New approaches for improving the management of torrent control works in mountain catchments

In mountain basins, controlling sediment transport during floods often involves installing hydraulic structures. However, the effectiveness of these measures requires regular monitoring and maintenance is often lacking. This study proposes new tools to assess torrent control works' status and functionality and prioritize management interventions, and then to quantify their effects on sediment (dis)continuity, based on field assessment and high-resolution terrain data. The development and application of a workflow to assess the maintenance status of torrent control works (e.g., check dams and bed sills) was accomplished in the Vegliato catchment (FVG Region, Italy), where the Maintenance Priority index (MPi) was first tested to evaluate the status and functionality of torrent control works, distinguishing those needing maintenance or re-planning to those in good conditions. The MPi results show that 16% of control works require immediate maintenance, while 45% need intervention to ensure durability. Additionally, 13% require re-planning due to low functionality. The remaining 26% was found in good condition. High-resolution topography data from ALS (Airborne Laser Scanning) surveys were used to analyze multi-temporal geomorphic changes by means of DTM (Digital Terrain Model) of Difference (DoD) analysis. From the DoD, the quantification of sediment mobilization helped to construct a Sediment (dis)Continuity Ratio (SCR), capable of assessing how the continuity of sediment fluxes along the channel is influenced by the torrent control works. In this way it is was possible to identify those structures impeding or promoting the passage of sediment cascade throughout the whole torrent control system according to their degree of maintenance. The analysis of SCR showed structures in the upper catchment promoting continuity, while those in the middle and downstream sections primarily promoting discontinuity. These findings, obtained thanks to simple, innovative and robust parameters, provide insights for prioritizing maintenance and planning interventions for effective sediment control in mountain basins.