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河口湾定义Dalrymple,Zaitlin,andBoyd(1992)arguethattheconceptofnetlandwardmovementofsedimentderivedfromoutsidetheestuarymouthisnecessarytodistinguishestuariesfromdeltas.Theydefineanestuaryas“theseawardportionofadrownedvalleysystemwhichreceivessedimentfrombothfluvialandmarinesourcesandwhichcontainsfaciesinfluencedbytide,waveandfluvialprocesses.Theestuaryisconsideredtoextendfromthelandwardlimitoftidalfaciesatitsheadtotheseawardlimitofcoastalfaciesatitsmouth”.Estuariescanformonlyinthepresenceofarelativesea-levelrise(transgression).Progradationtendstofillanddestroyestuaries,causingthemtochangeintodeltas.Aerialviewofestuary.LakeClarkNationalPark,Alaska,USATheCamelestuaryStreamonbeachandestuaryOregon,USASaltmarshandmud杭州湾significancePhysiographySimilarestuariesthatareseasonallyblockedbylongshoredriftordunemigrationarecalledblindestuaries.Bar-builtandblindestuariesareverysimilartolagoonsandmightbeconsideredlagoonsbysomeworkers.Deltaicestuariesoccurondeltafrontsasephemeraldistributaries.Flask-shaped,high-reliefriasbackedbyalow-reliefplaincreatedbytectonicactivityarecalledcompoundestuariesortectonicestuaries.Hydrologicandsedimentcharacteristics-Partialmixing:onmesotidalcoasts,tidalcurrentsareincreasedsothatriverflowdoesnotdominatethecirculation.Tidalmixingaffectsthesharpboundarybetweensalt-andfreshwaterlayers,causingpartialmixingalongtheinterface(e.g.ChesapeakeBay).Landwardcurrentflowisstrongenoughtotransportsedimentinalandwarddirection.Whereriverdischargevariesseasonally,however,thedominantdirectionofsedimenttransportmayreverseinresponsetodischargefluctuations.-well-mixed:wheretidalrangeandcurrentvelocitiesaregreatenough(macrotidal),verticalsalinitystratificationbreaksdowncompletelytogeneratewell-mixedestuaries(e.g.DelawareBay).Thereislittlelandwardflowbutmainlylateralmovementandmixing.Suspendedsedimentisdispersedawayfromlateralorweakriversourcesand,also,abovethebedbytidalresuspension.Wave-dominatedestuaryDepositionofmudisenhancedbymixingofriverandmarinewater,whichcausesflo
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