高抒,贾建军,于谦. 海岸冲淤动态的理论分析:物质收支、剖面形态、岸线进退[J]. 海洋地质与第四纪地质,2023,43(2): 1-17. doi: 10.16562/j.cnki.0256-1492.2023021501
引用本文: 高抒,贾建军,于谦. 海岸冲淤动态的理论分析:物质收支、剖面形态、岸线进退[J]. 海洋地质与第四纪地质,2023,43(2): 1-17. doi: 10.16562/j.cnki.0256-1492.2023021501
GAO Shu,JIA Jianjun,YU Qian. Theoretical framework for coastal accretion-erosion analysis: material budgeting, profile morphology, shoreline change[J]. Marine Geology & Quaternary Geology,2023,43(2):1-17. doi: 10.16562/j.cnki.0256-1492.2023021501
Citation: GAO Shu,JIA Jianjun,YU Qian. Theoretical framework for coastal accretion-erosion analysis: material budgeting, profile morphology, shoreline change[J]. Marine Geology & Quaternary Geology,2023,43(2):1-17. doi: 10.16562/j.cnki.0256-1492.2023021501

海岸冲淤动态的理论分析:物质收支、剖面形态、岸线进退

Theoretical framework for coastal accretion-erosion analysis: material budgeting, profile morphology, shoreline change

  • 摘要: 海岸线动态经常被作为海岸冲淤的判据,然而,由于未能涵盖物质收支和海岸剖面形态的双重因素影响,此判据具有局限性。基于沉积物收支方程性质和海滩-潮滩剖面形态的理论分析,认为将物质收支与岸线进退速率或海岸剖面形态相结合,才能准确判别海岸冲淤状态。沉积物收支方程含有沉积体系规模、冲淤强度、系统生长极限等信息;海滩剖面形态决定于物质粒径、波能大小,波能耗散最小原理决定了海滩均衡剖面的存在性,而潮滩剖面形态决定于沉积物供给、粒径组成和潮汐动力。根据沉积物收支方程和海岸剖面理论,融合极端事件(风暴等)和海面变化因素,可获取砂质海岸(以海滩为代表)、泥质海岸(以潮滩为代表)各种侵蚀现象的发生机制、速率和时间尺度信息,海岸线变化速率从低(<100 m/a)到高(101~102 m/a)有数量级的差异,冲淤过程的时间尺度包括10−2 a(风暴事件)到103 a(海面变化)的范围。根据沉积物收支和海岸线进退的不同组合,可将海滩、潮滩海岸冲淤动态分为4类,其中第一类为堆积海岸,其余三类为侵蚀海岸,与不同的地貌演化方向和时间尺度相联系。高强度、长时间持续侵蚀主要与物质供给中断和海面上升相关,同时也有人为因素影响。

     

    Abstract: Shoreline dynamics is often used as a criterion for coastal erosion or accretion. However, this criterion may not be valid because it does not incorporate the factors of material budget and coastal profile morphology. Based upon an analysis of the properties of sediment budget equation and the profile morphology of beach and tidal flat systems, it is argued that only by combining the material budget with the rate of shoreline retreat or the profile morphology can the status of accretion-erosion be accurately identified. The sediment budget equation contains the information on the magnitude of a sedimentary system, accretion-erosion intensity, and the growth limit of the system. The beach profile shape depends on particle size and wave energy. The minimum wave energy dissipation principle implies the existence of equilibrium morphology, while the tidal flat profile shape depends on sediment supply, particle size composition and tidal dynamics. On such a basis, the erosion of both sandy coasts (represented by beaches) and muddy coasts (represented by tidal flats) can be understood in terms its mechanisms, rate and temporal scales by taking into account the various factors such as extreme events induced by storms and sea level rise. The rate of shoreline change may vary by orders of magnitude, ranging from low values of <100 m/a to high values of 101~102 m /a, with time scales for accretion-erosion processes ranging from 10−2 a (storm events) to 103 a (sea level changes). According to the different combinations of sediment budget and shoreline advancing/retreating patterns, the dynamic behaviour of the coastal zone associated with beaches and tidal flats has four possible situations: one of them is related to accretion, and the others are linked with erosion. The different types of erosion are each determined by the geomorphic evolution direction and the temporal scale. High intensity, long-time persisting erosion is mainly related to material supply cutoff and sea level rise, and is influenced by anthropogenic factors.

     

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