Tide-Tsunami Interaction in a Highly Energetic Channel. a Case Study.

Abstract eng:
The present study is intended to improve the physical understanding of tsunami propagation in semi-confined water bodies where the interaction with tides plays a significant role. A case study in Canal Chacao, a highly energetic channel located at the norther extreme of Chilean Patagonia, is studied. The fundamental question addressed here is to understand the interactions when tides and tsunamis are linearly superposed and when they interact nonlinearly, thus enhancing or reducing the surface elevation and associated currents. To answer this question, we implemented a series of models based on the twodimensional nonlinear shallow water equations to simulate the propagation of i) a tsunami with a constant tide corresponding to the mean sea level, ii) a tide and tsunami under the assumption that both can be linearly superimposed and iii) a tide and tsunami nonlinear interaction model. Results are analyzed in the narrowest section of Canal Chacao, where tidal currents may reach up to 6 m/s during spring tides. For this site, the maximum surface elevation during the simulation is larger in the nonlinear model, while the maximum current speeds (and derived quantities such as the drag forces or sediment transport potential) are obtained with the linear model. The nonlinear model is also better in computing the time of arrival of the first wave. These outcomes provide guidelines for the improvement of tsunami hazard assessments for the coastal communities located in fjords, channels and estuaries with similar characteristics.

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