Assessing Erosion Mitigation Effectiveness of Nature-Based Solutions Using InVEST® SDR Modeling: Application to the Carapelle Basin

Mediterranean agricultural landscapes face significant challenges from soil degradation and erosion processes that compromise both productive capacity and downstream water resources, creating an urgent need for implementing sustainable conservation strategies through Nature-Based Solutions (NBSs). This research employed the InVEST Sediment Delivery Ratio (SDR) modeling framework to examine erosional dynamics and quantify the potential benefits of various NBS interventions within the 506 km² Carapelle catchment. Model calibration and validation procedures utilized empirical sediment yield observations from the 2007-2008 monitoring period, achieving optimal parameter adjustment with only 4.3% variance from field measurements. A 20-year measured weather data were used to run the InVEST SDR model. The investigation examined four distinct NBS implementation strategies: contour-based cultivation techniques (CF), conservation tillage practices (NT), vegetative cover establishment (CCs), and integrated management approaches (Comb). Annual soil displacement rates under baseline conditions ranged between 2.43 and 3.88 t ha⁻¹ yr⁻¹ across the study years, with corresponding downstream sediment delivery of 0.86-1.30 t ha⁻¹ yr⁻¹. Conservation tillage emerged as the most effective single intervention, achieving an average 72.2% reduction in sediment transport. The integrated strategy combining conservation tillage with cover crop establishment delivered optimal results, yielding 75.9% and 70.5% reductions in sediment export and soil displacement, respectively. Geospatial evaluation demonstrated that forested and shrubland areas exhibited the highest natural retention capacity, while cultivated landscapes presented the greatest opportunities for NBSs deployment. The findings confirm that NBSs substantially improve sediment retention ecosystem services within Mediterranean agricultural watersheds. The InVEST SDR modeling approach demonstrates robust capabilities for catchment-scale erosion assessment. These outcomes offer practical insights for developing evidence-based land stewardship policies and conservation strategies in erosion-vulnerable Mediterranean regions.