Historical scour data were collected by means of geophysical techniques and used to evaluate the scour-computation procedures recommended by the U.S. Federal Highway Administration and 12 other pub- lished pier-scour equations. Geophysical data were collected at 10 bridges in Indiana. For this evaluation it was assumed that the historical scour measured by use of geophysical techniques was associated with the peak historical discharge. The hydraulic conditions for the peak historical discharge were estimated by use of a model that computes water-surface profiles. For the evaluation, the results of the contraction and pier-scour equations were combined to determine a computed bed elevation, which was compared to the minimum historical bed elevation at the upstream end of the piers estimated from the geophysical data. None of the pier-scour equations accurately represented the historical scour at all of the study sites. On the basis of the limited data presented, the Federal Highway Administration procedures provided a combination of accuracy and safety, required by design equations, equal to or better than the other equations evaluated. The potential scour was com- puted according to the procedures recommended by the Federal Highway Administration. At two bridges, the procedures overpredicted historical scour by more than 10 feet, and at two other bridges, the proce- dure underpredicted historical scour by more than 5 ft therefore, the potential-scour computations need to be verified by additional data and sediment-transport modeling. Computed abutment scour appeared to be excessive at about half of the sites.
