Waves Across Shore Platforms

岩石海岸线通常以潮间带海岸平台前面的悬崖为特征，出现在英格兰和威尔士20%的海岸线上。这些岸上平台往往是缓坡的，它们总是代表着水动力学上非常粗糙的表面。悬崖和岸上平台是动态连接的，因为平台的特性直接控制着波浪在其上传播的转化过程，从而影响到悬崖和悬崖的侵蚀。对于多岩石的海岸，这种转变过程几乎没有人研究过。该项目的总体目标是提高对岩质海岸平台上波浪转化过程的理解和模拟能力。这项研究不仅有利于海岸工程界，有助于更好的海岸管理和规划，而且还将有益于其他海岸科学家，包括地质学家、地貌学家和生态学家。我们的总体假设是，跨海岸平台的海浪频谱转换主要受平台的高程、坡度、宽度和表面粗糙度控制。我们认为，在对平台表面的床面摩擦进行适当的参数化后，利用现有的波浪数值模型来模拟这种波浪变换过程，从而将能量输送到悬崖底部是可行的。我们进一步提出，平台表面的床面摩擦力可以根据岸上平台的特性，即平台的坡度和粗糙度(微地形)来参数化。我们的目的是对6个不同海岸平台在各种波浪/潮汐条件下的波浪变形进行全面而详细的现场测量，并从我们的观测中得出普遍有效的原理，以更好地描述和预测跨岩石海岸平台的波浪变形过程。每项为期8天的试验都将涉及部署一系列仪器，包括测量海浪和水位的压力传感器、记录近岸水流的声学海流计、监测波浪破碎模式和波浪爬升的数字摄像机、测量激流动力学的激光扫描仪和用于高分辨率测量岸上平台地形的地面激光雷达系统。现场数据将用于量化海浪能量通过基床摩擦和波浪破碎而耗散的能量，消散率将用于利用线性波浪理论反算波浪摩擦因数。进而，得到的波浪摩擦系数将与岸台表面的粗糙度相关联，与整体地貌和微地形有关。改进后的波浪摩擦参数将应用于开放源码的X海滩数值模式，该模式将用于6个地点中的每一个，以评估海平面变化对波浪能量输送到悬崖基地的影响，以探索海平面上升对沿海悬崖凹陷的潜在影响。该项目由来自普利茅斯大学、班戈大学、奥克兰大学和荷兰德尔塔雷大学的多学科研究小组参与。该项目将受益于两名海洋学家、两名沿海工程师、两名物理地理学家和一名地质学家的互补专业知识，他们都在与当前项目有直接关系的研究领域拥有公认的记录：实地实验、近岸和海浪带动力学、岩石海岸过程和数值模拟。主办机构还拥有一个实验基础设施，用于研究浅水海洋过程的野外工作，这在英国是首屈一指的，非常适合支持拟议的研究项目。研究基础设施和研究人员的综合实力，以及研究主题的相关性，使这一项目成为一个低风险、高影响的项目。

Rocky coastlines are generally characterised by cliffs fronted by intertidal shore platforms and occur along 20% of the coastline of England and Wales. These shore platforms tend to be gently-sloping and they invariably represent hydrodynamically very rough surfaces. Cliffs and shore platforms are linked dynamically because the platform characteristics directly control the transformation processes of waves propagating across it, and thus the impact on the cliff and cliff erosion. For rocky shores this transformation process is virtually unstudied. The general aim of this project is to increase both understanding and modelling capability of wave transformation processes across rocky shore platforms. The research will not only benefit the coastal engineering community and contribute to better coastal management and planning, but will also benefit other coastal scientists, including geologists, geomorphologists and ecologists.Our overarching hypothesis is that the transformation of the wave spectrum across shore platforms is primarily controlled by the elevation, gradient and width of the platform, and the roughness of its surface. We consider that it is feasible to model this wave transformation process, and thus energy delivery to the base of the cliff, using existing numerical wave models after appropriate parameterisation of the bed friction of the platform surface. We further propose that the bed friction of the platform surface can be parameterised based on the characteristics of the shore platform, namely its gradient and roughness (micro-topography). Our intention is to conduct comprehensive and detailed field measurements of wave transformation across 6 different shore platforms under a range of wave/tide conditions and derive universally valid principles from our observations that better describe and enable the prediction of wave transformation processes across rocky shore platforms. Each of these 8-day experiments will involve deployment of a range of instruments, including pressure sensors to measure waves and water levels, acoustic current meters to record nearshore currents, digital video cameras for monitoring wave breaker patterns and wave runup, a laser scanner for measuring swash dynamics and a terrestrial LiDAR system for making high-resolution measurements of the shore platform topography.The field data will be used to quantify wave energy dissipation by bed friction and wave breaking, and the dissipation rates will be used to back-calculate wave friction factors using linear wave theory. In turn, the obtained wave friction factors will be correlated to the roughness of the shore platform surface related to the overall morphology and micro-topography. The improved wave friction parameterisation will be implemented in the open-source XBeach numerical model and the model will be used for each of the 6 sites to evaluate the effect of changing sea level to the wave energy delivery to the cliff base to explore the potential effect of rising sea level on coastal cliff recession.This project involves a multi-disciplinary research team from the Universities of Plymouth, Bangor and Auckland, and Deltares (Netherlands). The project will benefit from the complementary expertise of two oceanographers, two coastal engineers, two physical geographers and one geologist, all with proven track records in research areas that have a direct bearing on the current project: field experimentation, nearshore and surf zone dynamics, rocky coast processes and numerical modelling. The hosting institution also has an experimental infrastructure for studying shallow water oceanographic processes for fieldwork that is second to none in the UK, and is ideally suited to support the proposed research project. The combined strength in research infrastructure and researchers, as well as the relevance of the research topic, makes this a low-risk high-impact project.