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The cutthroat flume can operate either as a free or submerged flow structure. Submerged flow calibration curves and free flow equations have been developed. Rectangular cutthroat flume sizes of 1, 2, 3, 4, and 6 feet were studied and tested in the laboratory. Trapezoidal cutthroat flumes having zero (or V-shaped), 6-inch, and 12-inch throat widths were calibrated. The value of transition submergence is listed for each of the rectangular and trapezoidal cutthroat flumes. The most obvious advantage of a cutthroat flume is economy, since fabrication is facilitated by a flat bottom and removal of the throat section. Another advantage is that every flume size has the same wall lengths in both the entrance and exit sections, allowing the same forms or patterns to be used for any flume size. The use of a consistent geometric shape allows accurate predictions of discharge ratings for intermediate flume sizes. The dimensions and criteria for constructing cutthroat flumes are given. Proper installation and maintenance procedures are described, as well as techniques for measuring flow depths which will yield satisfactory results.