induced current patterns and magnitudes and sediment tracer movement and 

 subsequent deposits. Experimental results obtained from these preliminary plans 

 were used as a basis for deterrnining the optimum improvement plan (Plan 19). 



Wave height experiments conducted for Plan 16 indicated that the raised 

 bathymetry southwest of the head of the causeway (representing shoaling over a 

 10-year period) slightly reduced wave heights in the harbor relative to the existing 

 depths of Plan 14. Since the area was raised expeditiously with gravel, however, the 

 additional bottom friction may have contributed to the reduced heights as opposed 

 to the bathymetry change. These results are, therefore, considered nonconclusive. 



Preliminary experiments with the dredged areas only (breakwater and causeway 

 extension removed) of Plan 17 revealed increases in wave heights at the causeway 

 docks. For 2-m (6.6-ft) wave conditions, maximum wave heights at the outer and 

 inner docks increased by 0.52 and 1 .49 m (1 .7 and 4.9 ft), respectively, due to 

 removal of the breakwater and causeway extension. Preliminary results also 

 revealed current magnitudes in excess of 0.61 mps (2.0 fps) along the outer 

 causeway dock and in the entrance channel for 2-m (6.6-ft) wave conditions for 

 Plan 17. In addition, the removal of the breakwater would increase the potential for 

 channel shoaling. 



During preliminary experiments, visual observations revealed that the 3.7-m- 

 deep (12-ft-deep) deposition basin was not very effective in catching and storing 

 sediment for waves predominantiy from the southwest. The slight deepening and 

 widening of the breach in conjunction with the 6.7-m-deep (22-ft-deep) deposition 

 (Plan 18) increased the effectiveness of the sand management system and was used 

 as a basis for the final design plan. 



Results of wave height experiments for the final (optimum) improvement plan 

 (Plan 19) revealed calm conditions (wave heights of 0. 15 m (0.5 ft) or less) in the 

 existing harbor (gauge 9) during typical storm wave conditions (2-m (6.6-ft) 

 waves). For 50-year storm wave conditions (6-m (19.7-ft) waves), wave heights of 

 0.52 m (1.7 ft) or less occurred in the harbor. Wave heights obtained along the 

 outer and inner causeway docks were 1.16 and 0.61 m (3.8 and 2.0 ft), respectively, 

 for predominant 2-m (6.6-ft) waves from 227 deg. For 50-year storm conditions, 

 wave heights along the outer and inner docks were 6.0 and 4.0 m (19.6 and 13.1ft), 

 respectively. Results indicated that wave heights for Plan 19 were substantially less 

 than those obtained for existing conditions. 



Wave-induced current patterns obtained for Plan 19, in general, indicated current 

 movement from west to east for waves from 227 deg with a counterclockwise eddy 

 east of the new breakwater. This eddy resulted in currents moving seaward along 

 the new breakwater. For waves from 182 and 137 deg, current movement was 

 generally from east to west with a clockwise eddy west of the existing causeway, 

 even though in some cases, movement east of the existing entrance was in an 

 easterly direction. Current patterns and magnitudes were similar to existing 

 conditions, except that currents moved along the eastern side of the new breakwater 

 as opposed to the eastern side of the existing causeway. The breaches in the 

 causeway and breakwater provided some circulation between the structures. 



34 Chapter 4 Experiments and Results 



