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Recent geomorphic changes in the Liaohe Estuary

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Recent geomorphic changes in the Liaohe Estuary

    Recent geomorphic changes in the Liaohe

    Estuary

    J.Geogr.Sci.2010,20(1):31-48

    D0I:l0.1007/s11442.010.0031.2

    @2010ScienceinChinaPressSpringer-Verlag

    RecentgeomorphicchangesintheLiaoheEstuary

    ZHULonghai',

    WUJianzheng'l_,

    XUYongchen.,

    HURijun,WANGNan.

    1.KeyLabofSubmarineGeosciencesandProspectingTechniques,MinistryofEducation,OceanUniversityof

    China,Qingdao266100,China;

    2.CollegeofMarineGeosciences,OceanUniversityofChina,Qingdao266100,Shandong,China;

    3.EngineeringSurveyandDesign&DevelopmentInstitute,Qingdao266100,Shandong,China

    Abstract:ThispapermainlyanalyzesthegeomorphologicaIchangesofthetidaIdepositionin theLiaoheEstuarybasedonthemulti?yearbathymetricchartsin1990.1996.2002and2005 andLandsatTMimagesin1987,1994.2002and2005.Evolutionofthetidaldepositional systemduringthepast20yearsintheLiaoheRiverwasstudiedonthebasisof50boreholes drillingand30kmshallowstratigraphicexplorationfrOm2002to2005.Themaintidaldepo. sitionaIbodyofthemodernLiaoheRiverdeltaisIocatedintheShuanataiziheEstuary.The stratumwithinthedepthof10mincludestidaIbankfacies.tidaIchanneJfaciesandneritic facieswithpaleo-deltafaciesunderlyingl}1em.ThesedimentsoftidaIbankfaciesaremainly composedofsandandsiltwiths_ltationloadandsuspendedloadofabout50%respectively inproportion.ThesedimentoftidaIchanneIfaciesandneriticfaciesiscomposedofclayeysilt

    andsiltyclaywhichbelongstosuspendedload.Thestudyareawasasmallbaybetweenthe oldDaliaoheRiver,theoldDalingheRiverandtheRaoyangheRivercomplexdeltasincethe Holoceneto1896.ManytidalbanksformedandexpandedrapidlyaftertheShuanataizihe RiverwasexcavatedbylaborIn1896.Therunoffandsedimentdischargehavedecreased sincetheconstructionofbrakeattheShuangtaiziheRiverin1958.TheShuanataiziheEstuary jsinthestateofdepositionasawholewhosetidalbankisincreasingandexpandingsouth. ward.westwardandnorthward.Themaximumexpansionspeedis87to683m/aandthe meandepositionalrateis0.189m/a.ErosionoccurredinsomepartoftidaIbankwithaverage erosiona}rateof0.122m/a.Thetidalchanne1wasfilledupwithsedimentatamigration speedof48-200m/a.GeomorphologicchangeshavehappenedunderthecombinedinfIu

    encesofrunoff.oceandynamicsandhumanactivities.Themainsourceofsedimentchanges frOmriversedimenttosedimentdrivenbytidalcurrentandlongshorecurrent. Keywords:LiaoheRiver;delta;geomorphology

    1Introduction

    Therehasbeenincreasingconcernaboutthepossibleeffectsofchangesinnaturalenviron

    mentalfactors,includingwaveclimate,meansealevelandstormsurge,aswellasofhuman activitiessuchastrainingwallconstruction,channeldredging,sandminingandembanking onestuarineenvironments(Blotteta1.,2006).Inordertopredictpossiblefuturechangesin Received:2009-05-04Accepted:2009--06--29

    Author:ZhuLonghai(1979

    ),Ph.DCandidate,specializedinthestudyofdeposition&geomorphology Email:zhulonghai@I63.corn

    WWW.scichina.comWWW.springerlink.corn

    32JournalofGeographicalSciences

    estuarygeomorphology,sedimentarycharacteristic,waterqualityandcorrespondingimpacts

    onbiotaandhumanusagesofestuaries,thereisaneedtounderstandthefactorsthathave influencedthepresentgeomorphologyandprocessregimeoftheestuary(Blotteta1.,2006). Erosion,transport,anddepositionprocessesofterrigenousclasticsedimentsareessen

tiallycontrolledbyriver,oceandynamics,humanactivityandclimate.Theseclasticsedi

    mentsaredeliveredtotheoceansbyriversfromthecontinentsandrepresentthearchivesof theEarth'sgeologicalhistorybyrecordingtheeffectsoftectonics,climaticchangesand eustasy.Sedimentsdeliveredannuallytotheoceansareestimatedatabout15x109w16x10 tons(Singheta1.,2007).

    Studiesoftheriverhavefocusedonvariousaspectssuchasr1weathering.erosionand

    sedimenttransport(Goodbred,2003;Zhangeta1.,2006);(2)fluvialgeomorphologyand sedimentology(Blotteta1.,2006;Cooper,2001;BaoandHuang,1993;Wilsoneta1.,2007); (3)hydrology(Lieta1.,2008);(4)sedimentmineralogy(Sondi,2008;Qiaoeta1.,2007);(5) geochemistry(ReevesandChudek,l998);(61deltacharacteristicanditsevolution(Pend6n eta1.,998;Lieta1.,2004);(7)environmentalstudies(Haoeta1.,2008;Harjieta1..2008); (8)lateQuaternaryclimaticstudies(Zhengeta1.,2005);(9)grainsizecharacteristicsand dynamicsofriversedimentstransport(Singheta1.,2007;WangandBao,1996;Anthony andH6quette,2007;Maren,2007),etc.Riversedimentsactasamajorcarrierfornutrients (suchasnitrogenandphosphorus)andcontaminants(suchasheavymetals,pesticides,and herbicides).Knowledgeoffluvialprocessesinvolvedinthegeneration,transport,anddepo

    sitionofriversedimentsisevidentlyoffundamentalimportancetotheEarthsystemscience andisthushelpfultoenhanceourunderstandingonthefateofchemicals.Itwillalsohelpto increaseourknowledgeofvariousprocessesofafinesandyfluvialsystemthatwillenable geomorphologists,hydrologists,fluvialgeologists,andcivilengineerstomakecredible longtermplansforbetteruseandmanagementoftheriverformillionsofpeople(Singhet a1.,2007).

    TheLiaoheRiveristhelargestriverintheLiaoningProvince.whichislocatedinthe northernLiaodongBayofBohaiSea.Manystudieshavebeenmadeonthetida1current featuresandtransportofsuspendedsediment.aswellasthedepositioncharacteristicsinthe northernLiaodongBaybasedonthesurveydatainthe1980s(Liu,1990and1996;Yanget ,1994;WangandBao,1996;Miaoeta1.,1996;HeandLiu,1991;BaoandHuang,l993; Fu,1989;Fuf,.,1993;Songeta1.,1997).However,thegeomorphologicalevolutionof theLiaoheEstuaryhasbeenrarelyreportedsofar.TheLiaoheRiverdeltaisrichinpetro.

    1eumresourcesastheLiaoheoilfield,thethirdlargestoilfieldinChina.islocatedthere. ThispaperaimsatrevealingthestratigraphicstructureoftheLiaoheRiverdeltasincethe Holoceneandanalyzingthemigrationtendencyofthetidalbankandtida1channe1inthe nearfuturebasedonthelatestdataofexplorationdrilling,

    shallowstratigraphicsection

    bathymetricsurvey,currentandsuspendedsedimentsoastoreconstructtheevolutionhis. toryoftheLiaoheRiverdeltaandtoprovideguidancefortheexplorationanddevelopment oftheLiaoheoilfield.

    2Regionalsetting

    TheLiaoheRiverenterstheseaintwobraches.OneistheShuangtaiziheRiver,which passesthroughtheTai'ancountyandthendebouchesintotheseainPanshan.Theotherone, ZHULonghmeta1.:RecentgeomorphicchangesintheLiaoheEstuary33

    lyingbetweenLiujianfangandShanchahe,istheWailiaoheRiver,whichjoinstheHunhe RiverandtheTaiziheRiverinthenameoftheDaliaoheRiverinYingkoucounty(Jineta1., 1996).TheaveragetidalrangeoftheLiaoheRiverEstuaryis2.7m.whichbelongstothe mediumleve1.TheLiaoheRiverdeltarangingfromtheDaqingheRiverinGaixiancountyin theeasttotheXiaolingheEstuaryinthewestinJinzhoucountywasformedunderthein. fluenceoftheShuangtaiziheRiver,theDaliaoheRiver,theDalingheRiverandtheXiaol

    ingheRiver(Cheneta1.,1998).ThetidalcurrentdepositionoftheShuangtaiziheRiverin thenorthernpartofLiaodongBayisthemainbodyoftheLiaoheRiverdelta,surroundedby manytidalbanksoutsidetheShuangtaiziheEstuary,amongwhichtheGaizhoutanTidal Bankisthe1argestonerJineta1..1996).

    ThestudyareaislocatedintheShuangtaiziheRiveratthenorthemLiaodongBay(Figure 1),wheretidalcurrentmainlyflOWSbackandforthfromnortheasttosouthwest.Theveloc. ityoffloodcurrentislargerthanthatofebbcurrent,andtheaveragevelocityoffloodtide andthatofebbtideis10-50cm/sand10-40cm/s,respectively(Liu,1990;Yangeta1.,1994; Liu,1996).Theaveragesuspendedsedimentconcentrationoffloodtideishigherthanthat ofebbtideobviouslywiththevalueof10-350mg/Land5-150mg/Lrespectively(Wang andBao,l996;Miaoeta1.,1996).Thereare8typesofsurfacesediments,amongwhichsilt andclayaredominant(HeandLiu,1991;BaoandHuang,1993;Fu,1989;Songeta1.,

    1997).Thefundamentaltendencyischaracterizedbythebeachfaceaggradationandthe seawardexpandedcoastlineinthetidalbankofLiaodongBay(Fueta1..1993).Theaverage depositionalrateof1.1cm/aintheLiaoheEstuaryishigherthanthatof0.53cm/ainthe centralareaofLiaodongBay(Yangeta1..1993).

    41.00N

    40.30N

    Figure1LocationoftheLiaoheEstuary

    JournalofGeographicalSciences

    3Dataandmethod

    3.1Stratum

    Morethan50boreholesdrillingand30kmshallowstratigraphicsurveywereobtained throughcruisescarriedoutfrom2002to2005intheShuangtaiziheEstuary(Figure21. 1o_30mdrillingsampleswereobtainedbyusingrotarydrillingandhammersampler.The diameterofthesampleis74inln.Thecohesivesoilsamplewasmaintainedintheoriginal conditionandpreservedbyPVC.Thesanddisturbedwaspackagedinthesamplecontainer. Screeningandhydrometermethodwereadoptedfortheanalysisofsediment,andgrainsize

    gradewasclassifiedaccordingtotheC.K.Wentworthgeometricproportioncriterion.The sizegradepercentageandaccumulativepercentwererepresentedby.Thesedimentwas categorizedaccordingtoShepardtrigonometricgraphicalmethod.Basedontheaccumula

    tivepercent,theparameterssuchasmeandiameterandstandarddeviationarecalculated. TheJapanSP3AforInequipmentwiththeresolutionOf0.3mwasusedfortheshallow stratigraphicsection.whichcanexploretheloosestratumwithinthedepthofabout25m. 121.40122.O0E

    Figure2Locationoftheinvestigationsites

    ZHULonghaieta1.:RecentgeomorphicchangesintheLiaoheEstuary35

    3.2Bathymetricdata

    Topographicmapsof1990,1996,2002and2005wereselected(Table1),scanned,digitized, andthenrectifiedforfurtheranalysis.Thedigitizedmapsofdifferentperiodsweretrans

    ferredintovectormaps.ThedepthcontoursweretheninterpolatedbytheKrigingmethod usingtheSurfersoftwarepackage.andthemapswerethentransferredintoGRIDmode.

    Basedontheprocessingstepsmentionedabove,thechangesofthegeomorphological changewerestudiedsystematically(Zhangeta1.,2007;Cressie,1990;IsaaksandSrivastava, 1989).Fortheconvenienceofstudy.thetidalbanksweredividedinto6blocksfromTBlto TB6whilethetidalchannelwassubdividedinto5blocksfromTC1toTC5(Figure2).TB5 namelytheGaizhoutanTidalBankisthelargestoneintheLiaoheRiverdelta.whichislo

    catedintheeastoutsidetheShuangtaiziheEstuaryandextendsnorthwardandsouthward. TheTB4situatesonthewestofTB5withmodestscale.TheTB2isthemidchannelbar

    whichliesneartheShuangtaiziheEstuary.Fiverepresentativesections,namelyA,B,C,D andE.wereselectedforthecomparativeanalysisofbathymetricdataindifferenttimes (Figure2).

    Table1BathymetricCha~sinLiaoheEstuary

    3.3Satelliteimage

    LandsatTMsatelliteimagesof1987.1994.2002and2005wereemployedfordiscussion. ThescopeofwavebandofLandsatTMsensorinvolves(Lin,1991):(1)0.45-0.52Bin;(2) O.52_0.60gin;(3)0.63_).69gm;(4)0.76-0.90gin;(5)1.551.75gm;(6)2.08_2.35gm;

    andr7110.4-12.5/.tm.Theimageresolutionis30mforal1.TM1,TM2andTM3belongto thevisible——lightbandswithstrongrelativity.TM5andTM7representthemidinfrared

    bandswithmediumrelativity.TM4andTM6arethenearinflaredbandswithweakrelativ. itvtootherbandsfLifa1..1990).Thetidalbankwasidentifiedfromthesatelliteimages andthegeomorphologicalevolutionwasstudiedonthebasisoffalsecolorimagescorn

    posedbybands3,4and5.

    3.4Tidalcurrentandsuspendedsediment

    Thesynchronic

    wereperformed

    observationand

    bottomlayer(1

    tidalcurrentobservationandsuspendedsedimentsamplingat3stations atspringtideandneaptiderespectivelyinOctober2002(Figure2).The samplingwasseparatedinsurfacelayer(1mbellowtheseasurface)and

    mabovetheseabed),respectively.TheRCM4sCurrentmeter(Aanderaa

36JournalofGeographicalSciences

    DataInstrumentsInc,Norway)wasemployedfortidalcurrentobservation.Thedatawas recordedevery10minutesfromthewholepointautomatically.Suspendedsedimentwas sampledonceevery2hours.Thesuspendedsedimentwasmeasuredbyfiltering,dryingand weighingtocalculatethesuspendedsedimentconcentration.

    4Results

    4.1Sedimentcharacteristics

    Inaccordancewiththedataofdrillingandshallowstratigraphicsection,thestratumwithin thedepthof15mwasdividedintotidalbankfacies,tidalchannelfaciesandneriticfacies, beneathofwhichbelongstothepaleodeltafaciesformedbeforethelastglacialperiod

    (Figures3and4,sectionlocationseeFigure2).

    4.1.1Tidalbankfacies

    Thesedimentoftidalbankfaciesconsistsofblue,linensand,siltandsandysilt,mingled withsomethinembeddedsiltyclay.Thesurfacesedimentofteninvolvesclayeysilt.which is0.2mdeep.andsomeshellfragments.Themaincomponentsweresandandsiltaccount. ingfor24.2%88.1%andl0.8%65.7%.respectively,withthemeandiameterMzof

    3.O

    5.60oandthestandarddeviationo1of0.71.6.Thecurveofgrain.sizepercentfrequency inthemiddle.easternandwesterntidalbankswastwostageandwascomposedofsaltated

    loadandsuspendedloadbutlackofrollingload(Figure5,.Thepercentageofsaltatedload andsuspended1oadwasabout50%respectivelyinthemiddletidalbank.about45%and 55%inthewesterntidalbank.andabout40%and60%intheeasterntidalbank. Thetida1bankwasformedundertheinfluenceoftidalcurrent.whichrevealedthefeature ofparallelbeddingofAlandA2subdivisioninshallowstratigraphicsection(Figure61

    O

    

    4

    营一6

    

    8

    l0

    

    12

    -

    14

    

    16

    

    l8

    Figure3Geologicalcrosssectionbetweenaandb(fromtheinvestigationdatain2002)

    ZHULonghaieta1.:RecentgeomorphicchangesintheLiaoheEstuary37

    吕一

    Figure4GeologicalcrosssectionbetweenCandd(fromtheinvestigationdatain2005)

    withclearinterface.Themiddle tidalbankwasthickerthanboth oftheflanks.Thenorthofthe GaizhoutanTidalBankwas 1.5-6.4mdeep.theSubstratal burieddepthwas4.0-4.8m (Figure3),thesouthwas

    0.7-3.8mdeepandtheSub. strata1burieddepthwas2.5-0.5 m(Figure41.Thethicknessof theGaizhoutanTidalBankde

    creasedfromwesttoeastrang

    ingfrom5.5-5.7mto1.4-2.1 m.Theneriticfaciesliedunder thetidalbankfacies.

    Theeasterntidalchannelof

theGaizhoutanTidalBankwas

    eroded.Thesedimentoftidal

    bankonthesurfacebetween

    drillinglland12revealedthe

    seaflooroftheneriticfacies

    (Figure3showsthenortheastof

    a6section)

    4.1.2Neriticfacies

    234

    Grainsize

    67

    Figure5Probabilitycumulativediagramofgrainsforsedimentsin

    theLiaoheRiverdelta

    Thesedimentofneriticfaciesconsistsofbluesiltyclayandclayeysilt,mingledwithsome sandysiltandshellfragments.Themaincomponentsaresiltandclay,whichoccupy %叩??如??加m,

    一一0I10uJaQ0All1IIlu

    38JournalofGeographicalSciences

    33.5%63.4%and19.2%53.8%respectivelywiththemeandiameterMzof5.7

    7.Oand

    thestandarddeviationo1of1.7-2.7.Thecurveofgrain.sizepercentfrequencywas twostagewithabout70%ofsuspension.revealingthecharacteristicofsuspendedload transportfFigure51.

    TheneriticfaciescorrespondwiththeA3subdivisioninshallowstratigraphicsection (Figure6,withclearinterface.Thethicknessis3.7-7.2minthenorthoftheGaizhoutan TidalBankandtheburieddepthofsubstratais7.6-11.7m.Theneriticfaciesliedunderthe tidalbankfaciesandtidalchannelfacies.Theneriticfacieswascomingouttotheseafloor intheeastoftheGaizhoutanTidalBankwiththeinconsistentdistributionofsomepeator plantdebris.Thepaleo.deltafaciesislyingundertheneriticfacies.Adeeptidalchannel existsundertheGaizhoutanTidalBankbetweendrillholeNO.8and9.cuttinginsubiacent

bodyabout10m(Figure3.

    0

    2

    4

    6

    8

    10

    

    ?

    12

    l4

    16

    18

    20

    22

    Figure6AcousticalstratigraphyintheLiaoheEstuary 4.1.3Tidalchannelfacies

    Thesedimentoftidalchannelfaciesconsistsofbluesiltyclayandclayeysilt.mingledwith

    somesandysiltandshellfragmentswithsomepeatorplantdebrislyinginthebottomofthe

    tidalchanne1.Themaincomponentsincludesiltandclay.whichoccupy43.6%64.6%and 25.1%-55.0%respectivelywiththemeandiameterMzof6.07_3andthestandarddevia

    tionGlof1.4-2.2.Thecurveofgrain.sizepercentfrequencywastwostagewiththeSUS. pendedloadofabout87%andthesaltatedload?

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