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The morphodynamic difference in the western and southern coasts of Laizhou Bay: Responses to the Yellow River Estuary evolution in the recent 60 years
Global and Planetary Change ( IF 3.9 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.gloplacha.2020.103138
Chao Zhan , Qing Wang , Buli Cui , Lin Zeng , Cheng Dong , Xueyan Li , Xiang Yu , Xin Wang , Xianbin Liu

Abstract The Yellow River Estuary (YRE), which is famous for its abundant sediment, rapid accretion, and frequent migration, has experienced a remarkable decrease of sediment transported by the Yellow River (YR) during the past 60 years. By taking the west coast (Yellow River Delta, YRD) and the south coast of Laizhou Bay (LZB) as a unified coastal unit, this paper has analyzed the evolution of shorelines, isobaths, and geomorphic erosion/accretion during the last 60 years based on the remote sensing images and nautical charts; these data were also used to reveal the depositional dynamic mechanisms controlling the coastal geomorphic responses to YRE evolution in a hydrodynamic numerical simulation. Then, the coastal dynamics, subaqueous slope accretion, and geomorphic evolution were integrated spatially. Finally, the impacts of YRE evolution, including changes of the position and amount of sediment loading into the sea, on the coastal geomorphic evolution of western–southern LZB during the recent 60 year period were elucidated. Results showed that outside of the YRE delta lobes, there has always been an arc high-velocity zone, outside of which there has existed a northeast arc tidal shear frontal zone during the last 60 years. As the estuary delta lobes extended into the sea, the high-velocity zone moved toward the southeast, where its range and velocity also increased. As an overall trend, the duration of the tidal shear frontal zone (TSFZ) has grown longer and longer over a whole tidal cycle, while the interval time has grown shorter and shorter; moreover, the span between the southern and northern endpoints has grown larger and larger, while the southern end always remained confined to a fixed position in the northeast sea area of Qingtuozi. Under the control of TSFZ, the suspended sediment of the Yellow River deposits nearly entirely in the arc area in the vicinity of the estuary delta lobes on the west coast, and thus, the sediment cannot cross TSFZ and move into southern LZB. As a result, the western and southern coasts of LZB have shown significant differences in the evolution of shorelines, isobaths, and geomorphic erosion/accretion during the last 60 years. That is, these features have changed dramatically in the west coast but have remained relatively stable in the southern coast, and sediment deposition is now greatly reduced in the southern LZB. Therefore, the YRE evolution had a significant geomorphic impact on the coast of western LZB where the YRD is located, while it had only a slight impact on southern LZB.

中文翻译:

莱州湾西岸和南岸地貌动力学差异:对近60年黄河口演化的响应

摘要 黄河口以泥沙丰富、堆积迅速、运移频繁而著称,在过去的60年中,黄河输沙量显着减少。以西海岸(黄河三角洲,长三角)和莱州湾南海岸(LZB)为一个统一的海岸单元,分析了近60年来海岸线、等深线和地貌侵蚀/增生的演变过程。关于遥感图像和海图;这些数据还用于揭示控制海岸地貌对水动力数值模拟中 YRE 演化响应的沉积动力学机制。然后,在空间上整合了海岸动力学、水下斜坡增生和地貌演化。最后,YRE 演变的影响,包括入海沉积物位置和量的变化,阐明了近60年来LZB西南部海岸地貌演化。结果表明,在YRE三角洲裂片之外,一直存在一个弧形高速带,在过去的60年里,在该高速带之外存在着一个东北弧形潮汐切变锋区。随着河口三角洲向海延伸,高速带向东南移动,其范围和速度也增加。从总体趋势来看,潮汐剪切锋区(TSFZ)的持续时间在整个潮汐周期中越来越长,而间隔时间越来越短;而且,南北端点之间的跨度越来越大,而南端则始终局限在青沱子东北海域的一个固定位置。在TSFZ的控制下,黄河悬浮泥沙几乎全部沉积在西海岸河口三角洲叶附近的弧形区域,因此沉积物不能穿过TSFZ进入LZB南部。因此,LZB 的西部和南部海岸在过去 60 年中在海岸线、等深线和地貌侵蚀/增生的演变方面表现出显着差异。也就是说,这些特征在西海岸发生了巨大变化,但在南部海岸保持相对稳定,现在LZB南部的沉积物沉积大大减少。因此,YRE 演化对长三角所在的 LZB 西部海岸有显着的地貌影响,
更新日期:2020-04-01
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