Estimation of Scour Depth Downstream of Grade-Control Structures

Grade control structures are hydraulic structures used to stabilize a river bed. Scour downstream of this structure is the main cause of its failure. Studies have developed numerous empirical relations for scour depth prediction that designers must choose between to decide the most effective equation for a specific application. This study tested the condition of submerged jets over beds of sediments (median size = 1.5, 2.4, 3.15 mm) downstream of a weir for discharges of 10, 15, 20 l/sec and tail water depths of 16, 21, 26 cm. The analysis applied multi-dimensionless group regression using Minitab software to predict maximum scour depth. All previous relations were compared to the data and it was found that the relations developed by Veronese A, Mason and Arumugam, Agostino and Ferro, and Chee and Padiyar predict the scour depth better than do other relations. In addition, a new relation was developed that produced better results at RMSE = 0.015 and coefficient correlation = 94%.