A conceptual model for inferring intertidal and subtidal bathymetry on mesotidal beaches using digital images

In this study, an empirical model has been developed to infer the beach nearshore bathymetry on mesotidal beaches using coastal videometry and statistical techniques applied to digital images. The model utilizes digital images captured throughout a tidal cycle, combined with sea level time series, to derive the Intertidal Bathymetry (IB). Additionally, Subtidal Bathymetry (SB) is inferred from low-tide images using an empirical function that assumes the detected features are affected by a combination of atmospheric, oceanographic and geometric, as well as the underlying bathymetry at the time of image acquisition. The model stablishes an empirical linear formulation where coefficients are calibrated using the IB and corresponding images. This approach was applied to Magdalena Beach, located on Santander Bay. Validation of the model was performed by comparing the results against measured bathymetry. Differences between measured and modelled bathymetry were of the order of 0.10 m for the IB and of 0.20 m for the SB, demonstrating the model accuracy and potential for practical applications.