Analysis of river dynamics of fiumare in southern Italy

The most peculiar fluvial environment in Southern Italy is the fiumara morphology, which identifies short braided rivers, which generally flows from steep valleys downwards to large riverbeds made of coarse sediment. These seasonal streams are subject to ephemeral and torrential regime, with continuous changes due to the discharge variability, passing from sudden catastrophic floods, when aggradation/degradation phenomena take place, to long inactive equilibrium periods, in which the riverbed assumes a final shape. Aiming at evaluating the main features of the erosion/deposition phenomena in the fiumara streams, two measurement surveys of the fluvial geometries, carried out at 20 years apart in 25 river sections of Calabria region, were compared. The results show a predominant though moderate erosion trend, which is more evident considering only the sections near the coasts. In all cases, the slight temporal variation indicates a substantial balance after years of heavy human activities, such as weirs constructions and uncontrolled inert removal in the riverbeds. Particularly, for the longest river of Calabria, the Crati River, a degradation phenomenon has been recognized, due to the reduced transport capacity and the huge coarse sediment removal. This trend is still being implemented, although greatly diminished compared to the past.