The impact of old abandoned weirs on sediment longitudinal connectivity

There is a lack of knowledge concerning the effects of weirs on sediment longitudinal connectivity. This issue is addressed through the multi-scale analysis of the impact of old abandoned weirs on bedload transport. Based on volume estimates of sediment trapped in reservoirs, grain size analyses and measurements of bedload transport, this study demonstrates that weirs act as leaky barriers that allow bedload to pass through, although the individual geomorphic setting plays a primary role in determining the local sediment continuity. These results suggest that river connectivity is less impacted than initially thought and is likely to increase over time as old weirs gradually fall into disrepair.