World’s largest Hydro-Brake® Stems Glasgow’s Floods

Written by: , 29 Mar 2011

THE WORLD’S largest ever Hydro-Brake® Flow Control devices have been installed as part of Glasgow City Council’s £53 million White Cart Water Flood Prevention scheme.  The scheme is designed to protect 1,750 properties in the South of the city from the risk of flooding.

Manufacturer Hydro International had to pioneer new manufacturing and installation techniques to construct the eight-metre long, six metre-high, cone-shaped Hydro-Brake® Flow Controls which were positioned by the scheme’s main contractor Carillion in dams at Blackhouse and Kittoch.

Carillion is responsible for constructing three flood storage areas on agricultural land in the hills upstream of Glasgow, which together have the capability to hold back more than 571 million gallons of flood water.  In June, Carillion positioned three Hydro-Brake® Flow Controls in the third dam at Kirkland Bridge.    With a combined stainless steel weight of more than 60 tonnes, all five are the biggest ever produced.

Normally, a shallow, fast-flowing river, White Cart Water is prone to flash-flooding and water levels can rise by six metres after only 12 hours of rain.  Since 1908 it has inflicted more than 20 serious floods on homes and other properties in the South Side of the City.

Scotland’s largest confirmed flood prevention scheme has been designed by consulting engineers Halcrow on behalf of Glasgow City Council.   During peak storms, the Hydro-Brake® Flow Controls will hold back the White Cart Water and its tributaries Earn Water and Kittoch Water causing the storage areas to flood.  Water will be released downstream at a controlled rate so that it does not overspill new flood defences being constructed in the City.

Upstream, a total of 90,000 sq metres of rich and diverse wetland habitats will be created.  Downstream, the flow of water will be reduced by up to 45% during peak storms, achieving flood protection to a 1 in 200 year standard or a 0.5% probability of a flood occurring in any one year, when combined with the new flood defences.

Since Hydro International invented and developed the Hydro-Brake® Flow Control’s unique vortex technology 30 years ago, it has become an industry-standard method of flow attenuation.  Most frequently used in much smaller dimensions as part of urban surface water drainage designs, the Hydro-Brake® Flow Control’s internal geometry is designed to enable water to flow through unrestricted for as long as possible.  A self-activating vortex is created when the water reaches a pre-determined height, for example in a flood situation, holding back the water, and releasing it at a measured, controlled rate.

The Glasgow flood alleviation project also involves the construction of further flood defences in selected parts of the river corridor downstream, including 4.5 km of urban flood defence walls and pumping stations.

Alan McGowan, Project Manager for Halcrow, said: “A flood attenuation solution allowed the height of the flood defences along the river banks in areas at risk to be lowered significantly.  The total length of walls required was also reduced, and in some areas, no flood defences were required.  With a one-metre high flood defence, people can still see the river and wildlife habitats, but a two metre high wall would have meant people would forget the river even existed.

“Hydro-Brake® Flow Controls enabled the storage capacity within the attenuation area to be used most effectively, because flows can pass unheeded through them for longer than other flow control devices.  Alternatives such as orifice plates, weirs or gates for example, would start to hold back the water at a much earlier stage and require more flood storage capacity.

“The Hydro-Brake® Flow Controls will reduce frequency and duration of flooding of the storage area, which is important given that most of the land upstream will return to agricultural use.

“Hydro-Brake® Flow Controls offer an efficient fail-safe, passive method of flow control.  They do not need power to operate, and once installed, they can be left alone to do their job with minimal maintenance for the foreseeable future.

In size, the Hydro-Brake® Flow Controls eclipse the 3.5 m high Hydro-Brake® Flow Control at Weedon Dam, previously Hydro’s largest installation, which has been serving a similar purpose in protecting the village of Weedon Bec in Northamptonshire since 2002.

Alex Stephenson, Director, Stormwater Division, Hydro International said: “The record size of Blackhouse and Kittoch Hydro-Brake® Flow Controls meant we had to develop ground-breaking methods of manufacture and work closely with Carillion to ensure their successful installation.

“Instead of a solid, and relatively thick stainless steel design like those at Kirkland Bridge, the two six metre high Hydro-Brake® Flow Controls have been designed as a thinner stainless steel shell former encased in 600 mm of concrete.

“The Hydro-Brake® Flow Control formers were brought to site and fixed into the dams, reinforced by temporary internal struts.   100 cubic metres of concrete were poured in to create the outer casing.   The resulting structures are able to resist the huge forces of the flood water, whilst retaining the unique vortex-control geometry.”

Mark Johnston, Carillion’s Project Manager for the scheme added: “Hydro and Carillion worked closely together to pioneer installation methods for the new Hydro-Brake® Flow Control design.    Constructing a dam with a device of this size and type has never been attempted before and a close working relationship between the manufacturer and ourselves was essential to the successful outcome.”

Said Iain Macnab, Head of Project Management and Design for Glasgow City Council: “The White Cart Flood Prevention Scheme will provide much welcome relief to an area of the city which has suffered with flooding for over a century.  In particular it is has removed the threat that properties and businesses will be uninsurable and therefore we are hopeful it will provide a spur to regeneration and development in this area of the city.”

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