Hydraulic Radius Calculator

Your details

Select the cross-section geometry of your channel or conduit.
Width of the flat base of the channel.
m
Vertical depth of water in the channel.
m
Longitudinal slope of the channel invert (dimensionless, e.g. 0.001 = 1 in 1000). Leave at 0 to skip Manning calculations.
m/m
Manning's roughness coefficient. Typical values: 0.010-0.015 for concrete, 0.020-0.035 for natural channels. Leave at 0 to skip.
Hydraulic radius (R)Moderate channel
0.6667

Flow area divided by wetted perimeter

Hydraulic diameter (D_h)2.6667
Flow area (A)3.6
Wetted perimeter (P)5.4
Manning's velocity (V)1.8564
Manning's discharge (Q)6.6829
Flow area3.6
Wetted perimeter5.4
Hydraulic radius0.6667
Hydraulic diameter2.6667

Hydraulic radius is 0.6667 m for the rectangular channel.

  • Flow area is 3.6000 m² and wetted perimeter is 5.4000 m, giving R = 0.6667 m.
  • Hydraulic diameter (4R) is 2.6667 m. This is the value to use in the Reynolds number or Darcy-Weisbach friction factor for non-circular sections.
  • Manning equation gives a flow velocity of 1.856 m/s and discharge of 6.6829 m³/s.

Next stepUse this hydraulic radius with Manning's equation (Q = (k/n) A R^(2/3) S^(1/2)) to find flow rate, or with the Darcy-Weisbach equation for head loss calculations.

 = Powered by OnlyCalculators