Coupling Probabilistic Flood Inundation and Road Network Accessibility Modeling to Assess Flood Risk and Cascading Impacts from Severe Storms in Houston, TX

Severe storm impacts in recent years (i.e., 2015 through 2017) have highlighted the vulnerability of Houston's infrastructure to both pluvial and fluvial flooding, signaling the shortfall of existing regulatory floodplain maps to represent actual flood risk. In fact, a significant portion of reported flood damages over the last decade originated outside of the regulatory floodplains. Having accurate flood risk maps, therefore, is crucial in aiding city-wide disaster mitigation planning and emergency response, and also in supporting the region's future growth and long-term resilience goals. To address this need, this work introduces a framework that integrates probabilistic flood inundation modeling with a road network accessibility model (i.e., Access to Critical Facilities or ACF model). A pilot study is conducted for a highly urbanized, flood prone watershed, Brays Bayou. Probabilistic inundation maps for recently updated design storms (i.e., NOAA Atlas 14 2018) are generated using HEC-RAS, a hydraulic model developed by the U.S Army Corps of Engineers. These maps are then used to inform the ACF model to provide valuable accessibility metrics including road link status, connectivity loss, and travel time to and from critical facilities such as hospitals and fire stations. This versatile framework could easily be extended to other flood vulnerable watersheds in Houston to evaluate current flood risks for future development and mitigation planning, and to help identify accessibility bottlenecks or vulnerable road segments in various storm conditions.