One noticeable difference in tlie behavior of the device during this 

 run versus its previous behavior was that the flotation pads rose and fell 

 vertically with considerable force. This flapping created what appeared 

 to be a possible pumping effect caused by the rapid passage of wave crests. 

 This phenomenon may or may not have had an effect on the creation of the 

 large mound of accreted material inshore from the device. 



h. Run 8 . The main purpose of Run 8 was to attempt to move the 

 large mound that accreted inshore of the device during Run 7, still farther 

 inshore, and up on the beach. As many be seen in Figure 13, this did not 

 happen. For Run 8, the wave period remained at 5 seconds, but the average 

 offshore wave height in 30 feet of water was i ncreased f rom I.I feet to 1.5 

 feet. The device remained at its same setting, with one flap operating, 

 for the entire run. The run was of the mobile type, and the device was 

 placed 3 feet seaward of its final position at the end of Run 7. The device 

 was moved 3 feet every hour and 56 minutes, without stopping wave action, 

 for a total running time of 38 hours and 44 minutes, covering a total dis- 

 tance of about 57 feet. The most noticeable effect of this run was the 

 total erosion of the large mound accreted in the previous run. This ma- 

 terial not only filled the trench made during Run 7, but caused a consider- 

 able amount of sediment to be accreted on the surface of the shelf near the 

 seaward edge of the device, but also down the steep offshore slope and beyond. 

 A small trench was dug during Run 8 at the location beneath the final device 

 position, and a small amount of accretion was noted adjacent to the device 

 on its landward side. Due to the proximity of the device to the shoreline, 

 as well as calibration difficulties, the inshore wave gage was not used 

 during this run, nor for the remainder of the test series. No measure of 

 wave height reduction by the device was thus obtained. 



Figure 10 shows the amount of accretion landward of the final position 

 of the device to be small; planimetric analysis showing that 30 cubic feet 

 of material were accreted, and 25 cubic feet were eroded, a net accretion 

 of 5 cubic feet. Seaward of the final location, however, some 483 cubic 

 feet accreted within the limits of the survey, while 472 cubic feet eroded, 

 a net gain of II cubic feet (the net value being within the errors of 

 measurement) . 



The pumping effect of the flotation pads of the device, as noted in 

 the discussion of Run 7, was not observed during Run 8, which may account 

 for the very limited amount of accretion that took place landward of the 

 device. This run destroyed all the good effects observed In the previous 

 run and showed essentially that a mound of material, accreted In shallow 

 water, landward of the device, could not be moved inshore to the Stillwater 

 line by the device in its present form for at least some common wave and 

 slope cond itions. 



i. Run 9 . For Run 9, the device was returned to deeper water and 

 set so that three of Its flap valves would be operable. The profile re- 

 mained as It was at the end of Run 8, which resembled the equilibrium profile 

 shown in Figure 5. The offshore water depth remained at 30 feet, but the 

 wave period was Increased to 9 seconds, and the average offshore wave height 



20 



