Nearshore bathymetric inversion from lidars during extreme events
The coastal science community currently lacks insights into the rapid morphological evolution of sandy beaches during extreme events. Sediment exchanges occurring between the subaerial and subaqueous regions of the beach are poorly understood, which is explained by the difficulty in measuring the seabed elevation under broken waves with sufficiently high spatial and temporal resolution. The lack of datasets which capture beaches morphological evolution limits the development of accurate numerical models for the morphological evolution of beaches and hence our capacity to predict their long-term evolution. To overcome these challenges, this project will develop lidBathy, a bathymetric inversion tool which uses high-resolution 2D lidar scans of surf zone waves. Lidar scanners have the unique capacity to directly measure both the intertidal beach topography and the sea surface elevation at high spatial (O(cm)) and temporal (O(s)) resolution. Long-range lidar and bathymetric data collected at Narrabeen (Australia) and the Field Research Facility (Duck, N.C.) will be used to validate lidBathy. Lidar data collected at these two sites during past storms will be used to create an unprecedented dataset of beach morphological evolution, in both the subaerial and subaqueous regions, during extreme events. This project will characterize sediment exchanges occurring between the swash and the surf zones by studying the role of surf zone wave properties, water levels, swash statistics and time-varying beach slope. This will provide the first study into the response of the beach system to extreme events at high spatial and temporal resolution at the two most heavily monitored sites worldwide.