Conservation: pressure's on to solve drainage issue

The floods two years ago, and resultant damage, remain fresh in the public's memory. With parts of the country severely water stressed, will the new measures being mooted for conserving water actually help to ease storm flooding?

Wars have been fought over many issues, but by the end of this century experts believe there could be serious conflicts over the availability of fresh drinking water. The UK has always been more famous for its rainfall than its droughts but areas of the South-east are now more water stressed than Egypt, Syria, Sudan or Morocco, and this summer, forecasters' predictions of dry and hot weather interspersed with storms are already proving to be correct.

As the temperature goes up, people use more water for showers, watering their gardens and washing clothes. And with increasing amounts of water being flushed down the drain, combined with the inevitable storms that follow periods of hot weather, the drains cannot cope and flooding ensues.

The UK has already had record temperatures this year, and Yorkshire, Wales and the South-east in particular have suffered flash flooding. In July, Hailsham in East Sussex had 4" of rain in four hours and London's Victoria Station was closed due to flooding.

With memories of the floods of 2007 - when £3B worth of damage was caused - still fresh in the public's minds, several key reports have been produced to try to address the impact of climate change on our water.

The far-reaching 92 recommendations of the Pitt Review, the first stages of the Floods and Water Bill and the government strategy Future Water all emphasise the need for a co-ordinated approach.

British Water, as the trade association representing manufacturers, design, construction and installation companies in the UK water industry, has specialist focus groups. These work with regulators, industry and environmental organisations to improve standards by concentrating on elements of good water usage, encouraging sustainable drainage and correct sizing and design (flows and loads) of small wastewater treatment systems.

Mike Norton, chairman of the Packaged Treatment Plant Focus Group, says: "The water industry can play a really influential role in helping this country to deal with problems now, rather than in 50 years time when we are at crisis point."

Intense use
In the UK, the density of population combined with minimal rainfall, especially in the South-east, increases the risk of flooding and water shortages. The drainage systems are often old, and as populations and housing estates grow, there is increased stress on systems that were not designed to cope with such intense use.

Where there are rural areas relying on old or badly maintained septic tanks and packaged treatment plants, the results can be unpleasant, posing a danger to wildlife. And in cases of pollution, the fine for a first time offence can be up to £20,000. "It is these stressed regions where the future case for water saving mechanisms is strongest," says Norton. "New homes should not be built in these areas without integral water saving technologies."

Norton, who is also chairman of the UK Rainwater Harvesting Association (UKRHA), believes that planning permission for new-build homes in flood plains must include rainwater harvesting and other water efficiency techniques such as SUDS and grey water reuse. Also, BS8515 now includes information on how to design/size tankage for rainwater harvesting so that it includes attenuation for floodwater storage.

Norton says: "These measures, combined with ponds in every new home in a flood risk area, and rainwater harvesting storage capacity, would help in flood situations. There should be a planning directive and it could be incorporated into building regulations."

Alex Stephenson, chairman of British Water's Sustainable Drainage Focus Group, agrees that we have to start thinking ahead: "We have to plan for dry weather followed by intense rainfall and flooding. Contingency plans should be incorporated in every new design.

"Surface water was a proven cause of the severe floods we have suffered. Sustainable drainage to manage surface water is essential - it is no longer an option."

The independent Review of Household Charging and Metering for Water and Sewerage Services, led by Anna Walker, published its interim report on June 29, 2009, and indicated that the current system needs updating.

Meanwhile the Environment Agency (EA) is urging that all households have water meters within the next 20 years. Water meters and water harvesting systems will probably become compulsory following the EA's Water Resources Strategy, published earlier this year.

The document warns that many rivers, particularly those in south-east England, could be reduced by 50% to 80% by the middle of the century, despite current worries about rivers overflowing.

At the moment, Britain's per capita daily use of water is 148 litres, which is one of the highest in Europe. Experts have estimated that we need to cut that figure to less than 130 litres, while the code for sustainable homes goes even further with a target of 80 litres a day per person.

Water harvesting is one measure that is exciting interest, where "grey water" (old bath or washing machine water) is used to supply toilet cisterns, and rainwater is collected to water plants and flowers.

Water harvesting can save up to 50% of mains water usage in the home and up to 80% in commercial / industrial installations. There is now pressure for legislation to make rainwater harvesting systems compulsory on all new buildings - a move that would be endorsed by British Water's focus groups.

An advantage of rainwater harvesting is that it can hold back stormwater run-off during downpours. As an integral part of SUDS, it can be considered as contributing towards discharge control consents for local planning purposes.

Not taking sufficient action could lead to rationing, standpipes and the loss of wetlands and native wildlife.

Future problems
Stephenson says: "One in six homes in the UK is liable to flooding. To qualify as being in a flood risk area, that meant that you were at risk once every 100 years. Now, experts are accepting that it is likely to be much more often than once in 100 years.

"The government is still committed to building three million homes by 2020, so many of those will inevitably be in flood risk areas. We have to build in systems that mitigate future problems, and that could be a combination of natural and proprietary solutions."

There have been some moves to pre-plan for more floods. The government's Code for Sustainable Homes has tried to encourage house builders to install rainwater harvesting and greywater reuse through a voluntary code that aims to improve energy efficiency, but Norton believes it will take government intervention to make any sort of significant impact.

"It will have to come from legislation," he says. "Rainwater harvesting will have to be mandatory on all new buildings."

Stephenson adds: "The problem is that instead of demand for water falling, it's actually increasing at 1% a year. Until we tackle our attitude to wasting water, all these warnings will be like water off a duck's back."

Note: The two British Water focus groups have produced two codes of practice - Flows and Loads and SUDS - that are intended to help the industry find the correct solution for individual sites in both treatment plants and sustainable drainage measures. They are free to download from www.britishwater.co.uk/publications/publications_and_technical_guides.aspxng.

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