Wave overtopping and overflow on inclined structures

Earthen levees are designed for little wave overtopping during a design storm but excessive overtopping and overflow can occur due to the combined effects of an extreme storm, sea level rise and land subsidence. The transition from little wave overtopping to excessive wave overtopping and overflow on an impermeable smooth levee is examined in wave-flume experiments consisting of 107 tests. A numerical model based on time-averaged continuity, momentum and wave action equations is connected to a new probabilistic model for the wet and dry zone to predict the cross-shore variations of the mean and standard deviation of the free surface elevation and depth-averaged fluid velocity from outside the surf zone to the landward slope of the levee. The new model is calibrated to predict the measured overtopping and overflow rates within a factor of about 2. The agreement is also shown to be similar for the water depths and velocities measured in the wet and dry zone on seven different structures in 118 Dutch tests.