Effect of Barrier Height on Magnitude and Character of Hurricane Harvey Washover Fans, Matagorda Peninsula, Texas

This study uses topographic profiles, washover fan volumes, and shoreline retreat rates to explore relationships between barrier types and Hurricane Harvey storm washover sedimentation. Pre- and post-Hurricane Harvey topographic profiles were created on 15 transects using Bare Earth LiDAR (2016) and surveyed elevations (2019). Depth and area of washover fan measurements were collected to estimate washover fan volumes. An inverse relationship was found between washover fan volume and pre- and post-storm barrier heights. Based on the topographic profiles, one section of shoreline had a scarp up to 3m high which blocked overwash, but appears to have increased shoreline erosion. In contrast, a low-lying section of shoreline generated relatively large washover fans, but experienced less shoreline retreat. Shoreline retreat was further quantified between 2014 and 2019 using Google Earth Imagery from 2014, 2016, 2017, and 2019 to track migration of the shoreline. The entire shoreline in the study area is undergoing relatively rapid retreat, but the results suggest that Hurricane Harvey increased erosional rates. The Colorado River Jetty borders the study area and may have acted as an anthropogenic barrier, likely reducing storm surge energy and contributing to marsh aggradation on transects in its close proximity. The study findings indicate that the identification and incorporation of other variables that influence washover magnitude would further the understanding of this complex natural system. The research results provide valuable information on the interaction of hurricane storm surge with natural and anthropogenic barriers, beach and dune erosion, and marsh aggradation along the coast of Texas.