For proper flow measurement, a flume installation must be periodically inspected.
This inspection should include the channel in which the flume is installed, the flow entering / exiting the flume, and the flume itself.
Channel inspection
The upstream channel banks should be clear of vegetation or debris that could affect the flow profile entering the flume (upstream) or restrict flow out of the flume (downstream).
Inspect the upstream channel to make sure that flow is not bypassing the flume.
Inspect the downstream channel to make sure that scouring is not occurring.
Any hydraulic jump should be at least (30) times the maximum head (Hmax) upstream of the flume.
Flow inspection
Flow entering the flume should be tranquil and well distributed.
Turbulence, poor velocity profile, or surging should not be present.
The Froude (Fr) number should, ideally, be 0.5.
As the Froude number increases so does surface turbulence.
Flumes accelerate sub-critical flow (Fr < 1) to a supercritical state (Fr 1>) . Flumes experiencing flows greater than unit (Fr = 1) will not measure flow accurately.
Flume Inspection
Flumes must be level from front-to-back and from side-to-side.
Earthen installations are particularly susceptible to settling due to wet / dry and freeze / thaw cycles.
Flow surfaces are to be kept clean of surface buildup or algal growth. Scrubbing or a mild detergent can be used.
Galvanized flumes should be checked for corrosion.
Any corrosion should be removed and then cold galvanization applied to the area.