An energetics total load sediment transport model for a plane sloping beach

TLDR

Bagnold’s energetics‑based total load sediment transport model for streams serves as the foundation for a time‑varying total load model on a plane sloping beach. The study applies this model to idealized surfzone conditions to estimate local longshore and onshore‑offshore sediment transport rates and equilibrium beach slope as functions of wave and current conditions. The model decomposes transport rates into velocity‑induced and gravity‑induced components, couples them with a nonlinear longshore current model, and spatially integrates to predict total longshore transport rates under varying wave conditions. Results confirm the general wave power equation form but show that the wave power coefficient varies as a complex function of incident wave and beach characteristics.

Abstract

Bagnold's energetics‐based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed. In both the bedload and suspended load, the transport rate vectors are found to be composed of a velocity‐induced component directed parallel to the instantaneous velocity vector and a gravity‐induced component directed down slope. The model is applied to idealized surfzone conditions, leading to estimates of the local longshore and onshore‐offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions. The model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions. The results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics.