Strategic nearshore placement of dredged sediment at Vilano Beach, Florida

摘要

Nearshore placement is becoming an increasingly utilized method for the beneficial use of dredged material from operations and maintenance dredging of navigation channels. It is important to have an understanding of what happens to sediment once it is placed in the nearshore. To that end, the U.S. Army Engineer Research and Development Center created the Sediment Mobility Tool (SMT) to estimate frequency of sediment mobility and general transport direction. During the summer of 2015, sediment dredged from the St. Augustine Inlet ebb and flood shoals and the Atlantic Intracoastal Waterway was placed in the nearshore of Vilano Beach, Florida. The site was monitored using topo-bathymetric surveys, the Radar Inlet Observing System (RIOS), and camera arrays to help quantify morphologic evolution of the nearshore berms. The Coastal Modeling System was used to qualitatively evaluate changes in the hydrodynamic conditions of the study area due to the placement of the material in the nearshore. The SMT calculated that sediment would mobilize frequently (under approximately 93%-99% of the waves), and migrate onshore with a predominantly southerly alongshore component. The CMS model predicted onshore migration with diffusion in the longshore. The RIOS bathymetric data showed that the CMS model predictions were true, and both were consistent with the SMT results. Additionally based on the camera arrays and the surveys, the CMS model correctly predicted that the presence of the berms caused waves to break further offshore, resulting in the formation of salients along the shoreline.