Enhancing Bridge Hydraulic Assessment through Integrated Bathymetric and Topographic Data: A Case Study of the Grafton Bridge on the Red River

Ensuring the structural integrity of bridges is crucial, with scour analysis playing a fundamental role in ensuring public safety and advancing civil engineering practices. This research develops and validates a method for deriving river bathymetry near a bridge crossing site (5872 in Minnesota and 0017-140.372 in North Dakota) on the Red River of the North to enhance bridge scour analysis. By integrating high-resolution bathymetry from an autonomous surface vehicle (ASV) surveys with LiDAR topographic data, we refined water velocity predictions in HEC-RAS 2D (The Hydrologic Engineering Center’s River Analysis System) modeling. Accurate bathymetric and topographic data have proven essential for improving flood simulations and bridge scour assessments. It underscores the need for refined survey techniques to achieve optimal results in these analyses. The best method to generate the raster file was found using the geoprocessing tool TopoToRaster, which enables the creation of elevation points in areas that neither LiDAR nor ASV data could cover. Our results show that using this method of generating a terrain file from the surveyed points greatly improves the quality of flood simulations and bridge scour assessments. The simulation of a 100-year flood shows a maximum water surface elevation of 243.70 m at the bridge cross section, a 30 cm below the bridge soffit. This is very close to the designed flood level.