Irregular Wave Reflection and Runup on Permeable Slopes

A one‐dimensional, time‐dependent numerical model is developed to simulate the flow over a rough permeable slope as well as the flow inside a permeable underlayer of arbitrary thickness for specified normally incident irregular waves. The derivation of the one‐dimensional continuity, momentum and energy equations employed in the numerical model is presented to clarify the basic assumptions made in these equations. The comparison of the numerical model with three test runs shows that the numerical model can predict the time series and spectral characteristics of the reflected waves and waterline oscillations on a 1:3 rough slope with a thick permeable underlayer. The computed results for the three runs indicate that the wave propagation, attenuation, and setup inside the permeable underlayer reduce the intensity of wave breaking and resulting energy dissipation on the slope but increase the energy influx and dissipation inside the thick permeable underlayer. Moreover, the permeability effects result in the time‐averaged landward and seaward mass fluxes above and inside the permeable underlayer, respectively.