Integrated assessment of flood and subsidence hazards: A strategic approach for risk mitigation and water sustainability

The city of Morelia has experienced flooding since its founding in the 16th century and land subsidence since 1983. Although both phenomena have traditionally been studied independently, recent research suggests that subsidence acts as a conditioning factor for more severe flooding. This study analyzes the subsidence-flooding interaction through an integrated approach, combining subsidence scenarios derived from SAR data with a hydrodynamic flood model (FLO-2D). Subsidence scenarios were generated using InSAR datasets and by modifying a high-resolution LiDAR DTM to represent both present and future subsidence conditions. The FLO-2D model incorporated the existing urban layout and projected developments to assess the influence of urbanization. Regional flood modeling indicates that under current conditions, nearly 64 % of Morelia is subject to some degree of flooding when considering a 50-year return period rainfall event. A detailed analysis was conducted for three sectors exhibiting the highest subsidence rates. In all cases, flood hazard variables increased under the future subsidence scenario compared to the present. Moreover, when accounting for the projected urban expansion, results indicate that inadequate urban planning exacerbates the subsidence-flooding phenomenon. Urbanization contributes to flow accumulation by obstructing natural drainage paths and increases flow velocities due to the reduction of hydraulic areas. Additionally, urban expansion induces a cascading effect, redirecting runoff toward adjacent neighborhoods. This integrated approach provides a valuable tool for understanding the subsidence-flooding phenomenon and supports the design of green infrastructure solutions that foster sustainable and resilient urban development in the context of climate change.