Measurement of bedload discharge in nine Illinois streams with the Helley-Smith sampler

Samples collected with the Helley-Smith bedload sampler provide useful information about transport of sand-size sediment in Illinois streams. Samples provide the basis for bedload-discharge rating curves for the Rock and Kaskaskie Rivers and Henderson Creek. Comparison of measured bedload discharge with bedload discharge computed for selected flow conditions from channel characteristics allows the selection of an appropriate indirect method for determining bedload discharge for the Spoon, Kishwaukee, and Edwards Rivers. No one indirect method best represents bedload discharge in studied streams. No bedload-discharge rating curve was developed for the La Moine River, because the two measured bedload discharges are not sufficient for development of a rating curve and do not agree well with discharges computed by any of the three indirect methods. The dominant size of bedload particles in all streams sampled give results which cannot be used at this time. Collection-bag clogging may have been significant in the Green River, and large bed material gains or high flow velocities may have interfered with the operation of the sample in the Vermilion River. (USGS)