b. Run 2 . For Run 2, the device was moved landward some 4.0 feet 

 from its location during Run I (see Figure 7). Ttie profile over which the 

 device was to operate was the same as existed at the end of Run I . For this 

 run, the wave period was the same as for the preceding run, 5 seconds, but 

 the average wave height in 30 feet of water was lowered to 1.5 feet. The 

 average wave height was decreased by the device only 7 percent, to 1.4 feet, 

 during this run. Run 2, like Run I, was a static test and lasted 50 minutes. 

 The setting, too, was the same, with 4 flap valves operating; the edge of 

 the deepest was about 20 feet below the Stillwater surface and in contact 

 with the bottom at the start of the run. On the landward side of the device, 

 thin layers of sediment, totaling 22 cubic feet and 21 cubic feet accreted 

 and eroded, respectively. In Run 2, most of the erosion that took place in 

 the trench dug by the device, both seaward and landward of its location. 

 The heaviest deposition took place on both sides just beyond the periphery 

 of the trench, with the main portion of landward deposition occurring within 

 about 32 feet of the trough rim. Most of the seaward deposition was occupied 

 with filling the trench dug during Run I, while some erosion took place sea- 

 ward of the trench in some of the accreted material that had been deposited 

 during Run I. On the seaward side, 19 cubic feet of sediment eroded and 25 

 cubic feet accreted, hence the device produced a net accretion of 6 cubic 

 feet on that side. This result is indicative of the increased hydraulic 

 activity that took place on the seaward side of the device although still 

 within the limits of measurement accuracy. 



c. Run 3 . The device was located about 32 feet farther landward 

 for Run 3 than for Run 2, and quite close to the base of a rather steep off- 

 shore slope in the bottom profile (see Figure 8). As the device was to be 

 operated in shallower water than the preceding two runs, its flap valves 

 were raised one setting so that the rod connecting the flap valve rack to 

 the vertical supports was passed through the uppermost flap valve, causing 

 the lower edge of the deepest valve to extend about 15 feet below the 

 Stillwater line, just in contact with the coal bed that existed after the 

 completion of Run 2. Four flap valves operated during the run, however. 



Run 3, like the two preceding runs, was static, with the device staying in 

 the same location for the 50-minute duration of the run. The wave conditions 

 were the same as during Run 2, with a period of 5 seconds, and an average 

 offshore wave height of 1.5 feet in 30 feet of water. The device reduced 

 the wave height quite significantly by 47 percent during the run, cutting 

 the average height from 1.5 to 0.8 feet. This was perhaps a consequence of 

 proximity of the device to the steep offshore slope. The effect of the slope 

 was very noticeable with regard to the volume and location of the sediment 

 transplanted by the device. On the landward side of the device, no accretion 

 occurred, but 4 cubic feet eroded. Again the erosion took place primarily 

 in the trench dug by the device on both the landward and seaward sides. 

 A very slight amount of erosion occurred for a short distance immediately 

 landward of the trough. On the seaward side of the device, 27 cubic feet 

 of material eroded, and 48 cubic feet accreted. 



As before, most of the erosion took place in the trench, the accretion 

 occurring as a sizable mound decreasing in thickness seaward, beginning at 

 the seaward rim of the trench and tapering in thickness downslope after 

 continuing to fill the trenches made during Runs I and 2. The net effect 



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