Validation of Some Bridge Pier Scour Formulae and Models Using Field Data

Estimation of maximum local scour at the pier site is necessary for safety and economy of the designed bridge. Numerous formulae are available for predicting maximum local scour depth at the pier site. Almost all of these formulae were developed based on laboratory data. Validation of these formulae using field data is necessary to recommend the formulae with a reasonable estimation. In this study, four formulae were selected for validation process using field data recorded from bridges subjected to scour in Pakistan, Canada and India and the data obtained from Qadar [7]. The selected formulae which were used for validation process had been proposed by Colorado State University (CSU), Melville and Sutherland, Jain and Fisher, and Lauren and Toch. Three statistical tests were carried out to determine the formulae equation with minimum prediction errors. They were mean absolute error (MAE), root mean square error (RMSE), and Theil's Coefficient (TC). The statistical tests showed that error in the prediction of maximum local scour depth using CSU formula was minimum compared to the errors in the prediction of the other three formulae. For CSU formula, the computed values of MAE, RMSE and TC were found to be 0.11, 0.93 and 1.24 respectively.