Climate Changes
It is generally accepted that the UK’s climate is changing and that our weather is becoming more extreme. Paradoxically, in the short term, it is not the overall levels of rainfall that influence the need for sustainable drainage but the ferocity and frequency of the single rainfall events that may cause flooding. These, combined with on-going development, add to the necessity for SUDS solutions.
The Key SUDS Principles
Sustainable drainage systems control surface water run-off as close to its origin as possible. This is termed ‘source control’. This minimises changes in the volume and rate of surface run-off from developed sites and thereby minimises flood risk and other environmental damage. Additionally, SUDS may offer an element of pollution control as well as ‘attenuation’ — where infiltrated water is stored before its controlled release.
These levels of control and treatment result from a series of techniques (‘management train’) that integrate with one another to gradually reduce levels of pollution.
Removing pollution from run-off is an important part of SUDS design. The use of SUDS to control pollution and replace oil separators is highlighted in the most recent edition of Pollution Prevention Guideline PPG3 published by the Environment Agency 2006.
Trees (the urban forest) are an important element in the biodiversity of urban areas and improve amenity by providing enhanced aesthetics, cooling and shading. SUDS can be designed to protect and enhance the health of existing and new trees by protecting the roots systems and providing irrigation and aeration to the soil.
Rainwater harvesting involves collecting rainwater in storage tanks and reusing it for non-drinking purposes such as watering gardens or flushing toilets. Rainwater harvesting can be incorporated into SUDS. The storage required for SUDS would be additional to that provided for the harvesting system.