Sun Limin, Palinkas Cindy M, Nardin William
Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD, United States.
Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD, United States.
Sci Total Environ. 2025 Aug 10;989:179863. doi: 10.1016/j.scitotenv.2025.179863. Epub 2025 Jun 10.
Rock sills are commonly placed at the seaward edge of constructed marshes in living shoreline projects to reduce erosion, stabilize shorelines, and improve coastal resilience. However, it is not clear how the design of these sills, whether continuous or segmented, affects sediment dynamics and marsh stability. In this study, we investigate two marsh sill living shorelines - one featuring tidal gaps and the other without - in comparison with an adjacent natural marsh in Ocean City, Maryland, USA. Our analysis focuses on changes in surface elevation, sediment and vegetation characteristics, and offshore suspended sediment concentration (SSC) through field survey. Building on previous research, we use the Delft3D-SWAN model to simulate sediment dynamics incorporating tidal gaps in the sills. Our drone surveys of surface elevation show a significant decrease within 1 m of the marsh edge and a noticeable increase beyond 2 m, suggesting that lateral marsh edge erosion supplies sediment for vertical accretion. Compared with the continuous sill living shoreline, we observe higher SSC in front of the natural marsh, along with higher sedimentation rates on the marsh platform. This indicates that while rock sills effectively reduce shoreline erosion, they may also limit the sediment supply needed to build vertical elevation. Segmented sill living shorelines with tidal gaps exhibit greater dynamism. Numerical modeling shows that erosion is more pronounced in marshes with segmented sills than in those with continuous sills. However, during high-energy events, the tidal gaps allow significantly more sediment to be transported to the marsh. Our study improves understanding of sediment dynamics in marsh sill living shorelines and offers insights for the practical design of tidal gaps.
在生态护岸项目中，岩槛通常设置在人工湿地的向海边缘，以减少侵蚀、稳定海岸线并提高海岸复原力。然而，这些岩槛的设计（无论是连续的还是分段的）如何影响沉积物动态和湿地稳定性尚不清楚。在本研究中，我们调查了美国马里兰州大洋城的两条带有岩槛的湿地生态护岸——一条有潮汐间隙，另一条没有——并与相邻的天然湿地进行比较。我们的分析通过实地调查，聚焦于表面高程、沉积物和植被特征以及近海悬浮泥沙浓度（SSC）的变化。基于先前的研究，我们使用Delft3D - SWAN模型来模拟包含岩槛潮汐间隙的沉积物动态。我们对表面高程的无人机测量显示，湿地边缘1米范围内显著下降，而超过2米处则明显上升，这表明湿地边缘的侧向侵蚀为垂直堆积提供了沉积物。与连续岩槛的生态护岸相比，我们观察到天然湿地前方的SSC更高，湿地平台上的沉积速率也更高。这表明虽然岩槛有效地减少了海岸线侵蚀，但它们也可能限制了形成垂直高程所需的沉积物供应。带有潮汐间隙的分段岩槛生态护岸表现出更大的动态性。数值模拟表明，与连续岩槛的湿地相比，分段岩槛的湿地侵蚀更为明显。然而，在高能事件期间，潮汐间隙能使更多的沉积物输送到湿地。我们的研究增进了对带有岩槛的湿地生态护岸沉积物动态的理解，并为潮汐间隙的实际设计提供了见解。
