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TRANSCRIPT
TSUNAMI IMPACTS IN THE REPUBLIC OF SEYCHELLES, WESTERN INDIAN OCEAN
BY
ANNELISEB.HAGAN,1THOMASSPENCER,1DAVIDR.STODDART,2MAURICELOUSTAU-LALANNE,3andRONNYRENAUD3
ABSTRACT
TemporalandspatialcharacteristicsoftheDecember2004tsunamiintheRepublicofSeychelles,WesternIndianOceanaredescribed,withparticularreferencetothedetailedwaterlevelrecordfromthePointeLaRuetide-gauge,Mahé,andtsunamirun-upcharacteristicsonMahéandPraslin.AssessmentsoftsunamiimpactsoncoastalandshallowmarineenvironmentsinthegraniticislandsoftheNorthernSeychelles,andonthecoralislandsofselectedlocationsintheSouthernSeychelles,arereported.Thelackofnoticeableimpactswithinthesouthernislandscomparedtothosefurthernorthappearstoberelatedtobothreducedtsunamiwaveheightstothesouthandtodifferencesinregionalbathymetry,thetsunamibeingaccentuatedbytheshelfseasoftheSeychellesBankinthenorthandnotamplifiedaroundthesouthernislandssurroundedbydeepwater.
INTRODUCTION
Atsome5000kmfromSumatra,the115islandsoftheRepublicoftheSeychelleswerenotinthefrontlineoftsunamiimpacts.Onlytwotsunami-relatedfatalitieswerereported.Nevertheless,thetsunamididhaveaconsiderableinfrastructuralandeconomicimpact,notablyonthenortherngraniticislands.Therewasprolongedfloodingofthecapital,Victoria,asaresultoftheblockingofthestormdrainagesystembysedimentsmobilizedbythetsunami,fissuringandfailureofdockwallsatPortVictoriafromrepeatedinundationanddrawdowncyclesonunconsolidatedfills(Plates1,2),washoutsofkeytransportroutesbythedrainageoftsunamiwatersfromcoastallagoons(Plates3,4),disruptionstowatersupplyandseweragenetworks(withinthecaseofthelatterattendantpollutionproblems)andextensivestructuraldamagetohouses,hotels,restaurantsandotherbeach-frontinfrastructure.TotalestimatesofdamagehavebeenassessedatUS$30million(UNEP,2005)duetobothstructuraldamageandlossofearningsfollowingtheevent.Thetsunamiwassaidtohavedamaged94fishingboats,athirdoftheentirefishingfleet,aroundMahéandfishcatchesforJanuary2005dropped1CambridgeCoastalResearchUnit,DepartmentofGeography,UniversityofCambridge,DowningPlace,Cambridge,CB23EN,UK.2DepartmentofGeography,501McConeHall#4740,UniversityofCaliforniaBerkeley,CA94720,USA.3SeychellesIslandFoundation,POBox853,Victoria,Mahé,Seychelles.
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by30%comparedtopreviouscatchesforthismonth(Payet,2005,pers.comm.).HerewedocumentthetemporalandspatialcharacteristicsofthetsunamiintheSeychellesandreviewitsimpactongeomorphologyandshallowmarineecosystems.WedrawheavilyontheCanadianUnitedNationsEducational,ScientificandCulturalOrganization(UNESCO)missiontotheSeychelles(Jacksonetal.,2005)andontheInternationalUnionfortheConservationforNatureandNaturalResources(IUCN)report(OburaandAbdulla,2005),supplementedbyourownobservationsinMahé(StoddartandHagan,1and4/2005)andtheremotesouthernislandsoftheAmirantes,Alphonse/St.FrançoisandProvidenceBank(Hagan,1/2005),AldabraandAssumption(Stoddart4/2005).
CHARACTERISTICS OF THE 26 DECEMBER 2004 TSUNAMI IN THE SEYCHELLES
TemporalCharacteristics:GraniticIslandsoftheNorthernSeychelles
TsunamiwavesreachedtheSeychellesataboutthesametimetheyimpactedMauritiusandSalalah,Oman,ca.7hoursaftertheearthquake(Fig.2;Merrifieldetal.,2005).
Figure 1.IslandsoftheSeychelles,westernIndianOcean(afterStoddart,1970).
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Figure 2.WaterlevelrecordsforIndianOceanstations,showingthetimingandmagnitudeofthe26December,2004tsunami.Top-to-bottom:Salalah,Oman;PortLouis,Mauritius;PointeLaRue,Seychelles;Lamu,Kenya.(CourtesyofJ.Huthnance;availableathttp://www.pmel.noaa.gov/tsunami/indo20041226/tsunami2.pdf).
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Tsunamiamplitudesaregreatestperpendiculartogeneratingstructures;thustheNNW–SSEorientationoftheearthquakefaultlinebetweenNWSumatraandtheAndamanIslandsputtheSeychellesBankdirectlyinlinewiththetsunamiwavefrontasasimulationofwaveheights15hoursaftertheearthquakemakesclear(Fig.3;Yalcineretal.,2005).
Waveapproachwas,however,complicatedbythelarge-scalerefractionofthewavearoundsoutheasternSriLankaandsouthernIndiaandbysmaller-scalerefractioneffectsacrosstheMaldiveschainandtheChagosArchipelago(NOAA2005b)whichwerecrossedbythetsunamica.4hoursand2.5hoursearlier(Fig.4;Merrifieldetal.,2005).
AlllocationsintheIndianOceantothewestoftheearthquakeepicenterfirstexperiencedawavecrest(Merrifieldetal.,2005).ThisfirstarrivalwasseeninthetidegaugeatPointeLaRueonMahéat08:08–08:12CoordinatedUniversalTime(UTC)(12:08–12:12localtime)(Fig.5).Thelevelreachedwas0.59mabovemeansealeveldatum(MSLD)(Fig.6).Thefirstarrivalwasonarisingtide,thepredictedlowtidehavingbeenat07:26UTC(11:26localtime);waterlevelswereraisedbutonlytotypicalhighspringtidelevelsandnotashighastheprecedinghightide(whichhadpeakedat0.74mMSLD).Thefirstlargewavearrivedat09:12UTC(13:12localtime),registeringapeakof1.16mMSLD.Boththefirstarrivalandthefirstlargewavewerefollowedbysignificantdrawdowneventsof–1.53mMSLDat08:56and09:36–09:40respectively.However,theselevelsrelatetothebaseofthetide-gaugestillingwelland,therefore,mostprobablydonotrecordthecompletefallinwaterlevel.Fromeyewitnessreports,Jacksonetal.(2005)estimatethatthetruefallinwaterlevelmayhavebeenaslowas–4.0mbelowmeansealevel.Thereafterasequenceof8waveswasrecordedbythetide-gaugeincoupletsofalargerwaveofamagnitudesimilartothefirstarrivalfollowedbyasmallerwave;superimposedonarisingtidallevelthetrendwasforanincreaseintsunamiwaveheightpeakingat1.24mat12:52UTC(16.52localtime)(Fig.6).Thiswavewasfollowedbyafurthernoticeabledrawdowneventbutafterthenexthighwave,therewasalesseningofactivityafterca.14:30UTC(18:30localtime).
Figure 3.Computermodellingofthe26December,2004tsunamiafter900minutes(courtesyofA.Yalciner,U.Kuran,T.Taymaz)(availableat:http://yalciner.ce.metu.edu.tr/sumatra/max-elev-sim-1.jpg).
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Figure 4. Water-levelrecordsforIndianOceanstations,showingthetimingandmagnitudeofthe26December,2004tsunami.Top-to-bottom:Hanimaadoo,Maldives;Male,Maldives;Gan,Maldives;DiegoGarcia,BIOT.(CourtesyofJ.Huthnance;availableathttp://www.pmel.noaa.gov/tsunami/indo20041226/tsunami1.pdf).
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However,activitycontinuedintothenexthigh-tidecycle.Thepredictedhigh-tidelevel(peakstage=75cm)wasconsiderablyhigherthantheprevioushigh-tidelevel(12cm)andwhenthetsunamiactivitywassuperimposedonthishightideitresultedinawaterlevelof1.41mat00:56UTC(04:56localtime)on27December,almostexactly24hoursaftertheearthquakeand17hoursafterthefirstarrivalintheSeychelles(Figs.5and6).
EyewitnessaccountsoftsunamiimpactontheeastcoastofMahébroadlycorrespondtothetimingsextractedfromthetide-gaugerecord.However,thereareobservationsofsignificantdrawdowneventsat07:45–08:00and08:00UTC(11:45–12:00and12:00localtime)atAnseRoyale/AnseForbansandPointeauxSelrespectivelywhichappeartoleadthetide-gaugerecord(situated14kmtothenorthofAnseForbansand7kmnorthofPointeauxSel)byalmostonehour.However,thetimingsofthefirstlargewavearebroadlycomparabletothetide-gaugerecordatthesesites.AtAnsealaMouche,onthesouthwestcoast,drawdownagainappearstohaveoccurredpriortothatrecordedinthetide-gaugerecord.Thefirstlargewave,however,appearstohavebeenalaterimpactthanontheeastcoast,timedat09:25UTC(13:25localtime),presumablyreflectingtheslowingofthetsunamiwavefrontonrefractionaroundtheisland.Victoria,AnseRoyaleandAnseForbansontheeastcoastallexperiencedasecondphaseoffloodingbetween12:30and13:00UTC(16:30–17:00localtime),asdidAnsealaMoucheonthewestcoasthalfanhourlater,apatternconsistentwiththelaterarrivalofthefirstlargewaveearlierintheday.InVictoria,itisclearthattherewassignificantfurtherfloodingduringthenightof26–27Decemberclearlyassociatedwiththewavepeaktimedat01:00UTC(05:00localtime)(Jacksonetal.,2005).ThetsunamistruckPraslin,40kmtothenortheastofMahé,intwoseparatesurges,thefirstbeginningat08:10UTC(12:10localtime).ThiswasonehourbeforethefirstlargewavewasregisteredbytheMahétide-gauge.Therewasamajordrawdowneventbetweenthiswaveandthesecondlargerwavewhichoccurredat08:24(12:24localtime).Somelocationsregisteredlargewavesatca.09:30and10:00–11:00UTC(13:30and14.30–15:00localtime)andthelateafternoonwaveof26Decemberwasseenatthenorthwesternendoftheislandat12:45UTC(16:45localtime)(Jacksonetal.,2005).
ThePointeLaRuetide-gaugeshowedthatactivitycontinuedthroughout27December(Fig.5),withanenvelopeofresidualsaroundpredictedtidallevelsdecliningovera24-hourperiod(Fig.7).On28Decemberresidualswerestillpresentbutoftheorderof10cmorless;by30Decembertheeventwasover(Fig.7).
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Figure 5. Predicted tidal-curve and water-level records, Pointe La Rue tide-gauge, Mahé, Seychelles, 26–30 December 2004. Heights in cm relative to Mean Sea Level Datum. (National Meteorological Service Seychelles / University of Hawaii Sea Level Center; available at: http://ilikai.soest.hawaii.edu/uhslc/iotd/plar1.html).
Figure 6. Detail of Figure 5 showing predicted tidal level and individual tsunami peaks and water-level drawdowns, 26 December, 2004. (National Meteorological Service Seychelles / University of Hawaii Sea Level Center; available at: http://ilikai.soest.hawaii.edu/uhslc/iotd/plar5.gif).
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OneofthestrikingfeaturesofthetsunamiatanIndianOceanbasinscalewasthedifferentiationbetweenstations,associatedwithshelfareas,whichshowedasustainedtide-gaugesignaloverseveraldaysandthosestations,predominantlyinmid-oceanlocations,whichexhibitedastronginitialsignalbutlittlesubsequent“ringing”(Merrifieldetal.,2005).TheSeychellesclearlybelongedtothefirstcategory.TheimplicationisthatthetsunamiexcitedsomeformofseicheontheSeychellesBankthatbothamplifiedandprolongedthetsunamisignal;disentanglingthetwoeffectsremainsamajoranalyticalchallenge.
SpatialCharacteristics:GraniticIslandsoftheNorthernSeychelles
Statisticsontsunamiwaveheightsattheshoreline,tsunamirun-up(thetsunami’sheightabovemeansealevelatitslimitofpenetrationinland)andinundationdistancearereportedinTable1.Theyshowtheconsiderablesite-to-sitevariabilityoverdistancesoftenoflessthan10km.Thus,forexample,AnseBoileauonthewestcoastofMahérecordedarun-upof2.5mwhereasGrandeAnse5kmtothenorthexperiencedinundationto4.3m.Whileimpactsingeneralweregreatestoneasternshoresfacingthedirectionofwavearrival,thesignificanttsunamisignalspresentontheleewardcoastsofMahéandPraslinarenoteworthyandsuggesttheoperationofaseriesofcontrolsatanumberofdifferentspatialscales.
Figure 7.Waterlevelresiduals,PointeLaRuetide-gauge,Mahé,Seychelles,26–30December,2004.(NationalMeteorologicalServiceSeychelles/UniversityofHawaiiSeaLevelCenter;availableat:http://ilikai.soest.hawaii.edu/uhslc/iotd/plarbr.html).
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Atthelargestscale,ocean-basinscalemodellingoftheDecemberevent(e.g.,NOAA,2005b)showsdivergenceofthetsunamiaroundtheshallowshelfareasoftheMascarenePlateau,thestreamingofthewave-frontaroundbankmarginsandtheconvergenceofthewaveintheleeofthePlateauatseverallocations,includingontheSeychellesBank(NOAA,2005b).RefractionattheBankscaleissupportedbytheobservationfromthenorthwestpointofPraslinthatthewavecamefromthenortheast(Jacksonetal.,2005).ItcanbeimaginedthatontheSeychellesBanktherewerefurtherrefractioneffectsaroundthelargerindividualislands.Thus,forexample,eyewitnessaccountsoftsunamiwavearrivalatAnsealaMoucheontheleewardsouthwestcoastofMahéreportedthatwavetrainsapproachedthebayfromboththenorthandsouth(Jacksonetal.,2005).Similarly,maximumwaveheightsonPraslinwereexperiencedontheleeshore(Table1).
Table 1. Maximum water levels at the coast and wave run-up, relative to mean sea level, of the 26 December, 2004 tsunami in the Seychelles (from Jackson et al., 2005).
Location Maximum Water Level Near Shoreline
(m)
WaveRun-up
(m)
InundationDistance (m)
North East Point Mahé 2.2 100 Victoria Mahé >1.7 >1.4 >200 SeychellesInternational Airport
Mahé3.0 200
Anse aux Pins Mahé >1.9 >50 Pointe au Sel Mahé 2.8 2.3 >35 Anse Royale (N) Mahé >3.8 3 >100 Anse Royale (S) Mahé >4.4 >45 Anse Forbans Mahé 2.8 20 Baie Lazare Mahé 1.6 20 Anse a la Mouche Mahé 3.0 (3.5)* 2.5 250 Anse Boileau Mahé 2.5 53 Grand Anse Mahé 4.3 nil Beau Vallon Mahé 1.7 10 Chevalier Bay Praslin 3.1 140 Anse Possession Praslin 3.0 35 Anse Petit Cour Praslin 2.5 225 Anse Volbert (1) Praslin 1.9 100 Anse Volbert (2) Praslin 2.0 >100 Grande Anse Praslin 3.6 >50 Baie Ste Anne Praslin 1.8 nil
*Figureof3.5matAnsealaMoucherecordsheightofwavesurgedamage.
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Withintheseisland-widepatternsofincidence,tsunamiimpactsweresensitivetochangesinshorelineorientation.Thus,forexample,atBeauVallon,Mahé,whichfacesnorth,themaximumrun-uplevelwasonly1.7m,slightlyaboveanormalhigh-tide.Similarly,thesoutheast-facingBaieSteAnneonPraslinonlysufferedinundationtotypicalhigh-tidelevel(Jacksonetal.,2005).Inaddition,waveswerefunnelledbetweenrockyheadlandsintoembaymentsandinfluencedbyoffshorefringingreeftopography,particularlythepresenceorabsenceofdeep-waterpassagesthroughthereefsystem.Inreef-frontedlocationsitappearsthatthetsunamiwavesbrokeonthereefandthenpropagatedacrossthereefasabore.Thesewaterflowswereinfluencedbywaveinteractions(includingwaverefractionandreflection)andinteractionswithbottomtopography.Inparticular,itappearsthattsunamirun-upwasoftengreatestattheheadofdeepchannelsthroughfringingreefs.Finally,attheverylocallevelitisclearthattouristdevelopmentverycloseto,orevenon,thebeachmademanybuildingshighlyvulnerabletowaterlevelsevenonlyslightlyabovenormalhigh-tidelevelsandtosurgevelocitiesof3.3–4.4ms-1,particularlywherethenaturalenergydissipationaffordedbythepresenceofupperbeachbermsand/orcoastalvegetationhadbeenremovedtoenhancebeachaccess(Jacksonetal.,2005).
ImpactsontheMarineEnvironment:GraniticIslandsoftheNorthernSeychelles
Aseriesofrapidassessmentsofmarineenvironmentsinthegraniticislandsbetween30December,2004and13February,2005(OburaandAbdulla,2005)identifiedtwomajorpatternsofcoral-reefdamagerelatedtolocationandsubstratetype.ThemostheavilyimpactedareaswerecarbonatereefsubstratesinthenorthernislandsaroundPraslin(includingCurieuse,LaDigue,Felicite,IsleCocoandSte.Pierre).Herelevelsofsubstratedamage(movementofrubble,erosiongullieswithinrubbledeposits)exceeded50%,andlevelsofdirectcoraldamage(coraltopplingandoverturning)exceeded25%.Bycomparison,aroundMahédamagelevelsoncarbonatesubstrateswerelessthan10%.ThroughoutthegraniticislandsoftheSeychelles,levelsofdamageongraniticsubstrateswerelessthan1%(OburaandAbdulla,2005).Cementedreefsubstratesshowedlittleevidenceofcoralbreakageoroverturning;wheredamagewaspresentitwasrestrictedtowaterdepthsoflessthan50cm.However,manyreefsurfacesinthegraniticSeychellesarecurrentlycharacterizedbypoorlyconsolidatedsurfacesresultingfromreef-frameworkdegradation,followingthecoral-bleachingandmass-mortalityeventassociatedwiththeIndianOceanwarmingof1998(e.g.,Spenceretal.,2000).Therewasconsiderablemovementofreefrubbleinsuchsettingsundertsunamisurgeconditions,andthedislocationanddamageoflivecoralcoloniesestablishedonsuchsurfaces(OburaandAbdulla,2005).
ItisimportanttorealisethatasubstantialsectoroftheeastcoastreefshasbeenprofoundlymodifiedsincetheclassicaldescriptionsofthembyLewis(1968,1969),Taylor(1968)andthesummariesbyBraithwaite(1984)andStoddart(1984).Startingwiththeconstructionoftheairstripin1971,large-scalereclamationnowextendsfor11kmfromnorthofVictoriatoPointeLaRue.Thereclamation,usedforhousing,light
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industry,andrapidroadaccesstotheairport,typicallyisseparatedfromtheoldislandshorelinebyopenwater.Surgesinsea-levelcanthusbepondedbehindthemandcanonlydrainbacktoseaviaegresschannels.ThisaccountsforthedestructionofthebridgeshowninPlate3.Drawdownandupsurgewerealsoseverelydampedintheleeofthereclamations.
Thetsunamiresultedinbeachcliffingof2.5matAnseKerlan,northwestPraslinandacalculatedlossof200x103m3ofbeachsandoffshore(UNEP,2005).Thewavesalsomobilizedmarinesediments,bothstrippingsedimentsfromcoral-reefrubblebedsanddepositingsedimentsinnewlocations;back-drainagefromrun-upmayhavealsodepositedterrestrialsedimentsonfringingreefs.Theseprocesseswereexacerbatedbystormyweatherinthedaysimmediatelyfollowingthetsunamiwhichgeneratedroughseas.Rainfalltotalsinexcessof250mmtriggeredlandslidesonMahéandledtohighterrestrialrunoffbutitisnotcleariffluvialsedimentsreachedreefenvironments.Fringingreefswereexposedbythesignificantdrawdownevents(e.g.,reportedforAnseRoyale,AnseForbansandAnsealaMouche,Mahé;exposureofmassivecoralsatAnsePetitCour,Praslinat08:00UTC,26December;Jacksonetal.,2005)butitisunlikelythattheseeventswereofsufficientdurationtocausecoraldeath.SeagrassesatBaieTernai,Maheweresmotheredbycarbonatesedimentsbutgeneraldamagelevelsinseagrassbedswerelow.ThecausewayenclosingthemangroveparklandatCurieusewastoppledinwardsbytsunamiwavesbutnodamagetothemangroveswasnoted(OburaandAbdulla,2005).
TsunamiImpactsintheSouthernSeychelles
AcollaborativeexpeditionbetweentheKhaledbinSultanLivingOceansFoundation,CambridgeCoastalResearchUnitandSCMRT-MPAtothesouthernSeychelleswasconductedonboardM.Y.GoldenShadow,10–28January2005.Althoughtheprimaryfocusofthisexpeditionwasairbornemappingoftheouterislands,duetothetimelynatureofthisexpedition,itwasexpectedthatimpactsofthetsunamiontheremotesouthernislandsoftheSeychellescouldalsobereported.TheexpeditionvisitedtheislandsofProvidence,St.Pierre,AlphonseandSt.FrançoisandthesouthernislandsoftheAmirantesgroup(D’Arros,Desroches,Desnoeufs,Marie-Louise,Boudeuse,EtoileandPoivre)somepreviouslydescribedbyStoddart(1970).StoddartalsovisitedAldabraandAssumptioninApril2005.
OnallthesouthernSeychellesislandsvisitednophysicaldamagetoeithertheterrestrialormarineenvironmentswasobserved.Thelittoralhedgewasintactinallcasesandtherewasnoevidenceofbeachsedimentmovementorwaterinundationinthelittoralarea.Underwatertherewasnoevidenceofreefdamage;thus,forexample,therewasnophysicaldamagetothebranchingcorals(principallyPocilloporaspp.)thatdominatethesereefsandnocoraltoppling.TheislandsofProvidence,Alphonse,D’Arros,Desroches,Marie-LouiseandPoivreareinhabited.Inallcases,islandpersonnelsaidthattherehadnotbeenanyimpactcausedbythetsunamiandtheyhardlynoticedtheevent.OnProvidenceIsland,theislandmanagerwasradioedfromMahéandwarnedofthetsunamiwavesapproaching.TheI.D.C.(IslandDevelopmentCompany)manager
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onAssumptionandthemanageroftheS.I.F.(SeychellesIslandFoundation)ResearchStationonAldabrabothstatethatinspiteofradiowarningstheydidnotdetectanytsunamisurges.Itisfairtoaddthatiftherehadbeenasubstantialsurgeitwouldhaveimpactedrockycoastlinesintheeastofeachisland,andthatinbothcasesthesettlementsareinprotectedwesternlocations.ProvidenceIslandisatthenortherntipofthelarge(approximately400km2)ProvidenceBank,andherethetsunamiwasobservedasasuddeninfluxofwaterapproximately10cmhigherthannormalthatremainedforafewminutesbeforedroppingtoanormallevel.Noaccuratetimecouldbegivenforthisobservation,butitwassaidtobe“aboutlunch-time”.UnfortunatelytherearenoreportsoftsunamieffectsonCoetivy.
ComputermodellingofthepassageofthetsunamiwavefrontindicatesaregionalscalerefractionofthewavefronttowardsthesouthwesternIndianOcean(NOAA,2005b).Thiswouldhaveledtoanincreaseinthelengthofwavecrestandhencelowerwaveheightstothesouth.Inaddition,thereareconsiderablecontrastsinbathymetricsettingbetweenthetwoareas.Incontrasttothenorthern,graniticislandsoftheSeychelles,thesouthernislandsaretypicallylow-lyingsandcays(islandsoftheAmirantes)andatolls(Alphonse,St.François;Desrochesisadrownedatoll)withtheexceptionofSt.Pierrewhichisaraisedplatformreefisland.ThegraniticislandsprotrudefromtheshallowSeychellesBank(meanwater-depth44-65m;Braithwaite,1984),butthesouthernislandsaresituatedinopenoceanandexhibitsteeplyshelvingfore-reefslopesorverticalreefwalldrop-offs,surroundedbydeepwater(>5,000m).Thuswhenthetsunamiapproachedtheregionofthesouthernislands,thewavespassedthroughthegapsbetweentheislandsandtherewasnoincreaseinwaveamplitudeduetothecontinuityofdeepwaterandlackofashallowbarrierintheflowpath.ThiswouldexplainthecontrastbetweenthelackoftsunamiimpactsobservedonthesouthernSeychellesislandscomparedtothesignificantimpactsobservedonthegraniticislandsoftheSeychellesBank.
ACKNOWLEDGEMENTS
ObservationsintheRepublicofSeychellesweresupportedthroughacollaborativeexpeditionbetweentheKhaledbinSultanLivingOceansFoundation,CambridgeCoastalResearchUnit,UniversityofCambridgeandSeychellesCentreforMarineResearchandTechnology–MarineParksAuthority(SCMRT–MPA).FieldworkinthesouthernSeychelleswasconductedonboardtheKhaledbinSultanLivingOceansFoundationvessel,theM.Y.GoldenShadow,10–28January2005.WearegratefultoCapt.P.Renaud,ExecutiveDirector,KhaledbinSultanLivingOceansFoundationforextensivelogisticalsupportandtotheSeychellesIslandDevelopmentCompanyforpermissiontovisitislandsintheSouthernSeychelles.
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REFERENCES
Braithwaite,C.J.R. 1984. GeologyoftheSeychelles.In:Biogeography and Ecology of the Seychelles
IslandsD.R.Stoddart(Ed.):TheHague:W.Junk,pp.17-38.Jackson,L.E.Jr.,J.V.Barrie,D.L.Forbes,J.Shaw,G.K.Manson,andM.Schmidt 2005. Effectsofthe26December2004IndianOceantsunamiintheRepublic
ofSeychelles/ReportoftheCanada–UNESCOIndianOceanTsunamiExpedition,19January–5February,2005.Geological Survey of Canada, Open File4359,73pp.
Lewis,M.S. 1968. ThemorphologyofthefringingcoralreefsalongtheeastcoastofMahé,
Seychelles.Journal of Geology76:140-153.Lewis,M.S. 1969. Sedimentaryenvironmentsandunconsolidatedcarbonatesedimentsofthe
fringingcoralreefsofMahé,Seychelles.Marine Geology7:95-127.Merrifield,M.A.,Y.L.Firing,T.Aarup,W.Agricole,G.Brundit,D.Chang-Seng,R.Farre,B.Kilonsky,W.Knight,L.Kong,C.Magori,P.Manurung,C.McCreery,W.Mitchell,S.Pillay,F.Schindele,F.Shillington,L.Testut,E.M.S.Wijeratne,P.Caldwell,J.Jardin,S.Nakahara,F.-Y.Porter,andN.Turetsky 2005. TidegaugeobservationsoftheIndianOceantsunami,December26,2004.
Geophysical Research Letters32:L09603,doi:10.1029/2005GL022610.NationalOceanicandAtmosphericAdministration(NOAA) 2005. TsunamiPropagationintheIndianOcean.
http://www.pmel.noaa.gov/tsunami/Mov/TITOV-INDO2004.movObura,D.,andA.Abdulla 2005. AssessmentoftsunamiimpactsonthemarineenvironmentoftheSeychelles.
http://www.iucn.org/info_and_news/press/seychelles-tsunami-22-02-05.pdfSpencer,T.,K.Teleki,C.BradshawandM.D.Spalding 2000. CoralbleachinginthesouthernSeychellesduringthe1997-98IndianOcean
warmingevent.Marine Pollution Bulletin40:569-586.Stoddart,D.R. 1970. CoralislandsofthewesternIndianOcean.Atoll Research Bulletin136:1-224.Stoddart,D.R. 1984. CoralreefsoftheSeychellesandadjacentregions.In:Biogeography and
Ecology of the Seychelles IslandsStoddart,D.R.(Ed.)JunkPublishers,TheHague,TheNetherlandspp.63-81.
Taylor,J.D. 1968. Coralreefandassociatedinvertebratecommunities(mainlymolluscan)around
Mahé,Seychelles.Philosophical Transactions of the Royal Society of London, SeriesB254:129-206.
162
UNEP 2005. Afterthetsunami:Rapidenvironmentalassessment.Chapter6.Seychelles,96-
111.http://www.unep.org/tsunami/tsunami_rpt.asp
Yalciner,A.,U.KuranandT.Taymaz 2005. ComputermodelingoftheDecember26,2004NorthSumatratsunami.
http://yalciner.ce.metu.edu.tr/sumatra/max-elev-sim-1.jpg
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te 1
Plate 1 Plate 2
Plate1.Internalfissuringandcollapseofdockquay,PortVictoria,Mahé.
Plate2.Failureofquayside,PortVictoria,Mahé.
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Plate 3. Road bridge washout from seaward drainage of tsunami waters from coastal lagoon, west coast of Mahé.
Plate 4. Road bridge washout following drainage of tsunami waters, southwest Mahé.