Dinamica del Legname nei torrenti montani

The management of large wood (LW) in Alpine torrents is a complex and ambiguous task where the flood risk mitigation, suggesting the LW and riparian forest removal, can be in contrast with the river ecology and morphology. This study focuses on real-scale field tests in order to evaluate the LW dynamics in a mountain river. Data and information collected during the tests can contribute to the implementation of a network model of LW transport, and to the improvement of LW management and of the in-channel measures for the assessment of the hydraulic hazard. The study site is a river reach of the high-relief catchment of the Cordevole torrent (Belluno, Central Alps, Italy). The reach is about 660 m long and it includes cascades, riffle pool, and sub-reaches conditioned by consolidation check dams. During the snow melting season, LW transport tests have been carried out introducing groups of logs in the channel, observing their passage through several control sections, and surveying their displacement velocities and the dynamics of entrapment. First results highlight: i) the importance of the river morphology on the LW velocity; ii) the mechanism of the entrapment processes driven mainly by the relative flow submergence.