Rock mound to reduce wave overwash and crest lowering of a sand barrier

Abstract

ABSTRACT The quantitative understanding of sand transport in the vicinity of porous coastal structures is still rudimentary. In this study, irregular wave overwash and landward migration of a narrow sand barrier were investigated in a laboratory experiment for three different barriers with no structure, a rock mound, and a rock cover. The rock mound consisting of three layers of stable stones reduced the landward migration and crest lowering of the sand barrier but sand transport through the porous structure was appreciable. The rock cover consisting of a single layer of stable stones was not effective in reducing the barrier deformation because of the stone settlement and spreading and the exposure of underlying sand to direct wave action. The cross-shore model CSHORE was calibrated for a rock structure placed directly on an eroding sand barrier. The mean and standard deviation of the free surface elevation and cross-shore velocity were predicted within errors of about 20 except for small transmitted waves. The bed load parameter was increased by a factor of five to reproduce the degree of the profile deformation of the sand barrier without and with the rock mound or cover.