Weighted C

[JeffM]

how does one go about using a weighted C utilized to compensate for a different travel time if something had 5 different drainage zones?

 

[LionCE]

If I am not mistaken you take the sum of C's times the areas and divide by the total area.

ex [c1*a1 + c2*a2 + c3*a3]/Total Area

 

[Dleg]

^^Correct!

I'm not sure I understand the significance of the part in the original poster's question where he referred to different times of concentration. In most real situations (when using the rational method, anyway) as well as practice problems, you use a weighted runoff coefficient even when dealing with a small lot with the minimum time of concentration.