Investigating Nearshore Circulation using Inverse Methods

Falk Feddersen, R.T. Guza, Steve Elgar

Proceedings of Coastal Dynamics 1997


The mean (time-averaged) nearshore circulation is often forced by breaking waves. For longshore homogeneous waves and bathymetry, the depth-averaged longshore current is also longshore homogeneous, and is described by a one-dimensional momentum balance between forcing, mixing, and bottom stress. However, the performance of a one-dimensional longshore current model can be degraded if the neglected effects of longshore inhomogeneities are significant or if the forcing and mixing are not parameterized correctly. The two-dimensional equations of motion, coupled with observations of the two-dimensional circulation, and inverse methods, can be used to infer the forcing and mixing and to examine the effect of longshore inhomogeneities. An idealized example of the inverse approach to solving the equations of motion is shown to predict a rip current through a gap in a longshore inhomogeneous sandbar for the case of normally incident waves.

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