Bedload transport rates in a step-pool channel at near-bankfull flows

Abstract

This paper examines unit bedload transport rates (BTRs) at near-bankfull flows within a small step-pool channel in the Ouachita Mountains of central Arkansas. For this study, five runoff events with peak discharges between 0.25 and 1.34 cms (1.0- to 1.6-yr recurrence intervals) were produced in a natural channel using a streamflow simulation system. BTRs range from 3.5x10^-6 to 3.3x10^-2 kg/sec/m during these events and are somewhat lower in magnitude than those reported previously for step-pool channels. BTR behavior is best modeled using discharge, but the relationship differs significantly between events with peak flows less than 0.61 cms (1.1 yr) and those greater than 0.88 cms, (1.2 yr). The smaller events exhibit higher BTRs than the larger events at flows from 0.11 to 0.35 cms, but similar rates at higher discharges. Slope coefficients are within the range Ryan and Troendle (1996) determined for two step-pool sites in Colorado. BTRs show similar positive relationships to both shear stress and stream power, but these relationships are weaker than the one with discharge. These results support the idea that sediment availability limits BTRs in step-pool channels.

Citation

Marion, Daniel A. 2001. Bedload transport rates in a step-pool channel at near-bankfull flows. In: Proceedings of the Seventh Federal Interagency Sedimentation Conference: 2001 March 25-29; Reno, NV. [No place of publication]: Subcommittee on Sedimentation: III-32 to III-39. Volume I.