Water sampler and flow measurement for runoff containing large sediment particles

A flow-measuring and composite water-sampler system was needed for sampling sediment-laden flows containing large rock particlebs from strip-mine spoil erosion plots. The median percentage of soil particle sizes greater than 16 mm of the greater-than 2 mm fraction was 25%. A modified drop-box weir was used for measuring flows, and for providing a well-mixed water and sediment flow that could be sampled. A "diverter" composite sampler was designed to divert the entire flow from a waste position to a sample position, and precluded the need to subsample (split) the sampled flows. Indoor testing of the sampler showed the sampler worked well with the modified drop-box weir Field evaluation showed the sampler and drop-box weir worked well under natural rainfall conditions. Recommendations for improvement in sampler and weir operation are given. Use of the sampler for other applications is also discussed.