Scour Development at Isolated River-Bed Obstacles

by Peter C. Klingeman, Oregon State Univ, Corvallis, United States,
Cheng-Chang Huang, Oregon State Univ, Corvallis, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

Development of local scour was investigated for isolated obstacles on movable beds subject to clear-water scour. The resulting maximum scour depths, scour volumes, and obstacle displacements were determined. Tests involved partly submerged and barely submerged cubes, cylinders and spheres in a flume. Flow fields around partly submerged test obstacles resembled those for piers. When obstacles were slightly submerged, the overtopping flow modified the flow fields. Scour development during all tests produced horseshoe scour patterns, although wake zones were altered by `hydraulic jumps' behind some obstacles subject to overflow. Scour development caused progressive obstacle displacement. Obstacles tended to shift upstream slightly by being undercut and then sliding downward and dipping forward into the developing scour hole. Shape effects of cylinders and spheres became negligible compared to cubes as water depth increased. Predictive equations were developed for the maximum equilibrium scour depths and volumes.

Subject Headings: Scour | River and stream beds | Submerging | Spheres | Cylinders | Submerged flow | Rivers and streams

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