Flood Mitigation and Water Resource Preservation: Hydrodynamic and SWMM Simulations of nature-based Solutions under Climate Change

Urban flood mitigation strategies are increasingly recognizing the potential of Nature-Based Solutions (NbS) to enhance city resilience while promoting water resource sustainability. This study presents a quantitative assessment of NbS implementation in Zaio, North-East Morocco, quantifying their dual benefits in flood reduction and water conservation. We evaluate the efficacy of detention ponds and riparian reforestation for fluvial flood mitigation, alongside vegetative swales, permeable pavements, and green roofs for pluvial flood risk reduction in a vulnerable urban neighborhood. To account for climate change impacts, we employed a modified Intensity-Duration-Frequency (IDF) curve adjusted for the Representative Concentration Pathway 8.5 (RCP8.5) scenario, forming the basis for our 100-year return period flood simulations. A 2D hydrodynamic model was utilized to simulate the effects of detention ponds on fluvial flood depths, while the Storm Water Management Model (SWMM) quantified the impact of green infrastructure on pluvial flood discharge. Our results demonstrate significant flood mitigation potential: the proposed fluvial flood NbS reduced riverine discharge by 28.95%, while the combination of green roofs, permeable pavements, and vegetative swales decreased pluvial water discharge by 44.7%. Furthermore, we quantified the water resource savings resulting from NbS implementation, highlighting their contribution to water conservation in this semi-arid region. This research provides robust evidence for the effectiveness of NbS in urban flood management and water resource preservation. The findings offer valuable insights for urban planners and policymakers, presenting NbS as a multifunctional tool to enhance urban resilience against flood risks while addressing water scarcity concerns. This study contributes to the growing body of knowledge on sustainable urban water management strategies in the face of global environmental change.