Scour at the Seawall in Surfside, Texas, During Hurricane Harvey (2017)

Abstract

Hurricane Harvey was a Category 4 hurricane on the Saffir-Simpson hurricane wind scale. National Oceanic and Atmospheric Administration (NOAA) water level gages documented 1.1 m of water level elevation over predicted tide in Freeport, Texas, on 25 – 26 August 2017. The NOAA wave buoy 42019 offshore off Freeport documented wave heights > 7 m. A reconnaissance team of the Geotechnical Extreme Events Reconnaissance (GEER) Association visited Surfside, Texas, on 3 September 2017. While no significant damage to infrastructure was observed, the GEER team identified a significant scour runnel parallel to the Surfside seawall. The purpose of this article is to present the detailed observations of the scour runnel parallel to the Surfside seawall during Hurricane Harvey (2017). The sloped seawall is separating a shore-parallel street from the beach and is composed of angular boulders of approximately 30-50 cm in diameter. The observed runnel represented a depression of up to ~ 0.3 m in depth and ~ 4 m in width. It maintained mostly a distance of 0-5 m from the visible toe of the seawall. Boulders seemed particularly misplaced where the runnel approached the seawall. Sediments at Surfside Beach, Texas, are predominantly clean sands. During a second site visit by the members of the initial team in May 2018, no runnel was observed.