Groundwater flood hazards and mechanisms in lowland karst terrains


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Groundwater flood hazards and mechanisms in lowland karst terrains

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Groundwater flood hazards and mechanisms in lowland karst terrains
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Geological Society, London, Special Publications
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Naughton, Owen
McCormack, Ted
Gill, Laurence
Johnston, Paul
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Groundwater Flooding ( local )
Karst Terrains ( local )
Flood Prevention And Mitigation ( local )
European Union Floods Directive ( local )
Lowland Karst Terrains ( local )
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serial ( sobekcm )

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The spatial and temporal complexities of flooding in karst terrains pose unique challenges in flood risk management. Lowland karst landscapes can be particularly susceptible to groundwater flooding due to a combination of low aquifer storage, high diffusivity and limited or absent surface drainage. Numerous notable groundwater flood events have been recorded in the Republic of Ireland throughout the twentieth century, but flooding during the winters of 2009 and 2015 was the most severe on record, causing widespread and prolonged disruption and damage to property and infrastructure. Effective flood risk management requires an understanding of the recharge, storage and transport mechanisms governing water movement across the landscape during flood conditions. Using information gathered from recent events, the main hydrological and geomorphological factors influencing flooding in these complex lowland karst groundwater systems are elucidated. Observed flood mechanisms included backwater flooding of sinks, high water levels in ephemerally flooded basins (turloughs), overtopping of depressions, and discharges from springs and resurgences. This paper addresses the need to improve our understanding of groundwater flooding in karst terrains to ensure efficient flood prevention and mitigation in the future, and thus helps to achieve the aims of the European Union Floods Directive.
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Geological Society, London, Special Publications, Vol. 466 (2017-12-11).

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Groundwater oodhazardsandmechanismsin lowlandkarstterrainsOWENNAUGHTON1,2*,TEDMCCORMACK2,LAURENCEGILL1&PAULJOHNSTON11DepartmentofCivil,StructuralandEnvironmentalEngineering,UniversityofDublinTrinity College,Ireland2GeologicalSurveyIreland,BeggarsBush,HaddingtonRoad,Dublin,Ireland *Correspondence: naughto@tcd.ieAbstract: Thespatialandtemporalcomplexitiesof oodinginkarstterrainsposeuniquechallengesin oodriskmanagement.Lowlandkarstlandscapescanbeparticularlysusceptibleto groundwater oodingduetoacombinationoflowaquiferstorage,highdiffusivityandlimitedor absentsurfacedrainage.Numerousnotablegroundwater oodeventshavebeenrecordedinthe RepublicofIrelandthroughoutthetwentiethcentury,but oodingduringthewintersof2009 and2015wasthemostsevereonrecord,causingwidespreadandprolongeddisruptionanddamage topropertyandinfrastructure.Effective oodriskmanagementrequiresanunderstandingofthe recharge,storageandtransportmechanismsgoverningwatermovementacrossthelandscapeduring oodconditions.Usinginformationgatheredfromrecentevents,themainhydrologicalandgeomorphologicalfactorsin uencing oodinginthesecomplexlowlandkarstgroundwatersystems areelucidated.Observed oodmechanismsincludedbackwater oodingofsinks,highwaterlevels inephemerally oodedbasins(turloughs),overtoppingofdepressions,anddischargesfromsprings andresurgences.Thispaperaddressestheneedtoimproveourunderstandingofgroundwater oodinginkarstterrainstoensureef cient oodpreventionandmitigationinthefuture,andthushelpsto achievetheaimsoftheEuropeanUnionFloodsDirective. GoldOpenAccess: Thisarticleispublishedunderthetermsofthe CC-BY3.0license .Karstlandscapespresentauniquesetofenvironmentalandengineeringchallengestoplanners,stakeholdersandthescienti ccommunity.Geohazards suchassubsidence,sinkholes,landslides, ooding andwatercontaminationarecommoninkarstenvironments( Santo etal. 2007 ; Zhou2007 ; Maréchal etal. 2008 ; Worthington etal. 2012 ; Gutiérrez etal. 2014 ; Martinotti etal. 2017 ).Floodingand oodriskmanagementisamajorchallengefacing societyinthecomingdecades,especiallyinthe lightoftheincreasedfrequencyofextremeweather eventsasaresultofclimatechange( IntergovernmentalPanelonClimateChange2014 ).Effective oodriskmanagementrequiresanunderstanding oftherecharge,storageandtransportmechanisms inoperationduring oodconditions.Inthecontext ofgroundwater oodingwithinkarstsystems,the heterogeneousandanisotropicnatureofwatercarryingfracturesandconduitsbeneaththesurface leadtoobviousproblemsindevelopingsuchan understanding( Field1993 ). Karstterrainsareuniquelysusceptibleto ooding fromgroundwatersourcesduetoacombinationof thelowstorageandhighdiffusivitycharacteristics oftheseaquifers( Parise etal. 2015 ).Waterlevels withinkarstgroundwatersystemscanrisedramaticallyduringperiodsofintenseorprolongedrainfall. Asthesubsurfacestorageanddrainagereaches capacity,therisingwatertablecanreachthetopographicsurfaceandproduce oods( Gutiérrez etal. 2014 ; Naughton etal. 2017 ).However,unlikelinear oodfeaturessuchasriverchannelsorcoastlines, themanifestationofgroundwater oodingmaybe discontinuousanddeterminedbythespatiallyvariablehydrodynamicpropertiesandresponseswithin thekarstsystem.Thesurfaceexpressionofgroundwater oodingmayonlyoccurduringextreme weathereventsandatrelativelylongrecurrence intervals.Thusthe oodfrequenciestraditionally usedin oodriskassessment(suchas10or1% annualexceedanceprobability)maybeunde nable. Theseinherentdif cultiesareexplicitlyacknowledgedwithintheEuropeanUnionFloodsDirective 2007 / 60 / EC ,wherebyMemberStatesarepermitted tolimitgroundwater oodhazardmapstoextreme eventscenariosonly. Groundwater oodinghasnottraditionallybeen recognizedasposingasigni cantriskandso remainsrelativelylesswellunderstoodthanother formsof ooding( Bonacci etal. 2006 ; MorrisFrom :PARISE,M.,GABROVSEK,F.,KAUFMANN,G.&RAVBAR,N.(eds)2018. AdvancesinKarstResearch: Theory,FieldworkandApplications .GeologicalSociety,London,SpecialPublications, 466 ,397 – 410. FirstpublishedonlineDecember11,2017, https: // doi.org / 10.1144 / SP466.9 ©2018GeologicalSurveyofIreland.PublishedbyTheGeologicalSocietyofLondon. Publishingdisclaimer: www.geolsoc.org.uk / pub_ethics

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etal. 2007 ).Consequently,investigationsintothe contributionofkarsthydrologytosurface ooding arestillintheirinfancy( Gutiérrez etal. 2014 ). Thishasbeguntochangeinthelastdecadeorso, driven,inpart,bytheintroductionoftheEuropean UnionFloodsDirectiveanditsrequirementtoconsiderallformsof ooding,includinggroundwater, butprimarilyduetoaseriesofgroundwater-related oodeventsacrossEurope – inFrance( Pinault etal. 2005 ; Maréchal etal. 2008 ),Spain( LopezChicano etal. 2002 ),theUK( Hughes etal. 2011 ; Morris etal. 2015 ),Croatia( Bonacci etal. 2006 ) andItaly( Parise2003 ).Studiesofpoljehydrology and oodingareperhapsthebestdescribedin theliterature. IntheRepublicofIreland,thelastdecadehas seentheworstgroundwater oodinginlivingmemory.Thedramatic oodsduringthewintersof2009 and2015causedwidespreaddamageanddisruption tocommunitiesacrossthecountry,particularlyinthe extensivekarsticlimestonelowlandsonthewestern seaboard( Naughton etal. 2017 ).Thispaperpresents adetailedexampleofthephenomenonofgroundwater oodinginthelowlandkarstterrainsofwestern Ireland.Usingexamplesandinsightsgainedduring therecentunprecedented oodevents,wedescribe themainhydrologicalandgeomorphologicalcharacteristicsin uencing oodinginthesecomplexlowlandkarstgroundwatersystems.BackgroundandgeologicalcontextLimestoneaccountsfor>40%(30000km2)ofthe surfaceornear-surfaceoutcropintheRepublicof Ireland,makingitthemostprevalentbedrock typeandprimaryregionallyimportantaquiferlithologyinthecountry( Simms2004 ; Drew2008 ).The mainIrishlimestoneswereformedduringtheEarly CarboniferousorDinantian( Drew etal. 1996 ) whenamarinetransgressionintheTournaisian periodinundatedmuchoftheOldRedSandstone continentandprovidedthedepositionalenvironment necessaryforlimestoneformation( Guion etal. 2000 ; Sevastopulo&WyseJackson2009 ).ThetelegeneticoriginofIrishlimestoneshasresultedinlittle primary(matrix)porosity;instead,moderngroundwatercirculationisdominatedbysecondary(joints, fracturesandbeddingplanes)andtertiary(solutionallywidened)porosity.Irishlimestoneshaveundergonekarsti cationmanytimessincetheirformation, withthemostsigni cantperiodbeingtheTertiary (65 – 2Ma)( Williams1970 ; Drew1990 ).Karstfeatureshavebeendocumentedin>80%ofthelimestoneoutcrop,indicatingthatkarsti cationhas occurredacrossmost,ifnotall,ofthelimestoneformationsinthecountry( Drew etal. 1996 ).More recentdissolutionprocessesduringtheHolocene (10katopresent)hasalsoresultedinthedevelopmentofaweatheredepikarstzonenearthebedrock surface,aswellasactivekarstfeatures,suchas streamcavesintheBurren( White1988 ; Drew& Jones2000 ; Drew2008 ). Thedegreeofkarsti cationvariessigni cantly acrossthecountryduetovariabilitiesinthebedrock purity,fracturingandlandscapehistory.Karstfeaturesaresparseorabsentacrossmuchofthecentral andeasternlimestones,wherenormal uvialdrainagesystemshavedevelopedwithlittleinteraction withtheunderlyingkarstaquifer( Coxon1986 ).By contrast,karstgroundwater owsystemsdominate ontherelativelypure,well-beddedlowlandlimestonesinthewestofthecountry( Fig.1 ).Theselowlandsexperienceawesternmaritimeclimatewitha long-termaverageannualrainfall(1981 – 2010)of c. 1100mm( Walsh2012 ).Rechargeisprincipally autogenicintheformofdirect(diffuse)andlocal pointrecharge;signi cantallogenicrechargeisrelativelyuncommon( Drew2008 ).OnenotableexceptiontothisistheGortLowlandcatchmentinsouth Galway,whichreceivesthemajorityofcatchment rechargefromtheadjoiningsandstoneuplands( Gill etal. 2013 ; McCormack etal. 2014 ). Over90%ofIrishkarstoccursinalow-lying orlowlandsetting,typically<100mabovesea-level ( Drew2008 ).AdistinguishingfeatureofIrish lowlandkarstterrainsistherelativelyshallow depthofthevadosezone,whereinthephreaticsurfaceremainsclosetooratthesurfacethroughout theyear.Thereiswidespreadwatercirculation betweenthesurfaceandgroundwater owsystems inthishydrogeologicalsetting,withfrequent reversalsofthehydraulicgradients.Theshallow depthtogroundwaterlimitsthebufferingeffectof aquiferstorageduringrechargeevents.Thelackof vadosezonestorageismitigatedbythepresence ofawell-developedepikarst,wheresigni cant weathering,fracturinganddissolutionofthenearsurfacebedrockprovidesadditionalstorage.Nonetheless,ephemeralsurface oodingfromgroundwatersourcesisaprevalentfeatureoflowland karstterrainsinIreland. Duringperiodsofhighrainfall,excessrecharge thatcannotbeaccommodatedbythesubterranean networkofwater-bearingfracturesandconduitsis temporarilystoredinephemeral,geographicallyisolatedwaterbodiesknownasturloughs.Turloughs varyinsizefrom 1hato>250haandmorethan 400activeturloughshavebeendocumented( Sheehy Skef ngton&Gormally2007 ).Turloughsareusuallylocatedalonglinesofconcentrated owwithin anaquiferandthusplayakeypartinlowlandkarst hydrology( SheehySkef ngton etal. 2006 );they actastemporarystorageforlocalandregional rechargeinaroleakintothatoftemporarybank and oodplainstoragein uvialsystems( NaughtonO.NAUGHTON ETAL. 398

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etal. 2017 ).Turlough oodingthusbearsmanysimilaritiestothatwhichoccurswithinpoljesinkarst,in thatbothactasasubsystemofsurfaceandgroundwater owthroughthekarstgroundwater owsystem( Bonacci2013 ).Infact,turloughshavebeen consideredtobeasubtypeofthepoljelandform. Bothkarstdepressionsdisplaycomplexhydrological andhydrogeologicalcharacteristics,suchasperiodic inundation,temporarysprings,lacustrinesediment deposition,swallowholesandestevelles.Aswith turloughs,the oodingwithinpoljescanbesevere andposeasigni cant oodhazardtosurrounding propertiesandinfrastructure( Mijatovic1988 ; Kovacic&Ravbar2010 ). Duringtypicalwinterrainfalllevels, oodingis con nedwithinthebasinandactsasanenvironmentalsupportingconditionforthewetland oraland faunalspeciesthathavecolonizedtheturloughhabitat( SheehySkef ngton etal. 2006 ; Moran etal. 2008 a ; Porst etal. 2012 ).Duringextremeand / or prolongedrainfall, oodwaterswithinthebasins canreachextremelevelsandcausewidespread damageanddisruptiontothesurroundingareas.It isinthiscontextthatturloughsrepresenttheprincipalformofrecurrent,extensivegroundwater oodinginIreland.Historically,groundwater ooding hasbeencentredonthekarstlimestoneplainsof thewesternlowlands,principallyincountiesRoscommon,Mayo,GalwayandClare( Fig.1 ).The lastdecadehasseentheworstgroundwater ooding thatthewesternlimestonelowlandsofIrelandhave experiencedinlivingmemory.Groundwater oodeventsof2009 – 10 and2015 – 16Thewintersof2009 – 10and2015 – 16wereexceptionallywetseasonsacrosstheRepublicofIreland. Althoughbothwintersrepresentextrememeteorologicalevents,theydifferedintheintensityand durationoverwhichrainfallpersisted.Theheavy rainfalleventsof2009werecausedbyaseriesof deep,fast-movingAtlanticdepressionscrossing Fig.1. ( a )AreasofCarboniferouslimestoneanddistributionofturloughsintheRepublicofIreland(geologicaldata fromtheGeologicalSurveyIreland).( b )Locationofgroundwater oodhazardzonesandsitelocationmap. GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS399

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thecountryduringNovember.Overtwicethelongtermaverageamountsofrainfallwererecordedat stationsacrossIreland,makingNovember2009 thewettestonrecord( Walsh2010 ; McCarthy etal .2016 ).Bycontrast,thewinterof2015 – 16 sawmorepersistentwetweather.Asuccessionof stormfrontsmovedacrossIrelandfromNovember toFebruary,bringingwiththemexceptionalrainfall accumulationsacrossmuchofthecountry( McCarthy etal. 2016 ).BetweenDecemberandFebruary,a totalof>600mm(189%ofthelong-termaverage) fellacrosstheislandofIreland,makingitthewettestwinteronrecordinarainfalltimeseriesstretchingbackto1850( McCarthy etal. 2016 ; Noone etal. 2016 ).December2015wasalsothewettest ofanymonthonrecordinIreland,with vestations exceedingthepreviousIrishrecordforthehighest monthlyrainfalltotal( McCarthy etal .2016 ). Theunprecedentedrainfalleventsduringthe wintersof2009 – 10and2015 – 16causedwidespreaddamageanddisruptiontoresidentialhouses, businesses,infrastructureandagricultureacrossthe region.Thesustainednatureofthe ooding,lasting formorethanthreemonthsinsomecases,caused prolongedhardshiptoruralcommunities,who struggledtopreventtheinundationofhomesand workplacesamidunparalleleddisruptiontotransportnetworks.The oodingoflargetractsofagriculturallandseverelyaffectedagriculturalactivity andposedaseriouswelfarerisktolivestock, whileanoxicsoilconditionsduetoprolongedsubmergencedamagedhundredsofhectaresofvaluable pastureland.Anideaofthescaleof oodingis givenin Figure2 ,whichshowstheextentof oods forsouthCo.Galwayduringthewinterof2015 – 16 derivedfrom eldandsatellitesyntheticaperture radarmeasurements.Thisregioniseffectively devoidofpermanentsurfacewater.The ooded extentsshown,encompassinganarea>38km2, areprimarilyassociatedwith oodingofthekarstic groundwatersystem.Furtherwidespread ooding wasalsoreportedincountiesRoscommonand Mayo,withmorelocalizedeventsinClare,LongfordandWestmeath. Fig.2. Groundwater oodextentmapfor2015 – 16 oodingintheGortLowlands,Co.Galway,Ireland(derived from eldmeasurementsandSARimagerycourtesyofCopernicusEmergencyManagementService). O.NAUGHTON ETAL. 400

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Groundwater oodresponseOfthesetwoexceptionalwinters,itwas2015 – 16 whichgenerallysawthehighestgroundwaterlevels andmostwidespread ooding.Althoughsomeof thedifferencecanbeaccountedforbyregional variationsinrainfall,theduration(orpersistence) ofheavyrainfallwastheprimarycause.Thecrucial durationsgoverninggroundwater oodingcanvary dramaticallydependingonthehydraulicproperties andstructureoftheaquifersystem,withresponse timesrangingfromminutesandhoursuptomultiannualtimescales( Maréchal etal. 2008 ; DeWaele etal. 2010 ; Hughes etal. 2011 ).Inthecaseof lowlandkarstgroundwater owsystemsinIreland, surface oodingisstronglyrelatedtothecumulative rainfalltypicallymeasuredinweekstomonths ( Moran etal. 2008 b ; Naughton etal. 2012 ). Figure3 showsthemaximumrainfalldepthsforarangeof durationsfromtheIrishMeteorologicalService (MetEireann)rainfallstationinGort,southGalway. Bothwintersshowedrainfalltotalssigni cantly abovethemedian(1981 – 2010)forthearea.For shorterdurations(<40days),therainfalltotalsin 2009exceededthoseexperiencedin2015,whereas forhigherdurationsthisreversed,withtherainfall totalsin2015signi cantlyexceedingthoseof 2009.Thisgreater oodingexperiencedduring 2015 – 16isanindicationthatthecrucialrainfall durationsin uencingthemagnitudeofgroundwater oodsinIrishkarstsystemsliesinthisrange. Therelationshipbetweenantecedentrainfall and oodmagnitudevariessigni cantlywithinand betweensystems,re ectingheterogeneitiesinthe extentofkarsti cation,hydraulicconnectivityand aquiferstorage.Thisvariabilitygivesrisetoaspectrumof oodingregimeswithinturloughs,ranging fromshortduration oodinginbasinswitharapid responsetorainfallevents,tolongduration ooding inresponsetolongertermprecipitationpatterns ( Naughton etal. 2012 ). Anexampleofthevariabilityinwaterlevel responseduring oodconditionsisdemonstrated inFigure4 ,whichshowsnormalizedwaterlevel hydrographs(relativetotheirpeaklevel)forthree turloughsinsouthCo.Galwayduringthe2009 oodevent.Substantialdifferencesareevidentin hydrographshapeandthetimingofpeak ood levels,despitecomparableinputsofrainfall.The oodmaximuminBlackrockturloughoccurredon 26November2009,aboutthreeweeksafterthe onsetof oodingwithinthebasin.Overthisperiod, the oodwatersreacheddepthsofupto18m,representinga oodvolumeof>15.6×106m3,which includeda2.9×106m3increaseoverasingleday. Blackrockturloughhasanextensiveallogenic uplandcatchmentwiththecapacitytorapidlydeliver largeamountsofrechargetotheturlough,which is,inturn,drainedbyalargeconduitnetwork ( McCormack etal. 2016 ).Bycontrast,thenearby CaranavoodaunandTermonturloughshavemore localizedautogeniccatchments.Caranavoodaunturloughshowedadampedresponsecomparedwith Blackrock,withpeaklevelslaggingbyabouteight daysandshowingarelativelyprolongedrecession. TermonSouthturloughdidnotpeakuntilmuch 0 100 200 300 400 500 600 700 800 900 1000110100Rainfall Total (mm)Duraon (days) 2009/2010 2015/2016 Median Fig.3. MaximumrainfalldepthsrecordedattheGort(Derrybrien)rainfallstation,Co.Galwayforwinter2009 – 10 and2015 – 16. GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS401

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laterinthe oodingseason,on6January2010. TheheavyrainfallofNovember2009contributed signi cantlytothestored oodwaterswithinTermon,buttheslowdrainagecharacteristicsofthe underlyinggroundwater owsystemmeantthat peaklevelsoccurredmuchlaterintheseasonafter furtherrainfall.The oodmaximuminTermon turloughisthusafunctionofarainfallduration measuredinmonthsratherthantheweeksofBlackrockturlough.Groundwater oodingmechanismsInresponsetothe oodingin2009and2015,wecarriedoutaseriesofstudiesforkeylocationsidenti ed bytheOf ceofPublicWorksandlocalauthoritiesas potentiallyaffectedbygroundwater ooding.The objectivewastoassesstheextent,natureandmechanismsof ooding,whetherasigni cant oodrisk existedandwhethergroundwaterwasthekeycontributortothatrisk.Consistentlong-termdataon groundwater oodinginIrelanddonotexistand informationwasthereforederivedfromdiverse sources,including eldmeasurements,hydrometric data,aerialphotography,satelliteimagery,historical landmaps,technicalreports,localauthorityroadclosurenotices,localaccountsandmediasources.What becameapparentduringthestudywasthatalthough theprimaryformofextensive,recurrentgroundwater oodinginIrelandoriginatesinturloughs, arangeofmechanismsbeyondsimpleturlough oodingplayakeypartduringextremegroundwater oodevents. FromexperienceintheChalkaquifersofsouthernEngland, Robins&Finch(2012) proposedtwo distincttypesofgroundwater oodevent:groundwater oodingandgroundwater-induced ooding. Theformerisconsideredasatruegroundwater oodinwhichthewatertablerisesabovetheground elevation,whereasagroundwater-induced ood occurswhenintensegroundwaterdischargevia springsandhighlypermeableshallowhorizonsdischargestothesurfacewater,causingoverbank ooding( Robins&Finch2012 ).Asimilardivisionis proposedhereforlowlandkarstgroundwatersystems,wherein oodmechanismscanbebroadly dividedintothosewherethedamagemechanismis primarilyduetoeitherhydrostaticactionorhydrodynamicaction.Theprincipalmechanismsidenti ed Fig.4. RainfallrecordfromGortrainfallstationandnormalizedwaterlevelhydrographsforBlackrock, CaranavoodaunandTermonSouthturloughs,Co.Galway. O.NAUGHTON ETAL. 402

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aregivenin Table1 and Figure5 andrepresentthe typeexamplesofhowgroundwater oodingmanifestsinIrishlowlandkarstcatchments.Themain damagemechanisminturloughandbackwater oodingofsinksisbyhydrostaticaction,whereby elevatedwaterlevelswithlowornegligiblewater velocitiesposearisktosurroundingreceptors. Mechanismswherehydrodynamicaction( owing water)posedariskincludedephemeraloverland owduetotheovertoppingof oodeddepressions, andexcessdischargefrompermanent / transient springsandresurgences.Turlough oodingTurloughsrepresenttheprincipalformofrecurrent, extensivegroundwater oodinginIreland.Dozens ofexamplesof oodingaroundturloughbasins wereidenti edacrossthewesternlowlands(e.g. Fig.2 ).Althoughthenumbersofreceptorsaffected atanyonesitewererelativelylow,cumulativelyturlough oodingcausedextensivedamageanddisruptiontocommunitiesacrosstheregion.Forexample, Rahasaneturlough,intheDunkellinRivercatchment,Co.Galway, ooded12housesalongits Table1. Groundwater oodingmechanismsinlowlandkarstgroundwatersystemsinIreland TypeDamageDescription Turlough oodingHydrostaticTurlough oodwatersrisetoextremelevelsandposea oodrisktothesurroundingarea Backwater oodingHydrostaticPointrecharge(sinkingstreams / rivers)exceedsthe groundwaterdrainagecapacity,causinginundationofthe sinkitselfandbackwater oodingupstream Overtoppingofsinks / basins HydrodynamicEphemeraloverland owduetoovertoppingof ooded depressions Dischargefromsprings andresurgences Hydrodynamic(a)Groundwaterspringsandrisingsattheperipheryof uplandareasexceednormaldischargelevels,causing oodingaroundanddownstreamoftheresurgence (b)Shallowlateral owpathsareactivatedwithinthe epikarstbyhighgroundwaterlevels,triggering ephemeralspringsand oodingof adjacentdepressions Fig.5. Groundwater oodmechanismsinlowlandkarstgroundwater owsystems:( a )turlough / backwater ooding ofsinks;( b )overtoppingofbasinsandsinks;( c )dischargefromspringandresurgencesattheperipheryofupland areas;and( d )lateral owthroughshallowepikarstpathways. GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS403

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banksduringtheNovember2009event.Floodingat Labaneturlough,Co.Galway,forcedtheclosureof theN18roadbetweenGalwayCityandLimerick Cityformorethantwomonths.Furthernorthat LoughFunshinagh,Co.Roscommon, oodwaters in2015 – 16werethehighestinlivingmemory,coveringanareaof4.6km2withapeakvolumeof>16× 106m3.LoughFunshinaghwasnotableduetothe lengthoftimethe oodwaterspersisted,withwater levelsfallingatarateofonlyafewcentimetresper week.Floodlevelsremainedhighthroughout2016 andwerestillabovethepreviousrecord ood (from2009to2010)afullsixmonthsafterthepeak. Thenatureof ooding,intermsoftiming,extent andduration,variedsubstantially,bothlocallyand regionally,inlinewiththespectrumof ooding regimesandmodusoperandicharacteristicofturloughs( Naughton etal. 2012 ).Thismayinsome partbeduetotheirpolygeneticoriginsandthecomplexlandscapehistoryofIrishlimestones.Turloughs wereoriginallyconsideredashollowsinglacialdrift withunderlyingkarstdrainagesystems( Williams 1964 ).However, Drew(1973) assertedthatturloughsinvariablylieinbedrockhollowsandwere solutionalfeaturesrequiringafarlongerperiodto developthanhaspassedsincethelastglaciation. Coxon&Coxon(1994) suggestedthatturloughs arepolygenetic,withglacialdepositionin uencing theirmorphology,butsolutionalratherthanglacial processesbeingthedeterminingfactorinturlough formation.Thelinesofhighpermeabilityassociated withturloughsmaythusrepresentthere-useof remnantsofkarstdrainagesystemscreatedduring Tertiarydissolution,butsubsequentlypartially blockedbyglacialdrift,ratherthanpost-glacialdissolutionpathways. Coxon&Drew(1986) suggested threemodelstoexplainturloughoriginandthepresenceofthehighpermeabilityzonesrequiredforturloughformation:(1)glacialhollowswith owpaths developedpost-glacially;(2)glacialhollowsthat developedalongthelineofexistingpre-glacial owroutes;and(3)pre-glacialkarstfeatureswith associated owpathsmodi edbyglaciation. Thehydrologicalbudgetofturloughscanbe describedusingtwogeneralconceptualmodels: throughowsystemsandsurchargedtanksystems ( Naughton etal. 2012 ).Rainfallonto,andevaporationfrom,thewaterbodyiscommonacrossallmodels,aswellassurfacerunofffromthesurrounding slopes.Surfaceevaporationisgenerallyofminor importancetothewaterbudgetduetotheseasonality ofturlough oodingbecauseittypicallyoccursduringthewintermonths.Directprecipitationandrunoffcanbesigni cant,particularlyinshallow, at basins,butunder oodconditionsgroundwater owisthedominanthydrologicalprocess. Inthroughowsystemstherechargeanddischargeprocessesworkinpartialisolation,withno directtransferofwaterbetweenthemwithout rst passingthroughthemainwaterbody.Theturlough basineffectivelyactsasasink,receivingrecharge fromthesurroundingvadosezone,shallowgroundwatersystemsand / orpointrecharge.Inthecaseofa purelydistributedthroughowsystem,drainage occursviaadistributednetworkofshallowfractures andconduits( Fig.6a).Throughowsystemscan alsoconsistofpointrechargeanddischarge ( Fig.6b ),butgroundwater owwithinthesystem elementsisunidirectional.Inasurchargedtank system( Fig.6c ),themainrechargeanddischarge processesdonotoccursimultaneously.Instead,the waterbudgetiscontrolledbyabidirectional ow systemlocatedatorneartheturloughbase,with theturloughactingasover owstoragefortheunderlyingconduitnetwork.Underthisscenariothereis nosigni cantdischargefromtheturloughduring llingperiods.Duringrecessionperiodsrechargeisstill derivedfromthelocal(proximal)shallowgroundwatersystems,butnotfromthedistalcatchment ( Naughton etal. 2012 ). Understandingthenatureofaturlough ’ shydrologicalbudgetiscrucialifactive oodmanagement measuresaretodelivertheintendedoutcomes.For example,theconstructionofsurfacedrainageis oftenthe rstalleviationoptionconsideredaftera oodevent.Akeyelementofdrainagedesignisan estimateoftherequiredchannelconveyancecapacity.Inthecaseofathroughowsystem,areasonablebasisforsuchacalculationwouldbethenet volumechangeswithinthebasinduringarepresentative oodseason.However,thisisnotthecase forasurchargedtanksystem.Arti ciallylowering thehydraulicheadwouldincreasethegradientinto thebasin,asthewaterbudgetiscontrolledbythe headdifferencebetweentheturloughandtheunderlyinggroundwatersystem.Theextraconveyance capacityprovidedbythechannelwouldthusbeat leastpartiallyoffsetagainstincreasedrechargefrom thedistalcatchment.Althoughtheeffectivecatchmentarearequiredtoprovidesuf cientrechargeto oodaturloughbasinmayberelativelymodestif operatingasathroughowsystem,oftheorderof afewsquarekilometres,thecatchmentfromwhich oodwaterscanpotentiallybederivedcanbeorders ofmagnitudegreaterinsurchargetanksystems.In thiscase,thecapacityofthedrain / culvertmay needtobesigni cantlygreaterthanthatinathroughowturloughofcomparablesize. Theexcavationandclearanceofswallowholesis oftencitedasapotentialsolutiontoturlough ooding.Althoughthismayimprovedrainageinsome circumstances,thedrainagerateisoftennotlimited bylocalizedconstrictionsattheinlet,butbythe capacityoftheunderlyinggroundwater owsystem. Inthecaseofsurchargedtanksystems,anysurface modi cationoftheestevelleisunlikelytoreduceO.NAUGHTON ETAL. 404

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oodingbecauseitservesasboththeentryandexit pointsfor oodwaters.Inthroughowsystemsthe rateofdrainageisdependentonthe owcapacity andtherelativehydraulicheadwithintheturlough andreceivinggroundwatersystem.Ifthisgradient issuf cientlysmall,asisoftenthecaseduring oodconditions,out owmayceasealtogetherand soanyperceivedimprovementindrainagedueto swallowholeenlargementisunlikelytoimprove thesituation.Moreover,theroleofturloughsas oodattenuationdeviceswithinlowlandkarst systemsmeansthatthereductionof oodriskin oneturloughislikelytobeattheexpenseofraising itinanother,soasolidunderstandingofbothsiteand catchmenthydrodynamicsiskey.Backwater oodingofsinksBackwater oodingoccurswhenexcesspoint recharge(sinkingstreamsorrivers)causesthe Fig.6. Conceptualdiagramsrepresentingpossibleturloughwaterbudgets:( a )distributedthroughow; ( b )throughowwithdistributed / pointrechargeandpointdischarge;and( c )surchargedtank. GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS405

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inundationofdolinesorsinkscapableofaccommodatingrechargeundernormalconditions( Fig.5a ). Thismodeisanalogoustotherecharge-relatedsinkhole oodingdescribedby Zhou(2007) ,whereby oodingoccurswhenthecapacityofthesinkhole isnotsuf cienttotransferstormwaterrunoffinto thesubsurface.Thedamagemechanisminbackwater oodingisprincipallyhydrostatic,butsuch casesclearlyhaveastrong uvialcomponentgiven theirdependenceonthedischargeofthein uentsurfacewater.Backwater oodingiscommonacross theIrishkarstlowlands,butintheclearmajorityof casesitisrelatedtosmallautogenicstreamswith lowbase owdischargesandsodoesnotposea signi cant oodrisk.Historically,large-scalebackwater oodinginkarstareaswouldhavebeenrelativelycommon.However,manyareasformerly characterizedbyinternaldrainagehavebeensystematicallymodi edbyarterialdrainageschemes builtduringthelatenineteenthandearlytwentieth centuries( Drew&Coxon1988 ).Forexample,the 1000km2ClareRivercatchmentinnorthCo.Galwayoriginallydischargedundergroundviaaseries oflargesinks,turloughsandsprings.Subsequent constructionandchannelizationoftheClareRiver alteredthenaturalkarsticgroundwatersystemand itissurfacewater,ratherthangroundwater,thatis nowthecontrollingfactorinpresentday ooding. Onecatchmentwherethekarstsystemhas remainedeffectivelyunmodi edisintheGortLowlands,southCo.Galway,andherebackwater oodingpersistsasasigni cant oodrisk.The500km2catchmentisdividedintosandstoneuplandstothe eastandalowlandlimestoneplaintothewest.Backwater oodingoccurswherepointallogenicrecharge fromthesandstoneuplands,intheformofthree rivers,dischargesontothelimestonelowlandsand sinksunderground.Themean owsintherivers rangebetween1.2and3m3sŠ 1,butdischargescan reach>40m3sŠ 1during oodconditions,causing widespread oodingupstreamandinundatinghundredsofhectaresintheprocess( McCormack& Naughton2016 ).Backwater oodingalsooccurs onthelimestoneplainduetotheintermittentrising andsinkingofdischargesfromthewell-developed conduitnetwork.Backwater oodingatonesuch sinkinKiltartanin2009incurredanestimatedcost of € 540000tothelocalcommunities( Jennings O ’ Donovan&Partners2011 )andcomparabledamagewascausedagainduringthewinterof2015 – 16.OvertoppingofbasinsandsinksThis oodmechanismisintrinsicallylinkedto oodingwithinturloughandsinkdepressionsbecauseit occurswhen oodwatersbuildupinsurfacedepressionstosuchanextentthatthelevelexceeds andovertopsthesurroundingtopographicdivide ( Fig.5b ).Whenovertoppingoccurs,ephemeral overland owroutesdevelop,bypassingthegroundwater owsystemsnormallygoverningwatermovementthroughthecatchment.Itthusdiffersfrom turloughandsink oodinginthatthedamagemechanismishydrodynamicandrelatesto oodwaters movingacrossthelandscape.This oodmechanism bearssomesimilaritytothekarst ash oods describedby Bonacci etal. (2006) ,wherebyoverland owplaysthedominantpartin oodformation andinter-basinover owand / orredistributionofthe catchmentareasoccursduetorisinggroundwater. However,where ash oodingistypicallyin responsetoshort(minutestohours),high-intensity storms,thecrucialrechargedurationfortheequivalentinlowlandkarstcanbemeasuredinweeksto months.Thisisduetothesigni cantsurfacestorage presentwithinthegentlyundulatingtopographyand lowreliefcharacteristicofthelowlandlandscape. Thedelayedbuild-upofwatersmakesthismechanismeasiertoforeseethan ash ooding,butthatis nottosaythatitiseasilypreventableormanaged. Forexample,abuild-upof oodwatersaroundKiltartan,southCo.Galwayin2009causedovertopping oftheN18NationalRoadwithtransient owratesof >30m3sŠ 1( Fig.7 ),forcingtheclosureofthehighwayandanearbyrailwaylineformorethantwo weeks.Anotherexampleofovertoppingoccurred duringthe oodsof2015 – 16furtherwestinthe GortcatchmentatCaherglassaunturlough.Flooding withintheturloughreachedrecorddepthsof14.6m, causingoverlanddischargeof>5m3sŠ 1northwards towardsCahermore,damagingpropertiesalongthe owrouteandaroundCahermoreturlough.DischargefromspringsandresurgencesFloodinginlowlandkarstaquiferscanalsobe causedbyhighdischargesofgroundwater,via springsandresurgences,duringwhichtimethe hydrodynamicforceofthe oodwateristhemain causeofdamage.This oodmechanismcanbeconsideredasgroundwater-induced,inthat ooding occursduetointensegroundwaterdischargevia springsorshallow,highlypermeablehorizons withintheepikarst( Robins&Finch2012 ).Inlowlandkarsticsystems,adistinctioncanbemade betweentwodischargescenarios:(1)groundwater springsandrisingsontheperipheryofupland areasexceedingnormaldischargelevelsandcausing oodingaroundanddownstreamoftheresurgence ( Fig.5c );and(2)shallow owpathswithinthe epikarstzoneareactivatedbyhighgroundwaterlevels,triggeringephemeralspringsand oodingof adjacentdepressions( Fig.5d ). The rstscenariooccurswherethelowlandkarst landscapeischaracterizedby atandundulating plainsseparatedbyisolatedareasofhigherground,O.NAUGHTON ETAL. 406

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suchascanbefoundinCo.Roscommonandnorth Co.Galway.Heretherechargezonesarelocated ontopographicplateaus,whichtypicallyhavethin orabsentsubsoil,haveahighdensityofrecharge landformsandawell-developedepikarstzone ( Hickey2010 ).In ltrationistransmittedthrougha well-developedepikarstsystemtospringslocated attheperipheryoftheuplandareas,wheregroundwaterisdischargedviaacombinationofperennial and / orover owsprings.Duringperiodsofintense recharge,dischargefromtheseperipheralsprings canposeasigni cant oodrisk.Excessspringdischargewastheprimarycauseofgroundwater oodinginFourRoads,Co.Galway,duringNovember 2009.Springsdischargingfromthebaseofanadjacentkarstplateaucausedlocalized oodingaround anddownstreamoftheresurgence,inundatingsix housesandacommunitycentre,aswellascausing theprolongedclosureofroadsandlimitingaccess tothelocalschool. Thesecondscenarioariseswhenelevated groundwaterlevelscausesigni cantlateral ow throughtheuppermostweatheredzoneofthebedrock,theepikarst.Karstaquiferscanhavesubstantiallyenhancedandhomogeneouslydistributed porosityandpermeabilityintheepikarst( Klimchouk 2004 ).Undernormalhydrologicalconditionsthis enhancedpermeabilityplaysanimportantpartin regulatingrechargetothephreaticzonebyconcentratingdiffuserechargetowardsareasofhighvertical permeability.However,whenphreaticgroundwater levelsrisesuf cientlyhigh,thesepathwayscan transfersubstantiallateral ows,givingriseto ephemeralspringsandseepsinadjacenttopographic depressionspreviouslyunaffectedby ooding.This mechanismcontributedtothe oodinginCarnmore, Co.GalwayinNovember2009,whenaseriesof temporaryspringsactivatedinresponsetohigh waterlevelsinanadjacentturlough.Discharge fromepikarstspringscausedthe oodingoffour houses,withafurthersevenhousesandtwobusiness premisesathighrisk.Therewasalsoasigni cant hydrostaticelementduetothepondingofspringdischarge,furtherhighlightingthat oodinginlowland karstgroundwatersystemsisoftentheresultofmultiplemechanismsactingincombination.ConclusionsLowlandkarstgroundwatersystemsrepresenta challengingenvironmentfroma oodrisk Fig.7. Over owacrosstheN18NationalRoad,Kiltartan,Co.Galway(imageprovidedbyGalwayCountyCouncil). GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS407

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managementperspective.Thediversityof ood mechanismsidenti edinlowlandkarstterrainsreinforcestheneedtodevelopagreaterunderstanding ofthecomplexhydrologicalandhydrogeological processesinoperationduring oodconditions. Althoughanimportantevidencebasehasbeencollatedongroundwater oodingfromrecentextreme events,signi cantgapsremaininourknowledge. The rstandmostpressingisthelackofhydrologicaldata,whichcouldbeaddressedthroughthe establishmentofapermanentmonitoringnetwork toprovidelong-termquantitativedataat ood-prone locations.Methodologiesforimprovinggroundwater oodhazardmapsandreal-time oodmonitoringarealsorequired.Aprerequisitetoeffective oodriskmanagementandmappingistheability tomonitorspatialandtemporalchangesin ood conditionsandextentatacatchmentscale.Traditional eld-basedmethodsareheavilyrelianton labour-intensive,site-speci cvisitsandinstrumentation.Theincreasingabilityandavailabilityofremote sensingdata,suchassyntheticapertureradar,offers thepotentialtodescribe oodconditionsquickly, accuratelyandatalargespatialscale,evenover remoteandruggedterrain. The oodsof2009 – 10and2015 – 16have broughtintofocussociety ’ sclose,andoftenturbulent,relationshipwiththewatercycleinkarst areas.Internationally,therehasbeenincreasingrecognitionofthe oodmitigationbene tsprovidedby functioningwetlands,nowheremoresothaninthe lowlandkarstlandscapesofIrelandandtheturloughs therein.However,theoften-competingprioritiesof oodmanagementandecologicalconservation meanthatinevitablecon ictslieahead.Aninterdisciplinaryapproachisthuscrucialtoenablecommunitiesinlowlandkarstregionstodevelopthe adaptationandmitigationstrategiesneededinthe faceoffutureclimateuncertainty.Thisworkwascarriedoutaspartofthescienti cproject GWFlood:GroundwaterFloodMonitoring,Modelling andMapping,fundedbytheGeologicalSurveyIreland andalsorepresentsoutputsfromresearchfundedbythe Of ceofPublicWorksandtheIrishResearchCouncil. TheauthorsthanktheIrishMeteorologicalService(Met Eireann)fortheprovisionofrainfalldata,GalwayCounty Councilfortheprovisionofaerialphotographyandgeographicalinformationsystemdata,andtheOf ceofPublic WorksfortheprovisionofLIDAR,hydrometricandaerial photographydata.ReferencesBONACCI,O.2013.Poljes,ponorsandtheircatchments. In :SHRODER,J.(Editor-in-Chief)&FRUMKIN,A.(eds) KarstGeomorphology ,TreatiseonGeomorphology, 6 .AcademicPress,SanDiego,CA,112 – 120. BONACCI,O.,LJUBENKOV,I.&ROJE-BONACCI,T.2006. Karst ash oods:anexamplefromtheDinarickarst (Croatia). NaturalHazardsandEarthSystemSciences , 6 ,195 – 203. COXON,C.E.1986. Astudyofthehydrologyandgeomorphologyofturloughs .PhDthesis,TrinityCollege Dublin. COXON,C.E.&COXON,P.1994.Carbonatedepositionin turloughs(seasonallakes)onthewesternlimestone lowlandsofIreland.II:Thesedimentaryrecord. Irish Geography , 27 ,28 – 35. COXON,C.E.&DREW,D.P.1986.Groundwater owinthe lowlandlimestoneaquiferofeasternCo.Galwayand easternCo.MayowesternIreland. In :PATERSON,K.& SWEETING,M.M.(eds) NewDirectionsinKarst .Geo Books,Norwich,259 – 279. DEWAELE,J.,MARTINA,M.L.,SANNA,L.,CABRAS,S.& COSSU,Q.A.2010.Flash oodhydrologyinkarstic terrain:FluminedduCanyon,central-eastSardinia. Geomorphology , 120 ,162 – 173. DIRECTIVE2007 / 60 / EC.2007.Directive2007 / 60 / ECof theEuropeanParliamentandoftheCouncilof23 October2007ontheassessmentandmanagementof oodrisks. Of cialJournaloftheEuropeanUnion , L288 / 27 . DREW,D.P.1973.HydrogeologyofthenorthCo.Galway& southCo.Mayolowlandkarstarea,westernIreland. In :PANOS,V.(ed.) Proceedingsofthe6thInternational CongressofSpeleology ,AcademicPress,Oloumec, C57 – C61. DREW,D.1990.ThehydrologyoftheBurren,Co.Clare. IrishGeography , 23 ,69 – 89. DREW,D.2008.HydrogeologyoflowlandkarstinIreland. QuarterlyJournalofEngineeringGeologyandHydrogeology , 41 ,61 – 72, https: // doi.org / 10.1144 / 14709236 / 07-027 DREW,D.P.&COXON,C.E.1988.Theeffectsoflanddrainageongroundwaterresourcesinkarsticareasof Ireland. In :YUAN,D.(ed.) ProceedingsoftheInternationalAssociationofHydrogeologists21stCongress ofKarstHydrogeologyandKarstEnvironment Protection , 4 .GeologicalPublishingHouse,Beijing, 204 – 209. DREW,D.&JONES,G.L.2000.Post-CarboniferouspreQuaternarykarsti cationinIreland. Proceedingsof theGeologists ’ Association , 111 ,345 – 353. DREW,D.,BURKE,A.M.&DALY,D.1996.Assessing theextentanddegreeofkarsti cationinIreland. In : ROZKOWSKI,A.,KOWALCZYK,A.,MOTYKA,J.&RUBIN, K.(eds) InternationalConferenceonKarstFractured Aquifers – VulnerabilityandSustainability ,June 10 – 131996,Katowice-Ustron,Poland.SilesiaUniversityPress,Katowice,37 – 47. FIELD,M.S.1993.Karsthydrologyandchemicalcontamination. JournalofEnvironmentalSystems , 22 ,1 – 26. GILL,L.W.,NAUGHTON,O.,JOHNSTON,P.M.,BASU,B.& GHOSH,B.2013.Characterisationofhydrogeologicalconnectionsinalowlandkarstnetworkusingtime seriesanalysisofwaterlevelsinephemeralgroundwater-fedlakes(turloughs). JournalofHydrology , 499 , 289 – 302, https: // doi.org / 10.1016 / j.jhydrol.2013.07.002 GUION,P.D.,GUTTERIDGE,P.&DAVIES,S.J.2000.CarboniferoussedimentationandvolcanismontheLaurussian margin. In :WOODCOCK,N.&STRACHAN,R.(eds) O.NAUGHTON ETAL. 408

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GeologicalHistoryofBritainandIreland .Blackwell Science,Oxford,227 – 270. GUTIÉRREZ,F.,PARISE,M.,DEWAELE,J.&JOURDE,H.2014. Areviewonnaturalandhuman-inducedgeohazards andimpactsinkarst. Earth-ScienceReviews , 138 , 61 – 88. HICKEY,C.2010.Theuseofmultipletechniquesfor conceptualisationoflowlandkarst,acasestudyfrom CountyRoscommon,Ireland. ActaCarsologica , 39 , 331 – 346. HUGHES,A.G.,VOUNAKI,T.ETAL.2011.Floodriskfrom groundwater:examplesfromaChalkcatchmentin southernEngland. JournalofFloodRiskManagement , 4 ,143 – 155. INTERGOVERNMENTALPANELONCLIMATECHANGE2014. Summaryforpolicymakers. In : ClimateChange 2014 – Impacts,AdaptationandVulnerability:Part A:GlobalandSectoralAspects:WorkingGroupII ContributiontotheIPCCFifthAssessmentReport . CambridgeUniversityPress,Cambridge,xv – xvi. JENNINGSO ’ DONOVAN&PARTNERS2011. Engineering ProposalsfortheReinstatementofCulvertsonthe N18andtheProvisionofNewCulvertsonMinor RoadsatKiltartan / FeasibilityofanOverlandChannel fromCooletoKinvarra .Of ceofPublicWorks, Galway. KLIMCHOUK,A.2004.Towardsde ning,delimitingand classifyingepikarst:itsorigin,processesandvariants ofgeomorphicevolution. SpeleogenesisandEvolution ofKarstAquifers , 2 ,1 – 13. KOVACIC,G.&RAVBAR,N.2010.Extremehydrological eventsinkarstareasofSlovenia,thecaseofthe UnicaRiverbasin. GeodinamicaActa , 23 ,89 – 100. LOPEZ-CHICANO,M.,CALVACHE,M.L.,MARTIN-ROSALES,W. &GISBERT,J.2002.Conditioningfactorsin oodingof karsticpoljes – thecaseoftheZafarrayapolje(south Spain). Catena , 49 ,331 – 352. MARÉCHAL,J.-C.,LADOUCHE,B.&DÖRFLIGER,N.2008. Karst ash oodinginaMediterraneankarst,theexampleofFontainedeNîmes. EngineeringGeology , 99 , 138 – 146. MARTINOTTI,M.E.,PISANO,L.ETAL.2017.Landslides, oodsandsinkholesinakarstenvironment:the1 – 6 September2014Garganoevent,southernItaly. Natural HazardsandEarthSystemSciences , 17 ,467 – 480. MCCARTHY,M.,SPILLANE,S.,WALSH,S.&KENDON,M. 2016.Themeteorologyoftheexceptionalwinterof 2015 / 2016acrosstheUKandIreland. Weather , 71 , 305 – 313. MCCORMACK,T.&NAUGHTON,O.2016.Groundwater oodingintheGortLowlands. GroundwaterNewsletter , 53 ,7 – 11. MCCORMACK,T.,GILL,L.W.,NAUGHTON,O.&JOHNSTON, P.M.2014.Quanti cationofsubmarine / intertidal groundwaterdischargeandnutrientloadingfroma lowlandkarstcatchment. JournalofHydrology , 519 (PartB),2318 – 2330. MCCORMACK,T.,NAUGHTON,O.,JOHNSTON,P.M.&GILL, L.W.2016.Quantifyingthein uenceofsurface water – groundwaterinteractiononnutrient uxina lowlandkarstcatchment. HydrologyandEarthSystem Sciences , 20 ,2119 – 2133. MIJATOVIC,B.F.1988.Catastrophic oodinthepoljeof CetinjeinFebruary1986,atypicalexampleofthe environmentalimpactofkarst. EnvironmentalGeology , 12 ,117 – 121. MORAN,J.,SHEEHYSKEFFINGTON,M.&GORMALLY,M. 2008 a .Thein uenceofhydrologicalregimeandgrazingmanagementontheplantcommunitiesofakarst wetland(Skealoghanturlough)inIreland. Applied VegetationScience , 11 ,13 – 24. MORAN,J.,KELLY,S.,SHEEHYSKEFFINGTON,M.&GORMALLY,M.2008 b .TheuseofGIStechniquestoquantifythehydrologicalregimeofakarstwetland (Skealoghanturlough)inIreland. AppliedVegetation Science , 11 ,25 – 36. MORRIS,S.E.,COBBY,D.&PARKES,A.2007.Towards groundwater oodriskmapping. QuarterlyJournal ofEngineeringGeologyandHydrogeology , 40 , 203 – 211, https: // doi.org / 10.1144 / 1470-9236 / 05-035 MORRIS,S.,COBBY,D.,ZAIDMAN,M.&FISHER,K.2015. Modellingandmappinggroundwater oodingat thegroundsurfaceinChalkcatchments. Journalof FloodRiskManagement , https: // doi.org / 10.1111 / jfr3.12201 NAUGHTON,O.,JOHNSTON,P.M.&GILL,L.2012.Groundwater oodinginIrishkarst:thehydrologicalcharacterisationofephemerallakes(turloughs). Journalof Hydrology , 470 – 471 ,82 – 97. NAUGHTON,O.,JOHNSTON,P.M.,MCCORMACK,T.&GILL, L.W.2017.Groundwater oodriskmappingand management:examplesfromalowlandkarstcatchment inIreland. JournalofFloodRiskManagement , 10 , 53 – 64. NOONE,S.,MURPHY,C.,COLL,J.,MATTHEWS,T.,MULLAN, D.,WILBY,R.L.&WALSH,S.2016.Homogenization andanalysisofanexpandedlong-termmonthlyrainfall networkfortheislandofIreland(1850 – 2010). InternationalJournalofClimatology , 36 ,2837 – 2853. PARISE,M.2003.Floodhistoryinthekarstenvironmentof Castellana-Grotte(Apulia,southernItaly). Natural HazardsandEarthSystemScience , 3 ,593 – 604. PARISE,M.,RAVBAR,N., ŽIVANOVIC ,V.,MIKSZEWSKI,A., KRESIC,N.,MÁDL-SZO NYI,J.&KUKURIC ,N.2015. Hazardsinkarstandmanagingwaterresourcesquality. In :STEVANOVIC ,Z.(ed.) KarstAquifers – CharacterizationandEngineering .ProfessionalPracticeinEarth Sciences.Springer,Berlin,601 – 687. PINAULT,J.L.,AMRAOUI,N.&GOLAZ,C.2005.Groundwater-induced oodinginmacropore-dominatedhydrologicalsysteminthecontextofclimatechanges. WaterResourcesResearch , 41 ,W05001. PORST,G.,NAUGHTON,O.,GILL,L.,JOHNSTON,P.&IRVINE, K.2012.Adaptation,phenologyanddisturbanceof macroinvertebratesintemporarywaterbodies. Hydrobiologia , 696 ,47 – 62. ROBINS,N.&FINCH,J.2012.Groundwater oodor groundwater-induced ood? QuarterlyJournalof EngineeringGeologyandHydrogeology , 45 ,119 – 122, https: // doi.org / 10.1144 / 1470-9236 / 10-040 SANTO,A.,DELPRETE,S.,DICRESCENZO,G.&ROTELLA,M. 2007.Karstprocessesandslopeinstability:someinvestigationsinthecarbonateApennineofCampania (southernItaly). In :PARISE,M.&GUNN,J.(eds) Natural andAnthropogenicHazardsinKarstAreas:Recognition,AnalysisandMitigation .GeologicalSociety,London,SpecialPublications, 279 ,59 – 72, https: // doi.org / 10.1144 / SP279.6 GROUNDWATERFLOODINGINLOWLANDKARSTTERRAINS409

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SEVASTOPULO,G.D.&WYSEJACKSON,P.N.2009.Carboniferous:Mississippian(TournasianandVisean). In :HEPWORTHHOLLAND,C.&SANDERS,I.S.(eds) TheGeology ofIreland .DunedinAcademicPress,Edinburgh. SHEEHYSKEFFINGTON,M.&GORMALLY,M.2007. Turloughs:amosaicofbiodiversityandmanagement systemsuniquetoIreland. ActaCarsologica , 36 , 217 – 222. SHEEHYSKEFFINGTON,M.,MORAN,J.,OCONNOR,A.,REGAN, E.,COXON,C.E.,SCOTT,N.E.&GORMALLY,M.2006. Turloughs – Ireland ’ suniquewetlandhabitat. BiologicalConservation , 133 ,265 – 290. SIMMS,M.J.2004.Tortoisesandhares:dissolution,erosion andisotasyinlandscapeevolution. EarthSurface ProcessesandLandforms , 29 ,447 – 494. WALSH,S.2010. ReportonRainfallofNovember2009 . MetEireann,Dublin. WALSH,S.2012. ASummaryofClimateAveragesfor Ireland1981 – 2010 .MetEireann,Dublin. WHITE,W.B.1988. GeomorphologyandHydrologyof KarstTerrains .OxfordUniversityPress,Oxford. WILLIAMS,P.W.1964. AspectsofthelimestonephysiographyofpartsofcountiesClareandGalway,Western Ireland .PhDthesis,UniversityofCambridge. WILLIAMS,P.W.1970.LimestonemorphologyinIreland. In :STEPHENS,N.&GLASSCOCK,R.E.(eds) Irish GeographicalStudies .Queen ’ sUniversity,Belfast, 105 – 124. WORTHINGTON,S.R.,SMART,C.C.&RULAND,W.2012. Effectiveporosityofacarbonateaquiferwithbacterial contamination:Walkerton,Ontario,Canada. Journalof Hydrology , 464 ,517 – 527. ZHOU,W.2007.Drainageand oodinginkarstterrains. EnvironmentalGeology , 51 ,963 – 973. O.NAUGHTON ETAL. 410


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