Effects of Climate Change and Urbanization on Bridge Flood Vulnerability: A Regional Assessment for Harris County, Texas

Abstract

The failure of stream-crossing bridges during flood events can endanger human life, impede evacuation planning and emergency response efforts, and cause long-term disruptions to transportation systems and local and regional economies. Expanding urban development and changing precipitation patterns due to climate change can increase the frequency and intensity of high-flow conditions at bridge locations, potentially exacerbating flood-related damages. Thus, there is a critical need to evaluate how shifts in extreme precipitation and continued urban growth will affect peak flows and hydraulic conditions experienced by bridges. This study applies hydrologic and hydraulic modeling to investigate the individual and combined effects of climate change and urbanization on the magnitude of peak discharge, bridge freeboard encroachment, and flow velocity at stream-crossing bridge locations in 19 watersheds of Harris County, Texas. The developed framework provides a screening tool to assess the vulnerability of regional bridge infrastructure to high-flow events and to prioritize maintenance, retrofitting, and replacement efforts. The model results demonstrate that peak flows during a 1% annual exceedance probability event can increase by up to 40% by 2100 when considering the combined impacts of climate change and urbanization, with changes in precipitation generally contributing more than changes in land use. In 16 of the 19 studied watersheds, the 1% annual exceedance probability event is projected to occur at least twice as frequently by 2100. Across the region, an additional 36 bridges experience loss of freeboard due to the effects of urbanization and climate change, while notable increases in flow velocity (≥10%) are observed at 93 bridge locations, five of which are considered scour critical. Overall, the results of this study show that climate change and urbanization will influence the hydraulic conditions at bridge locations and therefore should be carefully accounted for in the design, operation, and maintenance of bridge infrastructure in the future.