This paper describes the application of SWAN-VEG to the lake of Ilha Solteiras's dam-São Paulo, Brazil that is part of the Tietê-Paraná waterway, in order to analyze the influence of vegetation on the reduction of energy of the waves near the lake margins. First the model is applied considering a constant water depth in the entire dam reservoir and a small area of vegetation is implemented at the end of the dam. Several values of velocity and wind directions as well as different vegetation characteristics are tested. Then, the real bathymetry of the lake is considered as well as vegetation in certain margins of the lake. Several wind conditions are tested and compared with the situation with and without vegetation.waves, is an appealing option as it dissipates wave energy without environmental and economic loads. Therefore, it is fundamental to analyse the vegetation influence on the reduction of energy of the waves near the lake shore.