Influence of sediment supply on mountain streams bedload transport

Abstract

Sediment transport and storage in mountain stream channels are closely dependent on hillslope activities and bank erosion. This paper analyses bedload measured in 13 mountain streams (989 values with slope higher than 5%) in an attempt to investigate how much the sediment supply condition impacts bedload transport rates. First, the sediment supply condition of each stream was evaluated qualitatively using information available in the original studies. In the second step, the data set was analysed by comparing bedload transport rates considering a Shields stress ratio and by comparing transport rate efficiency with consideration of a dimensionless stream power. The two analyses indicate higher sediment transport rates for the streams identified as “connected” to an active source. The consequences for bedload transport prediction are discussed with a nonthreshold bedload equation. Even though predicting the exact sediment supply condition and the associated transport rate is not yet possible, this study suggests that defining an envelope delimiting minimum and maximum transport for a given river reach should be possible.