Better, more effective water management and harvesting techniques need to be designed into every element of a building

Andy Williamson

With wild and unpredictable weather regularly hitting the headlines (heatwave warnings one week, floods the next!), climate change is forcing us all to think differently about how we manage our resources and protect ourselves and our buildings from the elements. And managing water is one of the highest priorities – or should be. The technology is here already, but legislation and spending doesn’t seem to have caught up. Indeed, Government is increasingly handing responsibility for ‘green’ initiatives over to industry to drive.

Flooding is a very real issue for the UK. The increasing urbanisation of our landscape, and use of traditional, impermeable paving has reduced natural drainage and contributed to risks of flash flooding. If rainwater can’t be absorbed by the earth or managed in a sustainable and controlled way, run-off and overflowing drains become problems in storms. It’s affecting more of our homes, businesses, infrastructure than ever – and more frequently. London’s Victorian sewers, for example, regularly discharge raw sewage into the Thames and streets in heavy rainfall – and the UK has been taken to court by the European Commission for it!

Government introduced a £2.5 billion investment in flood defence after the devastation caused by floods in 2007 and in 2014, which caused two months of chaos. The scheme will provide funding to over 1,400 projects in a six year plan to protect 300,000 homes. But is this enough when over this past year alone flash flooding caused £3 billion worth of damage? The Flood and Water Management Act in 2010 was supposed to tackle this problem, making SuDS (Sustainable Urban Drainage Systems) mandatory on all new developments – but it doesn’t look like the legislation will be implemented.

We need better, more effective water management and harvesting techniques designed into every element of a building. For example, the Thames Tideway Tunnel is a £4.3 billion fix for London’s ageing sewer system. But a more holistic approach – combining SuDS, green roofs and other initiatives – would be cheaper and more effective according to an Ofwat study.

Thinking differently means building differently. Too often, tried and tested solutions such as green roofs are seen as an optional extra to tick a box, when they should be built-in.

Green roofs and podium decks are viable SuDS solutions for modern flat roofing systems. They help manage water in a number of ways. Water is taken up and used by plants on green roofs, while rain droplets are trapped within vegetation to evaporate back into the atmosphere. Water can also be held within the drainage system of the green roof build up. Finally, the runoff rate is reduced in the time it takes water to percolate through the green roof and out via drainage outlets. This releases excess water more slowly so standard drainage systems cope better in heavy rainfall or storms. Managing rainwater when and where it falls is more cost-effective.

Green roofs are just part of the answer, but an essential part often neglected.

Andy Williamson is group managing director of IKO