Which type of flow measurement is typically used in a rectangular open channel?

In rectangular open channels, flow measurement techniques typically employed include V-notch weirs and Parshall flumes.

V-notch weirs are specially designed weirs that create a controlled flow of water. The flow rate can be determined based on the height of the water flowing over the notch. This method is particularly effective in open channels as it provides a simple and reliable way to measure small to moderate flows and works well with the conditions found in rectangular channels.

Parshall flumes are another type of flow measurement device specifically designed for open channels. They utilize a shaped constriction that allows for a precise measurement of flow rate. The flow rate can be determined from the head measurement upstream of the flume, ensuring an accurate assessment of the water flow within the channel.

Both V-notch weirs and Parshall flumes have unique advantages, allowing them to function effectively within the dynamics of rectangular channels. This makes the combined usage of these methods an appropriate answer to the question regarding flow measurement in rectangular open channels.