z\ 



-DRIVE MECHANISM 



BASIN 3s 



BASIN 2 



BASIN 1 



VERTICAL - * FL0W 

 INPUT 

 PIPE 



BASINS 



6.1m 



TESTING SECTION 



FLOW RAMP 



Figure 21. Test section used in sand trapping tests 

 Flow and Transport Conditions 



Comparison with other measurements 



63. During the transport rate tests, the condition of the bed surface 

 was recorded. The type of sand motion and the configuration of the bed 

 surface were characterized by the Reynolds and Shields numbers, as will be 

 discussed in this section with reference to Figure 22. 



64. Figure 22 may be compared to a three-dimensional diagram proposed 

 by Southard (1971) to characterize bed configurations in uniform open- channel 

 flow. He used the variables of depth, mean flow speed, and sediment grain 

 size. Southard's diagram was presented as a series of depth-flow speed 

 sections (graphs) for various sediment grain sizes. Therefore, the bed 

 configuration and transport rate in uniform flow are functions of water depth, 

 indicating that Figure 22 is not universal but pertains to the 20 -cm depth 

 used in the experiment. Simons, Richardson, and Nordin (1965) discuss 

 bedforms generated under uniform flow in a large tank. 



45 



