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Urban flooding has been escalating risks in rapidly urbanizing regions, particularly under climate change. This study evaluates flood management strategy in a 297-Ha catchment of Pokhara, Nepal, by integrating Low Impact Development (LID) measures with conventional drainage upgrades under a 25-year design storm. Hydrological and 2D flood modeling in PCSWMM revealed that urbanization and inadequate drainage capacity have caused severe inundation along Lamachaur section, even during relatively frequent 2-year storms. Climate projections indicated no major increase in extreme rainfall depth but a higher frequency of intense events, highlighting increasing flood exposure. Implementation of LID strategies including permeable pavements, bioretention cells, and green roofs reduced total runoff by up to 67% and peak flows in several sub-catchments by more than 40%, demonstrating the effectiveness of decentralized, nature-based solutions. A combined approach of LID with upgraded drainage improved performance even with less LID measures, lowering total runoff by around 20%, reducing peak discharge, and significantly minimizing junction flooding. The study’s novelty lies in applying an integrated LID-structural framework under climate change in a Himalayan urban context, where such approaches often remain underexplored. These results provide clear, actionable guidance for sustainable flood risk management in data-scarce, rapidly growing cities.
Biswash et al. (Mon,) studied this question.