Evaluating offshore sediment resources for non-traditional coastal restoration projects

Abstract

Open coast beach-dune environments are vulnerable to erosion, due to storms, lack of sediment, or coastal squeeze; however, they serve important societal and ecological functions. Backbarrier shorelines are also susceptible to erosion, often due to tidal currents or boat wakes. Beach erosion is often mitigated using offshore, upland, or channel sediment resources for restoration projects. However, dune restorations generally use upland mine sediments and backbarrier restorations typically use sediments dredged from channels. Offshore resources are not often considered for dune or backbarrier shoreline restoration. However, because the geotechnical properties suitable for dunes and backbarriers differ from beach quality sediment, offshore sediments may provide an alternative source for restoration of lower-energy environments without adversely impacting the available volume of sediment needed for beach nourishment. This study presents an approach to evaluate sediment borrow area for suitability in non-traditional coastal restoration projects (i.e., dune and backbarrier shorelines). Kriging interpolation provided a better estimation of volume than using a linear average method based on comparison with simulated models of known volumes and should be used when a limited number of cores are available. The volume of sediment suitable for dune or backbarrier placement based on a case study in Palm Beach County, FL was much lower than the volume of beach compatible sands, suggesting that other regions require exploration for potential use in low-energy environments.