsduetotheunpredictablenatureofcoastalstorms,nonlinearinteractionsofphysicalprocesses(e.g.,tidalcurrentsandwaves),andvariationsincoastalgeomorphology.Towhatextentacertainamountofsea-levelriseincreasesfloodfrequencymaybecompletelydifferentatdifferentlocations,becausethecombinationofthesefactorsisdifferentfromoneplacetoanother.

Stormsurge,wavesandtides

Coastalfloods


Tides

StudiesindicatedthattheheightofextremewavesalongthewesternEuropeancoastwillincrease.However,fortheNorthSearegionreliablepredictionsconcerningstronglywind-influencedcharacteristicssuchaslocalsealevel,stormsurges,andwavesarestillimpossible;thelargenaturalvariabilityhasagreaterimpactonthelocalNorthSeawindfieldthanpotentialanthropogenic-inducedtrends.

AtmanycoastalregionsinEuropeextremestormsurgelevelmayincreasebyaround15%,andlocallyevenupto40%,ofrelativesealevelriseformostofEurope’scoastline.Thecombinedeffectofrelativesealevelriseandstormsurgeincreaseattheendofthiscenturyisprojectedtoexceed1mformanyregionsinEurope.ProjectedstormsurgechangesstronglyvaryfordifferentpartsofEurope,however.EspeciallythereisadifferencebetweenthenorthernandsouthernhalfofEurope.IncreaseishighestalongtheeasternpartoftheNorthSeacoast,alongthewest-facingcoastlineoftheIrishSea,andattheBalticSeaandtheNorwegianSea.AlongthesouthernEuropeancoastlineprojectedstormsurgeshardlychangeorevendecrease.

Theprojectedchangeoftidalelevationbetweennowand2100isnegligiblefortheentireEuropeancoastline.

Stormsurge

Waves


Coastalfloods


Thecombinedeffectofsealevelrise,astronomicaltide,andstormsurgesandwavesetupontheonce-in-a-hundred-yearsextremesealevelsalongEurope’scoastsisarisebyaround25cmonaverageby2050,andariseby57-81cmby2100.StrongestrisewasprojectedfortheNorthSearegion:upto75-98cmby2100.

Tides

StudiesindicatedthattheheightofextremewavesalongthewesternEuropeancoastwillincrease.However,fortheNorthSearegionreliablepredictionsconcerningstronglywind-influencedcharacteristicssuchaslocalsealevel,stormsurges,andwavesarestillimpossible;thelargenaturalvariabilityhasagreaterimpactonthelocalNorthSeawindfieldthanpotentialanthropogenic-inducedtrends.

AtmanycoastalregionsinEuropeextremestormsurgelevelmayincreasebyaround15%,andlocallyevenupto40%,ofrelativesealevelriseformostofEurope’scoastline.Thecombinedeffectofrelativesealevelriseandstormsurgeincreaseattheendofthiscenturyisprojectedtoexceed1mformanyregionsinEurope.ProjectedstormsurgechangesstronglyvaryfordifferentpartsofEurope,however.EspeciallythereisadifferencebetweenthenorthernandsouthernhalfofEurope.IncreaseishighestalongtheeasternpartoftheNorthSeacoast,alongthewest-facingcoastlineoftheIrishSea,andattheBalticSeaandtheNorwegianSea.AlongthesouthernEuropeancoastlineprojectedstormsurgeshardlychangeorevendecrease.

Theprojectedchangeoftidalelevationbetweennowand2100isnegligiblefortheentireEuropeancoastline.

Stormsurge

Waves

+


Coastalfloods


ExtremestormsurgesinCopenhagenarelimitedandcannotexceed2metresaccordingtostatisticalanalysis,makingitveryeasytoprotectthecitywithseawallsanddikes.

Whenseveralunfavourableconditions(windspeedanddirection,generalwaterlevelandlongwaves)coincideintheBalticSea,ashort-timesealevelriseof1-2metersmayoccurandseveralplacesmaybeinundated.TheareasthataremostinfluencedbythisarethecoastalzonesofshallowbaysinWesternEstonia.Themainthreatsforthecoastal

areaofLatviaaretherelativelyfrequentandseveresouthwest,westandnorthdirectionstormsthatmakeconsiderabledriftsoftheBalticSeawatermassinthecoastalzonewiththerelativesealevelrisesof1.7-2meterandhigher.

IntheEmsestuarynearthebordertoTheNetherlands,thestormsurgeofJanuary1994wasthehighesteverrecorded.Asignificantincreaseinthefrequencyof(moderate)stormfloodscanbeshownstatisticallyfortheNorthSeaandtheBaltic.

RelativesealevelrisealongtheFinnishcoastlineisthecombinationofglobalsealevelrise,postglaciallandupliftandwaterlevelfluctuationsduetochangesinthewaterbalancefortheBalticSea(westerlywindspushingwaterintotheBalticSea);thelattermayresultinavariationinmeansealevelofapproximately1m.

Stormsurge,wavesandtides:Afewnumbers

Coastalfloods


Stormsurgeheightsintherange50-100cmareincreasinginfrequencyaroundallIrishcoastalareasfrom1961-1990to2031-2060;upto20%inthewestandnorthwest.Thereisalsoasignificantincreaseintheheightoftheextremesurgesalongthewestandeastcoasts.

TheaveragewindchangesovertheNorthAtlanticbytheendofthecenturyaresmallandnegativeandlessthanthehighnaturalinterannualvariabilityoftheregion.StudiesshowthatwindextremesandstorminessovertheNorthAtlanticOceanwillalsodecrease:accordingtostudiesthe5%strongestwindswilldecreasebyupto15%.Asaresult,waveclimateovertheNorthAtlanticOceanwillalsochange,withlowerheightsof‘storm-waves’.

ForDutchpolicyonfloodprotectionitisconsideredunlikelythatthestormregimealongtheDutchNorthSeacoastandtheassociatedmaximumstormsurgeswillchangesignificantlyinthe21stcentury.Thereare,however,severalpublicationsinthescientificliteraturethatpointatapossiblestormsurgeincrease.IntheNorthwestofEurope,extremewindspeedsareprojectedtoincreaseandbecomemorenorth-westerlythanatpresent.ThiswouldleadtomoreNorthSeastormsandacorrespondingincreaseinstormsurgesalongcoastalregionsofHolland,GermanyandDenmark,inparticular.ModelstudiesindicatethatstormsurgealongthecoastoftheNetherlands,intheGermanBay,alongthewestcoastofDenmark,andforthenorthwestBritishIsleswillincreasewith8to10%,andwithintheGermanBightupto20%between1961-1990and2071-2100.

ModelprojectionsfortheSpanishnorth(Cantabrian)coastindicatethatwaveheights(boththemeanregimeandextremeevents)willincreaseby2050.Theprevailingdirectionofthewavesisalsoexpectedtochangeandtobemorewesterly.Thenumberofstrongstormsurgeeventswillreducebuthavethesameintensitycomparedtothecurrentsituation.

ExtremewaveheightalongtheSpanishMediterraneancoastlineisprojectedtodecline,althoughtheseprojectionsarehighlyuncertain.

MajorchangesinstormsurgefrequencyareunlikelyalongtheUKcoastlineoverthecomingdecades.

Stormsurges,suchastheoneof4matStPetersburgin1924,maybesevere.Theareacanalsobemarkedlyaffectedbychangesinatmosphericsealevelpressure.

Decrease

Nochange

Increase

Changestormsurgeandwaves


Coastalfloods


AtthePortuguesecoastandtheGulfofCadiz,thecontributionofstormsurgesandwavesetupisprojectedtodecreasewith30%by2050and20%by2100.Theonce-in-a-hundred-yearseffectofstormsurgesandwavesetupcombinedmaybe5-12cmlowerin2050and10-20cmlowerby2100comparedwiththecurrentsituation.

Stormsurgeelevationsareprojectedtoincreaseby15-25cmattheendofthiscenturyalongtheBelgian,Dutch,DanishandGermancoastline.Thisagreeswiththeprojectedincreaseinfrequencyofstrongersouth-westerlyandwesterlywindswhichenhancethewind-setuptowardtheeast.

InDenmark’sadaptationstrategiesanincreaseintheset-upofseverestormsurgesof0-0.1mby2050and0-0.3mby2100isassumedduetohigherwindvelocitiesresultinginhigherandlongerwaves.Thecombinedeffectofsealevelriseandincreasingsurgeset-upisupto0.6mby2050andupto1.7mby2100.

Ifthefrequencyandintensityofwesterlystormscontinuetoincrease,thischangeinwindregimemayadd8-10cmtototalaveragesealevelrisealongtheEstoniancoast.

IntheGulfofFinland,aprojectedincreaseofstormsurgelevelscouldbalanceapotentialdecreaseinfuturesealevels,resultingincomparablelevelsofcoastalhazardinthefuture.

StormsurgelevelsalongtheFrenchcoastwillprobablyberelativelystableorevendecreasethiscentury.

TheheightofextremewaveswillprobablynotchangemuchalongthePortuguesecoast.Also,stormsurgelevelswillprobablyberelativelystableorevendecreasethiscentury.

Thesurgelevelthatisexceededonaverageoncein2,10,20or50yearsisnotprojectedtoincreasebymorethan9cmby2100anywherearoundtheUKcoast.IntheThamesregion,the‘oncein50years’stormsurgelevelcouldincreaseuptoalmost95cm.However,accordingtoseveralstudiessmallornostormsurgechangesareprojectedforthiscenturyalongthesoutheastcoastoftheUK.Combiningtheupperendsofsealevelriseandstormsurgelevelincreaseresultsinanincreaseofthe‘oncein50years’extremewaterlevelby2100ofupto3m.

TherearelargeuncertaintiesassociatedwithprojectedchangesinwavesalongtheUKcoast.By2100,extremewavesaregenerallyexpectedtoincreasetothesouthwestoftheUK,reducetothenorthoftheUKandexperienceasmallchangeinthesouthernNorthSea.Changesintheannualwaveheightmaximaareprojectedtobebetween-1.5and+1m.

Decrease

Nochange

Increase

Changestormsurgeandwaves


Coastalfloods


InJanuary1928,thelasttimecentralLondonsufferedserioustidalflooding,14peopledrowned.

The1953floodwasacatastrophefortheeastcoastofEnglandandthelowerThamesEstuarywithover300deaths.

InFebruary1962largeportionsofHamburgCityandtheneighbouringNorthSeacoastallowlandswerefloodedwhendikesbreached.ThiscausedseveredamageallalongtheGermanNorthSeacoast;morethan300liveswerelostinHamburg.Sincethen,sixstormsurgeshigherthanthe1962levelhavebeenrecordedatHamburg'stidegaugestation.

1962

InEstoniain2005thestormGudrunresultedinthehigheststormsurgeeverrecordedandtheworstnaturaldisasterforEstoniaintermsofpropertydamageduetostormwindandflooding.Denselypopulatedurbanareaswereflooded.

2005

InNovember2007theUKwasremindedofthethreatthatitfacesfromcoastalfloodingwhenastormsurgecameextremelyclosetobreachingdefencesalongtheEastCoast.

1836peoplelosttheirlivesinthe1953floodintheNetherlands.

InFebruary2010thecoastalflooddefencesbetweenBordeauxandtheLoireestuarybreachedatseveralpoints.41peopledrowned,therewas€2.5billionofdamage.ThefloodwasoneofthemostexpensiveanddeadliestintherecenthistoryofFrance.

1953

1953

1928

2007

2010

CoastalfloodsRecentexamples


SealevelriseisaconcerninIceland,asthepopulationisprimarilylocatedinsettlementsalongthecoast.

IntheeventofanextremestormsurgeinBelgium,damageisassessedat€410millionandthenumberofvictimsat10.

InLatvia,stormsinducehigherwaterlevelsoftheBalticSeaandoverflowoflowcoastalterritoriesandwash-offofthecoast,dunes,populatedterritories,buildings,roadsandforestandagriculturalareas.

Thesafetystandardof1/10,000peryearfortheDutchcoastalflooddefencesystemmeansthatthecoastalflooddefencemustbehighandstrongenoughtowithstandstormsurgesthathavealikelihoodofoccurrenceof1/10,000peryear.Actualcoastalfloodprobabilityismuchlower,maybeevenlessthan1/100,000peryearforthemajorcitiesinthewest.70%oftheDutchGrossNationalProductisearnedbelowsealevel.Theembankmentsprotect9millionpeople.

Over30millionpeopleliveinTurkishcoastalareasandmorethan60%oftheGNPinTurkeyisproducedinthecoastalstripalongthenorthernshorelineoftheMarmaraSea.ThepopulationinTurkeyexposedtosea-levelriseisestimatedaround428,000alongtheMediterraneancoast,208,000alongtheAegeancoast,842,000intheMarmararegionand201,000alongtheBlackSeacoast.

AtpresenttheusualstandardoffloodprotectionintheUKissuchthatestuarine&coastalareasareprotectedagainst‘oncein200years’floodsandriverineareasagainst‘oncein100years’floods.ThestandardoffloodprotectionishigherfortheThamesEstuary.Londonisprotectedbycomprehensiveflooddefences.EastLondonisanexception:here,thetributariesintotheThamesareprotectedagainst‘oncein75years’floods.

Atpresent,around5millionpeoplein2millionpropertiesliveinareasatriskfromfloodinginEnglandandWales.Anestimated75%ofthepropertyvalueatriskfromtidalfloodsinEnglandandWaleslieswithintheThamestidalfloodplain.

Withoutflooddefences,almost6%oftheEuropeanpopulationwouldbelivinginthe‘oncein100years’floodarea(coastalandriverfloods).Currentfloodprotectionreduceseconomicdamageofa100yearfloodeventby67to99%andthenumberofpeoplefloodedby37to99%.

CurrentfloodriskCoastalfloods


In2000,over10%oftotalglobalurbanlandwaslocatedwithinthelow-elevationcoastalzone:theareaalongthecoastlessthan10mabovesealevel.

In2030,forWesternandEasternEurope,respectively,13%and2%oftheurbanareawillbelocatedinthelow-elevationcoastalzone;anincreaseby100%and7%,respectively,since2000.

NoEuropeancitiesintheTop20forcitiesrankedbyeconomiccoastalfloodriskin2050,assuming20cmofsea-levelrisebetween2005and2050andapolicywherethecurrentfloodprobabilityismaintained.However,5Europeancities(Marseille,Napoli,Athens,IstanbulandIzmir)areintheTop20citieswhereeconomiccoastalfloodriskisestimatedtoincreasemostbetween2005and2050.

Low-elevationcoastalzone

High-frequencyfloodzones

Cities NoEuropeancitiesintheTop20ofcitiesrankedbyeconomiccoastalfloodriskin2005.

In2000about30%oftheglobalurbanlandwaslocatedinhigh-frequencycoastalandriverfloodzones.ForWesternandEasternEuropethesenumbersare34%and9%,respectively.

Withrespecttohigh-frequencyfloodzones,includingexposuretobothcoastalandriverfloods,in2030about40%oftheglobalurbanlandwillbelocatedinthesezones.ForWesternandEasternEuropethesenumbersare34%and10%,respectively.

Exposuretocoastalfloods

Coastalfloods


FutureprojectionsforEurope

Source:Vousdoukasetal.(2018)

0

1000000

2000000

3000000

4000000

2010 2050 2100

NumberofpeopleexposedtocoastalfloodsinEuropeannually

Lowestimate

Highestimate

0

200

400

600

800

1000

2010 2050 2100

EconomicdamagebycoastalfloodsinEuropeannually(billionEuros)

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Currently,underthepresentclimateconditions(referenceyear2010),Europe’sexpectedannualdamagefromcoastalfloodingis€1.25billion.By2050,thisdamageisprojectedtoincreaseto€12.5-39billiona10-to30-foldincrease.Inthesecondhalfofthiscentury,theprojecteddamageevenincreasesto€93-961billion,astaggeringincreaseof75to770times.Thecurrentexpectedannualnumberofpeopleexposedtocoastalfloodingequals102,000.By2050thisnumberisprojectedtorisetoaround533,000–742,000,furtherclimbingto1.52-3.65millionpeoplebytheendofthecentury.

Coastalfloods(assumption:noupgradefloodprotection)


Coastalfloods(assumption:noupgradefloodprotection) FutureprojectionsforEurope


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PreviousestimateBrownetal.(2015,in:EEA,2017):Mid-century:WithoutadaptationtheestimatedcostsofclimatechangetocoastalzonesintheEUinthe2060sare€6to19billionperyearforalow-endscenarioofclimatechange,€7to27billionperyearforamoderatescenarioand€15to65billionperyearforahigh-endscenario(climateandsocio-economicchangecombined,currentprices,nodiscounting).Endcentury:WithoutadaptationtheestimatedcostsofclimatechangetocoastalzonesintheEUinthe2080sare€18to111billionbillionperyearforalow-endscenarioofclimatechange,€40to249billionperyearforamoderatescenarioand€153to631billionperyearforahigh-endscenario(climateandsocio-economicchangecombined,currentprices,nodiscounting).


Coastalfloodscomparedwithriverfloods FutureprojectionsforEurope


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Expectedannualdamagefromcoastalfloodingiscurrentlyaround0.01%ofGDPforEurope,comparedtonearly0.04%(approximately€6billionperyear)forriverflooding.Thisshareisprojectedtogrowinthecomingdecadestorangebetween0.29and0.86%ofGDPbytheendofthiscenturyforthescenariosconsidered,whichisfarlargerthantheshareoffutureriverfloodrisktoGDPinhigh-incomecountries.

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EconomicdamagebyriverfloodsinEuropeannually(billionEuros)

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Source:Alfierietal.(2015)


FutureprojectionsforEurope


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NumberofpeopleexposedtocoastalfloodsinEuropeannually

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NumberofpeopleaffectedbyriverfloodsinEuropeannually

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Source:Alfierietal.(2015)

Coastalfloodscomparedwithriverfloods


ThenumberofpropertiesatriskoffloodingineasternEnglandrisesby48%from270,000to404,000followingariseinsealevelsof0.4m(thisassumesnonewbuildingbetweennowandthemiddleofthiscentury).AssumingcurrentlevelsofflooddefencesineasternEnglandarenotimproved,thefinancialcostofasinglemajorcoastalfloodingeventwillrisetobetween£7.5billionand£16billiononcesealevelsriseby0.4m.Thisisacautiousestimate,sinceitdoesnotincludethelong-termeconomiceffectsofthismajorlevelofdisruption,northeimpactonessentialpublicservicessuchashospitals,schoolsandemergencyservices.

ForeasternEnglandresearchersreportthatthe1in100yearflooddefencestandardcouldbereducedto1in2-8yearsby2050withmanydefencesatorbelowthe1in1yearstandardby2080.

ForEurope,thenegativeeconomiceffectsarenotparticularlydramatic.Onanannualbasis,andcomparedtonationalGDP,thecostsofoptimalcoastaldefencearequitesmall.Thecombinationof

sea-levelriseandpostglacialsinkingmakesthelowlyingcoastalareasofEnglandandWalesincreasinglyvulnerabletotheeffectsofextremestormsurges.

SealevelriseisnotconsideredaseriousthreatforNorway.Itmayhavesomenegativeimpactsoninfrastructure,though,particularlyalongthewesternandnortherncoastline.Morethan40%oftheNorwegianpopulationissettledalongthecoastline.

ParticularlyvulnerabletotheprojectedsealevelriseisRussia’ssecondcity,St.Petersburg,whichisalreadyregularlyatriskoffloodingwhenstrongwindsblowtotheeastfromtheGulfofFinland.LittleisknownontheimpactofclimatechangeonRussia’scoastalregions.

VulnerabilityofTurkeytosealevelriseisintermediatebetweennorthernandsouthernMediterraneanstates:lessvulnerablethanEgyptandtheNiledelta,butmorevulnerablethanFranceandSpain.RiskishighforIstanbul,however:‘Flagship’’culturalandhistoricalsitesalongtheBosphorusinIstanbularedefinitelythreatenedbytheprojectedriseinsealevel.

SomeofthemostimportantinfrastructuresofCyprusarelocatedinlow-lyingcoastalareasliketheLarnacaairport,thedesalinationplantaswellasthemajorpowergeneratingstations.

Coastalfloods FutureprojectionsforEurope


Copenhagenisverywellprotectedagainststormsurges.IntheCopenhagencitycentreandintheharbour,quaysareatmorethan2mabovecurrentsealevel.Consideringthemaximumpossiblestormsurgeinthecurrentclimateisestimatedat2m,thisprotectionlevelsuggeststhatthehistoricalcentre–wherepopulationdensityisveryhigh–isnotatriskofcoastalfloodstoday.Evenalargeamountofsealevelrisecouldbemanagedbythecurrentprotectionsystem.

A1mglobalsea-levelrisewouldinundate3%ofEstoniaandjeopardise‘only’40,000inhabitantssincepopulationdensityinthecoastalzoneislow.

3.2millionpeoplelivewithinthelow-lyingcoastalregionofGermany,concentratedmainlyinanumberoflargecoastaltowns(Hamburg,Bremen,KielandRostock).Withoutfurthercoastalprotectionmeasures,1msea-levelrisewouldincreasefloodprobability,andpeopleandcapitalatriskatleasttenfoldupto309,000peopleandmorethan300billionUS$.

Inthe‘worstcase’scenariofor2100,breachesintheBelgiancoastlinemayleadtoatotaldamageof€17billionEURandcouldresultinupto6,700victims.Floodscouldposeathreattoover200,000people.

InIrelandtheeffectsofsealevelrisemaynotbefeltasseverelyasinsomeothercountriesinEurope.Theimpactswillbemostapparentinthesouthofthecountry,inthemajorcitiesofCork,Limerick,DublinandGalway.

InItaly,about4500km2ofcoastalareasandplainswouldbeatriskofcoastalfloodingin2080;floodsmightoccurinnorthernItaly(UpperAdriaticSea),centralItaly(thecoastlinebetweenAnconaandPescara,thecoastsnearRomeandNaples)andinsouthernItaly(GulfofManfredonia,coastsbetweenTarantoandBrindisi,eastern-southernSicily).

By2040thepotentialeconomicdamagebycoastalandriverfloodsintheNetherlandswillhaveincreasedby100to250%,andby2100betweentwo-foldandtenfold.

1metresea-levelrisewilltriplethenumberofinhabitantsandassetsinthe100-yearfloodzoneofPoland,andcouldincreasethedamagebya100-yearfloodeventfrom€1.5blnundercurrentconditionsto€4.6bln.Withoutanyactions,0.6msea-levelrisemayresultinlosingaround120km2ofthelandduetocoastalerosion,whereas2,200km2canbefloodedbystormfloods.Thiswillbethedirectthreatfor300,000peopleandindirectlyforanother1.7millionpeopleduetofloods,erosionandlandfalls.

ThenumberofpeoplevulnerabletofloodingintheUKbythe2080svariesfrom4,300peopleannuallyfloodedunderalowsealevelrisescenariowithadaptationmeasurescarriedout,upto986,300peopleannuallyfloodedunderthehighsealevelrisescenarioandwithoutadaptation.

Coastalfloods FutureprojectionsforEurope


TheParisAgreementsetsoutactionstolimitglobalwarmingwellbelow2°C,andpreferablybelow1.5°Ccomparedtopreindustriallevels.

Source:Jevrejevaetal.(2018)

Futurefloodrisk:theglobalpicture

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Mediansealevelrise: 52cm 63cm 86cm

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