An Overview of Scour Types and Scour-Estimation Difficulties Faced at Bridge Abutments

The paper describes the range of scour types that may occur at bridge abutments, and addresses the extensive attendant difficulties confronting accurate estimation of abutment-scour depth. The difficulties, which include similitude aspects of laboratory experiments on scour at bridge abutments, complicate the development of reliable scour-estimation relationships. In a practical sense, the difficulties imply that estimation relationships can only be of approximate accuracy. They stem from the nature of the approach flow–field, the soil and sediment conditions at typical abutments, and thereby from the mix of scour and slope-stability failure processes potentially at play in the vicinity of bridge abutments. The full set of failure processes has yet to be determined and documented, and inevitably entails extensive investigative experiments using laboratory flumes. Arguably, the difficulties have muddled perceptions of scour extents observed at bridge sites, and have contributed to a certain level of skepticism regarding existing relationships used for scour-depth estimation.