Evaluation of the Vulnerability of the Upper Houston Ship Channel to Transport and Deposition of Contaminated Sediments By Coastal Disasters

Abstract:

The Port of Houston is the second busiest port in the US in terms of overall tonnage, and the sixteenth busiest port in the world. It is served by the Houston Ship Channel, a federally-maintained waterway which is regularly dredged and widened to accommodate increasing vessel traffic. The Houston Ship Channel traverses Galveston Bay, the largest estuary in Texas and the second largest estuarine source of seafood in the US. The Bay is also the site of significant contamination (dioxins, PAHs, pesticides, PCBs, and metals), much of which is bound up in the benthic sediments. While dredging and other anthropogenic means of mobilization are generally quite controlled and governed by environmental regulations, there is a significant potential for mobilization of these sediments by natural hazards (primarily storm surge due to hurricanes). This can lead to deposition of contaminated sediment by surge in the industrial and residential neighborhoods surrounding the Channel, as well as re-deposition of this sediment within the Channel and away from monitoring locations. The redeposition potential of these sediments within the Channel is studied using a hydrodynamic model for tides, surge, waves, and sediment transport in Galveston Bay and the Houston Ship Channel. Historical hurricanes (notably Hurricane Ike) are used to force the model and determine the surge and resulting sediment redeposition. In addition, synthetic scenarios redolent of possible global warming trends and natural climatological variability are also used to simulate surge and sediment transport. Despite high surge potential in this region, it is anticipated that significant on-land deposition of sediment along the western branch of the Channel may not be a major threat. However, mobilization of contaminated sediment away from present monitored locations to other (unmonitored) locations in the Channel and Bay, as well as on the lower land elevations south of the western branch of the Channel, is much more likely.