Comparing the Cutthroat and Parshall Flume

If you’re interested in adding a flume to your water management system, then you need to be certain that you are choosing the right flume type. While there are a variety of flumes available to you, two of the most popular are the Parshall flume and the Cutthroat flume.

Although they are very different, both of these flumes provide distinct advantages, meaning the best way to decide which flume type is right for your system is comparing them head to head. Compare the Cutthroat flume and the Parshall flume so that you can find out which flume best meets your flow management and measurement needs.


The best way to differentiate between flumes is by examining their design. The Cutthroat and Parshall flumes have some similar design characteristics, including flat, vertical sidewalls and a wasp-waisted structure. However, there are also some big differences between these flumes, making it a good idea to examine them in closer detail.

A Parshall flume has a shape that resembles an hourglass. The inlet of this flume narrows to the throat as the flow enters the flume. Also, the convergence angle can differ depending on the size of Parshall flume you choose. The inlet of this flume is wider than the outlet, and the discharge walls flare outwards.

Cutthroat flumes have the same hourglass shape as the Parshall flume, but do not have a throat. Unlike Parshall flumes the convergence angle of a Cutthroat flume is fixed at a ratio of 1:3. Because there is no length to the throat section of this flume, the inlet walls narrow and then immediately expand. In addition, the outlet and inlet have the same width.

Flow Accuracy and Elevation

In addition to having some major differences in their overall design, the Parshall and Cutthroat flume also have different elevation layouts and levels of accuracy. Examining these issues can be particularly useful in deciding which type of flume is right for you.

The inlet floor of the Parshall flume is flat until it reaches the throat, which point the floor will drop. The inlet is has a higher elevation level than the outlet, and there will be a partial discharge recovery. Additionally, the sidewall height depends on the flume size. Under controlled conditions, Parshall flumes have an accuracy rate of +/-2%. In real-world applications, +/-3-5% is more realistic.

With a Cutthroat flume, there is no change in floor elevation. Instead, the floor of a Cutthroat flume is completely flat all the way through, making it a good retrofitting choice for existing channels. Cutthroat flumes also have a standard sidewall height that is 1/3 of the length of the flume. Typically, the accuracy rate of a Cutthroat flume is +/-3%.

Buy a Cutthroat Flume or Parshall Flume

As you can see, there are some major differences between the Parshall and Cutthroat flume, mostly in the way that they are designed. Consider the needs of your operation and you’ll be able to choose the right flume for you. If you’re interested in purchasing a Parshall flume or Cutthroat flume, you need to shop with Tracom, FRP.

Tracom produces a wide range of fiberglass flume styles, include Parshall and Cutthroat flumes, and we can help you find the flumes that match your needs. Contact Tracom today.