Large-scale flood risk analysis of distributed stormwater infrastructure serving 2300 catchments in New York State

Road overtopping leads to traffic disruptions, safety concerns, and structural stability issues. Large culverts are essential drainage structures that protect roads. Besides, large culvert installation can cost over a million dollars, and the whole portfolio of regional structures costs billions in replacement. In this research, we evaluated the flood resilience of large culverts serving 2,300 catchments across New York State. Equipped with terabytes of geospatial data and a scalable, uncertainty-aware modeling framework, we studied the spatial and temporal risk dynamics at systems-level. Our results indicate that about 16% (with an uncertainty range of 2-41%) of the culverts have hydraulic capacities below the 50-year design discharge, and 2-4% of them are expected to exceed their capacity annually, assuming the independence of the culvert capacity exceedance. The findings highlight that culverts that are a) located along main roads, b) exposed to pattern II rainfall, c) located within small watersheds, and d) constructed more recently, are, on average, more hydraulically resilient. Additionally, the analysis indicates that drier antecedent moisture conditions correspond to a significantly lower ratio of culverts facing capacity exceedance, whereas wet conditions exacerbate the system resilience. Also, we find that the probability of capacity exceedance increases over time, regardless of land use or precipitation projection scenario, but the rate of increase varies by the chosen scenario. Using the open-source repository developed for this study, this analysis can be scaled to other geographical regions globally.