KiawahIsland2016BeachMonitoring

StevenTraynumCoastalScience&Engineeringstraynum@coastalscience.com

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CoastalScience&Engineering• CSEfoundedin1984• MostSCnourishmentandgroin

experienceofanyprivategroup• Completedover40nourishmentprojects

sincethe1980s.• MajorprojectsatMyrtleBeach,Seabrook,

Hunting,Edisto,Kiawah,Folly,BogueBanks(NC),NagsHead(NC).

• Servicesincludecoastalerosionassessments,projectdesignandmanagement,coastalstructures,permitting,datacollection,coastalprocessmodeling,CADD.

• WasinvolvedininitialstudiesofKiawahtodevelopconstructionsetbacklines.

• Engineeredandmonitored2006and2015eastendprojects.

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KiawahIsland• ~10milesofbeachalongamostlyeast-westconfiguration

• Stono Inlettoeast,CaptainSams Inlettowest

• Mostoftheislandhasaccretedoverpastseveraldecades(1-10ft/yr)

• Developedafterstudiesofthebeachprocessescompleted

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ShoalBypassingatStono Inlet

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Large-scaleshoalbypassing

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1860sBeach

1960sBeach

1998

20032005

FlushingChannel

2006RestorationProject

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• Moved~550,000cy• Inletrealignmentplusbeachrestoration

• Usedland-basedequipment

Post-ProjectMonitoring

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A – DuneB – WashoverC – S. IntertidalD – S. SubtidalE – Vegetated MarshF* - E. IntertidalG* - E. Subtidal

HabitatAreas

2015Project

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2015ChannelRealignmentProject• Moved100,000cy• Limitedbeachrestoration

• Focusonhabitatconservation

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KiawahIslandBeachMonitoringStations

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KeyEvents2015-2016• ChannelRealignmentProjects– Spring2015• HurricaneJoaquin– October2015• 2015Survey– November• HurricaneMatthew– October2016• 2016Survey– Jan2017(delayedforenvironmentalmonitoring)

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HurricaneMatthewImpacts• Matthewimpactedthebeacharound8October2016asaweakCategory2storm.WindsinCharleston~75mph.

• Approachedonfallingtide• Resultedinsignificantdunerecession,damagedwalkovers,minorflooding

• Stormprofilevsnaturalprofile

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DuneErosionDuringMatthew

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Post-StormConditions

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OceanCourse EugeniaAve

Post-StormConditions

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2015-2017VolumeChangesReach Name 2015-2017Unit

VolumeChange2015-2017TotalVolumeChange

2007-2017Average

1 KiawahSpit* -10.7 -94,586 -9.2/-0.1

2 WestBeach -11.5 -135,187 0.7

3 TurtlePoint -14.3 -195,106 2.7

4 OceanCourse -3.8 -34,515 6.8

5 Lagoon -23.2 -185,717 1.8

6 StonoInlet -33.6 -201,328 -7.4

1-6 All -14.8 -846,439 -0.1

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~750,000cywerelostduetorelocationofCaptainSams Inletin2015.Accountingforthisresultsinthenetchangeof0.1cy/ftperyear.

2015-2017VolumeChanges• Overalltheislandlost~850,000cyofsand• ~Halflostfromeastendandhalffromdowncoastareas

• Residentialzonelost~330,000,whichis2-3yearsworthoftypicalaccretion

• ErosionmostseverebetweenMarinersWatchandTurtlePoint#14.

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BeachRecovery• Calmweatherpromotesbeachrecovery.• Sandmovesfromunderwaterbarstothedrysandbermanddune.

• Sandlostfromsystemneedstobereplacedbynewsandfromupcoast.

• EvidenceofrecoveryinJan2017andevenmoreinFeb2017.

• Recoveringduneshavewind-blownaccumulationsatthebaseandspreadingsparsevegetation,drysandseawardofdunetoe.

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PostStormandJanuary2017Conditions

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OceanCourse

PostStormandJanuary2017Conditions

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TurtlePoint

PostStormandJanuary2017Conditions

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EugeniaAve

PostStormandJanuary2017Conditions

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KiawahSpit

EastEndChanges

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~1,400ftmigration2015-2017

EastEnd– February2017

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ConstructedInlet

NewInlet

Flushingchannel

EastEndChanges

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CaptainSams Inlet• Inletrelocated~3,000fteastin2015

• 140,000cyremovedfromnewinletbasin

• Migrated~325ftfromJuly2015toJan2017.

• Historicalrate200-300ft/yr

• Endofspitisrebuildingnormalshape

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CaptainSams Inlet

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SummaryandRecommendations• Overalltheislandlost~850,000cyofsandfromNov2015toJan2017,mostlyduetoHurricaneMatthew.Erosionwaswidespread.

• Duneerosionbetween15and40ftalongresidentialarea,higheralongKiawahSpit

• RecoveryoftheduneisongoingandshouldbemonitoredbytheTown

• Noemergencyactionispresentlyrecommended• Shouldsandfencebeinstalled,itshouldbeplacedasclosetotheprimaryduneaspossible

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SummaryandRecommendations• Theeastendprojectareacontinuestoevolve• Matthewopenedanewchannelnearthe2006channellocation

• Thepondedareanearthedrivingrangeismostlycut-offfromtidalexchange,reducingerosionthreat

• Permitallowsforanotherprojecttobecompleted,ifnecessary,in2018

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