Houston-Galveston Navigation Channels, Texas Project. Navigation Channel Sedimentation Study, Phase 2 Plan Simulations

摘要

This report documents the results of several plan scenarios on the sedimentation behavior in the Houston-Galveston Ship Channel area. The U.S. Army Engineer District, Galveston, recently enlarged the Houston Ship Channel in depth and width. Preliminary evaluations of the enlarged channel indicate a higher than anticipated rate of deposition in the channel reach near Atkinson Island. A Coastal and Hydraulics Laboratory investigation (Tate and Berger 2006) was charged with determining if this higher deposition rate is a permanent feature or only a temporary issue. A preliminary study focused on the change in currents, as determined by the model, from the preenlarged channel to the new configuration and a sediment tracer analysis. The results of this study determined that the dredging should have been only about 20-30 percent higher than for the pre-enlarged channel. This implies that a large increase would be due to other considerations, such as dredged material resuspended from disposal areas and redepositing in the channel, channel dimension equilibration, or vessel impacts on the shoaling. This preliminary study used the sediment model in an unvalidated state for early results to aid planning. In addition to an unvalidated model, other limitations were that the sediment pathways and loadings were not modeled but assumed. A more general validated tool was needed to estimate the causes of the shoaling with the enlarged channel and suggest approaches to reduce the deposition rate. Knowing that there are many factors that contribute to sediment transport, the logical next step was to develop and validate the sediment model. With a validated sediment model, testing and decision making can be made while considering many factors simultaneously. In the validation process it was determined that vessel traffic was important in the deposition and resuspension of sediment. Vessel effects, therefore, are included in this model. The end result is a model that is capable of repro.