What is the broad-crested weir discharge formula?

Q = 1.704 × Cd × L × H^1.5, where Cd is discharge coefficient (0.848 for critical flow condition = 0.544 × √(2g/3) × √(2/3)), L is weir length (m), and H is upstream head (m). Broad-crested weirs achieve critical flow on the crest, making them self-calibrating per BS 3680 Part 4C.

How does a broad-crested weir differ from a sharp-crested weir?

A sharp-crested weir has a thin plate ( 0.067H so critical flow develops on the crest. Broad-crested weirs are more robust for field conditions; sharp-crested weirs are more accurate for laboratory flow measurement.

Broad-Crested Weir Flow Rate Calculator

Calculate discharge over broad-crested weirs and embankment weirs used in irrigation, stormwater management, and dam spillway design.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Calculate discharge over broad-crested weirs and embankment weirs used in irrigation, stormwater management, and dam spillway design. Use the broad-crested weir result to inform your clinical assessment.

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Frequently Asked Questions

What is the broad-crested weir discharge formula?

How does a broad-crested weir differ from a sharp-crested weir?