Nature-Based Solutions: An Effective Approach for Flood Mitigation and Resilience over Urban Areas

Flooding stands as one of the most pervasive and severe climate hazards worldwide, with over 20% of the global population directly exposed to extreme flood risks, particularly in urban, low-income regions. These threats are projected to escalate in coming decades, driven by increasingly intense and frequent rainfall events resulting from climate change, disproportionately affecting densely populated developing economies and areas prone to extreme meteorological phenomena. This study addresses the growing flood risks in urban areas and advocates for the sponge city concept as an innovative and sustainable approach to flood management. The focus is on the Quad Cities - Davenport, Bettendorf, Moline, and Rock Island - where the study analyzes precipitation changes, evaluates spatio-temporal variations in flood patterns, and assesses the effectiveness of Nature-based Solutions (NbS) in mitigating urban flood impacts. By adopting a systems-thinking approach, the study develops a comprehensive methodology for identifying the optimal combination of NbS interventions that can effectively manage stormwater flooding in urban catchments, considering both historical conditions and future climate scenarios. Key metrics - such as volumetric efficiency, runoff efficiency, storage efficiency, and potable water supply - are used to evaluate the performance of various NbS strategies. To simulate the impacts of extreme rainfall events, statistically downscaled CMIP6 climate projections for the Quad Cities are employed, illustrating how NbS can mitigate the disturbances to natural hydrological cycles caused by rapid urbanization while fostering more resilient urban infrastructure and sustainable water management. Ultimately, the findings underscore the critical need to integrate NbS into urban planning as part of a broader strategy to enhance flood resilience and effectively manage the mounting risks posed by climate change. The study offers a systems-based framework for urban planners, providing insights for the development of robust, adaptable, and sustainable water management strategies that account for the complex interactions between hydrological, sociopolitical, and environmental systems.