25 Nearshore and Estuarine Research: Dynamics and Future Resiliency in the Coastal Zone II

This session focuses on drivers of change in coastal environments as well as planning for future resiliency in tidal marshes, mudflats, estuaries, and barrier systems, including human activity impacts, sea level rise, & changing sediment supply.

Monday, 23 March 2026
1:30 PM - 5:30 PM
CCC, Room 22/23

Assessing the Decadal Recovery of Anthropogenically Modified Washout Channels: Follet’s Island, TX, USA

Paper number: 25-3
Program: Technical Sessions
Time: 2:15 PM – 2:35 PM

Authors

Abstract

Follet’s Island, TX is a 25 km long, narrow (<0.5 km) transgressive barrier island composed of fine sand in a micro-tidal wave-dominated environment. The island is moderately developed with a modified beach-dune system due to engineered restoration, beach wrack scraping, and frequent beach-driving traffic. Hurricane Ike (2008; Category 2) produced widespread beach and dune erosion, inundation overwash, and the formation of 31 washout channels across a ~2 km alongshore section of the island between 29°00′12.33″ N, 95°13′15.84″ W and 29°00′54.07″ N, 95°12′19.08″ W. These channels formed during a ~13-hour period of offshore-directed flow generated by elevated bay-side water levels, which established a hydraulic gradient between the back-barrier bay and the Gulf of Mexico scouring through the beach and dune system.

This project examines the decadal-scale recovery of anthropogenically modified washout channels using sediment cores, trenches, digital elevation models, and aerial imagery collected between 2008 and 2024. Following Hurricane Ike, the inundated washout channel area totaled 86,538 m² across 31 channels, with average channel lengths of 107 m and throat widths of 30 m. Restoration efforts in 2011 included construction of an engineered dune system and dune grass planting, completed three months prior to Hurricane Harvey (2017). Despite subsequent impacts from multiple low-intensity tropical cyclones, Hurricane Nicholas (2021) Tropical Storm Alberto (2024) and Hurricane Beryl (2024), the cumulative impacts of these storms was insufficient to promote substantial channel infilling.

Channel bathymetry measured from three channels in June 2024 exhibited average depths of 55–78 cm, with maximum depths exceeding 1.1 m near channel heads; 26 channels remain active as of September 2024. Lidar analyses indicate that total channel area has decreased by only ~12% since 2009, reflecting limited infilling over 17 years. Sediment cores reveal predominantly fine sand (D50 = 144 μm) with organic-rich layers accumulating in persistently inundated channel sections. 

Our results indicate that engineered dunes have raised the threshold for overwash, restricting landward sediment delivery that would otherwise promote channel infilling. The reduced clastic sediment supply prolongs channel persistence and facilitates the transition of washout channels into permanent or ephemeral wetlands that provide habitat and ecosystem services. Washout channels are likely to remain open unless filled by further restoration projects or washover events fill the channels.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411091

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