Forest Service Bridge Scour Evaluation: Screening, Analysis and Countermeasures

John Kattell

Scour, defined as "the erosion or removal of streambed or bank material form bridge foundations due to flowing water" is the most common cause of highway bridge failures in the United States. The Forest Service, U.S. Department of Agriculture, administers 7,650 bridges on National Forest lands and virtually all of them are over water. Scour is also the single most common cause for bridge damage and failure on National Forest lands. In 1998, the Forest Service Engineering Technology Development Center developed a scour evaluation program in response to a Federal Highway Administration Technical Advisory to require evaluation of all bridges for susceptibility to damage resulting from scour. The project was to outline a single process and establish criteria, methods, and guidelines that would ensure consistency throughout the agency and eliminate duplication of effort.