Post-Harvey Beach Morphology Change and Erosional Processes from repeat Terrestrial Laser Scans in New Brazos River Area, Freeport, Texas, USA

Abstract:

Coastal erosions, such as foredunes collapse, estuarine marshes overwash, and vegetation lines retractation towards land, present increasing after hurricanes and other high storm surge events. To map the morphological changes induced by the destructive force of winds, tides and surges during extreme weather and record the recovery process afterwards, we implement multiple point cloud data collections with LiDAR (RIEGL VZ200) and GPS (Trimble R10) devices at the new Brazos River beach and dune area in the Freeport, TX. Compared to traditional field surveys and recent rapid developing Airborne LiDAR measure strategy, modern mapping technique like Terrestrial Laser Scanning (TLS) integrated with GPS measures the landscapes with high efficiency as well as prominent spatial and temporal resolutions. Site location, tide type, dominate current direction, and wind direction are four main factors to transport sediments. Dune ridge line, dune toe line (vegetation line), and 0.35-m contour (a local modified mean sea level value refers to nearby water station records) shoreline were extracted from the bare earth DEM. Verified with Real Time Kinematic (RTK) measurement, the three extracted lines are accurate and representative to delineate the sand relief. In a four-year period, the shoreline moves inland 28m averagely at the non-Brazos-delta area; and the max change happens at the delta area is 70 m. For each set of point clouds, a Digital Elevation Model (DEM) and three coast feature lines are final products to archive.