NUMERICAL MODELING FOR BEACH NOURISHMENT DESIGN

Beach nourishment projects serve a range of uses in providing shore protection, natural habitat for terrestrial and aquatic life, and a recreational amenity. Beaches can be nourished without loss of public or private property. If viewed as infrastructure investment, pragmatic questions arise concerning construction and maintenance costs required for achieving design goals such as a certain level of storm protection, minimum width of beach, and maximum renourishment interval. Engineering parameters are those we can usually control in optimizing the project benefit-to-cost ratio to attain design objectives. These types of parameters include grain sizes of the native and fill material, gains and losses of sediment at project boundaries, length of the fill, configuration and volume of the dune and berm, and functioning of sediment-retention structures (which introduce another set of parameters). Oceanographic parameters, over which we have little or no control, include net and gross longshore sand transport, wave height and period, tide, offshore bathymetry, and storms.

Numerical models are capable of representing the evolution of a nourished beach as governed by the large number of parameters stated above that can vary in space and time. The coastal geology community is recognizing the utility of numerical models for examining the evolution of both small- and large-scale morphology, as reflected in the technical literature in recent years. The models commonly applied in design of beach nourishment projects are robust and highly flexible examples of a technology that has seen wide and varied application for more than two decades by coastal engineers and scientists around the world. Numerical models of coastal processes improve designs, advance understanding of coastal processes, and suggest fruitful areas of research. The presentation will discuss several applications of numerical models for designing beach nourishment projects and investigating coastal processes, while addressing some of the common criticisms of modeling.