Define the following: (a) drainage area, (b) run-off coefficient (C), (c) travel time (ti), and (d) time of concentration (tc).

Question

What will be an ideal response?

Answer 1

(a) Drainage area is that area of land that contributes to the runoff at the point
where the channel capacity is to be determined. This area is normally determined
from a topographic map.
(b) Runoff coefficient (C) is the ratio of runoff to rainfall for the drainage area.
The runoff coefficient depends on the type of ground cover, the slope of the
drainage area, storm duration, prior wetting, and the slope of the ground. For
small drainage areas, typically only type of ground cover and slope of the
drainage area are considered in determination of runoff coefficients.
(c) Travel time (ti) is the ratio of flow length to average flow velocity for a
specific watershed.
(d) Time of concentration (tc) is the time required for runoff to flow from the most
distant point, along hydraulic channels, to the point of interest in the watershed
and is therefore the sum of travel times for the various elements within the
watershed.