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In an open channel, freeboard is the head measured from the maximum water level to the uppermost watertight portion of the surrounding channel. Freeboard is an important consideration when evaluating the impact of the installation of a flume or weir. Weirs in particular require…

This overview provides information on the advantages and disadvantages of thin-plate, sharp-crested weirs for measuring the flow of water in open channels. Additional information is also provided on unique features and application notes on various weir types. Source: Teledyne…

When using a weir to measure the flow of water in a natural channel or man-made structure, one of two flow regimes are present: free-flow or submerged flow. Free-flow, also called modular flow, is when the discharge of the weir is not restricted by downstream conditions – where…

At its most basic a weir is nothing more than a structure over which water flows. Their simple design and wide range of styles offer certain particular advantages.

When mounting an ultrasonic sensor over a flume or weir one thing that frequently gets overlooked is the blanking distance - aka deadband - of the sensor. The blanking distance is that distance from the face of the ultrasonic transducer in which the flow meter will blank out (or…

Weir boxes provide the utmost in versatility when it comes to how the flow enters and exist the box. Flow can be piped inline, offset, or even free-spilling into and out of the box. However, sometimes this flexibility can cause problems when it comes to accurate flow measurement.

Flumes and weirs have historically been the tools used to measure the flow of water in natural and manmade channels. Either can be used by itself (with the operator taking manual level readings) or in conjunction with a secondary flow meter for automated data collection.

From time to time every weir installation will need periodic maintenance; whether to inspect the weir crest or to clean debris out of the weir pool. A simple and handy accessory to help with this is a clean-out opening or coupling. In weir boxes and manufactured channels, a…

The section of the weir that the water overflows is termed the notch or overflow section. If the notch plate is thin enough that the water springs clear of the downstream face, the weir is terms a sharp-crested or thin-plate weir.

Over the years, there are have been a number of developments to the thin-plate weir – expanding weirs beyond the V-notch and Rectangular styles commonly used. Each special weir type is an attempt to overcome very specific limitations of the thin-plate weirs in general.

The usual method of dissipating the energy of a weir's nappe is by a hydraulic jump downstream of the weir. In an earthen channel, if the is no provision for this dissipation of energy, there will be a tendency to sour the downstream channel. This scour and erosion of the channel…

The common sources of errors for weir installations can be broken down into four categories: Flow approaching a weir installation should be no more than 0.5 fps and the upstream channel (weir pool) should be straight and of uniform cross-section for 20 times the maximum…