There is growing urgency for new construction sites to meet sustainability targets.
As construction projects create carbon emissions and habitat loss, it is the responsibility of developers to ensure every aspect of a new site includes steps to reduce environmental harm.
Sustainable urban drainage systems (SUDS) provide opportunities to fulfil all environmental, legal and planning obligations while ensuring that aesthetics remain desirable.
SUDS basins, or detention basins, are designed into new developments primarily to prevent flooding. By collecting water and rainfall as close as possible to the source and fed by swales and drainage ditches, they ensure water is discharged sustainably either by infiltration or controlled discharge into nearby watercourses.
For further environmental benefits, they are also an opportunity to create practical and attractive areas for wildlife by completing them with vegetation. With incorporation of geosynthetic products including erosion blankets, basins can be landscaped to create areas for plants, insects, birds and small mammals to flourish.
In this way SUDS or detention basins can be doubly effective for developers, creating sustainable features which prevent flooding and promote biodiversity.
When incorporating one into a development is important to first note the environmental legislation in place to regulate their design and usage.
These regulations tend to be governed by environment agencies – the EA in England and SEPA in Scotland – with regular updates posted online, including here: www.susdrain.org/news/
In Scotland it is a requirement to discharge surface water through a sustainable urban drainage system (with the exception of single dwellings or discharge directly to coastal waters). Implementation of regulations – including the Water Environment (Controlled Activities) (Scotland) Regulations 2011 and Flood Risk Management Act 2009 – means SUDS have become standard practice in protecting watercourses and biodiversity in Scotland.
In England, standards for SUDS are governed by the Flood and Water Management Act 2010 as well as Flood Risk Regulations and general Building Regulations.
Both Scotland and England’s regulations are guided by the European Water Framework Directive
Guidance compiled by CIRIA (the Construction Industry Research and Information Association) – the SUDS Manual – informs on how to adhere to these regulations.
By improving a site’s ability to support wildlife and habitats, SUDS and detention basins can also help to deliver on the UK Environment Bill’s requirement for new developments to deliver a 10% ‘net gain’ in biodiversity.
Figure 1 – Detention Basin Construction
Designing and installing basins
Finding the most suitable location for a basin to effectively reduce flood risk and improve habitats will depend on how it needs to function and where will best capture water run-off and rainwater. Swales and drainage ditches will need to be located around a site, to direct water to the basin.
As well as the legislation and location, it is also vital to consider the type of vegetation appropriate to suit the native plants and soils. Once understood, this will inform on the best type of geosynthetic liner to use, with a variety available for different basin types, sizes and requirements.
For projects seeking to maximise the positive environmental impact of a basin, bentonite liners are optimal. Made from naturally derived bentonite clay they pose no risk of pollution or harm to biodiversity while being robust and impermeable once fitted. Thanks to their ability to be quickly and easily installed, without need for specialist equipment or personnel, bentonite liners also negate the need for carbon-emitting equipment and offer time-benefits during a basin’s development.
Additionally, non-synthetic liners – LLDPE or HDPE liners – are available, also offering robust, impermeable and low-cost solutions for lining basins.
The most optimal solution will depend on a number of factors, including soil and weather conditions, the depth and requirements of the basins, and the types of biodiversity to be established in, or attracted to, the area.
SUDs and detention basins are an important part of developments, offering long-lasting environmental benefits, as well as aesthetic appeal. It is vital that the relevant legislative requirements and environmental benefits are considered in the planning and delivery of construction works. And with good design they can provide habitats, food and foraging or breeding opportunities for a wide range of wildlife.
For advice on how to optimize your projects, including designing effective and attractive sustainable urban drainage systems, get in touch.