Relating Sediment Delivery Processes and Sediment Connectivity at the W2 Experimental Calabrian Basin

In the framework of soil erosion processes at different spatial and temporal scales, the concept of connectivity is applied to express the physical link among hillslopes and the channel network concerning flow motion and associated sediments. In this paper, basin sediment connectivity was used in the framework of the Sediment Delivery Distributed (SEDD) model together with sediment yield measurements performed at the W2 experimental basin (Calabria, Italy) in the period 1978–1994. The frequency distribution of the travel time was used to estimate the coefficient βL of the structural component of the sediment delivery ratio of each morphological unit. Then, using the event sediment yield data, the sediment balance equation was applied to estimate the coefficient βF of the functional component of the sediment delivery ratio. The analysis demonstrated that the increase in event intensity produces a decrease in βF and a consequent increase in the sediment delivery ratio. At the annual scale, the sediment balance equation, coupled with a relationship to estimate βF by the runoff coefficient, allowed for obtaining a good agreement between the measured and calculated sediment yields. The errors in the estimate of basin sediment yield were less than or equal to ±40% for 71.4% of cases. The reliability of the SEDD model is good for both the investigated event and annual scales and improves from the former to the latter, which is, therefore, particularly suited for applications. The model can also be applied to a variety of basins worldwide where it has previously been used without differentiating the structural and the functional connectivity components.