Living shorelines have been recognized for their potential to attenuate wave energy, reduce shoreline erosion, and enhance coastal resilience, and are gaining traction as a preferred method of shoreline stabilization. Yet much remains uncertain about their resiliency and effectiveness in reducing shoreline erosion during high-energy events. This study examines sediment dynamics at a relatively mature living shoreline (constructed in 2007 and comprised of a created marsh and rock sill at the land/water interface) in the Maryland Coastal Bays (USA) during a storm event via field surveys and numerical modeling. Results are evaluated within the context of observations at an adjacent natural marsh. Our study demonstrates that the mechanisms of marsh loss at the edge during these times differ between the living shoreline and natural marsh. Specifically, the living shoreline boundary is degraded through open-water conversion as ponds expand landward of the rock sills, but the natural marsh is eroded by undercutting at the scarp toe, triggering slumping and edge collapse. Sediments in the living shoreline marsh have larger particle sizes and lower organic content than in the natural marsh; vegetation has higher stem heights and lower stem densities compared to the natural marsh. These differences may drive differences in the stability of the marsh boundary. Numerical modeling indicates that bed shear stresses are higher landward of the rock sill at the edge of the vegetation in the living shoreline. This increase in shear stress under high-energy conditions occurs at both flood and ebb tide, potentially contributing to scouring and/or open-water conversion, as well as substantial sediment transport between the subtidal zone and the marsh platform of the living shoreline. Increasing the bank height (both sill and marsh) may reduce erosion at the marsh edge and/or prevent open-water conversion but should be carefully balanced with marsh ecology and processes during other times of the year.

中文翻译：

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高能条件下沼泽边界退化为生物海岸线的开放水域

活性海岸线因其减弱波浪能、减少海岸线侵蚀和增强海岸恢复力的潜力而得到认可，并且作为稳定海岸线的首选方法而受到关注。然而，它们在高能事件期间减少海岸线侵蚀的弹性和有效性仍存在很大不确定性。本研究通过现场调查和数值模拟，研究了马里兰州沿海海湾（美国）相对成熟的生物海岸线（建于 2007 年，由陆地/水界面处的沼泽和岩床组成）在风暴事件期间的沉积物动态。结果是在邻近天然沼泽的观察背景下进行评估的。我们的研究表明，在这些时期，生活海岸线和天然沼泽边缘的沼泽损失机制有所不同。具体来说，随着池塘向岩台向陆地扩展，生物海岸线边界因开放水域的转变而退化，但天然沼泽因陡坡趾处的底切而受到侵蚀，引发塌陷和边缘塌陷。与天然沼泽相比，活的海岸线沼泽中的沉积物具有更大的颗粒尺寸和更低的有机含量；与天然沼泽相比，植被具有更高的茎高度和更低的茎密度。这些差异可能会导致沼泽边界稳定性的差异。数值模型表明，在生物海岸线植被边缘的岩床向陆方向，床剪应力较高。高能条件下剪切应力的增加在涨潮和落潮时都会发生，可能会导致冲刷和/或开放水域转换，以及潮下带和生物海岸线沼泽平台之间的大量沉积物迁移。增加河岸高度（窗台和沼泽）可以减少沼泽边缘的侵蚀和/或防止开放水域转换，但应在一年中的其他时间与沼泽生态和过程仔细平衡。