Roughness · hydraulic radius · slope · area
Metric Manning uniform flow
Inputs
User-entered roughness coefficient; material, vegetation, geometry, and roughness selection are not derived.
User-entered hydraulic radius for the stated section; area and wetted perimeter are not inferred.
User-entered dimensionless energy slope for stated uniform, steady flow; a flow profile is not solved.
User-entered wetted flow area; no channel section geometry or water depth is derived.
Results
Literal metric Manning mean velocityv
1.0541
Literal metric Manning dischargeQ
5.2705
Declared hydraulic radiusR
1
Declared flow areaA
5
v = (1/n)·R^(2/3)·S^(1/2); Q = A·v (metric uniform-flow form)
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Hydrostatic pressure · Flow continuity · Pipe mean velocity · Bernoulli equation
Method
Formula, when it applies, and when it does not
Apply the metric Manning uniform-flow relation to hydraulic radius, energy slope, area, and roughness without inferring channel geometry or designing a channel.
v = (1/n)·R^(2/3)·S^(1/2); Q = A·v (metric uniform-flow form)
When
- Metric Manning coefficient form
- Declared uniform-flow condition
- Declared hydraulic radius, area, and energy slope
Don’t
- This applies only the metric Manning uniform-flow relation to user-declared roughness, hydraulic radius, energy slope, and area. It does not infer cross-section geometry, select roughness, calculate normal depth or a water-surface profile, model nonuniform flow, design a channel, determine flood flow or capacity, safety, suitability, or approval.