Along much of the world's coastline, coastal barriers serve as the first line of defense against oceanic and meteorological forces. Extreme storms cause large morphological changes on coastal barriers through high sediment transport rates, which may degrade their defensive capabilities. The understanding of morphological impacts is therefore important for coastal resiliency, but is often challenged by site-specific characteristics, such as land cover and sediment availability, and their poorly understood impacts on the governing physical processes. The Caminada Headlands, Louisiana, USA presents unique considerations for morphodynamic modeling with regard to its low-lying topography, variable land cover, nearshore muddy substrate and sand deficiency. This study investigates the effects of land cover and limited sediment supply on low-lying barrier island morphology under storm conditions by using physics-based numerical models. A high-resolution, local-scale sediment transport/morphodynamic model (XBeach) of the Caminada Headlands is verified for Hurricane Gustav's (2008) impact using pre- and post-storm LIDAR surveys. When accurate input data are used to create physics-based numerical models these tools are robust in hindcasting storm impacts and provide a wealth of information as to the governing processes, which is otherwise difficult to obtain observationally. The simulation results show that a short-duration overwash regime dominates the morphological change in this low-lying barrier and is influenced by backbarrier wetland deterioration. The morphological response to overwash is modulated by backbarrier land cover and topography, as reduced accommodation space limits landward transport during the subsequent inundation regime. An intact backbarrier marsh reduces landward washover sediment transport distances and promotes deposition at supratidal elevations. In light of these findings, simultaneous restoration/creation of backbarrier wetlands in conjunction with subaerial beach renourishment may be an effective form of increasing the resiliency of low-lying barriers subject to frequent overwashing.

在世界大部分海岸线上，沿海屏障是抵御海洋和气象力量的第一道防线。极端风暴通过高沉积物传输速率在沿海屏障上引起巨大的形态变化，这可能会降低其防御能力。因此，对形态影响的理解对于沿海恢复力很重要，但通常面临特定地点的特征（例如土地覆盖和沉积物可利用性）及其对治理物理过程影响的了解不足，因而受到挑战。美国路易斯安那州的卡米纳达岬角（Caminada Headlands）就其低地势，可变的土地覆盖，近岸的泥质底质和缺乏沙质提出了形态动力学模型的独特考虑。本研究使用基于物理的数值模型研究了风暴条件下土地覆盖和有限的泥沙供应对低洼障碍岛形态的影响。使用风暴前和风暴后的LIDAR调查，验证了Caminada岬角的高分辨率，局部尺度的泥沙输送/形态动力学模型（XBeach）对古斯塔夫飓风（2008）的影响。当使用准确的输入数据来创建基于物理学的数值模型时，这些工具在暴风雨的后向预报方面具有强大的功能，并且可以提供有关治理过程的大量信息，否则很难通过观测获得这些信息。仿真结果表明，持续时间过大的水淹状态主导了该低洼屏障的形态变化，并受到后屏障湿地退化的影响。过度冲刷的形态学反应受到后屏障土地覆盖和地形的调节，因为减少的居住空间限制了随后的淹没过程中的陆运。完整的后屏障沼泽减少了陆上冲刷沉积物的运输距离，并促进了上高海拔的沉积。鉴于这些发现，同时恢复/建立后壁湿地与海底海滩养育可能是增加低洼障碍物的韧性的有效形式，该障碍物经常被过度冲洗。