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FIELDOBSERVATIONSOFRIPCURRENTS By JAMESH.MACMAHAN ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 2003 Thisdissertationisdedicatedtomyfamilyandfriends,whosupportedmethroughoutthis process. ACKNOWLEDGMENTS Asmyacademiccareercomestoaconclusion,Ihavemanypeopletothankwho haveassistedmeeitherscientifically,socially,orboth,allofwhichhascontributedto makingthisawonderfulandrewardingexperience.First,Iwouldliketoexpressmy appreciationtoDr.RobertDean,whobelievedinmeinthebeginningandgavemethe necessarylatitudetoallowmetodevelopasapersonandascientist.ThelessonsIhave learnedfromthiswillaidinmyfutureandIamgratefulforDr.Deansunselfishnessand wisdom.ThoughIprobablyhavefmstratedhimattimes,heneverindicateditandhe alwayssupportedmeinmytimesofneed. BeforeIstartedattheUniversityofFlorida,Dr.Deanplantedanideaof investigatingripcurrentsinmyhead.SincethedayIsteppedfootinthedepartment,I wantedtostudyripcurrents.ThoughIdidendupstudyingripcurrents,thepathwayto thisgoalwasnotverydirect.Afterspendingthefirstspringsemesterwritingaproposal totheOfficeofNavalResearchwithDr.Dean,IworkedattheUnitedStatesGeological SurveywithDr.GuyGelfenbaumandDr.DougWilsoninvestigatingripplesoffthecoast ofSt.Petersburg,FL.WhileworkingattheUSGS,GuyGelfenbaumlearnedofmy interestinbuildingahydrographicsurveyingsystemusingapersonalwatercraftfor investigatingripcurrents.Afteranunsuccessfulfirstroundinobtainingfundingtostudy ripcurrents,GuysponsoredmetobuildthePWCsystemfortheSouthwestWashington CoastalErosionStudy.ThisiswhenImetthe“oneandonly”PeterRuggerio,whoisone cooldude.IhadablastthatsummercollectingbathymetricprofilesofftheWashington andOregonshorelinesandstayinginsomeoftheshadiesthotelsinthePacificNorthwest. IwouldalsoliketothankMarkHansenforsuggestingthatIgotoUFandworkwithDr. Dean.MarkalsoassistedmewithmysurveyingquestionsduringthedesignoftheUSGS PWC.DaveWegenerhelpedmeoutalotwiththeconstructionoftheUSGSPWC. Atthispoint,wefinallyreceivedfundingtostudyripcurrentsinFlorida.Ibegan collaboratingwithDr.RobertThieke,whoisoneofthemostarticulateandcaptivating professorsthatIknow.Ihaveenjoyedmanyofourlongconversationsthatoriginated overrathersimplequestions.Thoughourdreamdatasethasyettocometofimitionforan intensecollaboration,Ihaveenjoyedourdiscussionsandlookforwardtofutureones. IextendmyappreciationtoLyndaCharlesandTomWattersforfundingthe coastaldepartmentfordevelopingaUFPWC,whichhasallowedmetocollaboratein manyadditionalprojects,whicheventuallycontributedtothisbodyofwork.James JoynermadetheUFPWCtopnotchandhasalwayssupportedandassistedmeinmy efforts. IthasbeenapleasuretoworkwithSidneySchofieldandVikAdamsinthefield andoutatthelaboratory.VikisoneofthemostrelaxedfieldguysandIwillneverforget thetimehewasinvertedina5footdeepjettedsandpitontheshore-breakofDaytona BeachduringtherecoveryoftheAquadopp.Sidneywasalwaysavailabletoanswermy questionsandIenjoyedourdiscussionsofelectronics,biking,andhisextracurricular activities.Mr.VernonSparkmanalwaysgreetedmewithafriendly“hello”,butalways IV followeditbysomejokingremark. IextendmyappreciationtoDonaMossandLucyHammfortreatingmeas individualandnotasastudent,therebyallowingmetounderstandthefundingand proposalprocess.Ilearnedalotofvaluablelessonsfromthem,whichwillassistmein thefuture.Thankstotherestoftheofficestaff:Thelma,Donna,Carol,andDebra. Duringthesummerof2000,Dr.EdThorntoncametovisitthedepartment,ashe wasontheexternalvisitingcommittee.Thestudentshadtheopportunitytomeetwiththe committeeandIwasanxiouslyinterestedinchattingwithEd.IspokewithEdforabout anhourandhementionedthepotentialopportunityformetocometoMontereyinthe futuretoassistincollectingbathymetricmeasurements.Severalmonthslaterwhilesitting atmydesk,IreceivedacallfromDistinguishedProfessorThorntonaskingmeifIwas interestedinheadingtoMontereyinthespringof2001.1wasexcitedaboutthe opportunity,butIneverrealizedhowsignificantthisopportunitywouldbe.Iamprobably theonlystudenttoturndownaFulbrightFellowshiptostudyartificialsurfingreefsin NewZealandtoworkintheUnitedStates. DuringtheMontereyexperiment,knownasRIPEX,Igottheopportunityto participateinalargefieldexperiment.Thiswasadreamcometrue,asImissedallofthe Duckexperiments.Theexperimentwasablast.Duringthisexperiment,ImetEdand TimStanton’screw:EdithGallagher,RobWyland,MarkOrzech,andJimStockel.Greg MillerandIstayedatthebeachfrontNavalPostgraduateSchoolbedandbreakfast,where theshowersdidnotworkinitially.Afriendlyguy,AdReniers,Edspost-doctoralfellow, broughtGregandmeintohishouseforahotshowerandgoodmeal.Ididnotrealizeitat V thetime,butAdwouldbeeomeagreatfriend,amentor,andpersonforwhomIinspireto be.Adunselfishlyallowedmetoutilizetheripcurrentdataarray,whichhesuggestedfor hisownscientificpursuits,thathasnowbecomeasignificantportionofmydissertation.I mustthankStellaandFemkeforbeingmyadoptedMontereyfamily.Iwilltreasurerthe timesatChe’Renters.MycollaborationswithEdandAdhavejustbegunandIlook forwardtothefutureinteractions. IwouldliketothankDanHanes,anoriginalcommitteemember,forassistingme onproposals,providingusefulscientificdiscussion,andlettingmeteachinhisclasses.I wouldalsoliketoextendmyappreciationtotheremainingcommitteemembers.Dr.Ochi andDr.Mossa BesidesthescientificfolksthatIhavemetalongtheway,mycomradesin Gainesvillehavealwayssupportedme.Susan“Powell”DevineandKerryAnnDonahue introducedmetoGainesvilleallowingmetocontinuebeingmyselfwithoutskippinga beat.ThanksgoestoA1Browder,HugoRodquiez,andEricThostesonforteachingme thewaysofthedepartmentandsharingtheirenthusiasmforcoastalengineering.Ihave hadrewardingexperienceswithassistingJasonEngleandGregoryMillerintheir Masters.IextendmyappreciationtoJonMiller,Oleg,Justin,LoraineChiale,andJack Puleo.Thanksforatwogreatyearswithmyoriginalclass,thoughnotoneofthemare stillhere;CrisWeber,DaveAltman,LisaHeckman,BethCranston,HeatherSummerell, andSeanMulcahy.IextendmyappreciationtotheStatsgroupforprovidingsome diversityandthefootballblock(STA);JeffThompson,WolfgangYank,BrianCaffo,and PatchesJohnson.Thenewgroup(RobertWeaver,KristenSplinter,andJodiEshleman) VI ofcoastalstudentshavebeenalotoffun. IwouldliketothankPaulDevine,LeeGordon,andPaulGayesfortheirsupport invariousavenues.Iwillcontinuetointeractwiththesefolks. Iwouldliketothankmymomandmysisterforsupportingmeandunderstanding mygoalsanddreams. Finally,IwouldliketothankHeatherforemotionallysupportingmeduringmy highs,lows,andmyinjuries.Shetrulyunderstandsmyhardshipsanddreamsandhas helpedmeembraeethem. Vll 1 TABLEOFCONTENTS 2 Page ACKNOWLEDGMENTS 3 ABSTRACT CHAPTER INTRODUCTION 4 PresentWork . RIPCURRENTS-BACKGROUND RipCurrentMeasurementsandObservations 10 FieldSetting 10 LaboratoryExperiments 13 RipCurrentModeling 14 MassTransport 17 RipCurrentMorphodynamics 19 HYDROGRAPHICSURVEYINGFROMAPERSONALWATERCRAFT Introduction 23 NearshoreBathymetricSurveyingSystem 26 Instruments 26 SamplingScheme&Error 34 FieldTests 38 Results 39 Conclusions 43 FEASIBILITYOFMEASURINGCURRENTSINTHENEARSHOREFROMA PERSONALWATERCRAFT Introduction Vlll RipCurrentApplication 48 Instrumentation 48 FieldExperiment:RIPEX 50 SamplingErrors 55 Discussion 56 Conclusion 57 5 RIPCURRENTSTABILITY DatasetandMethodology .58 ConcurrentWaveandLongshoreCurrentMeasurements .64 ChronologicalStabilityofRipCurrentChannels .66 RRiippSSttaabbiilliittyyPPeerriioodd21::((SMeaprtcehm2b4e,r11909,819-9A8ug-uDsetc2e1m,b1e9r9288),1998) ..6678 RipStabilityPeriod3;(January19,1999-March3,1999) .68 RipStabilityPeriod4:(April10,1999-August27,1999) .68 RipStabilityPeriod5:(September25,1999-January12,0000) . .69 RipStabilityPeriod6:(March25,2000-July26,2000) .70 Discussion .70 Conclusion .77 6 RIPEXANDMORPHODYNAMICS Introduction ,83 RIPEX-SBEExperiment ,86 Instrumentation .86 BathymetricandBeachfaceSurveys .89 WaveClimate .92 ComplexBeachMorphology .96 SpatialSedimentDistribution .97 BeachCusps .99 BathymetricMeasurements 101 VideoImages 103 Erosional-AccretionsTrends 105 RipCurrentFlowKinematics 107 SeaBreezeInfluence 119 Summary 119 7 RIPCURRENTPULSATIONS 121 Introduction 121 TheRIPEX-SBEExperiment 126 IX ObservationofInfragravityEnergy Cross-shoreandAlongshoreSpectralStatistics 132 EdgeWavesandLeakyWaves Cross-shoreStructureofWaveGroupsandLongWaves 143 RipCurrentPulsations AlongshoreStructureofCurrentVelocities 151 Cross-correlationofInffagravityWaves 153 Cross-correlationsofInffagravityMotionswithRipCurrentPulsations156 Discussion 1CO Conclusion 8 VERYLOWFREQUENCYMOTIONS 163 Introduction ^63 FieldSite ^69 VeryLowFrequencyMotions 1^1 RipCurrentConceptualModeling 191 Discussion ^95 Conclusion 9 SUMMARY,CONCLUSIONS,ANDRECOMMENDATIONSFORFUTURE WORK REFERENCELIST 213 BIOGRAPHICALSKETCH 222 X