Wave‐current interactions play a major role in the dynamics of shallow tidal inlets. This study investigates these interactions at a natural inlet, with a strong focus on current‐induced changes on wave propagation. The analysis of hydrodynamic data collected at the Albufeira lagoon, Portugal, revealed spatiotemporal variations of water levels and wave heights along the inlet, attributed to wave‐current interaction processes. We compared the simulations of a coupled wave‐circulation modeling system, computed with and without waves, and propagated with and without current feedback. The wave‐induced setup inside the lagoon represented 7%–15% of the offshore significant wave height. The accuracy of the wave's predictions improved when current feedback was included. During ebb, the currents increased the wave height at the mouth of the inlet (up to 20%) and decreased the wave height in the inlet (up to 40%), due to current‐induced refraction, steepness dissipation, and partial blocking. During flood, the currents decreased the wave height in the inlet (up to 10%) and increased the wave height at the exterior parts of the ebb shoal (up to 10%), due to current‐induced refraction. These effects significantly attenuate seaward sediment fluxes during ebb and contribute to the sediment accretion in the inlet.
Recurrent monitoring of sandy beaches and of the dunes behind them is needed to improve the scientific knowledge on their dynamics as well as to develop sustainable management practices of those valuable landforms. Unmanned Aircraft Systems (UAS) are sought as a means to fulfill this need, especially leveraged by photogrammetric and LiDAR-based mapping methods and technology. The present study compares different strategies to carry UAS photogrammetric corridor mapping over linear extensions of sandy shores. In particular, we present results on the coupling of a UAS with a mobile laser scanning system, operating simultaneously in Cap Ferret, SW France. This aerial-terrestrial tandem enables terrain reconstruction with kinematic ground control points, thus largely avoiding the deployment of surveyed ground control points on the non-stable sandy ground. Results show how these three techniques—mobile laser scanning, photogrammetry based on ground control points, and photogrammetry based on kinematic ground control points—deliver accurate (i.e., root mean square errors < 15 cm) 3D reconstruction of beach-to-dune transition areas, the latter being performed at lower survey and logistic costs, and with enhanced spatial coverage capabilities. This study opens the gate for exploring longer (hundreds of kilometers) shoreline dynamics with ground-control-point-free air and ground mapping techniques.
12 April 2019 in Earth Surface Processes and Landforms