Development and Testing of a Numerical Model for the Evolution of Rocky Coastlines

世界上许多多岩石的海岸线以海岬和河口交替的形式呈现出平坦的粗糙度。沿着波浪主导的悬崖海岸，人们通常认为海岬是由岩石组成的，由于结构或岩性的变化，海岬比邻近的海湾更能抵抗海浪的袭击。然后，海湾会比海岬更快地向陆地撤退，形成起伏的平台轮廓，这是岩石海岸景观的特征。虽然沿岸岩石强度和近岸波浪能量之间的相互作用通常是对海岸线形状的基本控制，但沉积物也起着关键作用。少量的海滩沉积物可以作为磨蚀工具，促使海崖后退。然而，大量的海滩沉积物阻止了海浪对悬崖表面的攻击，起到了保护屏障的作用。这表明了一种新的、未被探索的岬角持续机制，即使在没有沿岸岩石强度变化的情况下：由于沿岸沉积物可用性的变化，裸露的岩石岬角可能比邻近的沉积物填充的海湾后退得更慢，或者以相同的速度后退。因此，近岸泥沙动力学（即海崖退缩产沙、沿岸输沙和海滩退缩产沙）可以促进稳定和持久的台地岩质海岸线特征的发展。为了探索这些想法，该项目将进行大规模（一公里）和长期（千年尺度）平台岩石海岸线演变的数值和分析建模，并将模型预测与实际景观进行比较。世界上大约80%的海岸线是岩石，海岸线的变化影响着个人、企业和政府。虽然已经对影响悬崖和海滩侵蚀的物理、生物和化学过程进行了一些研究，但对于包括沿岸因素在内的岩石海岸线的长期行为知之甚少。因此，这个项目将开启一条新的研究路线。因此，拟议的工作探索人类操作（例如河流筑坝和悬崖稳定）如何影响长期，大规模的海岸线演变的方面将引起广泛的兴趣。结果和模型本身，将随时可供沿海管理者和规划者使用，结果也将对公众、教师和学生有用。

Many of the world's rocky coastlines exhibit planform roughness in the form of alternating headlands and embayments. Along wave-dominated cliffed coasts, it is often assumed that headlands consist of rock that is more resistant to wave attack than in neighboring bays, because of either structural or lithologic variations. Bays would then retreat landward faster than headlands, creating the undulating planform profiles characteristic of a rocky coastal landscape. While interplay between alongshore rock strength and nearshore wave energy is certainly often a fundamental control on coastline shape, sediment also plays a key role. Beach sediment, in small volumes, can act as an abrasive tool to encourage sea cliff retreat. In large volumes, however, beach sediment discourages wave attack on the cliff face, acting as a protective barrier. This suggests a new, unexplored mechanism for headland persistence, even in the absence of alongshore variations in rock strength: bare-rock headlands could retreat more slowly than, or at the same rate as, neighboring sediment-filled embayments because of alongshore variations in the availability of beach sediment. Accordingly, nearshore sediment dynamics (i.e. sediment production from sea cliff retreat, alongshore sediment transport, and beach retreat) could promote the development of stable and persistent planform rocky coastline features. To explore these ideas, this project will undertake numerical and analytical modeling of large-scale ( one kilometer) and long-term (millennial-scale) planform rocky coastline evolution, and compare model predictions with real landscapes. Approximately 80% of the world's coastline is rocky, and coastline change impacts individuals, corporations, and governments. Although some research has been done on the physical, biological and chemical processes that influence the erosion of cliffs and beaches, very little is known about how rocky coastlines behave in the long-term when the alongshore dimension is included. This project, therefore, will initiate a new line of research. The aspects of the proposed work exploring how human manipulations (e.g. river damming and cliff stabilization), affect long-term, large-scale coastline evolution will therefore attract broad interest. The results, and the model itself, will be readily available for use by coastal managers and planners, and results will also be useful to the general public, teachers, and students.