Waves in Shallow Water: A new approach based on high-frequency remote sensing and wave-by-wave analysis

2013/2014年冬季在英国经历的风暴突显了海岸易受极端海浪和水位造成的结构破坏、洪水和海岸侵蚀的影响，以及此类事件造成的经济和社会损失。预测表明，由于海平面上升和更大的暴风雨，这些事件将变得越来越常见，对海岸的可持续管理构成重大挑战，大约30%的海岸已经受到英国大陆坚硬工程结构的保护。由于近岸海浪是海岸洪水和侵蚀的主要原因，这项研究项目的目标是增加我们对它们行为的了解，为改进对波浪过程及其对工程和自然海岸的影响的预测提供基础。沙质海滩约占世界不结冰海岸线的75%。当海浪接近海滩时，它们会经历快速的变化，因为它们在浅水中破裂，以白水钻孔的形式传播通过冲浪区，然后在冲浪区驱动海浪上升。浅水波对海岸结构物产生作用力，推动泥沙运动，导致海岸防御工事和沙丘被淹没，并造成海滩和悬崖侵蚀。因此，对波浪变换的了解对海岸工程师来说至关重要。然而，由于近岸波浪的复杂性质，理论描述有限，数值模拟方法通常依靠经验近似来描述破碎和破碎波，主要基于实验室结果，这些结果受尺度效应的影响，不一定再现波浪本质上的可变性。浅水波浪过程是海岸线变化和海岸洪水数值模型的关键，工程师们利用这些模型为海岸管理决策提供信息。为了提高这些模型的预测能力，需要高质量的现场数据，但由于浅水波覆盖范围有限和空间分辨率低，现有的测量数据无法完全捕捉到浅水波的变异性和高度非线性的形状。为了解决这一国际相关的研究差距，拟议的研究将应用一种新开发的遥感方法，在两个典型的海滩站点使用码头安装的激光雷达网络，以高频和空间分辨率获得整个海浪和波浪带上快速演变的海浪的测量结果，空间分辨率比以前高一个数量级。独一无二的是，这一功能允许跟踪从断点到海滩上最大波浪上升的极限的各个波浪，从而能够逐个波浪地分析波浪特征。选择这两个地点是为了在具有码头基础设施的地点获得广泛的波浪条件，但结果将使我们对波浪有基本的了解，因此与大多数沙质海岸线相关。新的数据与海滩地形信息和流速测量相结合，将形成一个有价值的现场数据集，将被分析以回答与近岸波浪转化有关的基本悬而未决的问题，并改进用于预测波浪模型的破碎波和破碎波的表示。此外，新的数据集将在项目完成后向研究界提供。我们对近岸波浪建模能力的提高将减少对工程结构和自然海岸环境的波浪强迫预测的不确定性。这将有助于更好地评估海岸线侵蚀和沿海危害，为更有效地进行海岸规划和设计海岸防御计划提供机会，这将直接或间接影响一系列学术、公众和行业利益攸关方，包括沿海工程师和科学家、沿海社区、保险公司和沿海管理人员。

The storms experienced in the UK during the winter of 2013/2014 highlighted the vulnerability of the coast to structural damage, flooding and coastal erosion due to extreme waves and water levels, and the economic and societal costs of such events. Predictions indicate that these events will become increasingly common due to rising sea levels and greater storminess, presenting a significant challenge for the sustainable management of the coast, approximately 30% of which is already protected by hard engineering structures on the UK mainland. As nearshore waves are a key cause of coastal flooding and erosion, the goal of this research project is to increase our understanding of their behaviour, providing the basis for improved predictions of wave processes and their effect on our engineered and natural coasts.Sandy beaches account for approximately 75% of the World's ice-free coastlines. As ocean waves approach beaches they undergo rapid transformation as they break in shallow water, propagate through the surf zone as white-water bores and then drive wave runup in the swash zone. Shallow water waves cause forces on coastal structures, drive sediment transport, lead to overtopping of coastal defences and dunes, and cause beach and cliff erosion. Consequently, an understanding of wave transformation is of critical importance for coastal engineers. However, due to the complex nature of waves in the nearshore, theoretical descriptions are limited and numerical modelling approaches typically rely on empirical approximations to describe breaking and broken waves based mainly on laboratory results which are subject to scale effects and do not necessarily reproduce the variability of waves in nature. Shallow water wave processes are key to the numerical models of shoreline change and coastal flooding which are used by engineers to inform coastal management decisions. To improve the predictive capability of these models, high quality field data are required, but existing measurements fail to fully capture the variability and highly non-linear shape of shallow water waves due to their limited coverage across the surf zone and low spatial resolution.To address this internationally relevant research gap, the proposed study will apply a newly developed remote sensing approach using a network of jetty-mounted Lidar at two typical beach sites to obtain measurements of rapidly evolving waves across the complete surf and swash zone at high frequency and a spatial resolution an order of magnitude higher than previously achieved. Uniquely, this capability allows individual waves to be tracked from the break point to the limit of maximum wave runup on the beach, enabling an analysis of wave characteristics on a wave-by-wave basis. The two sites have been selected to obtain a wide range of wave conditions at locations with jetty infrastructure, but the results will inform our fundamental understanding of waves and so be relevant to the majority of sandy coastlines. The new data, combined with beach topography information and measurements of flow velocities will form a valuable field-dataset, which will be analysed to answer fundamental unresolved questions related to wave transformation in the nearshore, and improve the representations of breaking and broken waves used in predictive wave models. Additionally the new dataset will be made available to the research community following project completion. Improvements in our ability to model nearshore waves will reduce uncertainty in predictions of wave forcing on engineered structures and the natural coastal environment. This would enable better assessment of shoreline erosion and coastal hazards, providing the opportunity for more efficient coastal planning and design of coastal defence schemes which would directly or indirectly impact a range of academic, public and industry stakeholders including coastal engineers and scientists, coastal communities, insurers and coastal managers.