The investigation of shape factors in determining scour depth at culvert outlets

Excessive scour at the culvert outlets is one of the main reasons for culvert failure. Many research have been proposed to investigate this phenomenon. However, no uniform equation can be found to predict the maximum scour depth in the literature. In the present study, a list of selected equations are tested and compared with experimental measurement. It is found that Valentin equation and Kerenyi equation can yield a good prediction for rectangular culverts. While Liriano and Azamathulla equation can provide better results for circular shape culverts. The impact of densimetric Froude Number (Fd) and flow shallowness (hd/R) on scour depth at culvert outlets is analyzed and presented. One empirical relationship is proposed to estimate the maximum scour depth by including shape factors. The proposed relationship is further tested using extra experimental data, and a good agreement has been noted.