CHARACTERISTICS OF BOTTOM SHEAR STRESS VARIATION UNDER SHOALING SOLITARY WAVE

In the coastal environments, detailed understanding of current or wave-induced bottom shear stresses, which are often associated to the steady friction law and wave friction law respectively, is essential to evaluate quantitatively the sediment transport and coastal morphological changes. Many previous studies have indicated that there was an influence of unsteady characteristics in the boundary layer beneath a long-period wave. Therefore, the bottom shear stress under shoaling tsunami should be considered the unsteady wave-like effects. A new correction approach has been proposed by comparing the wave friction factor to the steady friction factor. The current study aims to implement the new correction method for assessing the bed shear stress to the conventional model for tsunami. Application for a solitary wave, which propagates from the tsunami source to the shore, shows that bottom shear stress by the new method is ten times larger than the conventional method in a deep water and become smaller in shallow area. In addition, the location of the critical Shields parameter of 0.05 by the new method is situated in deeper water than the conventional method.