Wave action bottom reflection source term implementation

Wave bottom reflection induced by a changing bathymetry has a major impact on the near-shore environment, where harbors and other infrastructure are based. However, this reflection is only partially accounted for in large scale numerical wave prediction models. The present work implements the analytical bottom reflection source term derived in Yevnin and Toledo (2018) to WAVEWATCH III, a numerical prediction model based on the wave action equation. The new source terms reflection coefficient magnitude, reflection direction and directional spread are shown to produce good results with respect to analytical and numerical solutions, and are tested in a real-world example. The new term allows to better simulate the near shore environment, especially near islands, reefs, semi-enclosed basins or natural beaches with long mild slopes, where the directional changes can cause previously unaccounted for effects.