Vessel Wake–Induced Suspension of Bed Sediment in a Shallow Bay System

Wakes generated by deep-draft vessels are known to cause various environmental concerns, including erosion, increased sediment suspension, sedimentation, and ecological disturbances. This study employed field measurements in the Upper Galveston Bay, Texas (GBT) to record water-level fluctuations, 3D water velocities, and suspended sediment concentrations (SSCs) at a fixed location during wakes caused by deep-draft vessels transiting the Houston Ship Channel (HSC). The typical depths of the GBT and the HSC are 3 and 15 m, respectively, with over 20,000 deep-draft vessel movements per year. Using two SSC measurements at different elevations above the bed, a simple composite model was developed to estimate the vertical distribution of SSC during different phases of vessel wake influence. Correlations of vessel and wake parameters to SSC and sediment transport revealed that maximum secondary wave height and the combined drawdown-secondary height were the best predictors of SSC and total gross sediment flux out of all tested parameters. In contrast, the drawdown height was more effective at predicting total net sediment flux, as the unidirectional flow of the drawdown was the dominant contributor to overall sediment movement. The dominant transport direction was opposite the wake propagation direction, toward the HSC, with a high-level estimate of total sediment transported to the HSC of 8.05 × 108 kg/year, which is approximately 39% of typical shoaling rates for the area.