Question

Lacey's theory is used for the design of

• A. Canal
• B. Regulator
• C. Fish ladder
• D. Apron

Hint:

Associate key theories with their applications in irrigation design:
- Kennedy's & Lacey's Regime Theories $\rightarrow$ Design of unlined canals in alluvial soil.
- Khosla's Theory $\rightarrow$ Design of foundations for weirs/barrages on permeable soil (to prevent piping failure).
- Bligh's Creep Theory $\rightarrow$ An older, simpler theory for the same purpose as Khosla's.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
What is Lacey's regime theory used for?

Step 2: Key Application (Alternate):
Design of stable alluvial canals—no silting, no scouring. Gives dimensions (width, depth, slope) for given discharge and silt factor.

Step 3: Detailed Explanation:
Based on regime concept: canal achieves dynamic equilibrium with sediment transport. Kennedy's theory preceded Lacey's. Lacey provided equations for perimeter, area, slope. Not for dams, weirs, or bridges. Silt factor f = 1.76√d_mm.

Step 4: Final Answer:
Design of unlined alluvial canals.