Cross-shore irregular wave transformation and sediment transport in surf and swash zones

A time-averaged model based on the finite-amplitude shallow-water equations is developed to predict the root-mean-square wave height, wave setup, and free surface skewness and kurtosis from outside the surf zone to the inner swash zone. This model includes nonlinear correction terms in the cross-shore radiation stress and energy flux that become important in very shallow water. Calibration and initial comparisons to laboratory tests are presented; additional comparisons to independent laboratory tests and field data are presented as verification. The model is shown to predict the cross-shore variations of the skewness and kurtosis as well as the root-mean-square wave height and setup on laboratory and natural beaches.; Second, a time-averaged model to predict both erosional and accretional beach profile evolutions is presented. The cross-shore sediment transport is analyzed on the basis of the time-dependent, depth-integrated sediment continuity equation including sediment suspension, storage, advection and settling. The energetics approach is shown to correspond to the special case of local equilibrium between sediment suspension and settling. The corresponding time-averaged model with simplifying assumptions yields a uniform suspension rate for the standard equilibrium profile. The simplified time-averaged model with new moving boundary conditions is compared with erosional and accretional beach profile evolutions under regular waves. The sediment suspension rate estimated for the equilibrium terraced and barred beaches under irregular waves is found to be roughly uniform in the surf zone but increases significantly in the swash zone.; Finally, a time-dependent, cross-shore sediment transport model in the surf and swash zones is developed to predict both beach accretion and erosion. The model is based on the depth-integrated sediment continuity equation which includes sediment suspension by turbulence generated by wave breaking and bottom friction, sediment storage in the entire water column, sediment advection by waves and wave-induced return current, and sediment settling on the movable bottom. The developed model is compared with three large-scale laboratory tests and predicts sediment suspension and sediment concentration in a physically realistic manner. The present computation is limited to the initial beach profile change, but the model is capable of predicting the accretional, erosional and neutral profile changes.