Question

Consider the following statements:
1. A regime channel will have side slopes of value 0.5 H : 1 V.
2. Lacey's regime formula is applicable to regime channels with sediment concentration more than 5000 ppm
3. For a Lacey regime channel the Manning roughness coefficient is estimated by Strickler's formula
4. The mean velocity in a Lacey channel is proportional to $R^{2/3}$ where R = hydraulic radius.

Which of these statements are correct ?

• A. 1 and 2
• B. 1 and 4
• C. 2 and 3
• D. 3 and 4

Answer 1

The correct option is D 3 and 4

In open channels, the Darcy-Weisbach equation is valid using the hydraulic diameter as equivalent pipe diameter. It is the only sound method to estimate the energy loss in man-made open channels. Though for various reasons, empirical resistance coefficients like Chezy, Gauckler-Manning-Strickler equations are used to calculate roughness coefficient.