Outer causeway dock 



12-sec, 6-m (19.7-ft) waves from 137 deg 



6.98 m (22.9 ft) 



Inner causeway dock 



12-sec, 6-m (19.7-ft) waves from 137 deg 



5.63 m (18.5 ft) 



Existing entrance 



12-sec, 3-m (9.8-ft) waves from 257 deg 



3.7 m (12.0 ft) 



Existing channel 



12-sec, 6-m (19.7-ft) waves from 137 deg 



1.4 m (4.6 ft) 



Existing turning basin 



12-sec, 6-m (19.7-ft) waves from 137 deg 



0.49 m (1.6 ft) 



Current patterns and magnitudes obtained for existing conditions are presented 

 in Plates 11-21 for representative wave conditions and directions. For waves from 

 257, 227, and 212 deg, currents generally moved easterly along the shoreline, 

 southerly around the head of the causeway, and then easterly again. However, 

 currents in the lee (east) of the causeway moved southerly adjacent to the structure 

 and then in a counterclockwise eddy. For waves from 182 and 137 deg, currents 

 generally moved westerly along the shoreline, southerly around the head of the 

 causeway, and then westerly again. Currents in the lee (west) of the causeway 

 moved southerly adjacent to the structure and then in a clockwise eddy. Maximum 

 velocities, for the experiments conducted, occurred for 12-sec, 6-m (19.7-ft) waves 

 from 257 deg with the +4.0-m (+13.0-ft) swl. Maximum velocities of 2.2 mps 

 (7. 1 fps) were obtained around the head of the causeway for these extreme wave and 

 water level conditions. Maximum velocities identified for the +0.5-m (+1 .6-ft) swl 

 were 0.8 mps (2.6 fps) adjacent to the west side of the causeway for 9-sec, 2-m 

 (6. 6-ft) waves from 212 deg; 1 mps (3.3 fps) adjacent to the outer dock on the east 

 side of the causeway for 12-sec, 2-m (6.6-ft) waves from 137 deg; and 0.5 mps 

 (1.8 fps) along the shoreline between the causeway and the existing entrance for 

 9-sec, 2-m (6.6-ft) waves from 182 deg. 



The general movement of tracer material for representative waves from 212, 

 182, and 137 deg is shown in Plates 22-24 for existing conditions. Sediment 

 initially tended to move toward the shoreline and then, in general, moved easterly for 

 waves from 212 deg and westerly for waves from 182 and 137 deg. Tracer material 

 moved easterly through the breach in the causeway for waves from 212 deg and 

 westerly through the breach for waves from 137 deg. 



Improvement plans 



Results of wave height experiments for Plans 1-12 are presented in Table 2 for 

 representative waves for the +0.5-m (+1.6-ft) swl from various directions. For 

 Plans 1-3, for experimental waves from 137 deg, maximum wave heights obtained 

 without a dredged entrance channel were as follows: 



Chapter 4 Experiments and Results 



23 



