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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Lithological controls on soft cliff planshape evolution under high and low sediment availability
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Lithological controls on soft cliff planshape evolution under high and low sediment availability

机译：高和低含沙量条件下软悬崖平面形状演化的岩性控制

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This paper addresses a series of geomorphic questions relating to large-scale (> 1 km), long-term (100 - 1,000 years) coastal planshape evolution. Previous research on soft-cliff coasts has recognised the role of protective fronting beach volumes on reducing rates of cliff toe retreat. However, it is the maintenance of this critical threshold that ultimately determines two contrasting modes of shoreline behaviour: Mode A, in which there is little beach sediment and shoreline evolution is controlled by material strength; and, Mode B, when ample beach sediment means that shoreline evolution is controlled by longshore sediment transport. Here we use a numerical model (SCAPE) to investigate temporal and spatial changes in beach volume on a broader range of feedbacks than considered in previous models. The transition between Mode A and Mode B coasts is defined by relative sediment inputs to outputs and used to explore how these contrasting modes control the evolution of an initial linear frontage exhibiting longshore changes in cliff lithology (material resistance and the proportion of beach grade material in the eroded bedrock). Under Mode A, relative changes in material resistance result in long term heterogeneous rates of retreat, which result in the development of persistent headland and embayment features. However, under Mode B, feedbacks between coastal planshape, longshore sediment transport, beach volume and wave energy result in steady state retreat rates regardless of longshore variations in resistance. Results are compared and contrasted to previous simulations and site specific examples and a conceptual model of Mode A and Mode B interactions presented. Copyright (c) 2015 John Wiley & Sons, Ltd.
机译：本文讨论了一系列与大规模（> 1 km），长期（100-1,000年）的沿海平面形状演化有关的地貌问题。先前对软崖海岸的研究已经认识到保护性前沿海滩数量在降低悬崖趾撤退速度方面的作用。然而，正是这一临界阈值的维持最终决定了两种相反的海岸线行为模式：A模式，其中海滩沉积物很少，海岸线演变受物质强度控制;模式B，当海滩沉积物充足时，意味着海岸线的演变受长海岸沉积物的运输控制。在这里，我们使用数值模型（SCAPE）来研究比以前的模型所考虑的更广泛的反馈范围内海滩体积的时空变化。模式A和模式B海岸之间的过渡是由相对的泥沙输入到输出所定义的，并用来探索这些对比模式如何控制初始线性锋面的演变，该线性锋面表现出悬崖岩性的沿岸变化（物质阻力和滩涂物质比例）。被侵蚀的基岩）。在模式A下，物质抵抗力的相对变化会导致长期异质性退缩速度，从而导致持续的岬角和退潮特征的发展。然而，在模式B下，无论长岸电阻的变化如何，沿岸平面形状，沿岸沉积物迁移，海滩体积和波浪能之间的反馈都会导致稳态退缩速率。将结果与先前的模拟和特定地点的示例进行了比较和对比，并给出了模式A和模式B交互的概念模型。版权所有（c）2015 John Wiley＆Sons，Ltd.

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