Time of Concentration
Time of Concentration
(OP)
I have been told that the time of concentration can be lengthened by 5-15 min. when storm water is routed through a catch basin. I have not been able to find any technical data discussing this and was wondering if anyone has information on this subject.
RE: Time of Concentration
Engineering is the practice of the art of science - Steve
RE: Time of Concentration
RE: Time of Concentration
RE: Time of Concentration
The detention/retention basin or pond will hold water, and could make an impact.
Your pipe flow time may be used in the Tc, but it won't be very much time.
RE: Time of Concentration
RE: Time of Concentration
Tt = L / V
where V = sqrt( g D )
Tt = Travel time (seconds)
L = Flow length
V = wave velocity
g = gravitational constant
D = mean depth
RE: Time of Concentration
RE: Time of Concentration
The Rational Method was never intended to be used with Tc --this misconception was invented in 1890.
The Rational Method uses the IDF correlations that estimate the ability of a raincloud to generate rainfall. This ability is determined by rain gage data.
The minimum duration for IDF correlations is 5-minutes. This duration can be used as long as the pipe network travel time is less than 5 minutes. For example, a 1000-ft long storm sewer flowing at 3.3 fps has a travel time of 5 minutes.
Rational Method Runoff coefficients can be reduced to allow for ponding and/or the longer travel time for heavily vegetated areas.