U.S. Department of Transportation


Date of this Version



Published in Hydraulic Engineering: Saving a Threatened Resource—In Search of Solutions: Proceedings of the Hydraulic Engineering sessions at Water Forum ’92. Baltimore, Maryland, August 2–6, 1992. Published by American Society of Civil Engineers.


Tens of millions of dollars have been spent over the years on Federal-aid highway system bridges damaged by floods. Nearly 500,000 of the 577,000 existing bridges within the National Bridge Inventory are over waterways. The screening of these bridges over waterways for scour susceptibility will be completed, for the most part, by October 1992. The Federal Highway Administration has established January 1997 as the completion date for the scour evaluations of all existing bridges identified as scour susceptible. A cost-effective means of determining the specifics of bridges with unknown foundations is not currently available. Pending the development of technology to determine unknown foundations, these structures must be monitored during routine National Bridge Inspection Standards inspections and following significant flood events. The only exception to this course of action is for unknown foundation bridges on the Interstate system, which must be evaluated for scour before the January 1997 target date. This paper presents the existing bridge scour evaluation requirements, the magnitude of the overall scour evaluation program and the status of progress to date.