Sustainable drainage systems have in one form or another, been around for many hundreds of years, with some of the earliest examples being seen in Roman times. House builders are catching back onto the idea that drainage doesn’t have to mean huge pipes underground to hurry the water away from where it falls, turning more and more to the Sustainable Drainage Systems (also know as SUDS) while building their sustainable housing developments and to companies like Wavin who have designed their Osma and Intesio systems to help make drainage on housing developments, more efficient, less unsightly and better for the environment.
The problem with the drainage systems that have been used since Victorian times is that they were designed to take the run off of water on hard paving and roofs and transport it away from the source as fast as possible to a designated “discharge point” by means of a watercourse or soak. However, this just moves the problem further downstream where it can cause flooding there instead.
It also means away that the natural filtration process that water undergoes in its journey underground to natural reservoirs is removed, meaning any chemicals in the run off, like organic matter (something that was a big problem back in the days before reliable sewage systems), oil or other chemicals are transported straight into the rivers to the detriment of the animal life (both aquatic and land bound) that rely on that water.
Lastly by diverting the water away into pipes, it increases the risk of draught as the rainwater is prevented from returning to the water table, reducing the ground water reserves and the levels of water in drier weather.
Sustainable drainage systems encompass many different approaches meaning that for any development there is a system that can be implemented. They can be designed to help improve the biodiversity in developed areas, giving a much needed boost to some of our vanishing wildlife, as well as giving the residents of the local area greatly needed recreational areas.
They work by helping to reduce the quantity of runoff from the source, and slowing down the velocity of the runoff to allow for natural filtration.
Some of the methods used in sustainable drainage systems include:
- Rainwater harvesting – where rainwater is collected and stored so that it can be used in areas where fresh water isn’t required, such as flushing the toilet, watering the garden and washing the car.
- Green Roofs – where flat roofs are planted up with a mixture of plants, this helps reduce the amount of run off, improve water quality, improve insulation and extend the life of the roof. This is a technique is widely used in Germany and other European countries with great success.
- Permeable pavements – Allow water to filter through the paved surface rather then gather on it or run off of it onto the next permeable surface. It can either be gathered into a reservoir tank under the paving for reuse (flushing toilets, etc) or allowed to seep away into the water courses through natural or man-made filtration systems.
- Infiltration trenches and basins – Shallow ditches or basins that are backfilled with stone to allow water to filter slowly into the subsoil. The useful life of these structures is determined by the maintenance of them, however if they are properly maintained then they can remove a large proportion of solids from the runoff.
There are many other forms of sustainable drainage that are being put to use by house builders, commercial builders and developers, so next time you take a walk by the pond or stream in your housing development, remember that as well as being a thing of beauty in its own right, a haven for the local wildlife, it is also improving the quality of water for everyone and lowering your risk of flood damage.