Risk-based stormwater fragility curves for urbanized coastal flooding

• Published in: Journal of hydrology (Amsterdam) Vol. 661; p. 133436
• Main Authors: Shrestha, Ashish, Chini, Christopher M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2025
• Subjects: climate; Climate adaptation; climate change; Coastal stormwater infrastructure; Extreme events; Florida; Fragility curves; High-tides; infrastructure; Panama; risk; Risk-based approach; sea level; stakeholders; storms; stormwater; stream flow; United States Environmental Protection Agency; urbanization; watersheds; Florida; Panama; Climate adaptation; High-tides; Risk-based approach; Fragility curves; Extreme events; Coastal stormwater infrastructure
• DOI: 10.1016/j.jhydrol.2025.133436
• ISSN: 0022-1694

[Display omitted] •Hydrologic-hydraulic (SWMM) model was developed to assess airfield flooding.•Framework for stormwater fragility analysis using deterministic model is presented.•Risk-based fragility function consider extreme rainfall and sea level rise.•Fragility analysis informs infrastructure design and adaptation decisions. Stormwater infrastructure systems in urbanized coastal watersheds are subject to functional failure from storm surge and extreme precipitation under climate change, leading to cascading failure due to interdependencies of stormwater infrastructure with other critical coastal infrastructure systems. Adaptation planning and management of coastal stormwater systems requires a detailed understanding of system performance and the spatial distribution of flood risks across the watershed from multiple threats. Climate change-induced sea level rise and an increased occurrence of extreme weather events necessitate the incorporation of climate uncertainties into infrastructure design but come with challenges. An improved understanding of the risks from combined extreme events, such as high tides and heavy precipitation, within interconnected coastal stormwater systems is needed to begin addressing design challenges. We propose a risk-based approach to understanding the combined threat of sea level rise, storm surge, and extreme precipitation in a coastal stormwater system to offer climate-informed decision support tools for stakeholders. Fragility curves, which estimate the probability of functional failure of infrastructure components at a given stress level, are valuable risk-based planning tool for assessing critical infrastructure and identifying adaptation or upgrade needs. In this study, we create a framework for advanced, simulation-based stormwater fragility curves using a physically based hydrologic-hydraulic model for Tyndall Air Force Base near Panama City, Florida. The model was built using US EPA’s SWMM tool and was calibrated with high-resolution streamflow gauges. An overlay of spatial layers with the stormwater model helped identify critical areas within the catchment for specifying fragility curves under varying hazard magnitudes, represented as combinations of precipitation and sea level rise scenarios. The framework can be applied to other locations or restructured to generate fragility curves at the infrastructure component level, enhancing decision support. In summary, we found fragility curves to be an engaging and effective means of presenting risk under combined threats.