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ID:6041141
大小:8.87 MB
页数:61页
时间:2017-12-26
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1、CoastalProcessesandLandformsChapter13WavesMostaregeneratedbywindWavespropagateindirectionofprevailingwindSizeofwavesdependsonwindspeedwinddurationfetchWatermovementduetowavesForwavesindeepwater:Aswavespass,waterexperiencescircular(orbital)motion--nonetflowofwaterSizeofo
2、rbitsdecreaseswithdepthWavebase--depthbelowwhichoscillatorymotionceasesWavebaseexistsatdepthequaltoone-halfwavelengthofsurfacewavesDeepwaterwavesH-waveheightL-wavelengthWavesinshallowwaterWherewaterdepthislessthanwavebase,wavesexperiencedragfromseabedThisfrictioncausesw
3、avestoslowandsteepen(H/Lincreases)watermotionbeneathwavesbecomesellipticalWavesinshallowwaterWavesinshallowwaterWaveseventuallybreakwhendepthgetsveryshallow.Zoneofbreakingwavesiscalledthesurfzone.Swashzoneiswherewaterrushesupandwashesbackdownbeachface.SurfzoneSwashfaceT
4、sunamisTsunamis-generatedbyvolcaniceruptions,earthquakesorlandslides.Generatelarge,longperiodwavesthattravelquicklytoshore,steepeningastheyentershallowwater.Seiche--commononlakesSeicheresultsfromwindsetupordifferencesinbarometricpressurethatcauseelevationofwatersurfacei
5、nonearea.Resultsinperiodicfluctuationsinwaterlevelsaswates“sloshes”backandforth.EntrainmentthresholdforwavetransportTidesGeneratedbygravitationalpullofmoonandsunonseasurfaceInmostplaces,tiderises&fallstwicedaily(semi-diurnaltides)TidesHigher“springtides”occurwhenmoonand
6、sunarealigned(newandfullmoon);lower“neaptides”occurwhenmoonandsunareat90oEffectsoftidesInfluencesthelandwardextentofwaveactionCreatestidalcurrents,especiallyinestuaries,bays,lagoons,andinlets.Currents(otherthantidalcurrents)Longshorecurrents--shore-parallelflow;maybepar
7、tofcirculationcellthatincludeslongshoreandripcurrents,ormaybeprimarilywind-driven.Ripcurrents--narrow,offshoreflowofwaterseawardofsurfzoneFromKomar,1976RipcurrrentsCellsdevelopduetoalongshorevariationsinwaveheightWherewavesarehigher,setupisgreater(higherwatersurfaceelev
8、ations).Driveswaterfromtheseareastowheresetupisataminimum(locationofrips)LongshoreCurrents--originShore-parall
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