Harumi MURAKAWA
Research on interaction of rip current and coast transformation
Tokuzo HOSOYAMADA
The rip current is a strong offshore current caused by a nonlinear phenomenon of the waves such as breaking wave. In the littoral region, the nearshore currents form the circulation. There are close relationship between the circulation and the coastal bathymetry. However, the interaction of nearshore currents and geographical features is not considered fully in the past study by numerical calculation.
In this study, I aimed to examine the interaction of the rip current and the coastal transformation. Numerical models of waves, coastal currents, littoral drift and deformation of bathymetry is combined to simulate the interactions.Uniform slope and the beach cusp with regular spacing were used as representative coastal geography, and Tayuhama beach located in Niigata city, where the in situ rip current was observed was used as objective of field scale simulation. The wave condition for the field scale simulation was same as condition for that when the rip current actually occurred.
Results of the numerical study show that interaction between currents and geographical change enhances the rip currents more than calculation with constant bathymetry.For the case of uniform slope with constant bathymetry, no rip currents occurred. On the other hand, for the same case with interaction of currents and bathymetrical change, the almost regular rip currents with cellar circulation was formed clearly. The current velocity was approximately as much as 0.5m/s.
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