B
Publish and Present
Chris Stearns, S.E.
Bridge Engineer 6
Washington State Ferries
Seattle, Washington
Vessel propeller wash has been shown to cause scour in the marine environment [Chin et al., 1996, Tan and Yuksel, 2018, Yuksel et al., 2018]. We investigated the hydrodynamic causes of severe erosion at the Washington State Ferries ferry terminal in Kingston, WA, where a cliff-like bathymetric feature has shifted shoreward in recent years, forcing repairs on the slip’s bridge pilings. High resolution measurements of velocity and estimates of turbulent bed stress were made during vessel arrivals and departures during two deployment periods in March and April, 2018. Calculated bed stresses were found to be 100 times larger during vessel arrivals and departures than background levels. Bed stresses were higher during vessel departures than arrivals, corresponding to higher vessel acceleration during departures. Additionally, during departures, lower tidal stages correspond to higher bed stresses, because the propellers are closer to the seabed. During arrivals, larger vessels generated higher bed stresses. These results can be used to formulate an empirical model for the accumulated bed stress due to propeller wash at a ferry terminal.