Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305.
Department of Geophysics, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2020 May 19;117(20):10740-10745. doi: 10.1073/pnas.1911857117. Epub 2020 May 4.
Nature-based solutions are becoming an increasingly important component of sustainable coastal risk management. For particularly destructive hazards like tsunamis, natural elements like vegetation are often combined with designed elements like seawalls or dams to augment the protective benefits of each component. One example of this kind of hybrid approach is the so-called tsunami mitigation park, which combines a designed hillscape with vegetation. Despite the increasing popularity of tsunami mitigation parks, the protective benefits they provide are poorly understood and incompletely quantified. As a consequence of this lack of understanding, current designs might not maximize the protective benefits of tsunami mitigation parks. Here, we numerically model the interactions between a single row of hills with an incoming tsunami to identify the mechanisms through which the park protects the coast. We initialize the tsunami as an N wave that propagates to shore and impacts the coast directly. We find that partial reflection of the incoming wave is the most important mechanism by which hills reduce the kinetic energy that propagates onshore. The protective benefit of tsunami mitigation parks is thus comparable to that of a small wall, at least for tsunamis with amplitudes that are comparable to the hill height. We also show that hills could elevate potential damage in the immediate vicinity of the hills where flow speeds increase compared to a planar beach, suggesting the need to include a buffer zone behind the hills into a strategic park design.
基于自然的解决方案正成为可持续沿海风险管理中越来越重要的组成部分。对于海啸等破坏性特别强的灾害，植被等自然元素通常与海堤或水坝等设计元素结合使用，以增强每个元素的保护效益。这种混合方法的一个例子是所谓的海啸缓解公园，它将设计好的山丘景观与植被结合在一起。尽管海啸缓解公园越来越受欢迎，但人们对其提供的保护效益了解甚少，也不完全量化。由于缺乏这种了解，目前的设计可能无法最大限度地发挥海啸缓解公园的保护效益。在这里，我们对一排山丘与来袭海啸之间的相互作用进行数值模拟，以确定公园保护海岸的机制。我们将海啸初始化为 N 波，它向岸边传播并直接冲击海岸。我们发现，入射波的部分反射是山丘减少向岸传播的动能的最重要机制。因此，海啸缓解公园的保护效益与小墙相当，至少对于与山丘高度相当的海啸而言是如此。我们还表明，与平面海滩相比，山丘会增加山丘附近的潜在破坏，这表明需要在山丘后面的区域纳入一个缓冲区，以纳入到公园的战略设计中。
