Over-concreting in urban areas has been a significant factor in the rise in flooding in recent years, recently demonstrated by the floods in Somerset and the Thames Valley. Surfaces that are impermeable to water are unable to allow it to drain away, and instead divert it straight to our Victorian drainage system, which can struggle to cope with high quantities of water all at once. Sustainable Urban Drainage Systems (SUDS) are designed to minimise the risk of flooding by providing better opportunities for water drainage, without overburdening our traditional drain system.
SUDS are now mandatory in new developments in the UK, as of the 2010 Water and Flood Management Act, and it is hoped that SUDS will also become a popular addition when renovating older properties to reduce the risk of us seeing more devastating floods across the UK in the future.
The installation of SUDS addresses three key aims:
to slow down the flow of rainwater into the UK’s drains
to improve the quality of the water flowing into the UK’s drains
to minimise damage caused by heavy rainfall to the environment, including wildlife habitats
A number of techniques are used when installing SUDS measures, all of which help to achieve these three points.
Introducing more permeable surfaces
Making outdoor surfaces more permeable is crucial in improving drainage and reducing the risk of flooding. This means opting for gravel, or blocks or tiles with gaps between them, which allow drainage through to a layer of subsoil. This SUDS method is versatile and popular with the majority of properties, though in some cases it can be unsuitable. The underlying soil must also be permeable, which rules out the method in areas where soil is heavily clay-based. The soil must also be clean and free of contaminants, so as to avoid them being washed into nearby bodies of water where it can cause environmental damage.
Harvesting rainwater in a water butt is an effective way of reducing the water sent into nearby drains, reducing the risk of flooding. It also doubles up as a good way to reduce water consumption around the home, and can be used in gardening or car washing, or diverted for use in the toilet or washing machine.
Ditches, ponds and wetlands
Certain geographic features can be effective in controlling the rate of water drainage around a property. Ponds, ditches and wetlands can be incorporated into the spaces around new developments to collect heavy rainfall, then release it gradually when the drainage system is able to handle it, in a process called attenuation. When unfilled, attenuation ponds and ditches are usually covered in grass or similar vegetation and fit comfortably within the green space.
Green roofs are another good way of incorporating better drainage into urban areas using vegetation. Rainfall feeds the plants on the roof whilst slowing the release of water into the drainage system. Green roofs have a host of other environmental benefits such as insulation for the home and air purification.
Maintaining water quality
It’s not just the prevention of flooding that SUDS methods are used for. Implementing better drainage can help with the filtration of rainwater, helping to prevent the spread of contaminants such as salt, oil and sediment and preventing them from entering our water systems, where they can potentially harm wildlife and its habitat.
The management of rainwater is crucial to maintaining equilibrium when the country is faced with bad weather, and ensuring the efficiency of our now dated drainage systems, in order to prevent yet another flooding disaster.
Image sourced: Robert Murraytagsfloodingrainwater harvestingsudssustainable urban drainage systems