Shallow-bay ports and waterways in bay systems along the Gulf of Mexico coast are critical transportation infrastructure and the Nation’s economic drivers. Vessel propeller wash is the sediment movement induced by the hydrodynamic forces generated from propeller rotation. Especially deep-draft vessels with propellers located close to the channel bed during transit mobilize a large amount of sediment that may settle out in locations where it can cause unwanted extensive shoaling issues. As maritime traffic volume and vessel size are predicted to increase further in the future, so will the expensive maintenance dredging requirements. The hydro- and sediment dynamics of propeller rotation induced water jets and turbulence interacting with sediments on the channel bed and slopes are complex and depend on various parameters related to vessel geometry and propulsion, channel morphology, draft clearance, and sediment characteristics. While some limited studies on vessel-wake impact to sedimentation exist, no comprehensive field measurements of propeller wash sedimentation drivers have been conducted and it is thus not known to what extent vessel traffic is responsible for channel sedimentation issues.
The objective of this research project is to measure propeller wash dynamics and quantify resultant sediment suspension caused by deep-draft vessels in the field. This will be accomplished using a vessel-mounted Acoustic Doppler Current Profiler (ADCP) and echo sounder system capable of high-resolution 3D velocity and suspended sediment concentration (SSC) measurements throughout the water column. Transect surveys of the water column immediately following deep-draft vessel passage are conducted at select locations of the Houston Ship Channel (HSC) in Galveston Bay, Texas. HSC is one of the busiest waterways in the nation with over 22,000 deep-draft vessel passages per year. Multiple survey paths per deep-draft vessel are completed to capture extent and evolution of the sediment plume behind each vessel. Bed sediment grab samples and water samples are collected and analyzed to help calibrate SSC measurements and quantify propeller wash loads. Available Automated Information System (AIS) data for the deep-draft vessels and channel bathymetry data are used to correlate measured SSC values with vessel and site characteristics and to quantify mobilized sediment mass. Back to Current Projects …
