The piers can be placed on the spillway crest to hold the sluice gate for controlling the flow or support a service bridge. In addition, these piers to be placed on spillway body provide air entry to prevent negative pressure on the crest and eliminate the risk of cavitation. However, piers and abutments reduce the flow section area and it may cause increasing in reservoir water level. This contraction in the section varies depending on the thickness of the piers besides shape of the cross section. There are some theoretical methods in literature to calculate reduce in effective length of crest. In this study, experimental studies have been done on circular and square section bridge legs in laboratory environment. The results obtained from the studies showed that there are serious differences between experimental and theoretical calculations.