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Coastal zones are at the interface of land and sea and provide a buffer to storms, wave action, and coastal inundation. Bathymetric mapping of the submerged littoral zone is essential for the understanding of sediment transport and good coastal management and planning. Surf zones are dynamic areas, ever-changing, so there is a need for low-cost, rapid response aerial remote sensing techniques that can provide high temporal and spatial coverage of nearshore bathymetry. However, this is a challenging task given water turbidity, wave action, seafoam, and other issues. With this motivation, this study used a small unoccupied aircraft system (UAS) equipped with a digital RGB camera to collect video footage of wave action on the water surface. The video data was then used to apply a spectral depth inversion algorithm called cBathy and estimate nearshore bathymetry at high resolution. Ground truth data were collected using cross-shore transect surveys to a depth of 2 m for assessment of the UAS-based bathymetry estimates. The video data was split into frames with a frequency of 2 frames per second (fps), and ground control points (GCPs) laid out in the scene were used to perform image georectification. A time stack of image pixel values was then generated from the video data for the cBathy depth inversion algorithm. Accuracy assessment resulted in an overall RMSE of 0.2056 m for an area of 390 m offshore and 400 m alongshore, and the maximum depth achieved was up to 3 m. Results show the potential of the cBathy algorithm to provide reasonable depth accuracies in dynamic and turbid water surf zones. However, results also show that this method has constraints for which users need to be aware of prior to applying it, including the study site’s physical characteristics.
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