What is a good way to gage a stream without using a weir or an engineered flume? How about this stone control structure / flume?
Having a stable control is invaluable for developing a good stream flow rating curve. A rating curve relates the depth of the stream to the flow at a particular point. By a stable control I am referring to a cross-section of stream that will not change over time due to erosion, etc.
This large stone control structure provides a stable cross-section and controls the depth of the pool upstream for gaging. This particular structure is built like a flume, narrowing the width of the channel at its throat. The narrowing causes a larger change in pool depth for a given change in flow, increasing the resolution of the rating curve.
One advantage of a structure like this is that it allows the free passage of fish, unlike a weir or some engineered flumes. It is also aesthetically pleasing and fairly “natural” looking.
While this is a fairly simple structure, it was not easy to install. The 6 Stones used weighed over 500 pounds a piece. Next, we will be installing instruments in the pool above to gage the flow and collect water quality measures.