Assessing Future Urban Flood Risks: High-Resolution Modeling of Compound Coastal and Pluvial Flooding

Urban coastal regions are increasingly threatened by the compounded risks of high sea levels and intense rainfall, which are expected to worsen due to climate change. This growing threat necessitates more robust assessments of compound flood hazards and the development of climate adaptation measures. This study investigates the compound flood risks in a changing climate by utilizing a high-resolution flood model for a densely populated coastal urban area. A Super-Fast INundation of CoastS (SFINCS) model with a spatial grid resolution of 1.5 meters was developed to simulate compound flooding from storm tides and heavy rainfall in the Hoboken-Jersey City area of New Jersey. A constant infiltration rate is applied and used as a calibration parameter to represent the combined effects of stormwater conveyance systems without explicitly modeling the underground infrastructure. The model is validated against observed data from post-tropical cyclone Ida, using rainfall records, tide gauge data, and crowdsourced flood observations and imagery. Numerical experiments are conducted to evaluate the effectiveness of current flood adaptation measures under a range of future climate scenarios, including different sea level rise projections and increased rainfall intensity. The study demonstrates methods for assessing future changes to extreme compound flood extent, depth, and duration, that can help coastal communities and policymakers refine their flood management strategies.