A modified Catchment Connectivity Index for applications in semi-arid torrents of the Mediterranean environment

The importance of sediment connectivity for watershed management needs accurate quantification tools, particularly in Mediterranean torrents, where soil erosion and sediment transport are often not tolerable. This study proposes a modified version (mCCI) of the Catchment Connectivity Index (CCI), theorized by Quinonero-Rubio, Boix-Fayos, and de Vente (2013). The modified index improves the calculation procedure, providing a more efficient description of the hydrological and geomorphological factors ofCCIand making easier its applicability for the operators with less field experience. ThemCCIis applied to evaluate the sediment connectivity at the catchment scale in a torrent of Calabria (Southern Italy). This case study has shown how and by what extent the natural (climate changes) and human impacts (land-use changes and check dam installation) have influenced the geomorphic processes influencing sediment circulation in the studied basin throughout six decades. From 1955 to 2012, a general decrease in sediment connectivity has been caught bymCCI. This was the combined effects of greening-up processes of the catchment (due to both natural afforestation and human-induced reforestation) and the installation of check dams, which have decreased the catchment potential to circulating sediments. Overall, themCCIcan be used as an analytical tool to evaluate the influence of past or future changes in natural and human-induced changes in land use and climate actions by comparing scenarios of torrent connectivity.