Hydrodynamic modeling and flood mitigation strategies in an Andean Valley City

Abstract

This study introduces an integrated urban flood mitigation framework specifically tailored for Andean valley cities with complex river systems and steep topography, addressing a critical gap in hydrodynamic modeling for such challenging urban watersheds. Through a case study in Loja, Ecuador, high-resolution topographic surveys, distributed hydrological modeling (HEC-HMS), and two-dimensional hydraulic simulations (HEC-RAS) are employed to evaluate stormwater behavior across micro-watersheds for return periods of 10, 25, 50, and 100 years. The methodology informs the design of stormwater detention tanks, floodable parks, and parallel conduits to the existing U-shaped channel, forming a context-specific hybrid green-gray infrastructure strategy calibrated for extreme topographic gradients and constrained urban development patterns. Simulation results demonstrated the effectiveness of these interventions in preventing flooding under a 50-year return period and reducing flood-prone areas by 70% during a 100-year event. Importantly, this research introduces a transferable design framework for mountainous urban environments where conventional flood control is constrained by topography and land-use patterns. By integrating hydrodynamic modeling with scalable, low-footprint interventions, the approach offers practical solutions for climate-resilient urban planning in high-relief regions. This work contributes to Sustainable Development Goals (SDG 11.5, 11.B, and 13.1.1) by reducing flood-prone areas by 70% and protecting approximately 15,000 citizens. It further supports SDG 13 (Climate Action) through a 25.10% reduction in peak flow discharges, as demonstrated by hydrodynamic simulations. Limitations include assumptions inherent to static models and the absence of real-time hydrometeorological data. Future studies should incorporate sensor-based monitoring, refined climate projections, and economic assessments to enhance predictive capacity and long-term resilience planning.