sediment for the shoreline area accretion, but considerably more sediment 

 for accretion seaward of the device, which began on the offshore side of the 

 trench and continued seaward, filling the trench created during Run 15, then 

 tapering down the slope. The peaks of the accretion mounds remaining after 

 Run 15 were slightly eroded, also supplying some sediment. 



Planimetering the compared profiles from this run and Run 15 shows that 

 58 cubic feet accreted on the landward side of the device, 187 cubic feet 

 eroded, a net erosion of 129 cubic feet. Seaward of the device, 355 cubic 

 feet accreted and 205 cubic feet eroded, a net accretion of 150 cubic feet. 

 The rather small amount of accretion that occurred landward of the device 

 during this run would appear to demonstrate an unsuccessful dredging device, 

 especially in light of the beach-building wave characteristics employed 

 during this run. 



4. Cone I usions 



The results and analyses indicate that the device, in its present 

 form, is unsuitable for moving sand shoreward from offshore sources. Table 

 8 shows that the results are not entirely consistent. For example, during 

 Run 7, the novel behavior of the flotation pads acting in conjunction with 

 the flap valves appeared to produce a pumping effect that may well have 

 caused the resultant mound of accreted material. This mound was not moved 

 shoreward during Run 8 in spite of the similarity of the impinging wave 

 conditions. Run 14 is the only other run in which significant landward 

 accretion occurred, but the effect of the beach-building wave used for the 

 run is not known. The small positive net gain from Run 15, and the negative 

 result from Run 16, cast doubt on the usefulness of the device, even under 

 beach-building wave conditions. The offshore wave height was reduced 46 

 percent by the presence and operation of the device during Run 16. This 

 decrease represents a usage and reflection of about 70 percent of the off- 

 shore impinging wave energy, yet the energy was obviously used to move 

 sediment offshore rather than onshore. 



Such variegated results are more than likely byproducts of the scale 

 effects present in the test. For example, the device was tested over a 

 coal profile over slopes averaging about I on 18, while in nature, shore- 

 face slopes steeper than I on 60 are quite uncommon. Another area in need 

 of more understanding is that of the water mass transport profile, that is, 

 the onshore^off shore velocity distribution over the shoreface. A compre- 

 hensive understanding of this phenomenon and its relationship with the 

 presence and operation of the device would probably cast considerable 

 light on the results. 



The operation of the device, however, serves to illustrate the possi- 

 bility of a great potential for the utilization of wave power. It appears 

 that if the sediment placed in suspension with the passage of the wave trough 

 could be directed so as to remain within the region of the landward motion 

 of the next wave crest, and if this landward current could be directed to 

 place the sediment far enough inshore to be beyond the reach of the trough- 

 generated seaward current, a similar device might prove successful. 



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