Low impact development strategies for enhancing urban flood resilience: hydrological and socioeconomic insights from São Paulo, Brazil

Nature-based solutions (NbS), operationalised in urban contexts through Low Impact Development (LID) practices, are increasingly recognised as effective strategies for enhancing urban flood resilience while delivering environmental, social and economic co-benefits. This study evaluates the hydrological performance, as well as the associated economic and social benefits, of six LID practices implemented as NbS for urban flood mitigation in the Aricanduva River sub-basin, São Paulo, Brazil. Two hypotheses were tested: (i) that LID-based NbS can attenuate hydrological responses under multiple implementation scenarios, albeit with varying effectiveness; and (ii) that sub-basin-scale NbS interventions can generate meaningful economic and social benefits in addition to hydrological improvements. Hydrological simulations were conducted using the HEC-HMS model to estimate runoff volumes and peak discharges across 21 scenarios, while floodplain dynamics and inundation extents were assessed using the HEC-RAS model. Economic and social benefits were quantified using the Green Values Stormwater Calculator, with parameters adapted to local conditions in São Paulo. The results indicate that hydrological performance is strongly influenced by both the total permeable area and its spatial distribution across the sub-basin. Scenarios achieving approximately 63% permeable surface coverage showed the highest effectiveness, reducing peak discharge and surface runoff volume by 76 and 77%, respectively, relative to the baseline scenario without LID. Life-cycle economic assessments suggest substantial benefits, primarily associated with energy savings, carbon sequestration, stormwater regulation and property value enhancement. Overall, the findings provide evidence supporting LID-based NbS as an effective, economically viable and socially beneficial strategy for urban flood mitigation.