Surge waves in open channels can be simulated well by solitary waves if the peak values of the bottom attack are the goal of the investigation. In this paper, a theoretical model is presented for calculation of the bottom shear stress due to solitary waves. The wave parameters and the bottom roughness can be given arbitrarily. The model has been verified and calibrated by experiments using a shear plate. In a second step, the calculation model is employed on solitary waves causing onset of movement of a given sediment. The resulting peak shear stress under these waves is found to exceed the well-known Shields value considerably.