Generalizing Sediment Transport Experiments From Narrow Flumes to Wider Channels

Abstract

Laboratory flumes are powerful tools for investigating riverine processes in a controlled environment. However, the proximity of flume sidewalls modifies the flow relative to natural river channels, and sidewall corrections are crucial for obtaining accurate estimates of bed stress. Sidewall corrections are well‐studied for flumes with aspect ratios (width/depth) greater than one but not for narrower flumes. There has been an increase in grain‐scale dynamics research that uses flumes with widths of just a few grain diameters and aspect ratios down to 0.1 (very narrow flumes). We investigate whether sediment transport experiments in very narrow flumes can be generalized and compared to flow and sediment transport in wider channels. Using a compilation of 400 flume experiments, including 100 with width/depth <1, we find that the influence of sidewalls can be explained by the same theories in very narrow flumes as in wider flumes. However, the classic Vanoni‐Brooks sidewall correction makes an approximation that does not work as well in very narrow flumes. For very narrow flumes, we recommend a more recent sidewall correction. We also investigated whether the flume aspect ratio influences grain‐scale dynamics by applying the sidewall correction method to experiments on grain shape in bed load transport. Our results suggest that there is no effect of the flume aspect ratio on bulk sediment flux relations or on the influence of grain shapes, indicating that sidewalls do not strongly affect grain‐scale dynamics in bed load sediment transport.