Book excerpt: Water waves are one of the principal causes of shoreline changes. When waves break along the shore, they release their energy and momentum and give rise to a longshore current. The longshore current, along with the stirring action of the waves, is the primary mechanism for longshore sediment transport. The longshore sand transport rate is an essential factor determining erosion or accretion along a coast. If the longshore sand transport rate can be accurately estimated, a quantitative picture of shoreline evolution can be evaluated, including changes of the shoreline due to marine structures. In the present study, analytical and numerical models are developed based on a longshore current model for random waves and a sediment transport formulation by Thornton to predict the cross-shore sediment transport distribution and to compute the total volume of sand transport rate. The model is compared with the field data acquired from Leadbetter Beach, Santa Barbara, California.