Thursday, 17 December 2015 13:47

Hold back water in the hills to prevent urban flooding say engineering experts

An unconventional flood defence technology that holds back river water in the hills above low-lying towns and cities could help prevent future misery as climate change makes severe and intense events more likely, say engineering technology experts.

Hydro glasgow copyAs a review begins into the effectiveness of flood defences that were unable to fully protect thousands of homes from flooding following unprecedented levels of rainfall in North West England, one innovative technology is already helping to shield flood-prone communities using an approach that challenges conventions. Precision-engineered upstream schemes are already successfully protecting downstream communities from flash flooding.

Says Alex Stephenson, Market Development Director at Hydro International: "It's time to change the paradigm of flood defence thinking and move more fluvial flood defences upstream. In low-lying towns and cities such as those hit in this weekend's floods, it's already too late when water from the surrounding uplands has raced down highland slopes to the valleys below. Often, where agricultural practices have removed natural defences and altered surface water paths, water can run off hillsides quickly.

"Proven vortex technology such as that used in the White Cart Water flood alleviation scheme in Glasgow is already helping to protect vulnerable communities, by using an upstream solution that uses no power, requires minimal maintenance and creates wetland biodiversity. Environmentalists have long argued for more tree planting and green solutions upstream, but alone they may be insufficient to cope with flash floods like those just experienced in the North West.

hydro alex stephenson"Defences based on Hydro-Brake® Flood Alleviation technology are already helping to provide flood protection, and have so far prevented over £200million of flood damage to 6,000 properties. When combined with a range of measures as part of an integrated catchment approach, holding back floods upstream makes perfect sense. Innovative engineered solutions can be combined with natural features to avoid flash flooding downstream.

"The Government has already committed £2.3billion of capital investment for some 1,400 flood defence schemes to protect 300,000 homes as part of the National Infrastructure Plan. Once the grey clouds have cleared I would urge some 'blue sky' thinking that takes a holistic approach to flood defence planning.

"Carlisle has experienced its five worst-ever floods in the past 50 years. Climate change is expected to result in more intense rainfall events in future. To make the most of limited funding for flood management means challenging convention with engineering solutions and sustainable technologies.

"I make no apologies for being proud of Hydro-Brake® Flood Alleviation technology. We should be prepared to shout passionately about the best infrastructure engineering knowledge already available to alleviate flooding misery. Let's galvanise our efforts and harness science and technology to work in harmony with nature."

Alex Stephenson has 40 years experience in stormwater drainage design and related issues and has been chair of the British Water Sustainable Water Management (SuWM) Focus Group for over 10 years.

The Hydro-Brake® vortex flow control was invented and developed by Hydro International more than 30 years ago and has become an industry-standard method of flow attenuation. Increasingly, it is being used as a lower-impact technology for upstream attenuation flood defences, with the largest schemes controlling flows in excess of 33 m3/s and holding back millions of cubic metres of water.

• Hydro-Brake® Flood Alleviation installations form part of Scotland's award-winning and largest flood alleviation scheme, the White Cart Water Flood Prevention Scheme where 1,750 urban and suburban properties are protected, including commercial and residential. The flow controls hold back water behind three dams creating temporary storage areas on agricultural land in the highlands above Glasgow. The water is released downstream at a controlled rate so that it does not overspill flood defences protecting properties downstream.
• Hydro-Brake® flow controls have been installed installed in a flood alleviation scheme at Northallerton, North Yorkshire. They enable excess water to be held back in specially built flood storage basins in agricultural land on the outskirts of the town, protecting 170 properties. • A scheme in the valley of the River Douglas in Wigan protects 610 properties from flooding in the nearby city centre.
• Smaller communities from 70 to 300 homes have also benefited, for example at Portpatrick, Argyllshire, once devastated by flash floods through its streets, Weedon Bec in Northants and Devil's Bridge near Sheffield.

Hydro International hosts the Engineering Nature's Way website which shares many examples of innovative, sustainable surface water management projects and technologies. Visit
Glasgow's White Cart Water Flood Prevention Scheme
Northallerton, North Yorkshire
River Douglas in Wigan
Portpatrick, Argyllshire
Weedon Bec in Northamptonshire
Devil's Bridge near Sheffield