ENGINEERS CLAIMED to have significantly reduced the risk of recurrent flooding in the Buckinghamshire village of Weedon this week following installation of one of the largest flow control devices in the world.
The 6.5t, 3.5m long stainless steel cone shaped structure - a Hydro-Brake - was installed within a 6.5m clay embankment dam last week by contractor Edmund Nuttall.
Positioned where a flow outlet pipe would normally sit, the Hydro-Brake's inlet is set at right angles to its outlet. The conical body forms a volute into which water is directed tangentially.
This geometry automatically generates vortex action of the discharge when a specified flow rate is reached.
When this happens, the back pressure generated in the air filled core of the volute then limits the discharge.
Engineers had to wait until the end of last week for dry weather to prepare the ground for the £45,000 Hydro-Brake's concrete footing, before eventually installing it last Friday.
'Built with 10mm thick stainless steel, this device will last indefinitely - in fact it will probably outlast the concrete housing, ' said manufacturer Hydro International's quality and fabrication manager, Roy Brereton.
A major attraction of the device is the lack of maintenance or adjustments required.
At Weedon, the flow rate can be managed between 8,000 and 12,000 l/second, depending on the position of the stop logs upstream of the brake.
'The Hydro-Brake will ensure a steady flow downstream for a fluctuating head of water, ' explained Brereton.
'For low flows, the device can also increase flow if desired - cutting land-take for storage requirements.'
The scheme follows publication of guidance from client the Environment Agency. This recommends holding flood water in catchment areas where possible, rather than transferring the problem downstream.
For flood events the Agency had an arrangement with local farmers to allow their fields to flood rather than the town.
Before the brake was installed a weir was the only protection offered to Weedon, which suffered severe damage in the 1998 floods.
For the total £1.1M scheme, a 450m long 6.5m high earth bank was constructed, with a 15m long, 6.5m high concrete inlet that channels flow through the Hydro-Brake.