三角洲前缘岸滩对河流来沙减少响应的敏感性探讨——以长江口门区崇明岛向海侧岸滩为例

利用ArcGIS对1977—2004年不同时段的长江口崇明岛向海侧水下地形测量资料进行处理,并结合该区的潮滩历史遥感图片、现场高程测量以及同期大通站输沙率资料,探讨三角洲前缘岸滩冲淤演变对河流来沙减少响应的敏感性。结果表明:研究区岸滩的淤涨速率总体上在年代以上时间尺度随着长江来沙减少而下降,但由于局部滩—槽演变和海洋动力条件的影响,某些年代内和某些部位可能出现相反的趋势,使岸滩演变对河流来沙减少的响应变得复杂化。在此基础上预测今后几十年研究区的冲淤趋势。     

长江中下游河床沉积物分布特征

对长江中下游武汉至河口段304处河床沉积物样品进行了粒度测量与分析,通过各参数间的模拟、统计及对比,探讨了沉积物粒度、水动力因素及河床地貌三者间的关系。研究结果表明：本区河床沉积物以中、细砂为主,床底搬运十分微弱,河道相对稳定;从上至下沿程有明显的“粗-细-粗-细”粒径变化,主要反映河流动力地貌、动力沉积特征;粒径在河床的沿程分布总体为北粗南细,说明北岸侵蚀,南岸淤积的特点。研究同时也表明,颗粒因河型不同而迥异;颗粒偏态度-峭度在不同河型中表现各异,对区分顺直微弯分汊和鹅头形分汊河道尤为显著。     

黄河三角洲岸线及现行河口区水下地形演变

根据实测的岸线和水深数据,利用Surfer 和Mapinfo 等软件进行数据处理,结合不同阶段利津站输沙量,分析了黄河三角洲岸线及现行河口区水下地形演变。结果表明:1953-2000年,68%左右的入海泥沙淤积在口门和滨海区。由于入海流路变迁,不同岸段的岸线变化具有各自的特征。刁口河流路以西岸线基本稳定;刁口河流路以东—孤东油田以北岸线经历先淤后冲,属于强侵蚀岸段,但在防潮大堤的保护下得到人为控制下的稳定;清水沟流路形成的岸线整体向海淤进,但清8 出汊后,清水沟老河口沙嘴南侧出现侵蚀。1976-1996 年,现行河口(清水沟流路) 水下地形总体上表现为淤积,顶坡段变缓,前坡段变陡。1996-2005 年,清水沟老河口水下地形顶坡段和前坡段发生侵蚀,底坡段呈现淤积;出汊新河口水下地形继续淤积,但程度和范围都比1976-1996 年的小。孤东油田近岸侵蚀加剧。     

塔克拉玛干沙漠东北部纵向沙垄粒度分布特征

塔克拉玛干沙漠东北部纵向沙垄广泛发育,但沉积物粒度特征鲜有报道。基于筛析法测定了塔克拉玛干沙漠东北部一条上覆次级沙丘的纵向沙垄断面沉积物粒度特征。结果显示：（1）沙垄沉积物颗粒自垄顶向两侧坡底逐渐变细,分选变差;沙垄上覆次级沙丘亦同。（2）沙垄沙的频率分布曲线以双峰为主。（3）沙垄迎风坡中部沉积物平均粒径细于中下部;上覆次级沙丘迎风坡底部沉积物颗粒粗于迎风坡中部。该区域纵向沙垄粒度分布特征与前人提出的“脊部较粗型”一致。沉积物样品所表现的双峰分布特征受物源、风选影响显著。上覆沙丘断面上迎风坡底部粗化,可能是粗颗粒无法被带走而发生富集的缘故。沙垄上覆次级沙丘局部形态的变化影响了风沙流,从而导致了平均粒径和分选系数局部上的变化。在沙垄迎风坡一侧存在风沙流的二次输移过程。     

基于遥感的江苏省大陆岸线岸滩时空演变

基于江苏省1984-2016年61景多源遥感影像数据和部分实测潮位、坡度数据,利用遥感技术结合改进的水边线方法提取了多时相的海岸线和平均大潮低潮线,研究了江苏省绣针河口至连兴河口大陆岸线岸滩的时空演变特征。结果表明：1984-2016年,由于海岸带开发,江苏省的海岸线整体以向海推进为主,自然岸线由458.24 km逐渐减少至166.74 km,人工岸线由163.66 km快速增加至598.74 km,大陆岸线长度由621.90 km增加至765.48 km。发生位置和长度变化的岸段中,淤长岸段长127.62 km,年均向海推进83.03 m;围垦岸段长401.21 km,年均向海推进87.63 m;冲刷岸段长71.17 km,年均离海后退10.81 m;围垦被侵蚀岸段长25.95 km,年均离海后退8.64 m。海岸线的空间变化导致江苏省沿海陆地面积净增加104332 hm²,其中由于围垦增加的陆地面积98520 hm²,围垦是陆地面积增加的主要原因。海岸线的离海后退主要发生在废黄河三角洲岸段,但是到2008-2016年,岸线的侵蚀范围已向南扩大至新洋河口至斗龙港岸段。受围垦活动及岸线侵蚀影响,江苏省潮间带坡度不断变陡,统计断面的平均坡度由1.4‰增加至1.9‰,其中废黄河三角洲岸段的中山河口至扁担河口岸段坡度最陡,基本在3~14‰之间;辐射沙洲陆岸岸段坡度最为平缓,但坡度也在逐渐陡化,由0.9‰增加至1.5‰。潮间带面积由271747 hm²减少至168645 hm²,减幅38%;潮间带平均宽度由5064 m减少至3096 m,减幅39%。     

长江河口河槽近期沉积特征及影响因子分析

随着流域和河口水利工程建设,长江河槽沉积环境发生了巨大改变,对河势演变和河槽冲淤均产生重要影响。依据长江河口河槽大面积表层沉积物采样和各河槽定点水文观测资料,分析各河槽沉积特征,探讨其影响因子及作用机制。结果表明：河槽沉积物类型以砂质粉砂和粉砂质砂分布最广,粒径分布纵向上呈自西向东减小、横向上自北向南减小趋势,河槽总体主槽粗、边滩细。涨落潮泥沙输运和沉降过程影响河槽纵向沉积分布特征,风浪作用强化了口门段河槽南北沉积环境的差异,北支、北港口门段河槽受到偏北方向风浪作用强烈,沉积物粗化明显。不同泥沙来源是造成河槽整体沉积环境差异的主导因素,南支、南港上段表现为流域来沙的沉积特征,北港、南槽、北槽则表现为流域与海域来沙的混合沉积特征,口外沉积物对口内河槽的影响主要是为口内河槽提供细颗粒物质来源。     

江苏海岸侵蚀过程及其趋势

江苏省侵蚀海岸的总长度为 30 1 7km ,分为 4段 :废黄河三角洲海岸、港海岸、吕四海岸以及海州湾的沙质海岸。各段海岸侵蚀原因不同。废黄河三角洲海岸是因黄河改道失去泥沙来源 ;吕四与港海岸则因辐射沙洲调整过程中滨岸水道的向岸移动造成的 ;而北部沙岸则是因人类活动 (上游建设水库及开挖海滩沙 )的干扰。江苏海岸是一个沉积物准封闭系统 ,全球性海平面上升将加剧这一侵蚀过程 ,预计未来侵蚀海岸的长度将增加 ,辐射沙洲区的外围沙洲将因侵蚀而向中心区退缩。一些目前是隐型侵蚀的岸段将向显性侵蚀的阶段发展。由于连云港到长江口北支的岸段是软性海岸 ,缺乏硬质节点 ,在没有建造大型人工设施的前提下 ,估计江苏海岸动态及制定开发规划时必须考虑平直化的大趋势。     

长江三角洲前缘近十余年的冲淤演变及工程影响研究

根据1994-2008年国家专业部门测量的长江口口门区水下地形图及相关数据资料,分析了长江河口三角洲近十余年的冲淤过程:1)在长江来沙显著减少的背景下,三角洲出现了由淤到冲的转换,1994-2000年、2000-2008年,长江口门研究区(1 500 km2)净淤积量分别为7.25亿m3(1.21亿m3/a)和-1.23亿m3(-0.15亿m3/a),冲淤转换的临界输沙率约为2.97亿t(大通站).冲淤转换的时间大约发生在2000-2002年;2)三峡水库蓄水加速了长江来沙的减少,近几年入海泥沙减少和河口口门区出现的冲刷有一半左右归因于三峡工程的运行;3)2000年以来,河口口门外水深超过7 m的大部分区域处于蚀退,尤以10～20m区域侵蚀最为强烈,但0m以上潮间带滩地较前一时段淤积加强,1994-2008年,四大滩地的面积平均增长了约34.2％.研究结果表明:入海泥沙减少是长江三角洲由淤积转为侵蚀的主要原因,三峡水库蓄水加剧了长江入海泥沙的减少及三角洲的侵蚀,河口滩地的逆势淤积是近年一系列的河口重大工程影响的结果.     

长江河口悬浮泥沙的混合过程

根据准同步观测的悬浮泥沙及表层沉积物粒度、流速、含沙量资料, 分析了长江口及临近海域悬浮泥沙在河口的混合过程。长江河口-陆架系统悬浮泥沙中值粒径呈现“细-粗-细”的变化规律, 河口上段悬浮泥沙中值粒径为8.9 μm, 拦门沙海域为10.5 μm, 陆架区为4.5 μm, 北支为9.9 μm, 杭州湾口为5.6 μm, 泥沙类型为粘土质粉砂。河口上段和陆架区悬浮泥沙与表层沉积物的垂向混合作用较弱, 拦门沙区域二者发生强烈的混合和交换, 悬浮泥沙在由长江河口向陆架系统输移过程中仅有表层泥沙保留了流域输入的泥沙粒度特征。长江口悬浮泥沙中值粒径与含沙量呈良好的正相关关系, 水流的剪切作用是引起拦门沙海域泥沙再悬浮、近底高含沙量和悬浮泥沙粒径增加的主要原因, 悬浮泥沙粒径和含沙量的增加主要由粉砂组分的增加引起。2007 年长江河口区范围内悬浮泥沙中值粒径比2003 年普遍减小11％, 含沙量比2003 年减小22%, 河口上段含沙量对流域来沙减少的响应最为敏感, 而拦门沙区的泥沙粒径对流域来沙减少的响应最敏感。在长江流域来沙量减少的背景下, 河口拦门沙区域仍能维持较高的含沙量, 主要缘于河口系统内部的供沙     

38 ka以来海南岛东海岸风成沙的粒度特征及其反映的沉积环境演变过程

 木堆地层剖面是海南岛东海岸沙丘与丘间地沉积过程的典型记录。在对该剖面地层高密度采样和光释光定年的基础上,对风成沙及相关沉积物的粒度组成、粒度参数和概率累积曲线及粒度敏感指标（SC/D值）的分析表明,风成沙、弱沙质古土壤、风水两相沉积物和泻湖相沉积物的粒度特征各异,反映38 ka BP来海南岛东海岸沉积环境经历了阶段Ⅰ（38～22 ka BP）、阶段Ⅱ（22～17 ka BP）、阶段Ⅲ（17～10 ka BP）、阶段Ⅳ（10 ka BP至今）等4个演变阶段,气候环境经历了暖湿-暖干-暖湿-暖干-暖湿-干凉-温湿-波动-暖湿的演变,沉积环境也经历了泻湖沉积-沙丘与丘间地沉积-沙丘固定成壤-流沙沉积的演变过程。     

长江口拦门沙河段潮滩表层沉积物分布特征

基于2005年7月及2007年5月在长江订拦门沙河段崇明东滩、横沙东滩(浅滩)、九段沙以及南汇边滩等四大潮滩的水下滩地采集的大面积、高密度表层沉积物以及实测水文资料,对拦门沙河段潮滩表层沉积物颗粒度、参数、组成、类型以及分布特征进行分析,并在此基础上探讨影响沉积物分布的主要动力因子.结果表明:长江河口四大潮滩表层沉积物主要由砂、粉砂质砂和粘土质粉砂三种类型组成.沉积物中值粒径分布比较复杂,介于2.5～8ψ之间;沉积物分选系数集中于1～2左右,其分布与中值粒径具有一致性,其中物质组成相对较粗的颗粒分选性较好而较细的颗粒分选性较差:偏态与峰态跨度较大,分别介于0.1-0.8与1-4不等.崇明东滩、横沙东滩(浅滩)和九段沙的沉积物分选系数、偏态和峰态的分布具有一致性,三者相关性较强;南汇边滩的沉积物分选性、偏态及峰态值则因南滩与东滩所处位置差异而有较大差别.此外,河口潮滩表层沉积物分布显示泥沙输移的结果,其主要水动力因子包括潮流和波浪控制的泥沙输移:在受落潮优势流作用的地区普遍粗于涨潮优势流作用的地区;在波浪动力强、波能释放的地区沉积物普遍较粗且分选性较好:深水航道工程的堵汉、导流、破水波作用明显,使得导堤两侧的表层沉积物粒度出现粗细分布不均的特点.     

南黄海辐射沙脊群里磕脚11DT02孔沉积相分析及环境演化

11DT02孔位于南黄海辐射沙脊群东北部里磕脚沙脊南坡,通过沉积相分析、粒度统计,结合年代地层数据,重建晚更新世以来里磕脚沙脊的长周期环境演化,分析沙脊成因、厘定沙脊发育年代。研究表明:里磕脚沙脊从下至上由潮滩相、硬黏土相、潮滩相和潮流沙脊相组成。潮流沙脊和潮滩由粉砂、细砂和少量黏土组成,两者均成正偏态分布。潮流沙脊和潮滩在概率累积曲线上分别表现为三段式和四段式分布,以跳跃次总体为主,并呈双跳跃特点。研究区晚更新世经历海平面下降发育潮滩环境,到完全暴露形成标志性的“硬黏土”层;全新世初期经历海侵,研究区复又开始潮滩沉积,随后被海水完全淹没,潮流作用渐强,改造下伏潮滩和“硬黏土”,逐渐堆积成高差最大达30 m的脊槽地形。     

黄河三角洲潮滩潮沟近期变化遥感监测

Integrating remote sensing, geographic information system (GIS) and fractal theory, change characteristics of tidal flats and tidal creeks in the Huanghe (Yellow) River Delta over the period of 1986-2001 were discussed. The results show that evolutions of tidal fiats throughout the Huanghe River Delta are influenced by various factors, and that progressive succession and regression of tidal flats concur in different coastal segments of the delta. Human activities have played an increasingly important role in the succession process of tidal flats. Due to land reclamation in coastal zones of the delta in the last 15 years, lots of tidal flats were occupied, the artificial coastline migrated seaward (the maximum change rate was 0.8 kmyr^-1) and tidal creeks became sparser (the highest decreasing rate of length of tidal creeks was 14.9 kmyr^-1). Except for two coastal segments from the Tiaohe Estuary to the 106 Station and from the south of the Huanghe River mouth to the north of the Xiaodao River Estuary,fractal dimension values of tidal creeks in the remaining coastal segments of the delta decreased. In addition, the time dimension, sediment fluxes into the sea, waves and tidal-currents have profound influences on the evolution process of tidal flats. Four types of tidal flats-river-dominated tidal flats,tide-dominated tidal flats, wave-dominated tidal flats and man-dominated tidal flats can be identified.Owing to the intensification of human activities in coastal zones of the delta, man-dominated tidal flats have become the main kind of tidal flats.     

The variation of sediments organic carbon content in Chongming east tidal flat during Scirpus mariqueter growing stage

The investigations on the organic carbon (OC) of core sediments were carried out in Chongming east tidal flat (CM) during Scirpus mariqueter growing stage (from April to December 2004) in Yangtze Estuary. The Yangtze River annually transports a runoff discharge of 30,000 m3/s, carrying about 480 million tons of sediments to the estuarine and coastal area, which formed a great OC pool. In the sampling spots, seven quadrats of 50 cm × 50 cm and five sediments cores of 20 cm deep (40 cm deep in December) were randomly established in order to collect vegetations and core sediments samples during the low tide each month except November. After pretreatment, the core sediments were sieved and their OC contents were measured according to the potassium dichromate method. The results show that the higher surface sediment OC content in summer comes from allochthonous terrigenous particle settlements on the Chongming east middle tidal flat S. mariqueter zone. In autumn and winter, the decomposing of the defoliated S. mariqueter increases the surface sediments OC content. Settling velocity, sediment temperature and S. mariqueter growth are the main factors that can control the sediment carbon content. Summer is the "carbon losing" period of the tidal flat sediments, while from September, it changes into the "carbon accumulating" period of sediment OC pool because of the decomposing of dead S. mariqueter community in the sediments. From this alternation of "carbon losing" period and "carbon accumulating" period, we conclude that carbon in the OC pool of the middle tidal flat S. mariqueter zone sediments mainly comes from the atmospheric carbon rooted by S. mariqueter photosynthesis.     

黄河三角洲潮滩潮沟近期变化遥感监测

作者选用1986年和2001年两个时相的Landsat TM/ETM+影像,结合遥感、地理信息系统 (GIS) 和分形理论研究了黄河三角洲典型河口岸段潮滩潮沟的发育演变。结果表明：近15年来,挑河口~106站和现行水河口(1976~1996年黄河入海口,下同)~甜水沟岸段分维值D增大,呈顺向演替;其余岸段分维值均减小,表现为逆向演替。人工围垦挤占了大面积潮滩,人工岸线不断向海扩展,其最大推进速率达0.8 km/yr;同时,潮沟长度缩短,最严重的岸段每年减少14.9 km。通过分析表明,人类活动已成为影响三角洲潮滩发育的重要因子,其导致整个三角洲的潮滩体系严重退化,自然形成的潮沟时空谱系不复存在;另外,发育时间长短、入海泥沙、海浪和潮流对潮滩发育演变亦非常重要。目前,黄河三角洲潮滩可分为河口滩、潮控滩、浪控滩和人控滩4大类型。     

Recent geomorphic changes in the Liaohe Estuary

This paper mainly analyzes the geomorphological changes of the tidal deposition in the Liaohe Estuary based on the multi-year bathymetric charts in 1990, 1996, 2002 and 2005 and Landsat TM images in 1987, 1994, 2002 and 2005. Evolution of the tidal depositional system during the past 20 years in the Liaohe River was studied on the basis of 50 boreholes drilling and 30 km shallow stratigraphic exploration from 2002 to 2005. The main tidal depositional body of the modern Liaohe River delta is located in the Shuangtaizihe Estuary. The stratum within the depth of 10 m includes tidal bank facies, tidal channel facies and neritic facies with paleo-delta facies underlying them. The sediments of tidal bank facies are mainly composed of sand and silt with siltation load and suspended load of about 50% respectively in proportion. The sediment of tidal channel facies and neritic facies is composed of clayey silt and silty clay which belongs to suspended load. The study area was a small bay between the old Daliaohe River, the old Dalinghe River and the Raoyanghe River complex delta since the Holocene to 1896. Many tidal banks formed and expanded rapidly after the Shuangtaizihe River was excavated by labor in 1896. The runoff and sediment discharge have decreased since the construction of brake at the Shuangtaizihe River in 1958.The Shuangtaizihe Estuary is in the state of deposition as a whole whose tidal bank is increasing and expanding southward, westward and northward. The maximum expansion speed is 87 to 683 m/a and the mean depositional rate is 0.189 m/a. Erosion occurred in some part of tidal bank with average erosional rate of 0.122 m/a. The tidal channel was filled up with sediment at a migration speed of 48–200 m/a. Geomorphologic changes have happened under the combined influences of runoff, ocean dynamics and human activities. The main source of sediment changes from river sediment to sediment driven by tidal current and longshore current.     

长江江苏段末次盛冰期古河槽特征

选择长江江苏段作为研究河段,根据南京长江三桥、长江大桥、长江四桥、润扬长江大桥、扬中长江大桥、江阴长江大桥、苏通长江大桥7个断面的285个地质勘探钻孔资料及参考文献中的8个钻孔资料,建立了7个长江古河谷地质剖面图。在拟建南京长江四桥附近、扬中长江大桥附近的7个钻孔进行了采样分析,获得了8个14C年代、1个ESR年代数据。通过分析发现,末次盛冰期长江古河槽镇江以上切割到基岩,镇江以下嵌在老河床相沉积层上,河槽在南京下关-栖霞山段形成局部深切;南京段约-63 m以下的河槽为末次盛冰期的古河槽,相对狭窄陡峭,宽深比较小,向下游宽深比逐渐变大,扬中以下形成分叉河道体系;古河槽中自下而上充填了从粗到细的沉积旋回,河床相沉积物向下游逐渐变细。     

辽河三角洲地貌演化(英文)

This paper mainly analyzes the geomorphological changes of the tidal deposition in the Liaohe Estuary based on the multi-year bathymetric charts in 1990, 1996, 2002 and 2005 and Landsat TM images in 1987, 1994, 2002 and 2005. Evolution of the tidal depositional system during the past 20 years in the Liaohe River was studied on the basis of 50 boreholes drilling and 30 km shallow stratigraphic exploration from 2002 to 2005. The main tidal depositional body of the modern Liaohe River delta is located in the Shuangtaizihe Estuary. The stratum within the depth of 10 m includes tidal bank facies, tidal channel facies and neritic facies with paleo-delta facies underlying them. The sediments of tidal bank facies are mainly composed of sand and silt with siltation load and suspended load of about 50% respectively in proportion. The sediment of tidal channel facies and neritic facies is composed of clayey silt and silty clay which belongs to suspended load. The study area was a small bay between the old Daliaohe River, the old Dalinghe River and the Raoyanghe River complex delta since the Holocene to 1896. Many tidal banks formed and expanded rapidly after the Shuangtaizihe River was excavated by labor in 1896. The runoff and sediment discharge have decreased since the construction of brake at the Shuangtaizihe River in 1958.The Shuangtaizihe Estuary is in the state of deposition as a whole whose tidal bank is increasing and expanding southward, westward and northward. The maximum expansion speed is 87 to 683 m/a and the mean depositional rate is 0.189 m/a. Erosion occurred in some part of tidal bank with average erosional rate of 0.122 m/a. The tidal channel was filled up with sediment at a migration speed of 48–200 m/a. Geomorphologic changes have happened under the combined influences of runoff, ocean dynamics and human activities. The main source of sediment changes from river sediment to sediment driven by tidal current and longshore current.