Free Web Tool · FHWA HEC-18

Bridge Scour

CSU pier scour equation, simplified abutment scour, and contraction scour per FHWA HEC-18 — for design check at piers and abutments.

Input

1.0 cyl, 1.1 sq, 0.9 sharp
1.1 plane, 1.3 dunes

Results

Froude Fr
Pier scour ys (CSU)
Contraction scour Δyc
Total local scour at pier
Method

CSU pier scour: ys/y1 = 2.0·K1·K2·K3·K4·(a/y1)^0.65·Fr^0.43, Fr = V/√(g·y1). Live-bed contraction scour (Laursen): y2/y1 = (Q2/Q1)^(6/7)·(B1/B2)^k1; estimated here from area ratio.