# Investigating Nearshore Circulation using Inverse Methods

## Falk Feddersen, R.T. Guza, Steve Elgar

### Proceedings of Coastal Dynamics 1997

** Abstract **

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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