Abstract
In order to improve the accuracy of the original full-range equation for wave boundary layer thickness, with special reference to increasing its applicability to tsunami-scale waves, a theoretical investigation is carried out to derive a dimensionless expression which is valid under both smooth and rough turbulent regimes. A coefficient in the equation is determined through a comparison with k-ω model computation results for tsunami-waves along with laboratory scale oscillatory flow experiments. Thus, the improved full-range equation for wave boundary layer thickness enables us to cover a wide range of wave periods from wind-wave to tsunami.