Flowpath Engineering Portal
Open Channel Flow Calculator — Manning's Equation
Calculate flow rate, velocity, and depth in open channels using Manning's equation. Supports trapezoidal, rectangular, and circular cross-sections for NZ stormwater design.
What this tool does
Manning's Equation Solver
Calculate flow rate, velocity, and normal depth in open channels using Manning's roughness coefficient for a range of channel materials.
Multiple Cross-Sections
Analyse trapezoidal, rectangular, circular, and other common channel shapes used in NZ stormwater and drainage infrastructure.
Capacity & Freeboard Checks
Verify channel capacity against design flows and check freeboard requirements for safe conveyance of stormwater.
Graphical Output
Visualise the channel cross-section and water level to quickly verify design geometry and flow conditions.
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Open Channel Flow CalculatorPart of the Flowpath Engineering suite of free civil engineering tools for New Zealand.