This paper presents an incorporation of vegetation-induced wave dissipation in a planar numerical wave propagation model based on the extended mild-slope equation (EMSE). The implementation was incorporated in a purely mathematical method in the light of current theoretical studies. To examine the performance of the phase-resolving model, a comprehensive comparison with phase-averaged SWAN is made to test and validate the implementation. Moreover, new in-situ measurements in a mangrove forest are presented aiming to test the wave energy damping by vegetation using the observed wave spectra. From our validation results it can be concluded that wave dissipation due to vegetation is equally well reproduced in this model. It is found that the wave parameters (wave height and period) and vegetation parameters (plant width, height and density) are all influencing factors. An interesting finding is that relatively high-frequency waves are more dissipated than low frequency waves, especially for larger wave heights. In this study, we found that diffraction is of great significance in wave propagation over inhomogeneously distributed vegetation. Theoretically, the phase resolving EMSE represents the physical process of diffraction better than the phase-averaged model SWAN.