莱州湾东岸岬间海湾海岸地貌演变过程与影响机制

	莱州湾东岸岬间海湾海岸地貌演变过程与影响机制
	战超
学位类型	博士
导师	于君宝
	2017-05-07
学位授予单位	中国科学院大学
学位授予地点	烟台
关键词	海岸侵蚀岬间海湾砂质海岸人类活动动力地貌演变
摘要	针对莱州湾东部砂质海岸人类活动剧烈、河流输沙变化显著等问题，选取莱州湾东部4个岬间海湾所构成的整体岸段作为研究对象，综合使用野外调查、3S（RS/GPS/GIS）技术、沉积物分析、数字海岸分析、数值模拟和平衡岸线推算等方法，研究最近60年海岸动力地貌演变过程及其影响机制。研究内容主要包括最近60年岬湾海岸地貌演变、人类活动的沉积动力效应以及海岸冲淤动态，以揭示河流入海输沙减少、潮上带土地利用变化和海岸工程对海岸地貌演变的影响机制，查明海岸侵蚀发生的地貌冲淤背景、发展过程和时空差异，并建立最近60年来莱州湾东部砂质侵蚀海岸动力地貌演变差异性分析。主要结论如下：（1）莱州湾东部海岸兼具岬湾和平直砂岸的基本地貌特征。在60年时间尺度上海岸形态特征摆动于两者之间，导致沿岸输沙变化频繁。在自然状态下屺坶岛—石虎嘴岬湾的不稳定性参数值最大（11.15%），其下游的三个岬湾不稳定性依次降低。故输沙减少情况下，屺坶岛—石虎嘴岬湾的海岸侵蚀最强烈，尤以界河口附近岸段最为显著（后退2.31km）。且遮蔽段均较切线段侵蚀调整显著。海岸系统对河流入海泥沙减少的地貌冲淤调整需要30年。入海泥沙减少与否及比例，对岸线调整至动态平衡的时间影响差别不大。入海泥沙量变化对不同岸段影响差异显著，且平衡岸线差别较大。（2）莱州湾东部岸线迁移和水下岸坡冲淤具有非线性的显著特点，呈现冲淤交替的特征。1959-2013年，岸线侵蚀速率波动起伏，以1985年为界先减后增。各岬湾的岸线变迁与整体并不一致。除了三山岛—刁龙嘴岸段一直处于淤积或平衡状态外，其余三个岬湾在十年尺度上岸线演变呈现冲淤交替分布的空间格局。1959-1985年，岸线整体向海推进，同时水下岸坡2m，5m和10m等深线处水深均淤积变浅，淤积面积和泥沙量分别为1.87×10⁸m²和1.15×10⁸m³。1985-2006年，岸线整体侵蚀后退，2m等深线处水深增加，5m等深线处水深基本不变，而10m等深线则淤积变浅，淤积面积仅为5.58×10⁷m²，淤积泥沙量为前期的8%。大部分岸段岸线外侧出现了连续展布的水下侵蚀条带。（3）莱州湾东部海岸埋藏样的沉积类型属于中、粗砂，分选程度中等-好，以正偏、极正偏为主， 66.67%源自浅海沉积，而目前浅海及古海滩沉积的出露则表明该岸段近期处于蚀退状态。148个海滩表层沉积物主要属于粗砂、中砂和极粗砂，分选程度以好和中等为主。位于界河口附近的剖面平均粒径最粗，向下游逐渐减小。（4）在河流上游大规模的修建水库, 导致莱州湾东岸河流入海泥沙量的减小，显著改变了地貌的冲淤演变。水动力数值模拟结果显示，随着河流入海泥沙量的减少，整体侵蚀作用越来越显著，范围不断扩大，强度不断加大。不同岸段呈现不同的冲淤状态，侵蚀条带主要分布在2—5m等深线之间，且靠近岸河口处侵蚀严重。但是，除了界河口、王河口、刁龙嘴西南等个别地点有较强的侵蚀发生外，2m等深线以浅区域均处于冲淤平衡或轻微淤积状态。（5）莱州湾东部海岸土地覆被变化的总趋势是风沙地、林地和耕地向养殖池及居民地转化。在多年大潮平均高潮线和特大潮高潮线之间形成了一条平行于岸线、宽达数百米，纵向基本连续展布的水产养殖设施带。水动力数值模拟结果显示，风暴潮时岸线附近波高和流速变化显著。随着养殖设施覆盖比例的提高，沿岸侵蚀条带向下游延伸，向外海展宽；岸线附近侵蚀深度和范围均明显增大，水下岸坡闭合水深加大，闭合位置向外海推移。（6）龙口人工岛一期工程改变了屺坶岛-石虎嘴岬湾的上游控制点，导致沿岸输沙速率与方向显著变化。根据一线模型预测结果，界河口东侧岸段，沿岸输沙方向发生逆转（由NE-SW向转为SW-NE向），造成了后方掩护区域的淤积，而下游岸段（界河口东侧至诸流河西南1.5km处）强烈蚀退。利用抛物线模型对静态平衡岸线的模拟结果显示，界河口附近及其西南侧岸线将侵蚀后退；石虎嘴岬角岸段将向海淤进，强烈侵蚀岸段与一线模型预测结果一致。（7）莱州湾东岸海岸地貌冲淤演变具有显著的不稳定性，不同时期、不同岸段分别处于侵蚀后退或淤积前进状态并呈交替式时空分布。受海岸边界条件的控制，再加上风暴潮作用的高频率出现，至少在60年尺度上该段海岸地貌冲淤变化不稳定；在海滩—水下沙坝泥沙交换、岬湾—平直砂岸转换以及水库拦沙、潮上带工厂化水产养殖、大型海岸工程等人类活动的地貌效应共同作用下，最近60年来发生了至少5次岸线进退以及冲淤速率大小的交替，平均10年就发生一次转换，且不同岸段不同步。其未来50年尺度上的海岸地貌冲淤变化趋势为总体侵蚀后退背景下的冲淤交替。
其他摘要	In view of the violent human activities and the significant changes of sediment transport, we studied the morphodynamic evolution and influence mechanism of erosional sandy coast along the eastern Laizhou bay which is regarded as a unitive coast system made up of four neighboring headland-bays with the comprehensive usage of several relevant methods, such as field investigation, 3S(RS/GPS/GIS) technologies, sediment analysis, numerical coast morphological analysis, numerical hydrodynamic model and.it has been significantly changed from four headland harbors, using field survey, 3S (RS / GPS / GIS) technologies, digital coast analysis, numerical simulation and equilibrium shoreline estimation. The main research contents included the coastal morphological evolution, coastal erosion-sedimentation changes, and coastal morphological response to human activities of the eastern Laizhou bay in recent sixty years. We have discovered the affecting mechanism of river sediment load decrease and land use/land cover change in the supratidal zone on coastal geomorphic evolution of the coast firstly, investigated the morphological erosion-sedimentation change background, evolution history and differences of spatiotemporal of coastal erosion secondly, and establishing a morphodynamic evolution model of the erosional sandy coast along the eastern Laizhou bay in recent sixty years thirdly. The main conclusions included: (1) The basic geomorphic features of the eastern coast of Laizhou Bay are both headland and straight coast. On the 60-years scale, the coastal morphological characteristics oscillated between headland bay and straight coast, leading to frequent changes in alongshore sediment transport rate. In the natural state, the instability value of Qimudao-Shihuzui (11.15%) is largest among each headland bays, and the instability values of the three downstream headland bays decrease in turn. In the case of sediment loss or disappearance, the coastal erosion of the Qimudao-Shihuzui bay is the most significant. Especially in the vicinity of the mouth of the Jihe River, erosion back to 2.31km. The erosion of the cover segment of the four bays is more severe than the tangential section. It takes 30 years for the coastal system to adjust the sediment reduction of the river into the sea. The effect of reduced sedimentation on the time of shoreline adjustment to dynamic equilibrium is not significant. The effect of the change of sediment volume into the sea was significant difference among different segments. (2) The characteristics of the time course of shoreline migration were non–linearity, showed the alternately erosion and sedimentation. From 1959 to 2013, the proportion of erosion shoreline fluctuated, divided into two stages in 1985. The differences in the spatial distribution of shoreline migration were not consistent with the overall changes in the coastline of the headland Bays. In addition to the Sanshandao-Diaolongzui section, the other three headland bays in the ten-year scale shoreline evolution showed scouring and silting alternate distribution pattern. And Sanshandao-Diaolongzui section, although the rates of different periods were significant differences, the coastline has always been shown siltation or balance.The evolution of underwater slope and shoreline was in close contact. The shoreline of the coast is advancing to the sea as a whole during the period of 1959-1985. The water depth of the contours of 2m, 5m and 10m were also shallow. The area of siltation was 1.87 × 10⁸m². The volume of sediment was 1.15 × 10⁸m³. The shoreline of the coast is erosion as a whole during the period of 1985-2006. The water depth of the contours of 2m was increase, 5m was equilibrium and 10m shallow. The area of siltation was 5.58 × 10⁷m². The volume of sediment was only 8% of the original period. The continuous erosional band of underwater was emergence in the majority of the shoreline outside the coastline. (3) The particle size analysis of the buried samples showed that the sedimentation types belonged to medium and coarse sand, and the degree of sorting was moderate – good. The skewness were positive and extreme positive. 66.67% of the samples were shallow sea sediments. At present, the release of shallow sediments indicates that the shore is in an eroded state. The particle size analysis of the 148 surface sediments showed that the average particle size was mainly coarse sand, medium sand and very coarse sand, and the sorting degree was mainly good and medium. The average particle size of the profile located in the vicinity of the mouth of Jiehe River (medium sand, coarse sand and gravel) was the coarsest, and gradually reduced to the downstream. (4) Large-scale construction of reservoirs in the upper reaches of the river resulted in a decrease in the amount of sediment into the east coast of Laizhou Bay, which significantly changed the geomorphic evolution. The results of numerical simulation of hydrodynamics show that the erosion effect of the east coast of Laizhou Bay is increasing with the decrease of sediment concentration in the river, and the erosion extent is enlarge and the intensity of erosion is increasing. There have been different scouring and silting conditions in different sections. The erosion bands are mainly distributed between 2m and 5m isobaths, and the more serious the erosion where near the estuary. However, in addition to the strong erosion of the estuary of Jiehe River, Wanghe River, and southwestern of Diaolongzui, the entire east coast of Laizhou Bay shallower than 2m isobaths are in the state of equilibrium of scouring and silting or slightly siltation. (5) The main evolution trend of land use along the eastern coast of Laizhou bay is the transition from aeolian sandy land, woodland and farmland to aquaculture ponds and residential land. A belt zone of aquaculture facility parallel to the coastline has been formed and dykes are constructed along the outside of the coastal aquiculture zone. The significant land cover change in the supratidal zone has profoundly modified the boundary conditions of storm surges. The hydrodynamic modeling results show that the ocean dynamics near the coastline are enhanced and caused severe erosion of the coastline, beach and underwater coastal sea slope along the eastern coast of Laizhou Bay. (6) The upstream control point of headland bay was changed by the Longkou Artificial Island Phase I project, which resulted in the significant changes of the rate and direction of coastal sediment transport. According to the simulation results of the one-line model, the direction of the sediment transport in the east of the estuary of the Jiehe River estuary was reversed (from NE-SW to SW-NE). The cover area of the Artificial Island was in the state of siltation, and the downstream section was strong erosion (from the eastern of Jiehe estuary to the southwestern of Zhuliuhe estuary 1.5km). The simulation results of the static equilibrium shoreline from the parabolic model show that the shoreline near the Jiehe estuary and its southwest coastline will be eroded and retreated. The headland of Shihuzui will be deposition. The result of strong erosional section is consistent with the one-line model. (7) The evolution of siltation and sedimentation on the east coast of Laizhou Bay was significant instability. The distribution of erosion and silt section was spatiotemporal alternate during different times, in different sections. The coastal geomorphic erosion and sedimentation evolution is unstable at least on the 60-yeard scale, under the control of the coastal boundary conditions, and coupling with the high frequency of storm surge. In the last 60 years, there have been at least 5 times of coastline advancement and the rate of scouring and silting changing, and an average frequency of 10 years, and the different sections are not synchronized, under the joint action of the sediment exchange between beach-submarine bar, the conversion of headland bay and straight coast, the construction of reservoir, industrial aquaculture in supratidal zone and coastal engineering. The trend of scouring and silting in the future 50-year scale is the alternative of erosion and deposition on the background of the overall erosion
文献类型	学位论文
条目标识符	http://ir.yic.ac.cn/handle/133337/22455
专题	中国科学院烟台海岸带研究所知识产出_学位论文
推荐引用方式 GB/T 7714	战超. 莱州湾东岸岬间海湾海岸地貌演变过程与影响机制[D]. 烟台. 中国科学院大学,2017.

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