Theory

• Pollutants can harm fish and wildlife populations, kill native vegetation, foul drinking water supplies, and make recreational areas unsafe and unpleasant. Sediment from erosion can fill spaces between rocks on the stream bottom, thus reducing living space or habitat for the biological communities.
• Sustainable urban drainage systems manage rainfall by using natural processes in the landscape to reduce flooding, control flooding and provide amenity for the community.
• Roof water is collected in water butts for use in gardens or flows to grass channels called swales. It then travels on to grass basins where it is stored before being released into local ditches.
• Rain falling on roads or paths soaks through a permeable block paving where it is filtered and stored in the stone below, or it flows into grass channels, which have a stone filter drain underneath, before it joins the rest of the SUDs system.
• If it rains heavily, the swales and basins fill for a short period, protecting those areas downstream. Water is collected, cleaned and stored in the local landscape, providing an attractive place for play and wildlife.