What is a restriction in an open channel used to measure flow?

• A. Weir
• B. Box cord
• C. Packing
• D. Flume

Answer: (D)

A flume is an engineered constriction placed in an open channel to create a known relationship between water depth and discharge. By measuring the head at specific points upstream and at the throat, you can calculate how much water is flowing. This makes a flume a precise, calibrated way to measure flow, which is why it’s the best answer to a question about a restriction used for flow measurement.

A weir also measures flow by a head difference, but it works by water spilling over a crest and is described more as a barrier across the channel rather than a constricted passage. The other choices aren’t measurement devices for open-channel flow, so they don’t fit.