high energy phase II waves to transport sand over the phase I pulse of sand 

 into the deeper reaches of the trap. 



Summer phase III conditions (52 days) favored the continuation of phase II 

 depositional patterns. Sediments continued to move alongshore across the phase 

 I-phase II "ramp" and into the nearshore portion of the dredged trap (e.g., 

 about a 2-meter accumulation at location 10 and a little less at 5) . The shore- 

 line moved progressively seaward, about 0.50 meter of sediments accumulated at 

 most offshore locations, and erosion of the nearshore ramp (cores 9 and 14) 

 supplied sediments to the interior of the trap. 



Phase IV (122 days) is characterized both by slow rates of sedimentation 

 and by redistribution of sediments already deposited within the trap. Accumu- 

 lations were greatest along transect 260 (about 1.50 meters at location 6) 

 which continued the general seaward infilling of the trap as seen in previous 

 phases. A deep scour pocket developed along range 180, whose position suggests 

 that waves and currents from southerly directions may have entered the trap and 

 produced the observed erosion. Phase IV was also a time of major deposition 

 on the foreshore of "native beach" profile 914 (more than 2 meters at location 

 22, Fig. 3). 



Phase V (209 days) was the time of most rapid deposition during which the 

 dredged trap was essentially filled. Deposition was greatest in the offshore 

 dredge pits with the innermost pit filling generally before the depression 

 located offshore at the updrift entrance to the trap (e.g., compare the erosion- 

 deposition plots for phase V-1 versus V-2 , Fig. 4). Also erosion of the near- 

 shore "ramp" occurred during the winter of phase V (Fig. 4, V-1, 6b), whereas 

 during the spring and summer, deposition dominated both within the trap and on 

 native profile 914 (Fig. 3). 



Finally, Table 4 summarizes the rates and volumes and associated wave 

 energy factors for the five trap-fill phases. These data are presented by 

 Bruno, et al. (1981), and trap-fill volumes are accurate to ±5 000 cubic 

 meters. In total, 629 000 cubic meters accumulated during the 15-month study 

 period, which indicates a longshore transport rate of 463 000 cubic meters per 

 year, the lowest yearly rate since construction of the harbor (Table 1) . This 

 low rate reflects the fact that this study was conducted during a time when wave 

 energies were lower than average. In addition large volumes of sediment were 

 transported into the trap during the relatively high energy winter and spring 

 of 1976 which could not be included in the calculated rates because the sur- 

 veying program was not begun until April 1976. Trap filling is usually greatest 

 during the winter when wave energies are usually the largest. 



Table 4. Summary of the rates, volumes, and associated wave energy factors. 



Accumulation 

 phases 



Accumulated 

 volume 



(m3) 



Accumulation 

 rate 



(mVd) 



^P£g, longshore 

 energy flux 



(N/s) 



'l, immersed 

 weight trans- 

 port rate 

 (N/s) 



I 



30,100 



971 



-197.62 



113.8 



II 



120,800 



1,455 



-94.1 



164.3 



III 



68,000 



1,307 



-65.9 



144.5 



IV 



102,500 



840 



-244.3 



97.7 



V 



308,100 



1,474 



-287.3 



168.6 



^Pff and I values are taken from Bruno, et al. (1981). 

 Negative ?b values indicate sediment is transported toward the trap. 



19 



