Dwr Cymru Welsh Water has launched ‘Green Space Wales’ - an initiative to promote natural drainage to help the sewerage network cope better with climate change and increasing urbanisation to reduce incidents of sewer flooding. The company is engaging with partners throughout Wales to raise awareness of what can be done to reduce the risk of sewer flooding due to intense rain storms and the increasing amount of surface water run-off from roofs and paved areas.

Climate change is seeing more heavy rainfall fall on an increasingly developed urban landscape of roads, car parks, buildings and paved front gardens. With reduced green areas for drainage, rainfall is increasingly channelled into public sewers, sometimes overloading them and causing sewer flooding and pollution incidents.

Welsh Water managing director Nigel Annett said,

“We have a very large investment programme to improve the wastewater network to reduce the risk of storm water flooding. But this is not a problem that can be solved by Welsh Water alone. The answer cannot lie in upsizing all our sewers, as this would have a severe impact on bills – costing around £10,000 per customer. It would also cause massive disruption for only temporary benefit. Pumping rainwater through our wastewater network also uses a lot of energy, and that is something that we would like to avoid to help reduce our carbon footprint.

“We plan to spend around £800m by 2015 on necessary improvements to our wastewater system, but this will need to be supported by a change in the way we create and manage the built environment. To put the scale of the issue into perspective, in London an area 22 times the size of Hyde Park has been paved over since 1945 – applying this rate to Cardiff alone means an area equivalent of 300 Millennium Stadium pitches has been paved over. That is, grassland and open areas that have been built on with a consequent huge increase in surface water run-off to the sewerage network. Our long-term objective is to have drainage systems in developed areas that, as far as practical, mimic natural drainage to green areas.”

As part of the Green Space Wales initiative Welsh Water is linking with central and local government, planners, developers and other decision makers to seek support for legislative change and the adoption of sustainable drainage solutions for new housing and other developments. The company has taken a UK water industry lead by commissioning large-scale studies in Wales as part of its Surface Water Management Strategy.

Commenting on Welsh Water’s strategy, Richard Ashley, professor of urban water at Sheffield University explained,

“Welsh Water is visionary in tackling this issue and is approaching it in a different way to the rest of the UK water industry – perhaps because of their unique business model where they do not have shareholders to service. They realise that we can no longer do things the old way and are looking at how they can manage storm water where it lands on the surface.”

Mr Annett continued,

“To put it very simply, we need more green space in our urban areas so more rain water can be dealt with more effectively. As well as the technical approach to reducing surface water flows, legislative change to planning laws may also be needed. For example, we may need to factor sustainable urban drainage into plans for new developments. Change could also mean that householders would require planning permission before paving over their front gardens to create parking spaces, a requirement that came into effect in England on 1st Oct 2008. The surface water management strategy being developed will provide a long term vision as to how Welsh Water will deal with surface water flows for the next 25 years.

There will be a greater proportion of expenditure on preventative measures, rather than reacting to events. Reducing the amount of flow to the network will be by management of the system, so that it is not automatically chosen as the disposal route for surface water. We will strive to reduce the area connected to the system.