online_contraction_scour_live_bed:  Contraction scour under live bed conditions
using modified Laursen 1960 equation

Modified Laursen formula

ys / y1 = ( Q2 / Q1 ) 0.86 (W1 / [W2) k1  -  ( yo / y1 )

[ yo, y1, Q and W in any consistent set of units ]
[ S1 in m/m or ft/ft ]
[ T in °C or °F ]
[ D50 in mm or ft ]

Reference:

Evaluating Scour at Bridges, FHWA Hydraulic Engineering Circular No. 18,
 Fifth Edition, 2012.

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