Figure A7 . 



Nesper basket bed-load sampler 

 (from Hubbell 1964) 



0.2, depending on particle size and bed-load transport 

 rate. In general, a basket sampler has a sediment- trapping 

 efficiency of about 0.45 (Hubbell 1964). Box and basket- 

 type samplers were popular prior to 1940 and were used to 

 check the validity of various predictive relationships for 

 bed-load transport rates (Hubbell 1964). 



(2) Pan or tray samplers 



Pan or tray samplers consist of an entrance ramp leading to 

 a slot or slots. Sediment that has rolled, slid, or 

 skipped up the ramp is retained in the sampler. An example 

 of the pan or tray sampler is the Polyakov sampler, shown 

 in Figure A8 . Shamov (1935) found that the Polyakov 

 sampler sediment- trapping efficiency for flow speeds from 

 1.3 to 1.75 ft/sec (39.6 to 53.3 cm/sec) was about 0.46; 

 the sediment -trapping efficiency of the sampler decreased 

 at flow velocities greater than 2.1 ft/sec (64 cm/sec). 

 Several versions of these samplers were developed, with 

 varying ramp designs and numbers of slots. Shamov reports 



A12 



