# Hydraulics Flow Rates and Slope

## 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

## Resources

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