Abstract Coastal cliffs cover about 75% of the world's coastlines. Many of these cliffs suffer severe erosion problems, which are mainly caused by wave action and lead to important damages. The main objective of this work is to propose and apply a methodology to characterize and map wave exposure levels for the management of cliff coasts. The methodology proposed consists of a number of steps. First, a statistical characterization of the wave climate in deep water is performed. Second, relevant sea states are propagated towards the cliff by means of a numerical model. Then, the results are used to assess the distribution of significant wave heights and wave power along the cliff toe. Finally, four exposure levels are defined based on the wave power values at the cliff, and exposure zones are mapped accordingly along the cliff. This approach is illustrated with a case study – the Catedrales Cliffs and Beach, a tourism hotspot in Galicia (NW Spain) where erosion caused loss of human life. We find that exposure levels are primarily influenced by the nearshore bed morphology, which controls wave refraction, shoaling and breaking, as well as by the geometry and orientation of the cliff, with some parts more exposed than others to the prevailing wave direction. On the islets off the cliff the windward faces have a greater level of exposure, since the leeward faces are protected by the islets themselves and lower water depths. The rocky outcrops that occur at the cliff toe in some sections act as emerged (submerged) breakwaters under low (high) tide conditions, dissipating wave power and thus reducing wave exposure. The methodology proposed in this work enables coastal managers to prevent the personal and material damages derived from cliff erosion by focusing remedial measures where they are most needed.

中文翻译：

---

海岸悬崖暴露与管理

摘要 沿海悬崖约占世界海岸线的 75%。许多这些悬崖遭受严重的侵蚀问题，这主要是由波浪作用造成的，并导致严重的破坏。这项工作的主要目标是提出并应用一种方法来表征和绘制用于悬崖海岸管理的波浪暴露水平。提议的方法包括若干步骤。首先，对深水中的波浪气候进行统计表征。其次，通过数值模型向悬崖传播相关海况。然后，将结果用于评估沿峭壁趾部的显着波高和波浪功率的分布。最后，根据悬崖处的波浪功率值定义了四个暴露级别，并相应地沿着悬崖绘制了暴露区域。案例研究说明了这种方法 - Catedrales Cliffs and Beach，这是加利西亚（西班牙西北部）的旅游热点，侵蚀造成人类生命损失。我们发现暴露水平主要受近岸海床形态的影响，控制波浪折射、浅滩和破碎，以及悬崖的几何形状和方向，有些部分比其他部分更容易暴露于盛行的波浪方向。在悬崖外的小岛上，迎风面的暴露程度更高，因为背风面受到小岛本身的保护并且水深较低。在某些部分的悬崖脚趾处出现的岩石露头在低（高）潮条件下充当浮出（淹没）防波堤，消散波浪功率，从而减少波浪暴露。