Modeling Sediment in Gravel-Bedded Streams Using HEC-6

Abstract

Analytical tools are needed to evaluate the environmental impacts of sediment loading on gravel-bedded rivers. The HEC-6 version 3.2 sediment transport model was evaluated to determine its applicability, at different physical-model scales, to sediment transport and bed-particle-size studies in gravel-bedded systems. Data from flume studies, a man-made canal in south-central Colorado, and a reach of a salmonid spawning river in central Idaho were used to evaluate HEC-6 predictions. Bed degradation was simulated successfully in a flume study. The trends in bed-surface armoring in flume and canal studies were simulated using sediment transport capacity functions based on critical thresholds for sediment movement. Sediment transport at the field scale was overestimated at low flows and underestimated at high flows. The calculated long-term flushing of sand-size particles from the bed substrate of a natural gravel-bedded river successfully approximated field measurements.