| Summary: | Source: https://erdc-library.erdc.dren.mil/jspui/ A previously verified hybrid modeling system (coupled physical and numerical models) of the Kings Bay/Cumberland Sound estuarine system was used to investigate hydrodynamic and sedimentation variations associated with Trident channel expansion. The models generally demonstrated small velocity differences between the pre-Trident base channel condition and the enlarged Trident channel condition tested. Reduced velocity magnitudes in the deepened upper Kings Bay turning basin demonstrated the largest base-to-plan velocity differences. Subtle circulation differences were identified. The deepened and widened Trident plan channel increased flood and ebb volume transport efficiency of the submarine channel through St. Marys Inlet into Cumberland Sound and Kings Bay. Increased discharge through and past Kings Bay changed the phasing relationships north of Kings Bay. Although not an explicit objective of the modeling efforts, tidal effects were examined. The tested plan condition resulted in higher high-water and midtide level elevations in both the physical and numerical models. Variations were close to, but greater than, model detection limits. Low-water elevations between the models were inconsistent. Based on more recent field data, it was concluded that tide range will probably not change as a result of Trident channel improvements, and mean water level in Cumberland Sound may increase a small amount, less than the normal annual variation in mean sea level. The subtle base-to-plan hydrodynamic differences and the increased plan channel area resulted in dramatic sedimentation responses. The numerical model predictions indicated a 150 percent increase in required annual plan channel maintenance dredging. Based on previous shoaling history and this study's findings, the typical annual plan channel maintenance dredging requirement is predicted to vary from a low of about 0.9 million cubic yards per year to a high of about 4.9 million cubic yards per year. The long-term ...
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