Analyzing the Effects of Hurricane Harvey on Dune Morphology and Coastline Loss Using Terrestrial Laser Scanning: A Case Study at Bryan Beach, Texas

Abstract

The East Texas Coast is the most populated coastal area in Texas, making the region especially vulnerable to rising sea levels and intensifying storms. Hurricane Harvey made landfall at Rockport, Texas, between August 17, 2017, and September 3, 2017. Several studies have used LIDAR terrestrial laser scanning (TLS) and LIDAR airborne laser scanning to study beach morphology and erosion. LIDAR point clouds can be gridded to create high accuracy digital elevation models (DEMs) useful for performing raster calculations in several GIS software packages. This study analyzes several LIDAR TLS scans of Bryan Beach, near Freeport, Texas, taken on May 2017, September 2017, March 2018, and December 2017, to study the recovery of the beach following Harvey. This study uses volume metrics introduced by Morton (1994), in which beach recovery is defined as replenishment of the total percentage of sediment lost during a storm. Volume calculations performed on the DEMs in ArcMap showed that there was a 25% loss in sediment between May 2017 and September 2017 along the 7-km study area. By March 2018, this area had fully recovered the percentage of sediment lost and had also gained an additional 101,450,886 cubic m of sediment. However, cross-shore profile analysis showed varied local recovery responses along the coast influenced by both beach morphology and artificial constructions. Bryan Beach is nourished by a longshore drift that runs parallel to the Texas Coast. Breakwater structures such as jetties disrupt the longshore current, blocking sediment from reaching downcurrent beach areas, which results `in coastline loss. The Brazos River Delta is a salt-wedge estuary that forms when river discharge is low, as is evident from the emergence of a mouth bar after the sustained flooding and high river discharge caused by Hurricane Harvey. The jetty effect, along with the salt wedge, has resulted in significant shoreline loss along the study area.