Landward of the device final location, about M cubic feet of material 

 accreted, while 258 cubic feet eroded, producing a net loss of 247 cubic 

 feet. Seaward of the final position, about 228 cubic feet of material 

 accreted, while only 6 eroded, producing a net accretion of 222 cubic feet. 

 It appeared rather clearly in this run that the sediment eroded from the 

 landward side of the device was deposited on its seaward side. Tilting 

 the flap rack shoreward also seems to have produced negative results. 



k. Run II. For Run II, the device was relocated on the level 

 shelf inshore of its position during Run 10 (see Figure 16). Since it was 

 to operate in shallow water, the device was reset so that only one flap was 

 operable. It was to be operated while in a vertical attitude so the lowest 

 edge of the flap extended about 5 feet below the Stillwater surface. It 

 was hoped that a mound of accretion, similar to that created inshore of 

 the device during Run 7, would be repeated, and perhaps be even larger, 

 considering the 9-second wave period with an offshore average wave height 

 of 3.4 feet that was to be used during Run II. This run was of the static 

 type, with the device remaining on station for about one hour and 17 minutes 

 of wave action. As shown in Figure 16, no mound was accreted landward of 

 the device, but a very wide and deep trench was dug beneath its position. 

 Seaward of the rim of this trench was a rather thick layer of accreted 

 material covering the slope. At the downslope terminus of the accreted 

 material, a small pocket of erosion occurred. While no sediment was 

 accreted inshore of the device, 126 cubic feet eroded, all from the landward 

 portion of the trench. Seaward, however, 253 cubic feet eroded, mostly from 

 the trench, but 375 cubic feet accreted, producing a net seaward gain of 122 

 cubic feet. 



Run II tended to reinforce the idea that the flotation pad pumping 

 effect, noted in Run 7, was significant in the accretion of the large mound 

 inshore of the device, and that without that effect, with the device moving 

 normally as in Run I 1 , no landward accretion would be realized. 



I. Run 12. For this run, the device was moved only a short dis- 

 tance inshore from its position during Run M , so that a significant amount 

 of material would be accreted to landward. As may be noted in Figure 17, 

 this did not happen. Run 12, again, was of the static type and lasted for 

 one hour and 17 minutes, as did Run II. The wave period for this run was 

 9 seconds as before, but the average offshore wave height was increased to 

 3.6 feet in 30 feet of water. As the device was to be located just over 

 the inshore slope of the trench dug during the preceding run, it was set 

 so that two flaps would be operative, the edge of the lowest one extending 

 about 9.5 feet below the stillwater line with the device in a vertical 

 attitude. This run caused a small mound of accretion, about 19 cubic feet 

 in volume, to be created with its apex about 52 feet inshore of the device 

 location. The device eroded a trench almost as deep as that dug during 

 Run II, but of considerable width on its inshore slope. The creation of 

 this broad but rather gent.le inshore slope, beginning at the seaward limit 

 of the accreted mound and extending to the point of maximum trench depth, 

 succeeded in eliminating most of the level area inshore of the device 

 location noted in the two previous runs. 



22 



