Going Green - Drainage
Although it’s often known as Sustainable Urban Drainage Systems (SUDS), the principle of rainwater disposal which does not put undue pressure on existing resources and infrastructure is applicable to any site, rural or urban.
…new regulations will ensure all homes are carbon neutral by 2016.
In general, it is best to deal with rainwater discharge locally, returning the water to the natural drainage system as near to the source as possible.
- Good Drainage Practice Rain water harvesting and reuse (e.g. water butts or tanks)
- Green roof on building
- Retention of ’soft’ surfaces (grass); specification of porous hard surfaces; avoid concrete and tarmac
Most experts are agreed that one of the imminent major impacts of climate change - some would say that it is happening already - is an increase in ‘extreme weather events’ such as storms and floods. Periods of unusually heavy rainfall may result in antiquated or inadequate drainage systems, unable to take the increased flow and ‘backing up’, causing local flooding and pollution. Surface water runoff can contain contaminants such as oil, organic matter and toxic metals. Although often at low levels, cumulatively they can result in poor water quality in rivers and groundwater, affecting biodiversity, amenity value and potential water abstraction. After heavy rain, the first flush is often highly polluting.
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If we can slow down the rate of surface water runoff and provide temporary storage or ‘attenuation’ for rainwater on site, this will ease the pressure on existing drains. Minimising runoff can be achieved at the design stage by using ‘green’ or vegetated roofs, which will naturally filter and slow the rate of discharge. Porous surfaces, such as paving, gravel or grass, rather than seamless hard concrete or tarmac, will allow rainwater to percolate into the ground, eventually refilling underground aquifers which are much more important than reservoirs for our long-term water reserves. This will also reduce the flooding risk both on site and downstream.
Filter strips and swales are essentially grass banks and ditches which mimic natural drainage patterns by slowing and filtering the flow and removing pollutants. They provide temporary storage and can be integrated into landscaped areas and road verges. Basins and ponds can provide more permanent storage and should be designed with extra capacity to enable storage of flood water. Both will increase areas of wetland habitat which are important for biodiversity and providing educational and leisure amenitie.
Useful Contacts
The Environment Agency: www.ciria.org/suds/suds_techniques.htm
A new rainwater harvesting system which is designed for use in the garden has been launched by Klargester. Known as Raintrap, the system comprises a filter, an underground storage tank and a pump. Rainwater runs down the roof and into the guttering and downpipes before passing through a filter. The water is stored in an underground tank available in three sizes. You can then access the water at a constant pressure. From around £1,000. www.klargester.com
The Government has unveiled plans to encourage green homebuilding, saying that new regulations will ensure all homes are carbon neutral by 2016. The regulations will be launched in stages over the next ten years. Around 27 per cent of all carbon emissions in the UK are from energy used to heat, light and run homes.
Source: Homebuilding&renovation
Going Green
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