The value of maximum scour depth estimated using the Lacey’s formula is 9.0 m. The bridge site is at right-angled bend. The value of constant for maximum depth of scour at right-angled bend is 2.0. Assume Lacey’s silt factor for river bed as 1.0. Estimate the flood discharge under a bridge.
- A831 m³ /sec
- B841 m³ /sec
- C851 m³ /sec
- D861 m³ /secCorrect
Solution
Concept
Lacey regime
Formula
R = 0.473 (Q/f)1/3
Step-by-step solution
1. 9 = 2R ⇒ R = 4.5 m. 2. Q = f (R/0.473)³ = 861 m³/s.
Explanation
Right-angled bend factor 2.
Why the other options are wrong
Others do not follow.
Correct answer: D) 861 m³ /sec