Flumes are used to measure flow in what type of channel?

• A. Closed conduits
• B. Open channels
• C. Pressure pipes
• D. Pipelines

Answer: (B)

Flumes measure flow in open channels because they rely on a free water surface to relate depth to discharge. In open channels, the water surface is exposed to the atmosphere, so the height of the water as it moves through the flume can be calibrated to a specific flow rate using a rating curve or standard formulas for that flume type. The fixed throat or constriction creates a predictable change in velocity and depth that directly ties to how much water is moving downstream. In contrast, closed conduits, pressure pipes, and pipelines have no free surface and are pressurized, so a flume cannot provide an accurate discharge measurement there. Those systems are measured with other methods tailored to pressurized flow.