First Evaluation of Soil Erosion and Sediment Delivery in the High Part of the Tevere Watershed

In the Mediterranean area, soil erosion is a physical process of degradation caused by losing particles from soil surface due to raindrop impact and run-off events. It is important to analyse and study erosion effects on hydraulic constructions, river-beds and so on, because predicting soil loss is necessary to establish and value the soil conservation measures and the variability of the geo-hydrological parameters in the mathematical simulation. Firstly, we analyzed the erosive processes on the Tevere watershed (Italy) by using the RUSLE equation. Furthermore we determinated the real morphology of the Montedoglio lake before construction and four years ago by using photogrammetry and bathymetric measurement. The downstream section for the analyzed watershed is placed on Montedoglio dam, in the province of Arezzo (Italy). So, we have estimated the theoretical sediment quantity moved every year in the watershed by RUSLE (potential erosion) and the real quantity of sediments deposited in the lake every year (net erosion). In addition, we analysed an empirical method to estimate, point-by-point, the Sediment Delivery Ratio (SDR). We were then able to value the total error committed by using the RUSLE equation and the SDR method to determinate the annual quantity of sediment deposited in the lake.