Date of Award

Summer 2019

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Dr. Davin J. Wallace

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Maarten C. Buijsman

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Stephan D. Howden

Committee Member 3 School

Ocean Science and Engineering

Abstract

Horn and Petit Bois islands are two of five Mississippi (MS) barrier islands that provide physical protection from tropical cyclones threatening the MS Gulf Coast, in addition to critical habitat for the northern Gulf of Mexico (GOM). In September 2004, Hurricane Ivan removed a large volume of sediment from the eastern ends of Horn and Petit Bois islands with its 1-2 m storm surge and ~194 kph wind speeds. Then, in August 2005 Hurricane Katrina severely impacted the two islands again with its 3.5-5.5 m storm surge on Horn and Petit Bois islands, and up to 204 kph wind speeds at landfall. Using topographic light detection and ranging (LIDAR) datasets from 2004 to 2016, spatial and temporal changes of the islands’ area, sediment volumes, and shorelines were measured to ascertain their geomorphic responses and recovery rates following the impacts of these devastating tropical cyclones. During the 2004–05 hurricane seasons, Horn Island lost 13.3% of its pre-hurricane Ivan land area, lost 35.9% sediment volume, and had a total average shoreline change rate of –10 m/yr. Petit Bois Island lost 13.3% of its pre-Ivan land area, lost 27% sediment volume, and had a shoreline change rate of –33 m/yr. Between 2005 (post-Katrina) and 2016, Horn Island recouped 6.6% of its pre-Ivan land area and ~4.3% sediment volume, while Petit Bois Island recovered 4% of its pre-Ivan land area and ~22.9% sediment volume. The overall averaged shoreline change rates between 2004 and 2016 were –2 m/yr for Horn Island and –3 m/yr for Petit Bois Island. These changes reflect that Horn Island is no longer stable, as its sediment supply cannot keep pace with the current rate of sediment loss, and that because Petit Bois Island’s narrow central shoreline is retreating at a rate of ~9 m/yr, the island is at risk of breaching during the next storm.

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