EPISODIC STORM DRIVEN IMPACTS ON BARRIER ISLAND MORPHODYNAMICS IN THE NORTHERN GULF OF MEXICO: IMPACT OF HURRICANE IKE ON GALVESTON ISLAND SHELF

September 13, 2008 Hurricane Ike made landfall on Galveston Island, Texas. Hurricane Ike had a storm surge of 4 meters with sustained 20m/s winds for 18 hours with wind gusts exceeding 40m/s. The subaqueous changes Ike catalyzed are measured in this study through several time series methods including beach profiles, side-scan sonar, and swath bathymetry. Multiple surveys using these methods were completed prior to and immediately after Hurricane Ike allowing for a unique analysis of the impact episodic storms have on the geological sustainability of beaches and barrier islands along the Texas coast of the northern Gulf of Mexico. Galveston Island experiences background erosion rates averaging 1 m/yr. However, one event (Hurricane Ike) caused beach retreat on the order of (~50 m), equivalent to 50 years of non-event based erosion. Historically events of this scale occur on a 25 year cycle so the resulting conclusion is the sediment transport in this region is driven by episodic events. Side-scan and bathymetry data reveals that ~10% of the eroded sediment is trapped in bars seaward of the fairweather depth of closure.