Analysis of Packery Channel Public Access Boat Ramp Shoreline Failure

Abstract

The shoreline stabilization adjacent to the public access boat ramp in the Packery Channel basin has been damaged in two separate events. For the shoreline damage at the boat ramp bulkhead, toe scour is the likely mechanism for failure. Typical sources of hydrodynamic forcing that can lead to toe erosion include storm currents, locally generated storm waves, and offshore storm waves propagating into the basin through Packery Channel. Quantitative analysis of storm induced wind generated waves and currents eliminated them as possible causes of the damage. However, photographic and movie evidence indicate the presence of low-frequency low-amplitude waves propagated into the basin and impacted the boat ramp. The Coastal System Model (CMS) was used to simulate a range of these low-frequency low-amplitude waves and the results demonstrated that these waves could produce sufficient flows in the vicinity of the boat ramp shoreline to cause the damage. Subsequent modeling was used to develop design criteria for additional shoreline stabilization.