High resolution simulation of urban compound flooding under climate impacts

Flooding in the coastal built environment poses significant risks to communities and infrastructure, with climate change expected to exacerbate these threats through sea level rise (SLR) and increasing storm intensity. This study investigates the effects of climate change on extreme compound flooding due to SLR) and intensified extreme rainfall in Hoboken, New Jersey. An ultra-high-resolution, “street-scale” hydrodynamic model, based on the computationally efficient SFINCS (Super-Fast INundation of CoastS) framework, is developed. By incorporating urban features, the model captures the interactions that govern flood dynamics in the built environment at a 1.5-m resolution. The model is calibrated and validated against post-tropical cyclone Ida observations, including crowdsourced flood reports and photographic evidence, achieving 84.8 % agreement with observed flood locations and matching flood depths within ±5 cm at validation points. Future climate projections under both moderate and high-emission scenarios are then applied to the validated Ida event to demonstrate how compound flood models can evaluate evolving flood risks under climate change. We find that while SLR primarily affects neighborhoods near the shoreline, rainfall intensification generates more widespread flooding throughout the study area. Most significantly, compound flooding scenarios produce substantially different and more severe impacts than the sum of individual drivers. The assessment of critical infrastructure reveals differentiated vulnerability, with some facilities showing greater sensitivity to SLR and others to rainfall intensification, necessitating tailored protection strategies.