Using Case Studies of Bridge Scour in Rhode Island to Evaluate Simplified Scour Equations

Document Type

Conference Proceeding

Date of Original Version



This paper uses case studies of scour at bridges in Rhode Island to evaluate the current HEC-18 scour equations used to assess bridge safety and design. The study utilizes data from two major historical storm events - a 500-year flood and a 25-year hurricane (Sandy). Hydraulic analyses were performed using the HEC-RAS program at three bridge study sites, two in riverine environments and one in a tidal environment. Detailed bathymetry and topography of each site was obtained using a variety of methods. Flow boundary conditions were obtained from USGS gages and a numerical storm surge model. Sediment samples indicated that the bed materials were cohesionless ranging from silts to boulders. Scour predictions were compared to sounding data collected before and after the historical events. The results of the analyses indicated that the HEC-18 equations yielded conservative predictions of scour at all bridges analyzed in this study. The level of conservatism depended on the particular equation that was utilized. The results also suggested that the level of conservatism could be reduced by better characterization of the D50 of the bed materials and consideration of the transient nature of storm events.

Publication Title, e.g., Journal

Geotechnical Special Publication




GSP 313