Product(s): |
StormCAD, CivilStorm, SewerGEMS |
Version(s): |
08.11.XX.XX and 10.00.XX.XX |
Area: |
Calculations |
Problem
In StormCAD (GVF-Rational Solver), how is the conduit property "System CA" computed?
Solution
When using the Rational runoff method, the conduit property "System CA" is the sum of the upstream "Catchment CA" and catch basin "External CA" values.
For Example:
Catchment (Upstream)
Runoff Coefficient = 0.9
Area (unified) = 2 acres
Catchment CA = 0.9 * 2 = 1.8 acres
Catch Basin (Upstream)
External CA = 1 acre
Conduit (Upstream)
System CA = Catchment CA + External CA = 1.8 + 1 = 2.8 acres
Catchment (Downstream)
Runoff Coefficient = 0.8
Area (unified) = 3 acres
Catchment CA = 0.8 * 3 acres = 2.4 acres
Catch Basin (Upstream)
External CA = 1.5 acres
Conduit (Downstream):
System CA = 1.8 + 1 + 2.4 + 1.5 = 6.7 acres
See Also
System CA results for a catch basin are lower than the CA results for the upstream catchment