A bathymetric survey was conducted to define the existing conditions in the Morehead City Harbor. Survey data (from ~200 ft cross-stream transects) were utilized to evaluate different channel alignments and compute volumes for dredging in the channel ranges.
CSE measured the discharge from two positions in the channel; the western end of Sugarloaf Island and the ship turning basin at the eastern end. Multiple tide gauges and current meters were also deployed to collect water level and velocity data for use in calibrating the numerical flow model. The channel was shown to be ebb dominated (the maximum ebb discharge velocities are higher than the maximum flood discharge velocities for the observed tide measurements).
A detailed numerical computer model simulation and analysis was performed to estimate the velocity within the Morehead City Waterfront Channel for conditions observed. Examination of the velocities along the channel is intended to provide insight into the magnitude of the currents at the peak ebb and flood of the tidal cycle. The model was developed for two scenarios, the first with existing bathymetric conditions and the second with groins in place at each end of Sugarloaf Island. The proposed groins are intended to minimize the amount of sand that flows into the waterfront channel following channel realignment. The numerical model is intended to show how the groins affect the currents in the channel at the measured peak ebb and flood velocities.
The proposed groins did not have a decreasing effect on the channel velocities except in the vicinity of the groins. The groins effectively shifted the higher velocities along the channel closer to the island. The addition of the eastern groin to the model caused the velocity at the peak flood discharge to be virtually zero, which would allow most sediment in suspension adjacent to the groin to settle. There was evidence that there could be some scouring velocities at the east end of the groin on flood conditions (i.e., depth averaged velocities greater than 2ft/s). An increase in velocity due to the presence of the proposed groins above the predicted existing condition discharge velocity may potentially cause sediment to move.
