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Evaluationandcausesanalysisofchangesinmorphologicaldiversityin
Yichang - Chenglingjireachdownstream oftheThreeGorgesDam
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2
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CHENLi,YUBowen,YANGChenggang,YUANJing
(1.StateKeyLaboratoryofWaterResourcesEngineeringandManagement,WuhanUniversity,Wuhan 430072,China;
2.BureauofHydrology,ChangjiangWaterResourcesCommission,Wuhan 430010,China)
Abstract:Thediversityofriverchannelmorphologylargelydeterminesthediversityofphysicalhabitatsforriverine
organisms,playinganimportantroleinshapingtheabundanceanddiversityofaquaticbiologicalspecies.Afterthe
impoundmentoftheThreeGorgesDam ,downstreamriverbedunderwentsevereerosionanddepositionadjustments,
leadingtochangesinriverchanneldiversity.Usingfield - measuredfixedcrosssectionmorphologydatafrom
YichangtoChenglingjiinthedownstream reachoftheThreeGorgesDam duringtheyears2003and2018 ,the
compositediversityindexoftheriverchannelwasconstructedbasedonindexesoflongitudinaldiversity ,lateraldi
versityandbathymetrichabitatintegrity.Theseindexeswereemployedtoanalyzethedifferencesindiversitybe
tweendifferentriverpatternsandreachesaftertheimpoundmentoftheThreeGorgesDam ,andthecausesofthe
changes.Theresultsrevealedthat,morphologicaldiversityvariedacrossdifferentriverpatterns,withcorrespond
ingdifferencesinmorphologicaldiversityamongdifferentreaches.Meanderingriverpatternsexhibitedalowerkur
tosiscoefficientandahigherproportionoflowbars ,resultinginhigherdiversitycomparedtootherriverpatterns.
Consequently ,theLowerJingjiangRiver,primarilycharacterizedbymeanderingriverpattern,exhibitedgreater
diversitythanotherreaches.Followingreservoirimpoundment ,overallmorphologicaldiversityinthedownstream
reachesgenerallydecreased.However ,changesinmorphologicaldiversityvariedamongdifferentriverpatternsand
reaches.Kurtosiscoefficientsincreasedsignificantlyinstraightriverpatternsunderbothlowandbankfulwaterlev
els ,andwasincreasinginbifurcatedriverpatternsunderlowwaterlevel,butdecreasedformeanderingpatterns
underbankfulwaterlevel.Accordingly,thekurtosiscoefficientoftheLowerJingjiangReach,dominatedbymean
deringpatterns ,decreased.Thedifferenceinpost - damerosionanddepositionadjustmentpatternsbetweendifferent
riverpatternswastheintrinsicmechanismthatledtodifferenttrendsindiversitychange.Theresearchfindingscan
supporttounderstandthechangesinriverinehabitatsundertheinfluenceofhumanactivities.
Keywords:riverhabitat;diversity;ThreeGorgesDam;riverchannelerosion
(责任编辑:王 婧)
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