Flowpath Engineering Portal
Weir Flow Calculator for Civil Engineering Control Structures
Calculate flow through common weirs and hydraulic control structures with free-flow guardrails, rating curves, and printable schematic diagrams.
What this tool does
Common weir families
Calculate rectangular sharp-crested, V-notch, Cipolletti, and broad-crested weirs from one consistent engineering interface.
Scruffy dome overflow chambers
Model circular overflow shafts in wetlands and raingardens as broad-crested weirs with debris blockage allowance and a Manning outlet pipe capacity check.
Solve for flow or head
Enter measured head to calculate discharge, or enter design discharge to estimate required head over the crest.
Guardrail checks
Review validity warnings for minimum head, H/P, H/L, contraction clearance, coefficient ranges, and tailwater submergence.
Diagram and rating curve
Generate a printable weir schematic and Q-versus-H rating curve to support design notes and reports.
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Open Weir & Control Structure CalculatorPart of the Flowpath Engineering suite of free civil engineering tools for New Zealand.