Cross-shore sediment transport determined by EOF method

Laboratory and field data of beach profile changes are used to study the cross-shore transport rate. The Empirical Orthogonal Eigenfunction analysis is applied to separate the temporal and spatial variability of the onshore/offshore transport. Laboratory data are used to avoid the measuring errors in field surveys and the longshore transport that can mask the cross-shore transport. Results show that when the EOF method is applied to the cross-shore transport rate, the eigenfunction have a physical analog. The first eigenfunction represents the bar-berm generation, and shows a pivotal point for bar-berm sand movement. The second eigenfunction accounts for the bar-berm displacement along the profile. The bar-berm displacement is accomplished by the existence of more pivotal points. When the equilibrium conditions of a profile are suddenly changed, the temporal dependence of the eigenfunctions exhibits a oscillatory transient pattern. Transients show different features, depending on whether the changes lead to an erosional profile or an accretionary profile. Similar results are obtained when the method is applied to field data.