As may be seen in Figure 17, much of the 228 cubic feet eroded from 

 inshore of the device during Run 12 was accreted seaward, partially filling 

 the trench dug during Run II, and spilling down the slope into deeper water. 

 The erosion of several steps of the slope was noted, alternating with rather 

 thin layers of accretion, with the result that 152 cubic feet eroded seaward 

 of the device, while 486 cubic feet accreted, a net seaward accretion of 334 

 cubic feet, versus a net landward erosion of 209 cubic feet. Even with the 

 rather long wave period, the device was unable to create a sizable mound of 

 accretion landward of its position. It is also worth noting that the pre- 

 viously mentioned pumping effect of the flotation pads was not noted in 

 Run 12. 



m. Run 13 . After Run 12, the wave period was changed to 7 seconds. 

 The post-Run 12 profile indicated that an equilibrium profile was needed for 

 the third wave condition of the test series. Accordingly, a 1:15 molded 

 slope was made in the flume and waves having an average wave height of 4.4 

 feet in 38.7 feet of water, and a 7-second period were allowed to impinge 

 on it for approximately 154 hours at the end of which time near equilibrium 

 was reached. This equilibrium profile is shown in Figure 18. Since Run 13 

 required a new set of wave conditions, the test was to be a static one, with 

 the device being set so that 3 flaps were operative, the lowest of these 

 extending to a depth of about 14 feet below the still water line. Run 13 was 

 of about II minutes duration, but of profound effect oh the profile. The 

 change in the equilibrium profile was so great that it was almost certainly 

 caused by the presence of the device in operation, although the trench dug 

 during Run 13 was neither especially wide, nor deep. As may be seen in 

 Figure 18, a small mound of accreted material (about 17 cubic feet) was 

 present inshore from the trench rim after Run 13. In this case, the inshore 

 terminus of this mound has been considered the landward limit of the direct 

 effect of the device operation. A rather long seaward accretion layer was 

 noted extending from the offshore trench rim about 66 feet seaward to the 

 shelf break. In the region near the Stillwater line, a considerable amount 

 of headward erosion occurred, causing a rather large amount of sediment to 

 be deposited seaward in a layer of tapering thickness terminating on the 

 shelf a short distance landward of the small accretion mound inshore of 

 the device. 



On the landward side of the device, 572 cubic feet accreted, 587 cubic 

 feet eroded. On the seaward side, 61 cubic feet eroded, and 101 cubic feet 

 accreted. Thus a net loss of material attributable to the operation amounting 

 to 15 cubic: feet accrued on the landward- side of the device and, a net gain of 

 40 dubic feet was registered on the seaward side. 



n, Run 14. for Run 14, the offshore water depth was lowered to 

 34.5 feet, but the average wave height of 4.4 feet and period of 7 seconds 

 remained, as in Run 13. For this mobile run, the Initial position of the 

 device was identical with that in Run 13. With the exception of the second 

 position, the device was moved 3 feet every II minutes. The 22-minute stay 

 at the second position produced no noticeable effect on the final profile, 

 which was taken after about 2 hours and 20 minutes of running time, when 



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