Irrigation in the Pacific Northwest

Trapezoidal Flume

This calculates the flow rate through a trapezoidal flume. A trapezoidal flume comes in standard sizes and has a flat bottom with sloped sides that contract in the center. The height change is the difference between the upstream water height and the downstream water height. Learn more about the units used on this page.


Height Change:
Bottom Width (b in the diagram):
Flow Rate:

The Equations

The equation used to determine the flow rate of a Trapezoidal Flume depends on the width of the bottom of the flume.

For a bottom width of 1' use:

For a bottom width of 2' use:


= Flow rate in cfs.

= Height of the upstream water above the bottom of the flume in feet.





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