Vc = Ku y1/6D501/3
Fc = Vc /(gy)1/2
For clear-water scour (F - Fc ≤ 0.2):
ys = 1.84 a Fc0.25 (y /a)0.3
For live-bed scour (F - Fc > 0.2):
ys = 2 a (F - Fc)0.25 (y /a)0.5
[ SI Units (metric): ys, y, a, and D50 in m; Ku = 6.19 ]
[ U.S. Customary Units: ys, y, a, and
D50 in ft; Ku = 11.17 ]
[ F = Froude number; g = gravitational acceleration ]
To determine the bridge scour depth ys,
the calculator requires the following input data:
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).
Median diameter of the bed material D50, in mm.
Fig. 1 Definition sketch.