Wave Reflection and Overwash of Dunes

Seven tests consisting of 72 runs were conduced to measure wave reflection, overtopping, and overwash of dunes. The measured reflection coefficients and overtopping rates are compared with the empirical formulas developed for coastal structures. The equivalent uniform slope for reflection is assumed to be the beach slope at the still water shoreline. The equivalent uniform slope for overtopping is assumed to be the overall slope between the dune crest and the point where the water depth equals the significant wave height. The toe depth of the coastal structure is assumed to correspond to the water depth immediately seaward of the breaker zone on the beach. The formulas with these adjustments are then shown to predict the order of magnitude of the measured reflection coefficients and overtopping rates. Furthermore, the average volumetric sand concentration in the overwash flow was measured to be approximately 0.04 for these small-scale tests.