Section 4: Soil and Water Conservation Engineering
Gully Control Structures & Drop Spillways
Subtopic: Straight drop spillway inlet capacity
Question Statement:
A straight drop spillway has a horizontal rectangular weir crest of length $L = 2.5\text{ m}$. For a design total head over the crest of $h = 0.60\text{ m}$, using the broad-crested weir equation $Q = 1.77 L h^{3/2}$, the discharge capacity is ________ $\text{m}^3/\text{s}$ (round off to two decimal places).
Answer Key:
2.06
Step-by-Step Solution & Explanation
Applying the drop spillway inlet equation:
$Q = 1.77 L h^{3/2}$
Substituting $L = 2.5\text{ m}$ and $h = 0.60\text{ m}$:
$Q = 1.77 \times 2.5 \times (0.60)^{1.5} = 1.77 \times 2.5 \times 0.4648 = 2.06\text{ m}^3/\text{s}$