Influences of Geometrical and Structural Configurations on Beach and Sea-Dike Toe Scour During Storms

Abstract

Toe scour and wave overtopping during storms are the main failure mechanisms of sea-dike failure in Vietnam. As realized from the across-shore mass flux balance and the resulting undertow it is commonly presumed that the scour depth increases as wave overtopping decreases and vice versa. However, post-storm field surveys suggest that this perception is not always true as wave overtopping and the return flow (and thus scour depth) both are the result of the complex wave-structure interaction. The sloping revetment and the crest configurations appear to have important effect on the toe scour depth. This paper presents a mobile-bed laboratory investigation on the effect of dike geometrical and structural configurations on the storm-induced toe scour. It is shown that under the same offshore forcing conditions the scour depth is considerably larger in the case of low dikes with crown-wall (severe overtopping) than that of high dikes without crown-wall (minor overtopping). Also, the scour depth reduces with the increase of the slope roughness.