Calc Q value
Calc Q value
(OP)
I need to calculate the amount of cfs overflowing a road
at a maximum of twelve inches. How can I do this? For
example... I have 12" of water running over a road sloped a 2% and 26' wide, how do I calc the CFS for it.
at a maximum of twelve inches. How can I do this? For
example... I have 12" of water running over a road sloped a 2% and 26' wide, how do I calc the CFS for it.





RE: Calc Q value
Q = CL(H^1.5)
L = weir length
H = head above weir
C = weir coefficient (for roads, typical is 2.65)
RE: Calc Q value
RE: Calc Q value
Q = 2.65*26*(1^1.5) = 69 cfs
RE: Calc Q value
Briansch
RE: Calc Q value
RE: Calc Q value
like this:
A negative slope of 6.81% down to a tangent 20' vertical curve connecting to a tangent flat road lower than the BVC. The road is 40' wide and then another tangent vertical curve 20' wide upward to a tangent slope of 4%.
At a 100 year event, the maximum amount of water overflow needs to be 12". I need to calc how much CFS the road will carry at 12" overflow.
Example:
slope in (negative) slope up (+)
\ /
\ Water Overflow /
\------------------------/
\ Bottom of Road /
---------------------
RE: Calc Q value
RE: Calc Q value
I'm afraid you'll need to run a backwater profile to determine your discharge and change your discharge until you get the depth of flow you are looking for.