considering all test conditions, wave heights along Camp Ellis Beach were 

 comparable to those obtained for existing conditions. Wave height data 

 secured in the navigation channel for Plan 9 revealed significant increases in 

 wave heights, as opposed to existing conditions, which will result in hazardous 

 navigation conditions and possible damage to vessels and coastal facilities 

 inside the river mouth. 



Sediment tracer tests for Plan 9 revealed sediment movement to the north 

 for test waves from 101, 88, and 75 deg with the +2.7-m (+8.8-ft) swl. 

 Extreme storm waves with the +3.7-m (+12.0-ft) swl washed sediment onto the 

 overbank, and test waves from 56 deg resulted in sediment material remaining 

 in the immediate vicinity of Camp Ellis Beach. A comparison of these results 

 with existing conditions reveals very similar sediment patterns, except the 

 Plan 9 condition appeared to erode at a slightly increased rate for the smaller 

 (1.8 to 2.4 m (6 to 8 ft)) wave conditions from 101, 88, and 75 deg. Results 

 also indicated that the 91 nr'/s (3,200-cfs) river discharge for Plan 9 had no 

 impact on sediment movement along Camp Ellis Beach. Wave-induced cur- 

 rent patterns and magnitudes for Plan 9 also were similar to those obtained for 

 existing conditions. This test series indicates the north breakwater's impact on 

 hydrodynamic conditions is only minor and results in insignificant changes in 

 the northerly sediment transport which exists at Camp Ellis Beach. 



Sediment tracer tests conducted for the pre-breakwater conditions of 1866 

 indicated that the shoal at the river mouth tended to meander forming offshore 

 bars and building the beach for the storm wave conditions tested. The shoal at 

 the river mouth at this time was characteristic of an ebb tidal delta. Mean 

 river flow used during model testing appeared to be of little benefit in keeping 

 the river channel open since a bar formed across the entrance. In the proto- 

 type, tidal flows through the entrance would likely prevent it from closing but 

 not necessarily keep the entrance navigable. However, these flows were not 

 reproduced in the model. Tests conducted for this study compare relative 

 changes for the various alternatives based on the hydrodynamic conditions 

 tested. The original -i-3.0-m (-i-lO-ft) el breakwater completed in 1873 had 

 little impact on bar formations. For the conditions tested, sediment material 

 moved over and through the structure and resulted in a very similar bar forma- 

 tion across the entrance as pre-breakwater conditions. Historical records indi- 

 cate channel shoaling during this period due to material penetrating over the 

 original breakwater (USAED, New England 1992), which was the reason the 

 structure was raised. The raised +4.6-m (-t-15-ft) el breakwater completed in 

 1897 was effective in reducing the amount of shoaling in the navigation chan- 

 nel. Some material moved through the structure and formed a bar adjacent to 

 the channel side of the breakwater, but most the sediment in the shoal formed 

 bars north of the raised structure seaward of Camp Ellis Beach. It was noted 

 that, for all the conditions tested, sediment constantly moved northerly out of 

 the Camp Ellis Beach area. None of the test conditions resulted in a reversal 

 of sediment movement from north to south back toward Camp Ellis Beach. 

 Test results suggest that regardless of the condition of the north breakwater, 

 without natural nourishment or replenishment. Camp Ellis Beach will erode 

 with net sediment transport to the north. 



Chapter 4 Tests and Results 



33 



