Evaluation of Natural, Existing, and Proposed Conditions of a Railway Arch Bridge over Limestone Creek in Jefferson County, Illinois

Hydraulic modeling holds great significance in the assessment of railway infrastructure, particularly in areas susceptible to flooding and changing river dynamics. This study investigates a railway arch bridge’s hydraulic performance under natural, existing, and proposed conditions, including two alternative modifications: replacement with a new three-span bridge and concrete liners with additional culverts. To conduct this analysis, the study employs 1D HEC-RAS hydraulic modeling, utilizing data obtained from field surveys of the river channel and bridge structure and a digital elevation model of the floodplain. StreamStats batch processing tool was used to calculate the peak discharges. Findings reveal that the existing structure is inadequate for handling flow, resulting in significant backwater and high outlet velocities during a 100-year flood event. The recommendation is to replace the existing structure and emphasize regular maintenance to prevent debris blockages and remove obstructions to ensure unimpeded water flow. This study demonstrates the precision of HEC-RAS in assessing hydraulic vulnerabilities, enabling informed decision-making for railway infrastructure enhancement and flood risk mitigation in vulnerable regions.