Wave-gravity-induced sediment transport on steep shoreface

This research is dedicated to examining downslope sediment transport on steep shorefaces. We present a model that incorporates nonlinear surface wave profiles, sediment movement thresholds, and slope effects, utilizing a set of semi-empirical formulas. The model quantitatively assesses the disparity between wave-augmented upslope transport and gravity-augmented downslope transport, and computes sediment transport rates using a single calibration coefficient. Validation of the model is carried out in the Fuji coast of Japan, where offshore wave conditions and seabed topography with a uniform grain size distribution serve as inputs. The computational outcomes reveal that sediment transport primarily occurs under high wave conditions, and downslope transport dominates on steep slopes. The calibration coefficient is determined through a comparison with observed data, demonstrating a strong agreement in the average annual sediment loss in the target area. Moreover, the model offers insights into the possible mechanism behind the existence of a transition area between the upper and lower shoreface, marked by an abrupt change in seabed slope.