COASTAL RESILIENCE SURGES AS LIVING SHORELINES REDUCE LATERAL EROSION OF SALT MARSHES

A growing suite of research has demonstrated that nature-based shoreline stabilization methods can increase resilience of coastal ecosystems by improving their capacity to return to pre-disturbance states. Previous work suggests that during hurricanes, living shorelines promote vertical accretion and experience less damage than traditional shoreline stabilization alternatives. Nevertheless, there is limited research looking at the impacts of major storm events on living shorelines and most studies have investigated a small number of sites. This study used in situ real-time kinematic (RTK)-GPS surveys to quantify the resilience (via the lateral change in shore position) of 17 living shoreline sites before and after a Category 1 hurricane event (Hurricane Florence, 2018). By doing so, this study seeks to understand the capacity of living shorelines (marsh with seaward breakwater or sill) to provide storm protection as compared to unaltered natural fringing salt marshes. After Hurricane Florence, living shorelines on average experienced significantly less lateral erosion compared to unprotected control segments (shoreline change rates of 0.015 m y-1 and -0.31 m y-1 , respectively). This study also explores how environmental siting variables (i.e. scarp presence, fetch, and bottom sediment) and sill design variables (i.e. sill material, width, and height) influence short- and long-term erosion. Living shorelines were found to reduce erosion of fringing marsh edge among projects with a range of installation ages, structural materials, sill widths, and sill heights, and they were able to provide protection from erosion across a range of fetch, scarp, and bottom sediment conditions. Living shoreline siting and sill design may be suitable for broader environmental conditions than previously known. This study shows that living shorelines can increase resilience, by reducing erosion of fringing salt marshes, and even in some cases promoting lateral building up of shoreline zones during short-term disturbance events and from their long-term presence. This article is protected by copyright. All rights reserved.