Tilting dam could save UK homes
An award-winning tilting barrier developed by UK company Tilt-Dam promises to avert the risk of flooding near to homes adjacent to rivers that are prone to bursting their banks. Journalist Mike Walter reports on the permanent barrier that can be raised in minutes, on behalf of Tilt-Dam and UK groundwork specialist Roger Bullivant Limited.Protecting low-lying residential areas from flooding is a serious concern in the UK. Methods of flood defence have begun to spring up close to waterways in sensitive urban locations, but there is one fundamental drawback with many of the current crop of temporary barriers.
Structural engineer John Forrest, director of Tilt-Dam, says that the problem is that conventional barriers are often temporary dams which have to be transported to site before being erected hurriedly, before water breaches a bank and causes a flood. With this in mind, Forrest set about inventing an alternative form of flood defence that promises to take little time to raise.
His answer is a tilting barrier that is built into a quayside or riverbank and remains in a horizontal position when not required. This permanent form of flood defence is known as Tilt-Dam, and can be deployed within minutes when the alarm is raised that water levels are about to rise fast.
Concrete barrier panels remain at a low level when the tilting dam is not in use, so as not to disrupt views across waterside locations or access along towpaths. The barrier can even be used as a towpath when resting in the horizontal position.
By unhinging easy release locks by hand, a section of barrier is swung to a vertical position with the help of concrete counter-balancing weights positioned on the underside. A lightweight rubber seal is then dropped into a cavity between two sections of barrier to ensure the tilting dam remains impermeable when flood waters rise.
A section of the Tilt-Dam flood barrier is currently being demonstrated in a lakeside dock at Lea Marston in the West Midlands of England, and groundwork specialist Roger Bullivant Limited (RBL) is developing a system of piled foundations on which the flood barrier can be firmly secured.
"Speed of erection and ease of maintenance make this system far superior to other forms of flood defence, such as temporary demountable barriers," says Forrest. "Two people can put up a long length of Tilt-Dam barriers in a matter of minutes and seals between the barrier panels can be replaced very easily.
"Many temporary flood defence barriers, on the other hand, are erected using components that have to be brought from a store and installed while waters rise."
For the Tilt-Dam system to work effectively, the barriers must be deployed with the minimum of effort. Locks holding the barrier in the horizontal position, for instance, are easy to get at and simple to release, while no machinery or electrical power is required to lift the barriers. The locks are hidden by hinged covers which remain unlocked.
"Nothing must interfere with the ability to operate the locks in times of a flood," adds Forrest.
The height and width of each steel composite panel can be tailor-made for an individual site and a 2m high barrier is said to be capable of withstanding floodwaters up to 1.2m high. Several local authorities in areas prone to flooding, and the Environment Agency, are reported to be seriously considering use of the Tilt-Dam barrier.
A 250m installation is likely to be placed by the River Trent in West Bridgford near Nottingham next year. A further installation may also get the go-ahead in Glasgow city centre, to protect new developments at Lancefield Quay.
The system can also be used as a secondary line of flood defence in coastal areas, behind concrete wave breakers, and the company has received an enquiry from the Cayman Islands about such an application.
"Ensuring the tilting dam stands firm in the event of a flood largely depends on the strength and durability of its foundations," says Roger Bullivant director, John Patch.
The company is developing a range of below ground supports for the dam, such as 150mm diameter mini-piles that would either be driven, bored or vibrated into the ground, where local conditions are less than favourable. Firmer ground could be pressure treated without the need for piles.
"The foundations have got to accommodate dynamic loadings to support the tilting mechanism, as well as overturning forces when holding back a large volume of water," says Patch.
Complex in-situ concrete connections have also to be designed to link the precast barrier panels and foundations together.
"Our intention is to manufacture the component parts and install sections of Tilt-Dam to sit on our foundations. We are approaching selected house-builders in the Midlands who are looking to develop properties on low level sites that could benefit from a method of flood defence such as this."
John Forrest, along with colleagues Jim Barrack and David Smith, were recognised for their work in developing the flood barrier in May when they received the 2005/06 UK Chartered Institute of Building award for innovation.
"Half a million houses in the UK are either at risk from flooding or have been flooded in recent years," adds Forrest. "This is a valuable system for communities at risk from flooding and I have agreed to pay a royalty to the Institution of Civil Engineers, based on the annual metre run of Tilt-Dam, to help train engineers involved in flood defence work."