Clear Water Scour at Circular Piers: A New Formula Fitting Laboratory Data with Less Than 25% Deviation

In this paper, we propose a new predictor for the time-dependent, spatially-maximum scour depth at a circular pier in clear-water flow conditions. In spite of a number of approaches used in scour research, a simple predictor based on data correlation still has merit because more insightful studies of the process dynamics lack engineering impact. Furthermore, the simple condition of a circular pier is a reference for several variabilities to be considered afterwards. The present formula is obtained using laboratory data from 30 sources, corresponding to 328 experiments over 66 years. The predictor accounts for 5 dimensionless parameters (pier slenderness, flow intensity. sediment coarseness, sediment uniformity. and time) and has a good predictive ability, largely outperforming that of 27 literature equations. The proposal of a new formula is accompanied by several considerations based on additional parameters and operational conditions, as well as by an analysis of the uncertainty of the computed scour values and recommendations for conservative predictions of the scour depth in engineering practice.