Topographic Evolution of Scour Hole Around a Cylindrical Pier: An Experimental Investigation

Local scour occurring around bridge pier is three-dimensional in nature. A clear understanding of the scour evolution is essential for ensuring bridge safety, flood management, and the associated fluvial process. Evolution of the topography of the scour hole around a cylindrical pier was investigated based on long period, clear-water experiments. Results show that the evolution of the different dimensions of the geometric-parameters, like the depth, the width, upstream extent, plan area and the volume, all follow the logarithm law. The associated rate of change of the parameters follows the power law. The scour hole pattern exhibits self-similarity during the whole scouring process. The upstream part of the scour hole geometry can be described by a “Scour-Ellipse”, and the evolution of the ellipse and its geometric parameters follow the logarithm law. The area in the scour hole, where the bed slope angle exceeds the angle of repose is designated as the “Steep Slope Region”, and it is quite unstable during the initial stage of growth. The other portion of the scour hole area is defined as the “Gentle Slope Region”. Empirical formulas have been proposed to estimate the different scour parameters which can be adopted as a reference during bridge design and scour protection measures.