Functional Trends of Scour at Bridge Piers

The functional trends of the local scour depth at a bridge pier in subcritical flow are discussed and related to flow and sediment parameters leading to a framework within which the scour depth under given conditions can be estimated. The local scour depth is shown to depend primarily on the shear velocity or mean velocity ratio to the value at the beginning of sediment movement, u*/u*c or U/Uc, the grading of sediment and flow depth relative to pier width. The functions presented are based on laboratory data.