Question

Permissible velocity in earth channel having sandy loam soil is

• A. 45 cm/s
• B. 60 cm/s
• C. 75 cm/s
• D. 90 cm/s

Hint:

Channel non-erosive velocities:
Sand = 45 cm/s
Sandy loam = 60 cm/s
Loam = 75 cm/s
Clay = 90--120 cm/s.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Non-scouring permissible velocity is the maximum mean water velocity that an unlined earthen irrigation channel can safely carry without causing bed and bank erosion.
Key Formula or Approach:
\[ v_{\text{actual}} \le v_{\text{permissible}} \]

Step 2: Detailed Explanation:
According to standard USDA-SCS and Central Water Commission (CWC) hydraulic design tables for unlined earthen channels:
- Fine sand: \(45\text{ cm/s}\) (\(0.45\text{ m/s}\))
- Sandy loam: \(60\text{ cm/s}\) (\(0.60\text{ m/s}\))
- Silt loam Loam: \(75\text{ cm/s}\) (\(0.75\text{ m/s}\))
- Clay loam Stiff clay: \(90 - 120\text{ cm/s}\) (\(0.90 - 1.2\text{ m/s}\))
Therefore, the recommended maximum permissible velocity for sandy loam soil is 60 cm/s.

Step 3: Final Answer:
Hence, the permissible velocity in sandy loam soil is 60 cm/s, matching option (B).