flow speed at the nozzle mouth to such a degree that it 

 buried itself during a 5-min testing period. Sand was 

 observed to move upflow from the rear of the sampler to be 

 collected in the sampler bag. A sand -trapping efficiency of 

 10.0 was calculated from two measurements. The H-S sampler 

 is not recommended for use in the near shore zone where sand- 

 sized particles are present. 



Tests employing two closely spaced streamer traps in the surf 

 zone gave comparable results, both in the magnitude of sand 

 transport and in the shape of the sand flux vertical distribu- 

 tion. If it is assumed that the transport rate was uniform over 

 a distance of approximately 2-3 m in a plane normal to the flow, 

 then the DUCK85 nozzle was from 50 to 90 percent consistent, and 

 the SUPERDUCK nozzle was from 50 to 100 percent consistent. 



Recommendations 



129. Based on the results of this study, it is concluded that the 

 streamer trap is an accurate and reliable apparatus for measuring rates and 

 vertical distributions of sand transport in the nearshore zone. The SUPERDUCK 

 and C streamer trap nozzles were judged to have fair to excellent sand-trap- 

 ping efficiencies . Qualitative observations of nozzle behavior on the bed 

 indicated that scour may occur at the lower lip of the SUPERDUCK nozzle for 

 approximately half of the testing period. It is recommended that the testing 

 period not extend past the 5- to 10-min interval presently employed. Behavior 

 of the C nozzle at the sand bed was observed to be ideal in the laboratory 

 tests. The sand- trapping efficiencies developed in this study can correct for 

 the effects of scour, although it is cautioned that the sand- trapping effi- 

 ciencies pertain strictly to unidirectional flow. 



130. A more extensive laboratory calibration program could be conducted 

 to better simulate wave -induced turbulence in the surf zone and more fully 

 explore the relationship between nozzle size and efficiency. A wider unidi- 

 rectional flow tank could be slightly modified to house a wave paddle that 

 could introduce an oscillatory motion perpendicular to the direction of flow, 

 similar to that which exists in the surf zone. If funding allowed, different 

 types of apparatus and instruments used to measure flow speed and ambient sand 

 transport could be employed to obtain more accurate measurements. The rela- 

 tionship between the length of the test section and the rate of sand transport 



98 



