“…Both active and passive tracers have played an important role in the research on bedload transport (Bravard and Petit, 2000). A number of studies have focused on the relationship between the distance and the size of the transported elements (Helley, 1969;Butler, 1977;Ergenzinger et al, 1989;Church and Hassan, 1992;Hassan et al, 1999;Pyrce and Ashmore, 2003;MacNamara and Borden, 2004). Other studies have examined the limits to bedload mobilization (Petit, 1987;Schmidt and Ergenzinger, 1992;Barta et al, 1994;Wilcock et al, 1996;Wilcock, 1997;Ferguson, 2005;Petit et al, 2005a).…”