Assessment and Prediction of Beach-Nourishment Evolution

Abstract

Field data from Perdido Key, Florida, describing the response of an evolving beach nourishment project and the causative forces are analyzed in terms of sediment-transport rates and gradients. Numerical models for planform and profile evolution are applied and tested against the field data. Commonly applied concepts within the coastal engineering community regarding the “depth of closure,” profile “equilibration,” and the best-choice coefficient for use in a predictive equation for longshore sediment transport rate are discussed. The results indicate that the beach planform may be described qualitatively by an analytical solution, and a one-line numerical model gives a reasonable quantitative description of the longshore gradient of longshore sediment transport. The depth to which longshore sediment transport gradients affect the profile appears to be much less than the depth to which profile changes are observed, illustrating the importance of cross-shore sediment transport. An existing profile-response model, slightly modified, yielded good results immediately following nourishment, but poorer results as the beach profile approached a more natural configuration.