学科分类
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5 个结果
  • 简介:Thispapersummarizesthelatestdevelopments,futureprospects,andproposedcountermeasuresofreservoirsedimentationandchannelscourdownstreamoftheThreeGorgesReservoir(TGR)ontheYangtzeRiverinChina.Threekeyresultshavebeenfound.(1)TheincomingsedimentloadtotheTGRhasbeensignificantlylowerthanexpected.(2)TheaccumulatedvolumeofsedimentdepositionintheTGRissmallerthanexpectedbecausetheoverallsedimentdeliveryratioisrelativelylow,andthedepositioninthenear-damareaoftheTGRisstilldeveloping.(3)RiverbedscourintheriverreachesdownstreamoftheGezhoubaDamisstilloccurringandchannelscourhasextendedtoreachesasfardownstreamastheHukoureach.Significantly,sedimentationoftheTGRislessproblematicthanexpectedsincethestartofoperationoftheTGRontheonehand;ontheotherhand,thepossibleincreasesinsedimentrisksfromdependenceonupstreamsedimentcontrol,depositioninthereservoir,andscouralongmiddleYangtzeRivershouldbepaidmoreattention.(1)SedimenttrappedbydamsbuiltalongtheupperYangtzeRiverandbilliontonsofloosematerialsonunstableslopesproducedbytheWenchuanEarthquakecouldbenewsedimentsourcesfortheupperYangtzeRiver.Moreseriously,possiblereleaseofthissedimentintotheupperYangtzeRiverduetonewearthquakesorextremeclimateeventscouldoverwhelmtheriversystem,andproducecatastrophicconsequences.(2)IncreasingsedimentdepositionintheTGRisharmfultothesafetyandefficiencyofprojectoperationandnavigation.(3)ThedrasticscouralongthemiddleYangtzeRiverhasintensifiedthedown-cuttingoftheriverbedanderosionofrevetment,ithasalreadyledtoincreasingrisktofloodcontrolstructuresandecologicalsafety.ItissuggestedtocontinuetheFieldObservationProgram,toinitiateresearchprogramsandtofocusonrisksofsedimentation.

  • 标签: YANGTZE River Three Gorges RESERVOIR SEDIMENTATION
  • 简介:从地区性的网络基于地震数据最后34年,我们在Mabian区域附近分析了主要差错地区的现在的差错行为,南部的四川,并且鉴别为在分析的future.The方法的潜在的强烈、大的地震的危险差错片断是有历史的强烈地震的活动背景的b值的空间分发的联合,当前的seismicity.Our结果主要出现:(1)b值的空间分发显示重要h

  • 标签: 川南 风险 强震 地震活动 空间分布 中强地震
  • 简介:TheGarouaZoneinNorthCameroon,thesubjectofthisstudy,isknowntohaveundergonetectonicmovementsduringtheCretaceous,butthezone’sstructuraldataremainpoorlyknown.ThisstudyexploitstheBougueranomalytoimproveknowledgeofGarouatectonicsstructures.Inordertocharacterizethesestructures,twomethodsareused:Euler’sdeconvolutionmethodandthemethodofthehorizontalgradientoftheverticalderivative.SuperpositionoftheEuler’ssolutionsmapforindexN=1withthemapfromthehorizontalgradientoftheverticalderivativemethodallowsdeterminationofgravimetriclineaments,interpretedasfaultsoraslinearcontacts,fromwhichwededuceastructuralmapofthestudyarea.Basedonthismap,weidentifysixteenlineaments,ofwhichwecounteightaslinearcontactsandeightasfaults.Amongthefaults,wedenoteoneofdepthbetween4and8km,fivefaultsofdepthrangingbetween8and13km,andtwofaultsofdepthsbetween13and36km.Analysisofthesefaultsshowsthatthesevendeepestfaultsmightpresentanaturalriskinourstudyarea.Forpurposesofcivilprotection,suchdeepfaultsshouldbemonitoredandtakenintoconsiderationintheimplementationoflargepublicworks.Thestructuralmap,establishedhereinfromdataonthein-depthextensionofeachfault,thusincreasesscientificknowledgeintheareathatcanbeusedtositepublicworksinwaysthatreducerisk.

  • 标签: Bouguer ANOMALY horizontal DERIVATIVE vertical DERIVATIVE
  • 简介:应付事件和它气候引起的相关气候的灾难改变的极端气候成为了一个全球问题并且从科学家,决策者和公众引起了宽注意。计算的这份报纸包括热带气旋,洪水,山崩,暴风雨巨浪,沙灰尘暴风雨,干旱,热浪,冷波浪和野火基于九气候的危险的结果期望年度多重气候的危险紧张索引。然后与死亡率,影响人口率和GDP损失率包含处理能力指示物的一个危险模型,被开发估计期望的年度影响人口,死亡和GDP损失风险。结果显示出那:有最高的风险的国家也是有大人口或GDP的国家。为了实质地减少全球全部的气候的危险,冒险,这些国家应该减少暴露并且改进综合气候的风险的统治;没有考虑全部的暴露,有高死亡的国家评价,影响人口率或GDP损失率,也有更高或更低的处理能力,孟加拉国和越南,是为气候的灾难风险减小计划并且策略做的热点并且应该集中于支持处理能力。

  • 标签: 国内生产总值 气候灾害 灾害风险 死亡率 损失率 人口
  • 简介:Thisstudydeterminesthepollution,fractionation,andecologicalrisksofsediment-boundheavymetalsfromcoastalecosystemsofftheEquatorialAtlanticOcean.ContaminationFactor(CF),pollutionloadindex(PLI),andgeoaccumulationindex(Igeo)wereusedtoassesstheextentoftheheavymetalpollution,whilethepotentialecologicalriskwasevaluatedusingtherisksassessmentcode(RAC)andH?kansonpotentialecologicalrisk.Theanalysisrevealedconcentrations(mg/g,dw)ofthecadmium(Cd),chromium(Cr),copper(Cu),nickel(Ni),andlead(Pb)insedimentsforwetanddryseasonsvaryfrom4.40-5.08,14.80-21.09,35.03-44.8,2.14-2.28,and172.24-196.39,respectively.Theresultsalsoshowedthatthemetalfractionationpercentagesintheresidual,oxidizable,andreduciblefractionsarethemostsignificant,whiletheexchangeableandcarbonateboundtracemetalsarerelativelylow.TheRACvaluesindicatenoriskforCdandNiandlowriskforothermetalsatallthestudiedsitesduringbothseasons.PotentialecologicalriskanalysisoftheheavymetalconcentrationsindicatesthatCdhadhighindividualpotentialecologicalrisk,whiletheothermetalshavelowriskatallinvestigatedsites.Themulti-elementalpotentialecologicalriskindices(R1)indicatehighecologicalriskinalltheecosystems.

  • 标签: SPECIATION Heavy metal pollution ECOLOGICAL risk