Fluctuations of bed load solid discharge and grain size distribution on steep slopes with image analysis

A new device using image analysis has been designed to measure the grain size distribution and the solid discharge of natural particles downstream of an experimental mobile bed flume. Experiments were performed in a 10 cm wide, 15% steep flume, with both uniform (4–5 mm) and non-uniform materials (3–15 mm). For the uniform material, outgoing solid discharge fluctuations were not significant, whereas they were large for the non-uniform material. The lower solid discharges were coarser than the higher solid discharges; this behavior is associated with the smallest particles playing a major role through building and destroying transient antidune-like bedforms.