Table 2. Vibracore specifics: Channel Island 



s Harbor, 



California. 



Core 



Core 



Core 



Active 



Core 



Core 



Core 



Active 





elevation 



length 



thickness^ 





elevation 



length 



thickness 





(m) 



(m) 



(m) 





(m) 



(m) 



(m) 



1 



2.44 



7.47 



6.10 



21 



4.26 



6.16 



1.21 



2 



-3.35 



4.27 



2.74 



22 



2.43 



6.19 



1.76 



3 



-5.18 



4.54 



1.98 



23 







6.16 



1.83 



4 



-8.23 



3.08 



1.89 



24 



-1.83 



6.55 



1.21 



5 



2.74 



9.20 



7.92 



25 



-3.66 



6.19 



0.91 



6 



-0.30 



8.84 



7.62 



26 



-6.40 



5.33 



0.30 



7 



-4.26 



8.20 



5.33 



27 



-7.32 



6.04 



0.45 



8 



-9.44 



2.80 



0.98 



28 



-8.84 



4.75 



0.45 



9 



3.35 



4.15 



3.05 



1 



10 

 11 



0.61 

 -3.65 



7.96 

 5.85 



4.42 

 4.57 









_2«- 



12 



-10.36 



1.92 



1 . 22 



\ ^'^^^11 1 



13 



14 



3.05 

 0.61 



4.32 

 8.29 



3.35 

 3.41 



• 



^-s^LL.'*-" c «- 



3 7^11-15 19---— -3„ 2S 



15 



-3.05 



7.83 



7.16 





— '^^^ \ 24 



16 



-9.45 



4.51 



0.91 





—^ 5 9 13 17 



17 

 18 

 19^ 





 -1.83 

 -2.43 



5.58 

 5.39 

 7.28 



2.59 

 0.91 

 8.23 





Core Loco 



-iti " 



21 



tions 



( sKelch not drown to scole 1 1 



20- 



-9.45 



3.11 



0.91 



m 







% 







Active thickness is difference of highest and lowest surveyed elevation for 

 18 months preceding coring. 



■^Location where core length is less than active thickness. 



The cores were retained in 7 .6-centimeter-diameter clear plastic liners. 

 Ultimately, these were split and the cores were photographed and the sediment 

 channel-sampled (Krumbein and Graybill, 1965) within 0.3-meter intervals for 

 textural analysis. Grain-size distributions were determined for each sediment 

 sample using sedimentation tube size analysis techniques. Phi mean and phi 

 sorting data for these samples appear in the Appendix. 



2. Hydrosurveys and Surface Sand Samples . 



The rate and patterns of trap infilling were determined from hydrosurveys, 

 and surface sand samples were used to characterize the texture of trap-fill 

 sediments. Twelve hydrosurveys were conducted between trap dredging episodes; 

 five sets of samples were collected (Table 3). Monthly surveys using an auto- 

 mated system mounted aboard a LARC V amphibious vehicle were initially 

 planned to monitor trap filling but actual times between surveys varied from 

 25 to 76 days to accommodate adverse weather, equipment failures, and sched- 

 uling difficulties. U.S. Army Engineer District, Los Angeles, personnel 

 assisted with the surveys and with sand sample collection. Sand sampling was 

 initially planned for alternate surveys with samples being collected by scuba 

 divers, where necessary, at the same grid locations in the trap and along the 

 same upcoast profile line as those locations subsequently cored in September 

 1977. Inclement weather prevented the planned sampling episode following the, 



10 



