Recent channel adjustments of major rivers in southern Apennines (Italy): a contribution to the understanding of fluvial response to human impact and climate change

As highlighted by several studies, many Italian rivers have been affected at least since the mid-1950s by relevant channel adjustments, mainly consisting in pattern changes, channel narrowing and lowering, which are largely thought to be controlled by human interventions on the catchments and/or directly on the river systems. This is true also for major rivers of southern Italy, but the case studies are still limited especially when compared to those available for central and northern Italy. Our contribution deals with the analysis of channel adjustments that have affected some of the major Southern Apennines rivers: the rivers Biferno, Trigno and Volturno (Molise), Calore (Campania), Fortore and Ofanto (Puglia), Sinni (Basilicata) and, finally, Crati and Savuto (Calabria) which during the last decades, have all been undergone some type of human intervention such as the construction of dams, in-channel mining, etc. Our reconstruction of channel adjustments is based on a multi-temporal analysis in a GIS environment of topographic maps, aerial photos and orthophotos carried out on selected river reaches, and on the assessment of their actual morphological setting and dynamics by means of field surveys and DGPS topographic measurements. The comparison of obtained results highlight a common evolutive trend consisting in pattern changes from braided to wandering or sinuous, a strong channel narrowing, mostly exceeding 80%, and a moderate to very high channel incision, while, concerning the last 10 years only, some of the investigated rivers, the Savuto and Crati rivers, appear to be affected by an inversion of this trend, consisting in channel enlargement and the increase of fluvial bars. In order to investigate on the possible influence of anthropic and natural factors, the relationships between the reconstructed channel modifications and the main interventions on single river systems at the channel scale and rainfall trends are analysed