A circular pipe has a diameter of $1 \mathrm{~m}$, bed slope of 1 in $1000,$ and Manning's roughness coefficient equal to 0.01 . It may be treated as an open channel flow when it is flowing just full, i.e., the water level just touches the crest. The discharge in this condition is denoted by $Q_{\text {full. }}$ Similarly, the discharge when the pipe is flowing half-full, i.e., with a flow depth of $0.5 \mathrm{~m},$ is denoted by $Q_{\text {half }}$ The ratio $Q_{\text {fill }} / Q_{\text {half }}$ is:
(A) 1
(B) $\sqrt{2}$
(C) 2
(D) 4

A circular pipe has a diameter of $1 \mathrm{~m}$, bed slope of 1 in $1000,$ and Manning's roughness coefficient equal to 0.01 . It may be treated as an open channel flow when it is flowing just full, i.e., the water level just touches the crest. The discharge in this condition is denoted by $Q_{\text {full. }}$ Similarly, the discharge when the pipe is flowing half-full, i.e., with a flow depth of $0.5 \mathrm{~m},$ is denoted by $Q_{\text {half }}$ The ratio $Q_{\text {fill }} / Q_{\text {half }}$ is:
(A) 1
(B) $\sqrt{2}$
(C) 2
(D) 4