Unlocking sediment connectivity by the SEDD model and sediment yield measurements at the small experimental SPA2 basin in Sicily (Italy)

Studying erosion and sedimentation at different spatial scales, the concept of connectivity represents the physical linkage among different structural elements within a basin regarding flows and associated sediments. Sediment delivery ratio is considered a measure of sediment connectivity, and it can be related to the basin structural connectivity (morphological unit and travel time) and the hydrological connectivity (rainfall-runoff processes). In this study, sediment connectivity was assessed by the SEdiment Delivery Distributed (SEDD) model and sediment yield data for 73 events at the SPA2 experimental basin (Sicily, Italy) in the period 2000–2022. For this basin, the coefficient β L of the structural component of the sediment delivery ratio, SDR i , of each morphological unit was estimated using the frequency distribution of the travel time for each morphological unit. Subsequently, using event sediment yield data, the coefficient β F of the functional component of SDR i was estimated by SEDD. This analysis showed that the functional connectivity depends on the erosion event magnitude, and for low events, the global sediment connectivity is controlled by its structural component. At the annual scale, SEDD was calibrated establishing a relationship between the annual coefficient β F,a of the functional component and the rainfall erosivity. Finally, an uncertainty analysis was developed by Monte Carlo simulations to establish the influence of knowledge uncertainty and the stochastic variability of the model parameters on calculated sediment yield.