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United States Department of Agriculture

Agricultural Research Service

Drop-box Weir
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When steam flows contain a large percentage of sediment, flow measurements can be inaccurate because the sediment can deposit in typical devices and invalidate the rating curve of the device, or sediment deposits can alter flow directions and velocities. The drop-box weir is a flow-measuring device that was developed in the 1960's to measure flow rates laden with sediment. The Weir forces turbulent flow and keeps sediment suspended as flow rate is measured. The original weir was limited because the rating curve was only applicable when stream channel slopes were < 5% and stream approach angles to the weir were <50. Recent research at Coshocton has shown that the weir can be modified to allow stream-channel slopes up to 75% and approach angels up to 450.  Additionally, the weir can be used at the base of erosion plots when the approach angel is 900 from runoff-collection gutters. The Coshocton wheel sampler was modified for use with the drop-box weir, and another sampler was invented to sample large rock particles in the runoff when used with the drop-box weir.

Last Modified: 10/19/2005
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