Assessing the Rapid Coastal Erosion in Freeport, Texas using Terrestrial Laser Scan Data Collected before and after Hurricane Harvey



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The Bryan Beach and Brazos River delta has experienced significant coastal erosional changes for almost one-hundred years (Paine et. al. 2014). Hurricane Harvey caused high tides, extreme winds, and significant flooding. This study was focused on three Terrestrial Laser Scans (TLS) collected in May, September, and December. Light Detection and Ranging (LiDAR) scans were conducted using a GPS and TLS (Riegl VZ2000) integrated system before and after Hurricane Harvey, which occurred August 25-30, 2017. A thorough workflow, using digital elevation models (DEMs), was developed for this study based on recommendations from Xiong (2018) and Zhou (2017) in order to effectively manage the immense LiDAR data. Directly after the storm, the largest impact to the coast was seen in the beach area with the erosion of the shoreline up to fifteen meters and decrease in dune height of up to 0.85 meters, as well as a net volume decrease of 23,600 m3 within the beach and dune area, approximately 800 meters long. The delta area had the most changes in the months after the storm due to increased drainage from into the Brazos River. This can be seen in the continued erosion of the riverbank by up to sixty meters near the mouth of the river and a net loss volume in the area. The beach area began to recover after Hurricane Harvey with an overall volumetric net gain of 4,100 m3 within the front beach area, across a distance of approximately 800 meters, and a shoreline advancement of up to six meters. The beach area is in the early stages of beach recovery and could take approximately four years, consistent with previous studies (Morton 1985, 1994). However, the delta area has not seen any trend to recovery processes and could take much longer due to the sustained high-water levels and discharge rate of the Brazos River. As of December 2017, the shoreline has between ten and twenty meters to build out, the dune height needs to increase by up to 0.89 meters and increase in net volume of 19,500 m3 is needed to reach conditions prior to the Hurricane.



Coastal erosion, LiDAR, Terrestrial laser scanning (TLS), GPS, Dune, Delta, Beach