Commonly used bridge pier scour prediction equations have often employed the quantities of relative coarseness, flow shallowness, and flow intensity to yield a design value for maximum relative scour depth at equilibrium conditions. Predictive methods based on these quantities tend to over-predict scour. Moreover, these equations tend to yield different scour estimates for the same flow conditions. The equations, mostly derived from laboratory estimates of scour, have not considered the influence of the flume sidewall proximity. New experiments are conducted to specifically identify the role of channel blockage on scour. Evaluation of results indicates that the influence of blockage ratio on scour can be described using the value of mean flow velocity along the separating streamline and the ratio of the separation velocity to the critical velocity in the form of new parameter kc. A new scour prediction method is developed and presented.
