Evaluation Techniques for the Beneficial Use of Dredged Sediment Placed in the Nearshore

Abstract

Maintaining navigable waterways through dredging is vital to society and the economy, especially as global transport and cargo loads increase. Decision makers require rapid techniques to evaluate potential placement alternatives for the dredged sediment. When appropriate, dredged sediment can be placed in the nearshore as a berm or a mound, often with the expectations of dissipating wave energy further offshore and inducing shoreward sediment transport. However, the exact placement area requires the water depth, hydrodynamic climate, and sediment size to be considered. Previous work used the well-known depth of closure concept to assess berm stability. A web-based Sediment Mobility Tool (SMT) was recently developed to assess the probability of sediment transport and direction with the knowledge of a few simple parameters. In this study, 20 historical projects that placed dredged sediment in the nearshore are reviewed to evaluate the depth of closure equations predictive capability on berm stability. The frequency of sediment mobilization and cross-shore transport direction are estimated for nine historical projects. The evaluated projects represent a diverse range of construction methods, placement geometries, sediment characteristics, and wave climates. The techniques used to estimate sediment mobilization frequency and transport direction are universal. These techniques are an essential step for engineers and planners to evaluate the potential volumes of dredged material that nearshore placement operations might yield to nourish a beach profile.