Hydraulic resistances of large unlined canals in noncohesive soils

Conclusions

• 1. The hydraulic resistances of a large unlined canal in noncohesive soils (for conditions of a clarified flow) are determined by the uniqueness of the hydraulic regime during establishment of relative stabilization of all main elements of the flow and channel.

• 2. The use of the kinematic index x, characterizing the rate of change in velocities vertically and being a function of the hydraulic resistances, as a criterion of the mobility of bed forms makes it possible to estimate the state of stability of dune forms on various stretches of a large irrigation canal running in an earth channel.

• 3. An arbitrary assignment of the roughness coefficients n is impermissible when determining hydraulic resistances and longitudinal gradients of a large unlined canal with channel-forming elements. The hydraulic gradients providing longitudinal stability of a straight channel can be predicted both by the traditional method (in terms of n) but with consideration of the regular variability of n and on the basis of the established relationship between hydraulic resistances and the channel shape parameter.