Study on headland-bay sandy coast stability in South China coasts   总被引：1，自引：0，他引：1  

于吉涛  陈子燊 《中国海洋工程》2011,25(1):1-13

Headland-bay beach equilibrium planform has been a crucial problem abroad to long-term sandy beach evolution and stabilization,extensively applied to forecast long-term coastal erosion evolvement and the influences of coastal engineering as well as long-term coastal management and protection.However,little concern focuses on this in China.The parabolic relationship is the most widely used empirical relationship for determining the static equilibrium shape of headland-bay beaches.This paper utilizes the relation to predict and classify 31 headland-bay beaches and concludes that these bays cannot achieve the ultimate static equilibrium planform in South China.The empirical bay equation can morphologically estimate beach stabilization state,but it is just a referential predictable means and is difficult to evaluate headland-bay shoreline movements in years and decades.By using Digital Shoreline Analysis System suggested by USGS,the rates of shoreline recession and accretion of these different headland-bay beaches are quantitatively calculated from 1990 to 2000.The conclusions of this paper include that (a) most of these 31 bays maintain relatively stable and the rates of erosion and accretion are relatively large with the impact of man-made constructions on estuarine within these bays from 1990 to 2000;(b) two bays,Haimen Bay and Hailingshan Bay,originally in the quasi-static equilibrium planform determined by the parabolic bay shape equation,have been unstable by the influence of coastal engineering;and (c) these 31 bays have different recession and accretion characters occurring in some bays and some segments.On the one hand,some bays totally exhibit accretion,but some bays show erosion on the whole.Shanwei Bay,Houmen Bay,Pinghai Bay and Yazhou Bay have the similar planforms,characterized by less accretion on the sheltering segment and bigger accretion on the transitional and tangential segments.On the other hand,different segments of some bays have two dissimilar evolvement characters.Dacheng Bay,Shenquan Bay,Hudong Bay,Wukan Bay,Fengjia Bay,Wuchang Bay,Lingshui Bay and Tufu Bay produce accretion on the tangential segment,erosion on the transitional segment and accretion on the sheltering segment.However,Guang’ao Bay,Haimen Bay,Jinghai Bay,Sanya Bay(a),Dajiao Bay,Hailingshan Bay,Hebei Bay,Fuhu Bay,Shuidong Bay,Wangcun Bay and Bomao Bay generate erosion on the tangential part,accretion on the transitional part and accretion on the sheltering part.It seems to imply some relations between headland-bay beach evolvement and controls on headland-bay beaches,which may possibly to classify headland-bay beach types and should be further studied.  相似文献   

The Lake Lahontan highstand: age, surficial characteristics, soil development, and regional shoreline correlation     

Kenneth D. Adams  Steven G. Wesnousky 《Geomorphology》1999,30(4):631

The Lake Lahontan basin has been the site of numerous pluvial lakes during the Pleistocene. We address the question of whether or not the highest remnant shoreline features around the perimeter of the lake were produced during the most recent Sehoo highstand (13 ka), the penultimate Eetza highstand (140–280 ka), or both. To do so, we document surficial characteristics, morphologic preservation, and soil development on multiple Sehoo beach barriers in the Jessup embayment to define the range in characteristics displayed by latest Pleistocene beach features. Sehoo barriers generally exhibit original constructional morphology that has been little modified by erosion. Soils developed on Sehoo barriers are generally thin and weakly developed and are strongly influenced by the introduction of eolian fines into the predominately clast-supported coarse beach gravels. Similar observations from 13 other highstand barriers and from seven older-than-latest Pleistocene paleosols located around the basin form the basis for a regional comparison. Based on similar characteristics, including the degree of morphologic preservation and weak soil development, we conclude that the widespread and nearly continuous high shoreline around the perimeter of Lake Lahontan dates from the most recent major lake cycle in all areas except in the Walker Lake subbasin. In the Walker Lake subbasin, isolated early to middle Pleistocene lacustrine outcrops and landforms are elevated as much as 70 m above the late Pleistocene limit, but are differentiated by their degraded form and lack of continuity around the subbasin. Similar unambiguous landforms were not observed elsewhere and at similar elevations in the northern subbasins of Lake Lahontan.  相似文献   

The volume and paleobathymetry of glacial Lake Agassiz     

Jason D. Mann  David W. Leverington  John Rayburn  James T. Teller 《Journal of Paleolimnology》1999,22(1):71-80

During the last retreat of the Laurentide Ice Sheet in North America, many proglacial lakes formed as continental drainage was impounded against the southern and western ice margin. Lake Agassiz was the largest of these lakes. The bathymetry of Lake Agassiz at the Herman and Upper Campbell beach levels – formed at about 11.5–11.0 ka and 9.9–9.5 ka, respectively – was computer modelled in this study by first collecting data for the isostatically-deformed paleowater planes of the two lake levels (derived from isobase lines constructed from beach elevations), and then subtracting these from the modern topography of the former lake floor. Pixels with dimensions of 1/30 × 1/30 of a degree were used in the model. Using these data, the area and volume of the lake were also calculated: at the Herman level these were 152 500 km2 and 13 100 km3 respectively; at the Upper Campbell level these were 350 400 km2 and 38 700 km3. Contour maps showing the paleobathymetry of both periods in the lake's history were also constructed. Determining the paleobathymetry and volume of Lake Agassiz is an important step in understanding the impact that the lake had on its surrounding environment and on the rivers, lakes, and oceans into which it flowed.  相似文献   

应用遥感方法分析珠江口伶仃洋的海岸线变迁及其环境效应   总被引：11，自引：1，他引：11  

李学杰 《地质通报》2007,26(2):215-222

对伶仃洋1979年以来利用多时相遥感影像提取的岸线进行分析,结合地形图,得到近几十年来海岸线变化的特征,认为南沙区和蛇口半岛是岸线变化最快的2个区,而淇澳岛区和交椅湾区的变化相对较小。南沙区岸线变迁以沉积作用和围海造地形成的岸线向海延伸为主,延伸速率从1966年至2000年明显增大,2000年后有减缓的趋势。蛇口半岛区主要以码头、池塘等人工建筑形成的岸线向海延伸为主。从岸线变迁、悬浮沉积物分布及其沉积作用来看,伶仃水道西侧以沉积为主,可能不适合于大规模的码头建设。珠江口岸线变迁最主要的环境效应是河道变窄、增长,造成排洪不畅,上游的洪涝灾害增多。  相似文献   

差异可容纳空间背景下湖相层序样式与三角洲形态响应: 鄱阳湖与岱海湖对比研究^*          下载免费PDF全文

付超  于兴河  李胜利  李顺利  高明轩  彭子霄  赵海权 《古地理学报》2022,24(6):1084-1098

近年来随着层序地层学研究逐步走向定量化,将其标准化已成为沉积学界的共识。可容纳空间作为层序标准化中重要的参数之一,受到越来越多的关注。然而,不同可容纳空间背景下汇水盆地的坡度和沉积供给量均存在差异,其复杂的沉积过程造成当前研究难以准确刻画出对应层序参数演化与三角洲形态之间的耦合关系。本次研究选取中国2个典型的湖泊—三角洲进行对比研究,包括较为平缓的鄱阳湖赣江三角洲(地层倾角小于1°)与坡度相对较大的岱海湖周缘三角洲(地层倾角3°~10°)。通过对近30年不同水位期卫星照片解译,并将其与现代沉积剖面解释相结合,明确了: (1)可容纳空间快速增加背景下,湖岸线变化相对稳定,但平面影响范围较小; 三角洲在低位域(LST)时期主要发育帚状或朵状前积体,在湖侵域(TST)和高位域(HST)时期主要表现为朵叶状或鸟足状前积体。(2)缓坡低可容纳空间背景下,湖岸线变化较为剧烈,并且影响范围较大; 三角洲在低位进积域(RST)时期多以鸟足状前积体为主,内部发育指状沙坝,高位域(HST)时期表现为鸟足状前积体,同时沿岸沙坝较为发育。综合上述认识,结合沉积正演模拟结果,在经典层序和滨岸坡折岸线迁移模式的基础上,分别针对可容纳空间快速增加背景和低可容纳空间背景,建立了对应的层序—三角洲发育模式,并从长短周期尺度分析了不同可容纳空间背景下层序—沉积演化过程的控制因素。  相似文献   

High-Frequency Sequence Stratigraphy and Fine-Scale Reservoir Characterization of the Devonian Sandstone, Donghe Formation, North Uplift of the Tarim Basin     

WANG Ziyuan  LIU Li  PAN Mao  SHI Yongmin  XIONG Fengyang 《《地质学报》英文版》2018,92(5):1917-1933

The Devonian Donghe Sandstone complex in North Uplift of the Tarim Basin comprises of a series of diachronous sandy intervals deposited from the Late Devonian to Early Mississippian. They are constrained by a Late Devonian to Early Pennsylvanian 2nd-order supersequence and can be subdivided into five 3rd-order sequences, namely, S1, S2, S3, S4, and S5, from the oldest to youngest. Cores from four wells, 40 wireline logs, 410 thin sections, and porosity and permeability data from 639 spots from four wells were used to study the sediment provenance, build up the sequence-stratigraphic model of S5, and characterize the reservoirs at a feet scale. Detrital modes of sandstone from point counting indicate that Donghe Sandstone is directly sourced from recycled orogeny. The low content of feldspar and volcanic rock fragments suggests that Donghe Sandstone is recycled from sediment with a cratonic ultimate source. 1D and 2D chronostratigraphic correlation shows that at least 12 4th-order high-frequency sequences (HFSs), from the oldest HFS1 to the youngest HFS12, can be recognized in S5. Each HFS is characterized by a general trend of shallowing-upward facies assemblage. Sequence boundaries were defined at where regionally correlatable deep-water facies overlaying shallow-water facies. There is a general shallowing-upward trend in the S5 3rd-order sequence, characterized by a systematically increasing proportion of shallow-water facies (foreshore and upper shoreface), and a decreasing proportion of deep facies (offshore transition and lower shoreface). The shallowing-upward trend within both 3rd- and 4th-order sequences is resulted from a combined effect of eustatic sea-level change, tectonic activity, and sediment supply. The sequence-stratigraphic model of Donghe Sandstone S5 is similar to the rift-basin sequence-stratigraphic model. Sweet spots were defined as porosity >15% and permeability >100md intervals, and their distribution and lateral continuity were investigated. HFS is one of the primary controls on the distribution of sweet spots distribution and can be used to guide hydrocarbon exploration.  相似文献   

近三十年青藏高原内流区湖泊岸线形态的时空演变     

王哲  刘凯  詹鹏飞  王纯  范辰媛  宋春桥  汤国安 《地理研究》2022,41(4):980-996

湖泊岸线形态是描述和定量表达湖泊空间分布特征的重要维度。近年来,受气候暖湿化影响,青藏高原内流区湖泊总体呈现快速扩张趋势,湖泊的动态变化不仅体现在面积、水位、水量等水文参数上,还引起湖泊形态的显著变化。基于多期湖泊分布数据,结合分形和景观生态学理论,构建了湖泊岸线形态特征量化的指标体系,对1990年以来,青藏高原内流区湖泊岸线形态的时空变化特征及其影响因素进行定量分析。结果表明：① 近三十年来青藏高原内流区湖泊的分形维数和岸线发育系数总体呈上升趋势,湖泊的近圆率在此期间呈下降趋势,湖泊长宽比指数则无明显变化。② 青藏高原内流区湖泊岸线形态的总体演变特征受到地质构造的控制,体现出一定空间自相关性,断陷湖区的湖泊岸线形态及其变化要明显复杂于坳陷湖区。区域湖泊岸线的变化幅度大致从东北向西南递减,变化幅度在可可西里地区、羌塘高原中部以及羌塘高原东南部3个区域存在空间自相关性。③ 湖泊岸线形态的变化受岸线周边的地形影响,湖滨地形落差较大的区域,湖泊岸线相对稳定,变化速度较慢。岸线指数的变化量与岸线周边1 km缓冲区内的平均高差存在幂函数关系。④ 该区域湖泊岸线形态的变化和湖泊面积的变化幅度也存在一定相关性,当湖泊处于扩张阶段时,湖泊的分形维数和岸线发育系数总体呈现增加趋势,反之减少。本研究揭示了气候暖湿化背景下青藏高原内流区湖泊岸线形态的变化格局与影响特征,讨论了湖泊岸线形态及其变化格局与湖区的地质构造,气候与水文等多个要素间的关系,丰富了湖泊动态变化研究的视角与方法,为深入理解青藏高原湖泊对气候变化的响应特征,监测湖泊变化对湖盆地貌、水系连通度以及湖滨带生态环境等影响提供了科学参考。  相似文献   

加拿大北极地区的海岸后退与冻土热状况     

王保来 《冰川冻土》1992,14(1):55-62

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Monitoring of the sediment dynamics along a sandy shoreline by means of airborne hyperspectral remote sensing and LIDAR: a case study in Belgium     

B. Deronde  R. Houthuys  J.‐P. Henriet  V. Van Lancker 《地球表面变化过程与地形》2008,33(2):280-294

Airborne hyperspectral data and airborne laserscan or LIDAR data were applied to analyse the sediment transport and the beach morphodynamics along the Belgian shoreline. Between 2000 and 2004, four airborne acquisitions were performed with both types of sensor. The hyperspectral data were classified into seven sand type classes following a supervised classification approach, in which feature selection served to reduce the number of bands in the hyperspectral data. The seven classes allowed us to analyse the spatial dynamics of specific sediment volumes. The technique made it possible to distinguish the sand used for berm replenishment works or for beach nourishments from the sand naturally found on the backshore and the foreshore. Subtracting sequential DTMs (digital terrain models) resulted in height difference maps indicating the erosion and accretion zones. The combination of both data types, hyperspectral data and LIDAR data, provides a powerful tool, suited to analyse the dynamics of sandy shorelines. The technique was demonstrated on three sites along the Belgian shoreline: Koksijde, located on the West Coast and characterized by wide accretional beaches, influenced by dry berm replenishment works and the construction of groins; Zeebrugge, on the Middle Coast, where a beach nourishment was executed one year before the acquisitions started and where the dams of the harbour of Zeebrugge are responsible for the formation of a large accretional beach, and Knokke‐Heist, located on the East Coast and characterized by narrow, locally reflective, beaches, heavily influenced by nourishment activities. The methodology applied allowed retrieval of the main sediment transport directions as well as the amount of sediment transported. It proved to be specifically suited to follow up the redistribution and the re‐sorting of the fill in beach nourishment areas. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

华南西部火山岛地区滨海浅层地下水的水质现状研究   总被引：2，自引：2，他引：0       下载免费PDF全文

甘华阳  林进清  夏真  何海军  路剑飞  黄向青  张顺枝 《中国地质调查》2017,4(4):80-87

雷州半岛与海南岛一峡相隔,气候和地质环境相似。近年来,随着经济社会的快速发展,沿海地下水抽用频繁,发展和环境的矛盾日益突出。为了解滨海地区地下水的分布、变化及其与环境的关系,在雷州半岛和海南岛滨海地区进行了浅层地下水井钻凿和地下水潮周期化学连续取样及实验测试。对数据的分析与评价结果表明: 全部监测井为Na-Cl型,除个别监测井外,大多数监测井浅层地下水的溶解性固体总量(total amount of dissolved solids,TDS)和氯离子、硫酸盐、钠离子等含量较高,其中TDS和氯离子含量最高,分别接近39.00 g/L和20.00 g/L,取样时段内波动较大,类型以偏酸性重碳酸盐为主转为以偏碱性钠离子和氯化物为主; 受制于地质环境条件,地下水自我调节能力以“一般”和“弱”居多,水质为IV—V级,且不随测次而变化,表明至少在短期内不会改变。滨海地区浅层地下水水质既与地质环境条件关系密切,也与人类活动有关,还可能受到深层承压古海水释放的影响。影响地下水水质的因素较为复杂,需要进一步加强综合研究和监测。  相似文献