Wave breaking models for a Boussinesq model are widely proposed. Hirayama and Hiraishi (2004a) developed the one equation turbulence model in which the turbulent production would be estimated by the bore model. The calculation accuracy has been verified for the distribution of the wave heights, wave setups and wave-induced currents on surf zone in model experiments and field observations. However, the length of turbulent scale, which is the only free-parameter on the one equation turbulence model and affects both the production and dissipation process of turbulence during wave breaking, has not been enough argued yet. In this paper, the valid method for setting the turbulent scale is proposed and the effects of such improvement on the calculation accuracies are verified in order to archive the generalization of the proposed wave breaking model.
　The main conclusions are as follows;
　1) The parameter study focused on the turbulent scale in calculation indicates that the adequate turbulent scale is the limited wave height at wave breaking with the comparison of the distribution of wave height in surf zone obtained in model experiments and numerical simulations. The two kind methods for setting the turbulent scale with the estimation of the limited wave height at wave breaking are proposed.
　2) The observation of the process of regular wave breaking on a sloping beach indicates that it is important for the reproduction of wave breaking to estimate the turbulent energies remained in the field with the balance between production and dissipation of turbulence.
　3) The proposed models can reproduce not only the wave setup due to wave breaking but also the water surface elevation of the irregular waves in surf zone measured in model experiments. It is because these wave breaking models can estimate the distribution of the eddy viscosity coefficients in time and spatial domain, calculated with the turbulent energies and the turbulent scale.