Numerical Prediction of Tsunami-Induced Sediment Transport in the Harbor

Abstract:

Recent tsunami-related studies revealed that strong and energetic flow fields can be formed at the nearshore area during the tsunami event and hence affect coastal morphology significantly. In the present study, we investigate morphological changes by far-field tsunami impacts at the US west coasts via numerical simulations. Firstly, we develop a numerical model for predicting morphological evolutions by integrating a set of sub-models; hydrodynamics, sediment transport and morphological evolution models. Particularly, fully nonlinear Boussinesq-type equations are employed in the hydrodynamic model to the accurate calculation of nearshore current fields which tend to be easily chaotic and unpredictable due to the existence of various types of turbulence sources(e.g., wave-breaking). Then, the developed model is validated through benchmark tests of one-dimensional or two-dimensional sedimentation problems; dam-break flow over the movable bed, breaking solitary waves over a sloping beach, partially breached dam-break flow over the mobile bed, and dam-break flows over a movable bed with a sudden enlargement. Throughout tests, calculated results agree well with the experimental records when a reasonable parameter is chosen for an empirical formula. Lastly, a real-scale application of the model to the 2011 Tohoku-oki tsunami is presented with the results of tsunami-generated scouring and depositon in the the Santa Cruz Harbor and in the Crescent City Harbor, CA(USA). In both locations, strong currents are successfully generated through the model and cause severe depth changes through sedimentation process. Calculated area coverages for scouring and deposition in the harbor area also agree well with observations(Figure 1).