4 mm/hr

lOmm/hr

20 mm/hr

40 mm/hr

the time taken by rainfall water to run from most distant point of water shed to the inlet of sewer

the time required for flow of water in sewer to the point under consideration

sum of [a] and [b]

difference of [a] and [b]

much greater than 1

slightly less than 1

equal to 1

slightly greater than 1

less than 1.0 m/sec

1.0 m/sec to 1.2 m/sec

1.5 m/sec to 2.0 m/sec

3.0 m/sec to 3.5 m/sec

given in the direction of natural slope of ground

given in the direction opposite to natural slope of ground

zero

steeper than 1 in 20