Soil erosion and sediment transport represent major environmental challenges in semi-arid Mediterranean watersheds, where high erosion rates do not necessarily translate into high sediment delivery to river systems. This study assesses sediment regulation ecosystem services in the Nfifikh watershed (Morocco) to clarify how landscape connectivity controls sediment export, retention, and internal buffering processes. A spatially explicit connectivity-based modelling approach was implemented using the InVEST Sediment Delivery Ratio (SDR) model, integrating a 30 m digital elevation model, land use and land cover data (2019), soil properties, and rainfall erosivity factors within a GIS environment. The results reveal a marked decoupling between potential soil erosion and effective sediment transfer. Despite high erosion potential in upstream areas, sediment export remains spatially limited due to reduced connectivity, whereas midstream sectors with moderate erosion exhibit higher sediment delivery efficiency. High SDR values are confined to a limited number of well-connected zones, while large portions of the basin function as sediment sinks. Valley-floor deposition locally exceeds 1100 kg yr -1 , under-scoring their buffering capacity. Ecosystem service indicators further show spatial differentiation between avoided soil erosion and avoided sediment export, reflecting the role of land-cover configuration in regulating sediment fluxes. Overall, the findings demonstrate that sediment regulation is primarily governed by landscape connectivity and land-cover structure rather than erosion intensity alone, providing transferable insights for ecosystem-based watershed management in semi-arid Mediterranean environments.
Saleh Eddine ZAHLI (Thu,) studied this question.