Section 4: Soil and Water Conservation Engineering
Open Channel Flow
Subtopic: Open Channel Flow
Question Statement:
For the most hydraulically economical trapezoidal open channel section:
Options:
(A) The channel cross-section forms half of a regular hexagon, side slopes are $1 : 1/\sqrt{3}$ ($60^\circ$ to horizontal), and hydraulic radius $R = y/2$
(B) Side slopes are $1:1$ and $R = y$
(C) Bottom width equals $y/2$
(D) Side slopes are vertical
Answer Key:
A
Step-by-Step Solution & Explanation
A semi-hexagon inscribed in a circle with water surface as diameter yields maximum hydraulic radius $R = y/2$ and side slope $60^\circ$ (or $1:\sqrt{3}$ with vertical).