Restoration of the Sarca River (Trentino), a mesohabitat-based assessment approach

Restoration of selected reaches of the Sarca River was implemented/planned by the local man- agement entity (the Sarca Fluvial Park) in 2024-2026, and the outcomes of the restoration were assessed with an eco-hydraulic approach. One reach was restored with a very simple frame- work, i.e., the deposition of about 200 massive boulders in the riverbed, to improve the morpho- logical heterogeneity, thus creating habitat for fish fauna. However, the environmental amelio- ration, quantified by the macroinvertebrate communities, was less than expected. A second, morphologically-complex reach, was therefore extensively surveyed to propose a more effec- tive approach. We surveyed the reach twice in 2025, with drone imaging, hydrological sur- veys and modelling, mesohabitat surveys, and application of the mesoHABSIM methods to the macroinvertebrate communities, which represents a novel methodological approach. As a result of such multi-disciplinary survey, sediment injection rather than physical restructuring was recommended as the restoration method to apply in the reach.