Hydraulics Flow Rates and Slope
Slope Design
Neutral Slope:
Straight linear, no pitch, no rate of change
Step Slope:
External rate of change with different externalchannel depths
Continuous Slope:
Constant rate of change, typical slopes are .5%, .7%, 1%, 1.5% and 2.0% Swiftslope by Swiftdrain is a continous slope of .05% - 2.0%
Water Flow Design
Flow Rate Calculations:
Required water flow = Qr
- Qr = CIA
- Qr = C*I*A
- Let C = surface constant (pavement use 0.9)
- Let I = water fall intensity
Channel Flow Capacity = Qc
- Qc = A*(1.49/n)*(R)^2/3*(S)^1/2
- Let A = cross sectional area of the trench drain in square feet
- Let n = the coefficient of friction of the trench drain body
- concrete forming systems = 0.013
- polymer concrete systems = 0.010
- fiberglass & GFRPC systems = 0.009
- Let R = the hydraulic radius which is calculated by
- Hydraulic raidius = A / P
- A = the cross sectional area found above the trench
- P = the perimeter surface of the trench
- Let S = bottom effective slope of the trench
- Effective slope=site slope + built in slope of trench drain
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