Abstract
<jats:p>Large differences have been reported for gravel bedload transport rates and their associated particle sizes measured with different samplers, both in flume and field studies. However, the differences vary widely between studies, and little is known about the processes or mechanisms causing those differences. This monograph compares gravel bedload measurements made with the commonly used 76 by 76 mm opening Helley-Smith pressure-difference sampler (H-S) to those made with bedload traps during snowmelt seasons at 19 sites in Rocky Mountain streams. Bedload traps are samplers specifically designed for collecting accurate samples of gravel bedload in coarse-bedded wadeable streams. Their unflared openings are 0.3 m wide, and bedload is collected in a 1.2 m long attached bag (4 mm mesh width). Bedload traps are deployed on ground plates anchored in the bed and spaced by 1-1.5 m across the stream, and sampling duration is typically an hour.</jats:p>