Abstract

Understanding the complex hydrodynamic and morphodynamic processes associated with storm impact and subsequent recovery of barrier island systems is essential in developing appropriate coastal management strategies to protect these fragile resources. Measured morphology changes of the subaerial portions of a sediment-starved barrier island were analyzed using the process-based 2DH numerical morphodynamic model XBeach during hurricane impact, and LiDAR surveys covering five years of post-storm recovery. The recovered subaerial volume of the barrier island after five years exceeded prestorm volumes by up to 30%, suggesting that extreme events are necessary for barrier islands to sustain themselves in sediment-limited environments.

Introduction
Background and Motivation

Along many of our coastlines barrier islands are the first line of defense against wave attack and damage from storm surge. Understanding the complex hydrodynamic and morphodynamic processes associated with storm impact and subsequent recovery of barrier island systems is essential in developing appropriate coastal management strategies to protect these fragile resources. While some pre- and post-storm topography and bathymetry data of barrier islands inundated during a storm exist, very little information is available to help understand the complex hydrodynamic and morphodynamic processes during storm impact (i.e. Sallenger, 2000; Houser et al., 2008). These processes are crucial to understanding sediment budgets, potential threats to infrastructure and best coastal management practices for specific locations. For this study, Follet's Island (FI), a narrow, low-lying barrier island in a sediment-starved environment along the upper Texas coast (UTC) in the Gulf of Mexico was investigated. LiDAR and topographic surveys were collected before and after Hurricane Ike (2008) and on a yearly basis over the five years following the storm. The goal was to address how Hurricane Ike affected the sediment supply on the subaerial beach and foredune of FI, what physical processes governed the response of the island during the hurricane, and how the island recovered following the hurricane. The UTC is tentatively defined as the coastal region between the Sabine Pass and the Brazos River (Anderson, 2007) and is characterized by long, narrow barrier islands comprised of fine sand (less than 0.2 mm), and a microtidal wave-dominated hydrodynamic environment with a tidal range of 0.54 m between Mean-Lower-Low-Water (MLLW) and Mean-Higher-High-Water (MHHW). On average, approximately four hurricanes and four tropical cyclones make landfall per decade (Roth, 2010). Since the long term morphology of barrier islands is strongly influenced by the frequency of large scale episodic events, the UTC is particularly vulnerable to large scale erosion.

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