Composite Beaches and Dynamic Revetments - Coastal Protection Inspired by Nature

气候变化是海岸保护的一个重要问题，海平面上升和更强烈的风暴将导致对海岸线的侵蚀加剧。目前，据预测，24%的海岸线每年损失0.5米（Luijendijk等人，2018）。因此，设计新的保护方法至关重要，动态护岸可能是解决方案的一部分。这些都是基于复合海滩显示的自然形成的地层。它由一个由砾石或鹅卵石构成的后海岸山脊和一个由沙子构成的前海岸组成。后海岸脊在波浪冲击等影响下不断重塑，但整体结构表现出良好的稳定性。预计这将控制上游泳滩和腹地的侵蚀，并有效地保护堤顶。这一假设得到了DYNAREV实验（Blenkinsopp, et al., 2019）和少数现有结构（如华盛顿北湾的结构）的支持。目前对动力护岸的研究普遍缺乏，需要发展的一个领域是动力护岸的建模。目前，主要的工具是X-Beach软件及其许多变体。然而，现有模型存在许多问题，其中许多与无法准确模拟鹅卵石层内的沉积物运输有关。本项目主要建议开发x-beach模型，以更准确地模拟动态护岸，并使用该模型来回答与这些结构的长期可行性和实用性相关的问题。此外，这将得到第二个实验的支持，该实验将作为博士学位的一部分得到协助。目前，被命名为DYNAREV 1.5的拟议实验将在很大程度上模仿第一个实验，通过物理模拟一个大波浪水槽中的动态护岸。主要区别在于所使用的鹅卵石尺寸范围。将会有大量的数据需要分析，然后用作模型校准和验证的数据集。最后，通过利用天然和人工护岸，我们有可能了解这些结构将如何应对气候变化和海平面上升。所产生的模型将能够支持或减损目前的信念，即这些结构在很大程度上抵抗这种影响。

Climate change represents a significant issue for coastal protection, rising sea levels and more intense storms will lead to increased erosion of the coastline. At present it is predicted that 24% of coastlines are losing 0.5 m/yr (Luijendijk, et al., 2018). It is therefore vital that new protection approaches are designed, dynamic revetments could be part of that solution.These are based on naturally occurring formations displayed by composite beaches. It comprises of a backshore ridge constructed from gravel or cobbles and a foreshore of sand. The backshore ridge is reshaped continuously under influences such as wave attack, however, the overall structure shows a good level of stability regardless. It is expected to result in erosion control for both the upper beach and hinterland as well as effective overtopping protection. This hypothesis is supported by both the DYNAREV experiment (Blenkinsopp, et al., 2019) and the few existing structures, such as that in North Cove, Washington. At present there is a general lack of research into dynamic revetments, an area which needs development is the modelling of these revetments. Currently, the main tool is X-Beach software and its many variants. There are however issues with the existing models many of which relate to the inability to simulate sediment transport within the cobblestone layer accurately. This project primarily proposes to develop the x-beach model to more accurately simulate dynamic revetments and use this to answer questions related to the long-term viability and practicality of these structures.Further, this will be supported with a second experiment which will be assisted with as part of the PhD. Currently, named DYNAREV 1.5 the proposed experiment will largely mimic the first experiment by physically modelling a dynamic revetment in a large wave flume. The main difference being the range of cobble sizes used. There will be a wealth of data which will need to be analysed as a result and later used as a data set for model calibration and validation.Finally, through drawing on both the natural and artificial revetments it may be possible to understand how the structures will respond to climate change and rising seas. The produced model will be able to either support or detract from the current belief that these structures are largely resistant to such influences.