Internal Facies Architecture and Evolution History of Changxing Mouth-Bar Complex in the Changjiang(Yangtze)Delta,China

River-mouth bar is a fundamental element to constitute a delta system, and its internal facies architectures are vital to reconstruct delta evolution history and study high-resolution sequence stratigraphy. Changxing Island is a representative mouth-bar complex in the modern Changjiang Delta. Its vertical stacked strata produced by delta progradation were first studied by detailed facies analysis of core CX03, and then a general facies architecture and evolution history of mouth-bar complexes in the modern Changjiang Delta were discussed through a comparative study of 5 different cores and historical charts. A progradational deltaic sequence has generally a similar internal facies architecture, composed of massive muddy deposits of prodelta and delta-front slope facies at the bottom, sand-dominated deposits of delta-front platform, inter-bar channel and mouth-bar facies at the middle, and heterolithic deposits of tidal flat and saltmarsh facies at the top. There is a significant time lag for the initial formation of channel-mouth bar systems between Chongming and Jiuduansha Islands. Compared with subtidal flats, sedimentation rates on intertidal flats were highly accelerated, potentially resulting from weakening wave and tidal strength over extensive intertidal flats and increasing human embankment activities in the last few centuries. These findings provide some new clues to understand modern and ancient mouth-bar evolution and resultant sequence strata in tide-dominated deltas.

Evolution of shoals and vegetation of Jiuduansha in the Changjiang River Estuary of China in the last 30 years

The evolution of the shoals and vegetation plays an important role in maintaining the stability of the river regime and the estuarine ecosystem. However, the interaction between the evolution of shoals and vegetation dynamic has rarely been reported. In this study, we determined the interaction between the shoal and vegetation evolution of Jiuduansha in the Changjiang River Estuary in the last 30 years. We did this through the collection and summarization of the existing data of the regional hydrological processes, wading engineering, and vegetation,and combined it with the analysis of nautical charts and remote sensing images. During the past 30 years, the expansion of the shoals within the 0 m isobath in Jiuduansha was obvious, with an increase of 176.5%, while the expansion of the shoals within the 5 m isobath was relatively slow. The regional hydrological characteristics in the Jiuduansha area changed dramatically, especially the sediment discharges. The area of vegetation in Jiuduansha increased from 9.1 km^2 in 1990 to 65.68 km^2 in 2015, while the variations in the different vegetation types were different. The best combination of environmental factors with a significant correlation on the shoals within the 0 m isobath is the area of Spartina alterniflora and Phragmites australis. The evolution of Jiuduansha shoals was significantly affected by the variations in hydrological characteristics. Meanwhile, on a long-term scale, the expansion of the shoals could promote the regional vegetation expansions due to the suitable elevation and environmental conditions it provides. The interaction between the shoal and vegetation evolution varied in the different vegetation types and different elevations. In the future, long-term monitoring and detailed data are needed to the systematical analysis of the interaction between the hydrological processes and the evolution of the shoal and vegetation.

Relationship between suspended sediments from the Changjiang Estuary and the evolution of the embayed muddy coast of Zhejiang Province

South of Hangzhou Bay, Zhejiang Province, exhibits an embayed muddy coastline, with the muddy beaches of embayments extending continuously seaward.The source of sediments on this coast presents an interesting problem to marine geologists and geomorphologists .The total annual load of sediments from the rivers of Zhejiang is only 12×106t.These materials affect only the area near the river mouths. The paper showed that the sediment along the coast of Zhejiang mainly comes from the Changjiang Estuary through analysing the time and space variations of suspended sediment, the features of sediment and the sedimentary transport.The Changjiang River is the largest river system in China, its sediment to the sea amounting to 468×106t. The sediment during summer transports mainly eastward, and is affected by the water body with high temperature, salinity and transparency; the winter season is the period with high sediment concentration. The sediment of the Changjiang Estuary transports together with the longshore current of the East China Sea southward, the southern boundary can reach the sea region approximately 500 km from the Shacheng Harbour. The accretion rate seaward has been about 10 - 30 m since the 16th century. The sediment movement combined the longitudinal with the lateral, so that the muddy flats progress continuously seaward under the construction of the seashore profile .

Centurial Evolution of an Offshore Mud Deposition Area in the Changjiang (Yangtze) Estuary and Its Links to Environmental and Anthropogenic Activities

Large amounts of sediments originating from the Changjiang(Yangtze)River are deposited in the subaqueous delta and in the adjacent muddy area off the mouth and on the inner shelf of the East China Sea.The terrestrial sediments deposited in these areas not only contain information about the composition and environment of the source area,but they also record changes in anthropogenic activities.A sediment piston core(CJ0702)was extracted from the Changjiang subaqueous depocenter(31.00°N,122.67°E)in a water depth of 22.0 m.The core was subsampled at 1–2 cm intervals and analyzed for grain size,clay mineralogy,and major element geochemistry.Results indicate a relatively high sediment accumulation rate of approximately 3.11 cm yr−1.These parameters exhibited only minor cyclical fluctuations in the core,which resulted from many factors.During the past 120 years,the Changjiang River-derived sediment is the primary source of sediment in the offshore mud area without evidence for the Yellow River-derived sediment increasing.After the trunk stream shifted from the North Branch to South Branch,the variations of proxies are controlled by the periodic fluctuation possibly linked to El Niño-Southern Oscillation(ENSO)and the Pacific Decadal Oscillation(PDO).In addition,anthropogenic heavy metal concentrations can be divided into three stages,which coincide well with economic development and environmental protection policies.

新情势下长江河口南槽河床冲淤演变特征

随着长江流域来沙的锐减、河口涉水工程的建设、生态环境保护力度的加大和通航环境的高效利用,长江口河势将面临着新一轮的调整。以长江口南槽河床冲淤演变为研究对象,采用河床演变分析的方法对南槽近十年来多次水下地形和航道水深数据进行了分析,并对南槽航道治理一期工程效果进行了讨论。结果表明:2010-2018年,南槽主槽整体呈冲刷态势,江亚南沙头部窜沟冲刷发展,沙尾冲刷下延;2018年至今,江亚南沙头部窜沟由冲刷环境转化为淤积环境,其他区域冲淤形势基本未变;南槽断面主槽形态总体稳定,在主槽总体冲刷背景下,“拦门沙”逐渐被削平,加上南槽航道治理一期工程的作用,南槽6 m以深河槽容积明显扩大,且保持较好的稳定性。近期南槽河势变化是流域来水来沙和河口自然、人类活动影响的综合结果,南槽航道治理一期工程对近期江亚南沙的地形变化起到了重要影响,工程有效地控制了江亚南沙河势,遏制了局部冲刷发展的趋势,有利于稳定南槽航道的北侧边界。

昌江流域土地利用冲突时空演变及关键影响因子探析

科学认知土地利用冲突的时空演变规律,揭示其关键影响因子的作用,对区域可持续发展具有重要意义。以水土资源矛盾明显的昌江流域为研究区,利用景观格局指数构建土地利用冲突量化模型,以反映流域内2000—2020年土地利用冲突空间位置及强度变化,应用随机森林模型评判重要影响因子,以偏依赖关系图刻画影响因子对土地利用冲突强度变化的边际响应。结果显示:(1)2000—2020年昌江流域土地利用冲突总体处于基本可控状态,且高冲突值呈环绕城区、沿河流水系两侧分布的特点,城乡交错带成为冲突发生的主要空间单元,流域内对水资源的竞争矛盾突出,整体冲突强度大小表现为中游>下游>上游。(2)在影响因子中,距主要道路距离、人口密度等社会人为干扰及年均降水量、距主要水系距离等水资源条件对土地利用冲突强度变化起关键作用。(3)各影响因子与土地利用冲突强度之间呈非线性响应关系,人口的集聚效应、自然本底的约束性等是造成非线性响应的重要原因。昌江流域需要合理制定水资源配置方案,同时严格控制社会经济发展过快带来的城乡用地矛盾。

基于WEP-QTP的长江源区径流组分变化及驱动机制

为研究气候变化条件下高原寒区径流演变规律,利用WEP-QTP模型模拟了1956~2020年长江源区水循环过程,分析了长江源区径流及其组分演变规律,并基于多因素归因分析方法定量分析了径流变化的驱动机制。结果表明:1956~2020年长江源区径流组分中降雨径流、融雪径流及融冰径流占比分别为79.4%,17.2%和3.4%。对比基准期(1956~1998年)与变化期(1999~2020年),气候影响下径流变化量为21.4亿m^(3),气温和降水对径流增加的贡献率分别为-8.4%和108.4%。对径流组分进行分析,气候影响下降雨径流变化量为24.8亿m^(3),气温和降水对降雨径流增加的贡献率分别为36.2%和63.8%;气候影响下融雪径流变化量为-3.1亿m^(3),气温和降水对融雪径流减少的贡献率分别为348.1%和-248.1%;气候影响下融冰径流变化量为-0.3亿m^(3),气温和降水对融冰径流减少的贡献率分别为-21.5%和121.5%。对径流及其组分逐月过程进行分析,气候变化对径流及其组分的影响主要集中在6~10月。

三峡工程运用后荆江与洞庭湖关系变化研究进展

荆江与洞庭湖之间存在复杂的江湖水沙交换关系,水沙变化引起江湖冲淤变化,进而影响长江中游地区的防洪安全与水资源利用等。三峡工程运用后坝下游水沙条件发生较大改变,江湖关系进一步调整。从江湖水沙关系变化、荆江特别是分流口门附近河道冲淤演变、三口分流洪道冲淤演变、洞庭湖区冲淤变化及城陵矶水位变化等方面,系统梳理了三峡工程运用后荆江与洞庭湖关系变化研究进展,得到以下结论:荆江三口分流量略有减少,分沙量大幅下降,藕池口河势调整较剧烈,进流条件有所恶化,洞庭湖由淤积转为微冲,湖区水位下降,城陵矶—汉口河段冲刷,城陵矶水位下降等,江湖水沙驱动机制仍存在一定不足,在荆江洪水位变化及洞庭湖未来演变趋势方面仍存在争议;指出了目前研究中存在的不足,如缺乏定量分析和系统性与完整性研究,并提出了下一步研究需重点关注的问题。

高质量发展目标下湖北省特色文化产业空间演化及成因研究

特色文化产业作为文化产业重要分支,是支撑文化产业高质量发展的有效路径之一。以长江中游湖北省为例,利用数理统计和GIS空间分析法,探析了该省特色文化产业的空间演化特征及成因。结果表明:(1)1992—2021年,分布类型趋向“集聚分布型”,数量递增又促使集聚规模壮大,从而为高质量发展奠定规模基础。(2)市域起步和增长呈现非均衡性特征,使得不同市域在高质量发展中的演进趋势和区域地位呈现明显差异,具体表现为武汉一城独大。(3)产业空间分布由极核向四周辐射,呈现带状式演进趋势,推动缓解过度集聚困境,以及助力区域高质量协同发展。(4)产业类别在省域空间内持续扩容,其中2012年后新型业态发展提速,助推产业高质量转型升级。(5)自然环境、政策驱引、经济发展等因素深刻影响特色文化产业的空间演化发展,其中科技、消费等因素催生新业态现象突出。

1956~2018年长江上游寸滩站径流演变特征

厘清流域径流变化特征可为水资源利用开发、水环境污染整治和水旱灾害防治等提供重要的理论基础。基于1956~2018年长江上游寸滩水文站日径流资料,采用线性回归、Mann-Kendall突变检验、小波分析等多种方法,对近60 a长江上游径流的年内年际变化、突变性和周期性进行分析。结果表明:寸滩站径流主要集中在7~9月,约占全年的51.98%,且年际变化差异较大;年均径流以10.6 m^(3)/(s·a)的速率呈不显著减小趋势,该变化主要受夏季和秋季径流变化的影响;受夏季径流变化的影响,年均径流在1968年发生突变,突变后径流相对减少7.8%;年均径流变化的第一和第二主周期分别为28 a和14 a,第一主周期主要受秋季径流的影响,第二主周期主要受夏季径流的影响。研究成果可为流域水资源合理开发利用、生态规划和洪涝灾害防控等提供参考。

Morphological evolution of the channel-shoal system in the South Channel of the Changjiang Estuary during 1958–2018:Causes and future trends

The stability of estuarine channel-shoal systems is important for port utilization,navigation maintenance,habitat protection and ecosystem service functions.This paper uses the South Channel of the Changjiang(Yangtze River)Estuary as a typical example to investigate the channel-shoal adjustment mechanism and its future trend.The combined approaches of bathymetric data analysis and process-based modeling(Delft3D)are applied.Quantitative analysis of morphological changes indicates that the South Channel experienced remarkable channel-shoal adjustment during 1958–2018.Periodic evolution was identified,including shoal migration,incision and emergence under natural conditions before the mid-1980s.Since then,fluvial sediment decline and local human intervention have interrupted the periodic processes.After 1986,as river sediment discharge started to decline,the South Channel converted to net erosion,and both the mid-channel shoal at the bifurcation node and the tail of the Ruifeng Shoal showed significant scour.Process-based hydrodynamic simulations revealed that the northern rotation of the mainstream downstream of Wusong triggered the erosion of the Ruifeng Shoal,while unordered sand mining at the shoal tail in approximately 2002 enhanced shoal shrinkage.In addition,the self-adjustment of the transverse section shape resulted in abnormal accretion in 2002–2007.Afterward,the South Channel underwent overall erosion as sediment discharge decreased to a low level(<150 Mt/a).Five stages of channel-shoal pattern adjustment and accretion/erosion status during the past 60years were defined,i.e.,the accretion stage(1958–1965),remarkable channel-shoal adjustment stage(1978–1986),slow erosion stage(1986–1997),shoal scour and shrinkage stage(1997–2007)and overall channel-shoal erosion stage(2007–2018).Model prediction of the evolutionary trend indicates that overall erosion within the South Channel is most likely to continue in 2015–2050.Further adjustment of the South Channel under extremely low sediment discharge may threaten the riverbed stability and the sustainable development of this large-scale estuary.Future work on adaptive strategies for varying conditions is recommended.

近半个世纪长江口九段沙湿地的冲淤演变

根据1958—2004年的系列地形图，在地理信息系统软件ArcGis8．2的支持下，探讨近半个世纪九段沙湿地演变过程。研究表明：九段沙在长期的自然淤积过程中既具有趋势性的渐变，又存在非趋势性的突变，北槽深水航道工程改变了九段沙的自然冲淤模式，使九段沙顶端至江亚南沙大片区域显著淤积，工程后期，淤积速率回落，九段沙形态稳定。

都市圈旅游空间结构演变研究——以长三角都市圈为例

旅游空间结构演变研究,对优化都市圈旅游空间结构、促进都市圈整体旅游地形成和发挥都市圈旅游空间效应与功能有重要意义。以旅游人数和旅游收入为指标,利用赫芬达尔指数和位序—规模模型进行分析,并结合长三角都市圈旅游发展实际考察其旅游空间结构演变态势。结果表明,长三角都市圈旅游者和旅游收入空间分布趋向分散,各城市旅游发展相对差异不断缩小,其旅游发展趋向均衡化。长三角都市圈旅游发展实际也显示,其旅游空间结构呈现多中心、网络化和一体化特点。从长期来看,长三角都市圈旅游空间结构演变趋向高水平均衡。借鉴空间相互作用理论,认为以可达性、互补性和替代性为必要条件,以集聚和扩散作用为主要形式,以资金、技术、人员、信息和经验等的流动为主要内容,各城市旅游空间相互作用推动了都市圈旅游空间结构不断由低水平均衡向高水平均衡演变。旅游企业扩张和旅游客流流动带动了旅游资金、技术、人员、信息和经验等的集聚和扩散,推动了都市圈旅游空间结构演变。

基于分形的城市体系经济规模等级演变研究

利用区域城市体系经济规模等级分形理论,选取长江三角洲1995-2009期间4个年份的县级以上行政单位经济发展数据,计算了经济规模等级分形维数。以该地区城市体系经济规模等级分形维数的演变特征为载体,探讨了长江三角洲地区城市体系经济规模等级演变规律。结果表明：①虽然当前长三角地区各城市的经济社会发展水平差异较大,中心城市垄断性仍然较强,但其均匀化趋势明显。②经济规模等级的空间梯度特征明显,经济规模等级的均匀性随着距离区域核心城市距离的扩大而降低。③产业空间布局层次化逐步分明,中心城市的第三产业比重不断提升,区域控制能力不断增强,与以第二产业为主导的中小城市形成有机整体,区域经济竞争力整体得到提升。

长江口南汇嘴潮滩短期冲淤演变及其动力机制研究

潮滩地形的冲淤演变规律可以在一定程度上反映动力作用与地貌特征之间的相互耦合机制。根据近几年在长江口南汇嘴潮间带多断面连续观测资料,探讨区域内潮间带滩地的近期冲淤演变特征及其主要影响因子。研究结果表明:(1)南汇嘴潮滩近期主要呈现淤涨态势,而且年内过程季节性差异明显;受区位差异影响,不同观测断面的潮滩冲淤演变呈现特征不尽相同,断面1冲淤变化最为显著,年最大冲淤厚度均在10 cm以上;(2)在波浪、潮流的作用下,区域内沉积物很容易被掀动悬扬,而且输沙环流系统的存在有利于悬沙向浅水区输运且在该区域内沉降淤积,从而为潮滩发育提供泥沙来源;(3)受"碧利斯"台风引起的风暴潮天气影响,研究区域内潮滩出现"大冲大淤"现象,即台风强侵蚀期过后滩面高程短期内恢复明显。由此可见,潮滩短期冲淤演变特征是各种动力因素作用下的综合体现。

百年来长江口泥质区高分辨率沉积粒度变化及影响因素探讨

对长江口泥质区Chjk01与E4站位的沉积物柱状样进行了210^Pb测年和粒度分析，结果显示Chjk01孔与E4孔的沉积年代分别为132年（1873-2005年）与41年（1962-2003年），平均沉积速率达2.8cm/a与3.5cm/a。高密度间隔（0.5-1.0cm）粒度分析达到了反映粒度季节性变化的高分辨尺度。两孔粉砂含量随深度基本保持不变，粘土与砂含量则互为消长。Chjk01孔沉积物粒度自1873年以来明显呈三段式变化，1873-1957年间的84年中粒度稳定地逐渐变粗、砂含量增加、粘土含量减少、分选变差；1957-1981年间的24年中粒度逐渐变细、粘土含量增加、砂含量减少、分选变好，在1970-1981年间的11年中粒度最细；1981-2005年间的24年中粒度总体变粗、砂含量波动式增大，但变化趋势不明显。E4孔在1962-2003年间的41年中，沉积粒度特征与Chjk01孔基本一致。1873年以来的132年期间长江口泥质区粒度变化的阶段性特征，主要与同时期长江水沙入海主泓位置，以及主汊道的分沙比阶段性演变相对应；长江口泥质区粒度长尺度的阶段性变化，对长江大通站（1950-2004年）水沙变化和东亚季风强度指数（1873-1995年）变化不敏感。因此，长江水沙入海主泓位置与两孔位置距离的变化是影响泥质区粗、细粒级含量相对变化的主控因素，掩盖了其他因素的影响。

长江三峡大宁河流域3000年来的环境演变与人类活动

长江三峡大宁河流域张家湾东周—汉代古遗址的孢粉学和沉积学等分析结果表明 3 0 0 0年来该区环境演变与人类活动的互动影响。连续的孢粉和粒度记录证实 ,该区古人类活动初期处于暖湿的气候 ,东周—汉代时期转变为温凉略干的温带气候。东周—汉代后 ,该区经历了一次规模较大的大宁河洪水泛滥期 ,导致汉代文化层中断。此后不久 ,由于人类活动剧烈 ,自然植被严重破坏 ,水土流失比较严重 ,山洪灾害频繁 ,导致汉代之后该区没有连续的文化层堆积 ,而由于短暂洪水暴发引起大面积坡面片流 ,导致坡积物的大量堆积。

长江三峡大宁河流域三千年来沉积环境与河床演变初步研究

张家湾遗址T911剖面及双堰遗址T4 39剖面粒度、磁化率等环境替代指标的测试分析 ,并结合区域地质、地貌野外调查结果表明 :大宁河流域 30 0 0年来气候演变过程与中国东部地区存在着较大差异 ,中国的东部地区在公元初至公元 6 0 0年为寒冷期 ,而该区则为温暖期 ,笔者认为这是由于该区西北面与东南面均有高大山脉包围 ,这种特殊的地质地貌格局在一定程度上阻挡了来自北方冷空气进入本区的缘故。本区发掘的遗址多为单一时期的文化 ,其他时期的文化多以扰动层 (即含有两个或两个以上历史时期文化遗物的沉积地层 )的形式在沉积地层中出现 ,通过对沉积地层沉积物粒度 ,张家湾遗、大宁河河漫滩上的汉晋墓群、双堰塘遗址的相对位置及双堰塘生土层以下巨厚的鹅卵石层的比较分析 ,认为这与大宁河流域频繁发生的洪灾及河道变迁有关 ,大宁河频繁发生的洪灾及河道的变迁是影响该区人类生存环境的重要因素之一。

三峡水库建成后对长江河床演变的影响(英文)

长江三峡水库是特大型水库.长江三峡水利枢纽建成后,由于水动力条件改变,引起水库上、下河段河流地貌发育过程的一系列变化,对环境产生如下冲击和影响:①基准面抬高,流入水库各条支流在入库河口区及以下区域迅速产生水下淤积,形成河口拦门沙和水下三角洲.②水库上游河道发生变形.水库蓄水后引起库岸变形,这种库岸变形可能延续几十年的时间,影响到库岸的稳定性、水库库区附近淹没浸没以及水库渗漏等.水库运营时清水下泄,引起水库下游河床冲刷以及下游河道变形,受影响最大的是武汉及其以上荆江河段.根据三峡库区的实际情况,认为影响最大、最应该立项和进行综合研究的问题有3个方面:第一,入库河流河口地区的水下淤积问题;第二,水库运营过程中引起的库岸变形及库岸的稳定性问题;第三,水库下游清水下泄河床重新调整时,对下游荆江等河道的影响.

基于GIS的长江河口没冒沙动态演变及稳定性分析

根据该海区近百年来各个时期海图资料,运用Mapinfo软件分析没冒沙的形成及形成后的演变过程。结果表明:没冒沙的形成和发育经历了局部边滩冲刷、边滩沙嘴发育和沙脊形成三个阶段;无论是其横断面变化,还是平面变化,均反映了其沙头部位冲刷下移(但其移动距离不大);近半个世纪来,沙体中轴位置在稳定强劲的涨落潮流作用下呈现出西北-东南走向,位置基本不变,形态变化不大,其冲淤量在1959年后变化很小,0 m沙体变化基本不变,-2 m沙体略有冲刷,冲刷量为0.07×106m3/a,反映出没冒沙稳定性比较好。