PART VII: SUMMARY AND CONCLUSIONS 



137. To study the effects of proposed modification of the exterior 

 channels of St. Marys Inlet (the ocean entrance to Kings Bay Naval Submarine 

 Base) on coastal processes, the CIP system of numerical models of CEWES was 

 employed. The system included models for tides, waves, wave-induced currents, 

 and sediment transport. The system together with two computational grids 

 developed for the study was called Model B. 



138. Model B was used to study existing (base) conditions as well as 

 planned conditions. Plan 1 is to (a) widen the navigation channel by 100 ft 

 on the north side so the total width becomes 500 ft, (b) deepen the channel to 

 -49 ft mlw (46-ft project depth plus 3-ft advance maintenance) with side 

 slopes of 3H:1V, and (c) extend the channel on the ocean side with a 20-deg 

 bend to the south at sta -97+76. It is assumed also that the landward 



1,000 ft of the south jetty is made sand-tight for Plan 1. 



139. The tidal model was verified using the field data of 10 November 

 1982. This was achieved by forcing the model with measured tidal elevations 

 and matching observed velocities at ranges in the inlet, Cumberland Sound, and 

 St. Marys River. There was good agreement. 



140. The average year's wave climate for the study area was obtained 

 from WESWIS, on the basis of 20-year hindcast data. The data set included 

 normal storms but not hurricanes and tropical storms. This was used in run- 

 ning the wave and wave-induced current models. 



141. The sediment transport model determined noncohesive sediment 

 (sand) transport in the study area, under the combined action of tides, waves 

 and wave-induced currents. It considered a mean tide and the average year's 

 wave climate. 



142. The sediment transport model was verified by comparing computed 

 erosion/deposition rates in the navigation channel with those obtained from 

 field surveys taken by CESAJ during 1980-81. There was good agreement with 

 respect to both trends and magnitudes. 



143. While all four models were run for base conditions, only the tide 

 model and the sediment transport model were run for plan conditions (Plan 1) 

 to meet the urgent need for model results. (Plan conditions were expected to 

 influence the tide and sediment transport much more than the waves and 

 wave-induced currents.) 



80 



