A One-Dimensional Numerical Model for Storm-Breaching of Barrier Islands
Keywords:Dune / beach erosion, overwash, sediment transport model, tidal inlets, barrier breach.
A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension. The SBEACH model (LARSON and KRAUS, 1989) is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage 11 of overland flow is developed to simulate initiation of ocean flood propagation on initially dry barrier islands. The development of the Preissmann implicit scheme for water motion and a forward-time, centered-space explicit scheme for sediment motion in Stage 111 and IV of storm tidal flow provide a tool to study the volume change and centroid movements of the barrier cross-section above MLLW during various levels of storm activity.
The sensitivity studies show that most sediments are transported landward by large peak storm surge differences between ocean and bay with shorter time lag and longer duration and transported seaward by small peak storm surge differences with longer time lag and shorter storm duration. Grain size significantly affects the movements of the barrier. Median grain size, D50= 0.4mm results in maximum volume loss and barrier retreat speed in this study.
Finally, the integrated numerical model is found to produce reasonable result s from the various sensitivity tests, which reveal that the numerical model has properly responded to changes of each model parameter. Insight gained from the one-dimensional model will be valuable in the development of a two-dimensional (depth-averaged) model.