Field verification of predictive bedload formulas in a coarse bedload mountain stream

Field verification of the applicability of bedload predictive formulas to coarse-bedload high-gradient mountain streams has received relatively little study as compared to similar work in sand bed streams. This study attempted to verify the applicability of two types of predictive bedload formulas, a discharge type and a tractive force type, to Squaw Creek, a coarse bedload high-gradient mountain stream. The Schoklitsch (1934) formula was chosen as a discharge type and the Meyer-Peter and Muller (1948) formula was selected as a tractive force type. The predictions of these formulas were also compared to predictions generated from Bagnold's simple theoretical expression for unit stream power. Discharge, water surface slope, bed slope, water density, bedload particle size and bedload quantity were measured instantaneously during the 1983 and 1984 bedload transport events. A technique, which proved very successful, was developed for simultaneously measuring water surface and bed slope. The appropriate parameters were substituted into the formulas and the resulting predicted quantity of bedload was compared to the quantity actually measured in the stream. Field observations of channel features and changes in channel morphology were made to enable explanations for any variance between predictions and measurements.