ys /y1 = 2 K1 K2 K3 (a / y1)0.65 Fr10.43
[ SI Units (metric): ys, y1, a, and L in m ] [ U.S. Customary Units: ys, y1, a, and L in ft ] [ Fr = Froude number; g = gravitational acceleration ]
Reference:
Evaluating Scour at Bridges,FHWA Hydraulic Engineering Circular No. 18, Fifth Edition, 2012.
To determine the bridge scour depth ys, the calculator requires the following information:
Flow depth directly upstream of the pier y1, in m (or ft).
Mean flow velocity directly upstream of the pier v1, in m/s (or fps).
Pier width in a horizontal direction normal to the flow a (Fig. 1), in m (or ft).
Fig. 1 Definition sketch for pier scour.
Pier length L (Fig. 1), in m (or ft).
Angle of attack θ of the flow, in degrees, to determine the correction factor K2.
Pier nose shape (Fig. 2), to determine the correction factor K1.
Fig. 2 Common pier shapes.
The bed condition (a choice between clear-water, plane bed and antidune flow, small dunes, medium dunes, and large dunes), to determine the correction factor K3.