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Beef cattle feedlots contain unconsolidated surface material that accumulates within feedlot pens during a feeding cycle. Runoff from feedlot surfaces is diverted into settling basins. The storage capacity of the settling basins will be substantially reduced if large quantities of solid material are transported in runoff from the feedlot surfaces. The objective of this study was to identify the hydraulic conditions that will not move unconsolidated surface material located within feedlots in order to minimize sediment transport. Selected sizes and a composite sample of unconsolidated surface material were placed within 0.75 m wide by 4.0 m long metal frames. Flow was then introduced at the top of the frames in successive increments. The discharge rate and flow velocity necessary to cause movement of unconsolidated surface material was measured. Hydraulic measurements were used to determine the ratio of critical flow depth to particle diameter, critical flow rate, critical flow velocity, critical shear velocity, critical Reynolds number, critical shear stress, critical dimensionless shear stress, and critical boundary Reynolds number. Measurements of these parameters for the composite material were 0.

Beef cattle feedlots contain unconsolidated material that accumulates on the feedlot surface during a feeding cycle. This study was conducted to measure the effects of varying diameters of unconsolidated surface material and varying flow rates on nutrient concentrations in runoff. Unconsolidated surface material with an average diameter of 4.76, 9.53, 19.1, or 47.5 mm and a composite sample with a 15.2 mm mean diameter were placed within 0.75 m wide × 4.0 m long plot areas. Flow was then introduced at the top of the plots in successive increments, and runoff samples for water quality analyses were obtained. Particle diameter significantly influenced runoff concentrations of dissolved phosphorus (DP), particulate phosphorus (PP), total phosphorus (TP), NH 4-N, and solids transport.

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