online_scour_froehlich (1988):  Calculation of pier scour using the Froehlich (1988) formula   


Fr1 = v1/(g y1)1/2

ys = 0.32 b φ Fr10.2 (be / b)0.62 (y0 / b)0.6 (b / D50)0.08 + b

[ SI Units (metric):  ys, y0, b and be in m ]
[ U.S. Customary Units:  ys, y0, b and be in ft ]
[ Fr = Froude number; g = gravitational acceleration ]


DESCRIPTION      [Sample Input]     [Main page]

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 b (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.

  • Pier nose shape (Fig. 2), to determine the shape co-efficient φ.

  • φ = 1.3 for square-nosed piers.

  • φ = 1.0 for round-nosed piers.

  • φ = 0.7 for sharp-nosed piers.

Fig. 2  Common pier shapes.

Documents in Portable Document Format (PDF) require Adobe Acrobat Reader 5.0 or higher to view; download Adobe Acrobat Reader.