Correct Answer - Option 3 : Time of flow
Explanation:
Time of flow:
It is defined as the ratio of the length of the sewer to the velocity of the flow in that sewer when it is running at full depth.
\(Time\;of\;flow = \frac{{Length\;of\;sewer}}{{velocity\;of\;flow\;when\;running\;at\;full\;depth}}\)
