Submitted to: Proceedings of the World Water and Environmental Resources Congress
Publication Type: Proceedings
Publication Acceptance Date: 3/31/2005
Publication Date: 7/22/2005
Citation: Hua, L., Barkdoll, B., Kuhnle, R.A. 2005. Bridge abutment collar as a scour countermeasure. Proceedings of the World Water and Environmental Resources Congress. May 15-May 19, 2005; Anchorage, AK. p. 395. 10.1061/40792(173)395. Interpretive Summary: The channels of agricultural watersheds often are unstable and prone to erosion. Erosion caused by unstable channel boundaries may threaten agricultural lands as well as critical parts of transportation infrastructure such as bridge supports. Countermeasures to erosion are needed to protect lands and structures adjacent to unstable channels. A laboratory study was conducted using a model stream channel to develop and test new methods to prevent erosion in the vicinity of a model bridge support located on a stream bank. A protective sheet structure (collar) was designed to be placed at the foot of the bridge support to protect it and the adjacent bank from erosion in this study. The collars work by providing an erosion resistant surface to erosive high-velocity storm runoff flows. The collars designed and tested in this study reduced local erosion by up to 87%. This technology will provide a new method for use by managers to protect structures from erosion in agricultural and other watersheds. Countermeasures of this type provide protection for structures and provide improvements to aquatic environments by reducing the erosion, movement, and deposition of sediment in streams and rivers.
Technical Abstract: To mitigate abutment scour, flat, horizontal, steel collars were attached around a wing-wall abutment ending at the main channel edge in a laboratory flume channel under clear-water flow conditions. It was found that these collars were able to protect the bridge abutment efficiently by eliminating secondary vortices that ordinarily would cause local scour. The minimum collar dimensions that eliminated local scour were a width of 0.23 L perpendicular to the flow (L is the abutment length perpendicular to the flow direction) and a flow-parallel length of 0.7 times the flow parallel-abutment width. It was determined that a top-of-collar vertical location of 0.08 ym (where ym is the main channel flow depth) below the mean bed sediment elevation gave the best results of scour reduction. In addition, the collar not only reduced scour magnitude near the abutment, but also retarded the development of the scour hole.