Magnitude-frequency analysis of bed load data in an Alpine boulder bed stream

[1] The purpose of this study is to investigate the connection between bed load, channel processes, and sediment sources in mountain basins using data from the Rio Cordon basin (northeastern Italian Alps). The main channel is a steep, boulder bed, step pool stream, and bed load volumes are measured at a special facility where particles >20 mm are trapped. Results from a combined frequency analysis of peak water discharges and total bed load volumes based on 17 years of field data are presented, focusing on discrepancies between recurrence intervals of peak discharge and bed load volume for each event. A cause of major disturbance is a high-magnitude, low-recurrence event that occurred in 1994. Dimensional and nondimensional bed load intensity-duration curves are also reported, which emphasize differences between short- and long-duration events. The relationship flow–bed load rates (investigated using a total of 180 data) shows no breakpoints, and two different curves are evident, representing pre-1994 and post-1994 floods, respectively. The analysis demonstrates both the control exerted by sediment availability on bed load transport rates and the persisting long-term impact of major floods on mountain streams.