Run 5 was of 7 hours and 43 minutes duration in all and the device was 

 moved 3 feet landward about every hour and 10 minutes, for a total landward 

 movement of 15 feet. The wave period was 5 seconds and the average wave 

 height offshore in 30 feet of water was 1.5 feet. The device, over the 

 entire run, reduced this wave height only 27 percent to I . I feet. As this 

 run was the first of its type in the series, a survey of the whole bottom 

 profile was made after the run. Only a small amount of headward erosion 

 of the shoreline occurred, with, as in Run 4, some movement and enlargement 

 of the nearshore bars. In the vicinity of the device, however, some rather 

 spectacular changes occurred. Evidently, the usual trench was dug beneath 

 the device, but only that segment of the trench which was dug in the final 

 position is shown in Figure 10, with the rest having been backfilled. The 

 landward progression of the device eroded the steep slope, noted in the 

 discussions of the two preceding runs, and placed only a small mound of 

 accreted material on its landward side. This' landward erosion amounted to 

 218 cubic feet, while the amount accreted was only 134 cubic feet, a net 

 loss of some 84 cubic feet of sediment. Seaward of the device, however, 

 only 89 cubic feet of material eroded, all from the steep slope, i.e., that 

 portion of it that became the trench as the device was moved. Seaward of 

 the rim of the final position trench, all of the material, about 248 cubic 

 feet, accreted. This material took the form of a long, deep, flattopped 

 mound, extending from the final position trench of Run 5 to over the land- 

 ward rim of the trench created during Run 3. Offshore of this mound was 

 a dip reflecting the filling of the Run 3 trench, and a subsequent mound 

 reflecting the seaward rim of this now-buried trench. Beyond this point, 

 the mound of accreted material tapered down rather sharply to the pre-run 

 profile. In all, only 89 cubic feet of sediment eroded, while some 248 

 cubic feet accreted on the seaward side of the device, a net gain seaward 

 of 159 cubic feet. 



From the results of Runs 4 and 5, It was concluded that the device, 

 when backed by a rather steep slope, contributed sediment some distance 

 offshore; much of it to points seaward of the device. It is likely that 

 the steepness of the slope landward of the device was too great for any 

 accretion to take place on It. 



f. Run 6 . For Run 6, the device was located about 18 feet land- 

 ward from the apex of fhe mound accreted at the inshore rim of the steep 

 slope during Run 5 (see Figure II). Due to the shallow depth of the water 

 at this location, the device was set at its highest setting, that is, the 

 rod connecting the flap valve rack to the vertical supports was passed 

 through the lowermost flap valve, making only one valve operable, the re- 

 maining three being suspended above the waterllne. At this setting, the 

 lowest edge of the flap extended about 5 feet beneath the Stillwater surface. 

 This run was static, the device remaining at the same location for the hour 

 and 17-minute duration of the run. The waves had a period of 5 seconds and 

 an average height of 1.4 feet in 30 feet of water. The presence of the 

 device again served to reduce the average wave height inshore of the device, 

 but produced only a 14 percent lower wave, with an average height of 1.2 

 feet. The device dug the usual trench but during this run, probably due 

 to both the shal low water depth and the length of time the device was 

 operated at one location, the trench was wider and deeper than those noted 



