Leveraging soil diversity to mitigate hydrological extremes with nature-based solutions in productive catchments: an application and insights into the way forward

Abstract. Nature-based solutions (NbSs) are increasingly explored to mitigate floods and agricultural droughts in productive catchments. However, the influence of local factors, such as soil characteristics, on the effectiveness of these interventions is often overlooked, as commonly used modelling approaches oversimplify interactions across soil–water processes. This study presents an innovative approach to model NbS scenarios, revealing the influence of the spatial variability of soil properties on their performance. A fully distributed, physically based hydrological model was used to represent NbSs at the catchment scale, explicitly simulating soil–water fluxes (e.g. infiltration, evapotranspiration, runoff). This model uses measurable local parameters (e.g. topography, soil properties, vegetation) to capture small-scale hydrological processes and represents NbS scenarios via their adjustments. Simulations were conducted for two catchments: one agricultural and one forested. In the agricultural catchment, measures included hedgerows, reduced tillage and soil pitting in maize crops. In the forested catchment, NbSs focused on forest diversification, practices aimed at limiting soil compaction and the restoration of peatlands. NbS performance in mitigating floods and agricultural droughts was assessed using spatial indicators. The models accurately reproduced discharge and saturated zone dynamics, capturing natural soil drainage characteristics and their interaction with NbS effectiveness. Results highlight that NbS performance strongly depends on natural soil drainage characteristics. In well-drained soils, hedgerows enhanced infiltration by improving soil hydraulic properties and boosting evapotranspiration. In waterlogged soils, more limited gains were observed. Well-drained soils offer co-benefits to agricultural drought mitigation, as they are prone to water deficits that NbSs can mitigate. Future evaluation of NbS effectiveness should recognize the spatial variability in performance to better inform their selection and placement. This study may serve as a basis for discussion and action, supporting decision-makers in implementing these measures in a coherent territory-based approach. It also reveals current knowledge gaps and identifies avenues for future research to refine NbS effectiveness assessments, such as strengthening the availability of spatially distributed data and advancing uncertainty analysis.