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Chapter 3 - Theoretical considerations
agreement. Additional measurements in irrigation channels in San Luis Valley in Colorado did not
fit very well with the predicted values.
He concluded that
• a self-stabilization of the bed occurs, due to armoring of the bed surface
• the armoring layer is found to be essentially constituted of the biggest grain size fraction, but
some small and smallest fractions are found yielding behind the coarse grains.
• the grain size distribution of the armor layer depends on the grain size distribution of the
substrate and the average bed shear stress to which the bed was submitted.
• for too high bed shear stresses (about 2 ⋅ θ cr ), no self-stabilization takes place.
page 34 / November 9, 2002
Wall roughness effects on flow and scouring