Generally, wave transformation in shallow water should be estimated for a representative offshore wave spectrum. However it may be difficult for the Boussinesq wave model which requires a relative narrow computational region for calculating wave fields that an incident wave boundary is expanded to offshore. In this paper, multi-directional random waves for spatial distribution of directional spectra and shallow water depths are generated on the linear incident boundary in Boussinesq wave model. The applicability of the newly developed procedure of generation, which is based on the generation method for arbitrary spectrum proposed by Hirayama and Miyazato (2009), is verified by the reproduction of spatial distribution of wave height behind a spherical shoal for the transformed directional spectra estimated by energy balance equation. Thus the coupling between Boussinesq model and energy balance equation is realized.
　The characteristics of directional random waves generated with the coupling are investigated on some applications to actual harbors. The significant wave heights in front of the breakwater and revetment damaged with severe waves can be estimated larger than them calculated without the coupling. In addition, the statistic distribution of wave height observed at the wave station and reproduced with coupling becomes gentle around the peak for Yorimawari-nami, which causes many caissons of the offshore breakwater slide widely in Fushiki-Toyama port in 2008, instead of corresponding to the Rayleigh distribution at the foot.