Trapezoidal Flume Design
The Trapezoidal flume has a V-shaped cross-section and flat floor.
When flows are low and flowing through the “point” of the V, a relatively large amount of head (level) is generated, as the crest width of the water is small – providing low flow sensitivity and accuracy.
As the flow increases, the effective crest width increases (the V expands outwards) giving the Trapezoidal flume the ability to measure higher flows.
The ability to accurately measure low and high flows without the need for a change in channel / floor elevation (e.g. Parshall) or free-spilling discharge (e.g. H flume) make the Trapezoidal flume unique.
Trapezoidal Flume Dimensions
The dimensions for most Trapezoidal flumes used today can be found in three publications:
- Robinson, A., Trapezoidal Flumes for Measuring Flows in Irrigation Channels, USDA-ARS 41-140, March 1968
- Robinson, A., Measuring Water in Small Channels with WSC Flume, Washington Agricultural Experiment Station, Circular 200, 1952
- Robinson, A., Water Measurement in Small Irrigation Channel Using Trapezoidal Flumes, Transactions of the ASCE, Vol. 9, No. 3, 1966
The dimensions are Trapezoidal flumes are not standardized in a national / industry standard as is the case with most other flumes.