Distribution and dynamics of U.S. continental shelf ridge sediment and morphology: A brief review

Abstract

The U.S. continental shelf is an important sediment source for beach nourishment and restoration efforts that mitigate erosion, increase resilience to storm impacts, provide habitat, and support the economy. The continental shelf is the preferred source for borrow sediment to closely match the native grain size distribution and composition of the site being restored. However, spatiotemporal variability of continental shelf sediment ranges in size and composition, resulting from previous sea levels and contemporary variability such as normal shelf processes, storm waves, and anthropogenic activities. Understanding the nature and distribution of continental shelf ridge sediment changes over time should reduce costs of efforts required to explore offshore sediments for coastal restoration projects. This review examines the present state of knowledge on the availability, distribution, and characteristics of continental shelf sediment under normal conditions and potential variability after storms and dredging. Under normal conditions sediment on the shelf is easily located and characterized as potential borrow areas. However, storms can induce enough sediment transport to change the boundaries of sediment borrow areas and the location of known sand ridges. Dredging can also influence sediment infilling of the dredged borrow areas, which impact benthic infauna and introduce potential onshore impacts depending on the geometry and nearshore proximity of the excavation. The results of this summary have identified gaps in the present knowledge such as a need for additional sand searches in under-investigated regions, a better understanding of storm impacts on hydrodynamic-driven ridge migration and continuing to review best management practices when new research of dredging practices and impacts are presented. A brief review of the present state of knowledge on the distribution and dynamics of continental shelf sedimentology and morphology are presented here to aid in advancing the scientific and coastal management community’s knowledge of shelf sediments and dynamics as well as highlight potential future research needs.