This study evaluates the use of several pier scour equations for estimation of pier scour depth and then compare their results with the 3D model simulated using software like Flow-3D so that we may be able to conclude which equation yields closest value to the simulated model,which in our case is considered as a replacement for field data.Bridge piers scouring is one of the leading causes of bridge failure worldwide.Numerous pier-scour equations have been proposed – based on laboratory and field experimentations and data – for calculation of the potential scour depths at current and future（proposed）bridges.Since different pier-scour equations have been proposed using various criterions – based on the understanding of the author and the available resources like laboratory,equipment,field access,available data,parameters considered and time etc.– they tend to estimate scour depth with lots of variations from each other.Equation improvements continue to be made with the ultimate goal of minimizing underestimation and overestimation of scour.If pier scour is underestimated,scour depths assumed in the bridge design could be exceeded during large floods.Excess scour could lessen support for the bridge pier and destabilize the bridge.To ensure that pier-scour depth is not underestimated,some empirical equations have been adjusted to yield more conservative（larger）scour estimates.However,calculated scour depths from those equations might indicate that more bridges are scour-critical（subject to failure due to scour）than is actually the case and thus may lead to expensive over-design or unnecessary retrofitting of pier foundations.Hence a comprehensive study was needed to evaulate the different proposed equations,which is the purpose of our research.