CressHelp - Scour - Scour in free flowing water

Cress Help - Scour - Scour in free flowing water - Z22.1

Bend scour in a river

To make a preliminary prediction of the over depth in the outer bend of a river in relation the depth in a vertical, the following equation can be used:

equation 1

in which :

B = river breadth [m]
h₀ = depth of the river in a vertical [m]
R = curve of the centre line of the river bend [m]

This equation is based on both model and prototype experiments in major rivers in which the grain diameter of the bed/bottom material varies between 0.3 and 63 mm. The results obtained with the equation lie within an accuracy of 25 %.

If R/B falls outside the critical limit a calculation is still made, but with the remark that the validity limits of the equation have been exceeded.

The time scale for the changes in the transverse profile of a river bend can be given by:

equation 2

In which:

s = sediment transport per unit of breadth [m²/s]

y = Shields-parameter

The value of the sediment transport can be calculated with calculation rule 29, "Sediment transport".