cBathy Bathymetry Estimation in the Mixed Wave-Current Domain of a Tidal Estuary

The last decade has seen considerable progress in the development of algorithms for nearshore bathymetry estimation based on celerity observations of ocean surface waves. This work has evolved into a robust algorithm called cBathy which produces operational results that compared well to 16 CRAB surveys at Duck, NC, collected over two years (bias 0.19 m, rmse 0.51 m over a 1000 by 500 analysis region). However, cBathy is presently based on a wave dispersion implementation that neglects the effects of currents. In May 2012, cBathy was tested in a tidal inlet environment at the RIVET experiment at New River Inlet, NC, a location with a complex ebb tidal delta and strong tidal currents. Initial analyses without Doppler correction to the algorithm show up to 50% overestimation of depth excursions at tidal time scales, presumably associated with wave-current effects. Data from in situ instruments at the RIVET experiment are used to test the adjustments to the algorithm needed for Doppler shifting and found to explain some, but not all, of the bias. The algorithm also estimates dominant wavelengths and wave directions associated with a suite of incident wave frequencies. Both the dominant frequencies and wave directions were found to vary systematically through the tide as the changing water depths alter dissipation and refraction patterns over the shoals.