RAPID: Lidar and Sonar Surveys of a Dune Reinforced with Geotextile Sand Containers Impacted by Tropical Storm Hermine

2012年飓风桑迪对美国东北部造成的破坏性影响突出表明，需要提高沿海社区迅速应对自然灾害和从灾害中恢复的能力。 有一种趋势是实施“软”工程解决方案，如用土工布砂容器（GSC）加固沙丘，以提高弹性，而不是传统的硬化结构，如石头护岸。 这些措施有可能保护社区免受较小风暴事件（例如25年一遇的风暴）的影响，同时考虑到海平面上升速度和风暴频率的不确定性，在设计上提供灵活性。 “软”工程解决方案对屏障海滩系统的自然形态的破坏性也可能小于硬化结构。 然而，仍然有相当大的不确定性的机制，影响加固沙丘的稳定性下波攻击。 这个快速反应研究（RAPID）项目的目标是收集易腐数据，以评估2016年9月热带风暴Hermine影响的纽约州Montauk的GSC加固沙丘的1000米部分的稳定性和性能。 加固沙丘于2016年3月建成，热带风暴Hermine导致保护护堤完全侵蚀，GSC核心暴露，GSC下层移动。 将建立一个详细的侵蚀海滩（地形）和近岸水深的三维数字高程模型。 这将通过两项调查来完成：一项是利用无人机系统进行的空中激光雷达调查，另一项是利用舰载激光雷达和干涉声纳系统进行的联合调查。 这些数据将提供一个详细的案例研究的影响，波浪作用的沙丘与GSC加强。 这将允许从数值和波浪水槽研究的结果应用到一个实际的领域的情况下，在实验室中不可复制的规模。 据推测，目前的稳定性方程是不保守的，因为他们低估了与缩小规模的实验土工织物容器的水力稳定性。 对这一案例研究的分析也将提高我们对加固沙丘是否表现为“软”海岸结构的理解，并且不会显著改变海岸线的自然形态。

The devastating effects of Hurricane Sandy in 2012 on the northeast United States highlighted the need to improve the ability of coastal communities to quickly respond and rebound from natural hazards. There is a trend towards implementing "soft" engineering solutions such as dunes reinforced with Geotextile Sand Containers (GSC) to improve resiliency rather than traditional hardened structures like stone revetments. These have the potential to protect communities from smaller storm events (e.g. 25-year storms) while at the same time providing flexibility in design considering the uncertainty regarding rates of sea level rise and storm frequency. "Soft" engineering solutions may also be less disruptive to the natural morphology of barrier beach systems than hardened structures. However, there is still considerable uncertainty regarding the mechanisms that affect the stability of reinforced dunes under wave attack. The objective of this Rapid Response Research (RAPID) project is to collect perishable data to assess the stability and performance of a 1000 m section of a dune reinforced with GSCs in Montauk, NY that was impacted by Tropical Storm Hermine in September 2016. The reinforced dune was constructed in March 2016, and Tropical Storm Hermine resulted in complete erosion of the protective berm, exposure of the GSC core, and movement of the lower level of GSCs. A detailed 3-D digital elevation model of both the eroded beach (topography) as well as the near-shore bathymetry will be constructed. This will be accomplished through two surveys: an aerial LIDAR survey using an Unmanned Aerial System (UAS) and a combined ship-mounted LIDAR and interferometric sonar system. These data will provide a detailed case study of the effects of wave action on a dune reinforced with GSCs. This will allow for the application of findings from numerical and wave flume studies to an actual field case at a scale not reproducible in the laboratory. It is hypothesized that current stability equations are unconservative in that they underpredict the hydraulic stability of geotextile containers associated with reduced scale experiments. Analysis of this case study will also improve our understanding of whether reinforced dunes perform as "soft" coastal structures and do not significantly modify the natural morphology of the shoreline.