Sediment and channel mobility management: the Magra River project (Central Italy)

A research project was carried out with the aim of defining strategies for management of sediment and channel mobility, based on the comprehension and analysis of geomorphic processes. The research included the following phases: 1. Geomorphological study of channel evolution, morphological forms, processes, and sedimentary features of the main alluvial channels of the Magra catchment. The interpretation of present trends of channel adjustments was conducted by analysing geomorphological maps and by assessing the historical channel changes from the comparison of aerial photos, and by conducting intensive field surveys. 2. Identification of areas suitable for potential sediment recharge. Based on a series of main factors (lithology, landslides, physiography, and land-use), we defined an index of potential recharge by landslides and an index of potential direct recharge from the hydrographic network. We calculated such indices for all the sub- catchments, thus identifying the more suitable areas for possible coarse sediment supply. 3. Quantification of sediment transport and sediment budgets. Sediment transport was estimated by using hydraulic formulae.. 4. Definition of strategies and guidelines for managing sediments and lateral channel mobility. The concept of ‘erodible river corridor’ or ‘functional mobility corridor’ has been applied to the Magra and Vara rivers, and obtained through a GIS analysis by overlapping the corridor of historical (last 50 years) channel shifts with zones of possible future erosion (next 50 years). A ‘map of strategies for sediment management’ was obtained, as a synthesis of all the aspects previously studied (morphological evolution, sediment budgets, areas of potential sediment recharge in the catchment).