GIS modeling of wave exposure at the seabed:: A depth-attenuated wave exposure model

Several studies have documented relationships between wave exposure and distribution, density, and size of marine species. Hence, this factor is at a high level in the hierarchical habitat classification system EUNIS and is one of the Water Framework Directive water typology criteria of coastal waters. lsoeus (2004) has developed a continuous simplified wave model (SWM) that has been applied to several Nordic countries. Here we refine this model by introducing depth-attenuation, giving us the advantage of a model for wave exposure as it will actually work at the seabed. The values of the depth-attenuated model SWM(d) are approximately similar to the SWM model in shallow areas but noticeably lower in deep areas. The two models were compared in an analysis of the distribution of seabed substrate in the Stockholm archipelago. Using the depth-attenuated wave exposure instead of the SWM model as predictor in substrate modeling improved these models considerably.