THE MAGAZINE FOR THE DRAINAGE, WATER & WASTEWATER INDUSTRIES
FLOODS & SUDS
operations that also had a significant lead- in time to bring all the equipment to such a remote site. In addition, as a result of high tides and extreme weather, the outfall of the pipe was largely blocked by sand and shingle, which had to be removed during periods of flood risk. This process was inefficient, costly and time-consuming, so a second engineered outfall was developed.
Engineered outflow solution
The second, more advanced outflow was built in 2020 to largely eliminate the requirement for over-pumping. The additional capacity provided by the second pipe meant that the pool drains by gravity rather than costly and carbon-intensive pumping operations. “The new outflow featured penstocks, pumps, flow monitors and remote communications, and was developed to provide a number of important advantages,” says Will Hancock, Project Lead at the EA.
Level and flow monitors were installed in the River Cober, the Loe Pool and in the new outfall pipe. “This provided us with the
ability to monitor the site remotely,” Will explains, “which meant that less site visits were necessary, lowering project costs and carbon footprint, and enabling us to respond to flood risk in a faster and more timely manner.”
The new monitoring system was designed to detect the excessive accumulation of water in the pool, so that the second outflow could be implemented when necessary. Under such circumstances, an excavator is used to expose and open the outfall cover before the sluice gate is opened and the pumps are allowed to remove water from the pool, for discharge to the beach. Over the last 5 years, the second outfall has been opened on two occasions.
New flow monitoring technology
Prior to the installation of the new monitoring system from Nivus, flow was measured in Helston and in the discharge pipes with a traditional Doppler flow meter, and the failure of one of these units provided the EA with an opportunity to
review and upgrade the monitors.
Explaining the evaluation process, Will Hancock says: “These measurement instruments perform a critically important function. Not only do they help manage the Loe Pool to lower flood risk, they also feed data into our flood forecasting model, so it was essential that we utilise accurate, reliable instrumentation.
The EA has extensive experience with flow measurement technologies, including the cross-correlation method from Nivus, so it was determined that this would be the appropriate solution for the discharge pipes and the river monitor. The key advantage to this area velocity flow measurement technique over the instruments which it replaced is that it provides a 3-dimensional flow profile that is calculated in real-time to provide reproducible and verifiable flow values in full or partially filled channels or pipes. Older Doppler methods are less accurate because they only measure 2-dimensional flow.
The method utilises particles, minerals or
New NIVUS cross-correlation flow sensors fitted in the newer (2020) discharge pipe
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July 2025 |
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