Evaluating the role of hydrological and sediment connectivity in runoff and sediment transfer on the Loess Plateau: An in-situ field rainfall experiment

Hydrological and sediment connectivity are dominant factors to characterize hillslope erosion material transport. Large-scale interventions cause connectivity changes, which in turn affect sediment discharge rates. However, the relationship between erosion, sediment transfer and connectivity remain unclear. In this study, field in-situ rainfall simulation experiments were conducted with five treatments, namely, terrace plot (TP), root system plot (RP), upper terrace and lower bare land plot (TBP), upper terrace and lower root system plot (TRP) and control group to explore the connectivity changes between vegetation and terrace patches, as well as their regulation on erosion and sediment transfer. Results showed that the changes in hydrological and sediment connectivity among different treatments were not synchronized. RP has the lowest hydrological connectivity, while TBP was the highest. TRP, with a hydrological connectivity value of 0.54, showing no significant difference with RP (P > 0.05). In terms of sediment connectivity, TRP was the lowest. Meanwhile, compared with other treatments, the sediment connectivity reduction rate (ICRE) of TRP was as high as 12.1 % to 12.3 %. These results illustrated that if the rainfall duration continues to increase, the upslope terrace construction and downslope vegetation restoration (TRP) will be more stable. In addition, there was a certain interdependence between slope erosion and connectivity. As sediment connectivity increased, both runoff and sediment yield increased linearly. These results highlight the need to incorporate both hydrological and sediment connectivity into runoff and sediment control strategies. This study also suggests that, compared with a single measure, appropriate integrated measures can lead to better soil and water conservation outcomes.