Flooding in the UK is a serious hazard which is predicted to increase due to climate change. Existing drainage systems in towns and cities are under pressure as they were not designed to cope with the increased rainfall. Paving over front gardens adds to the problem as additional water enters the drainage system, rather than filtering away through the soil. Paving over front gardens can also damage water quality in drainage systems and the wider environment.
Permeable surfaces allow water to drain into the ground without adding to the local flood risk or causing pollution concerns.
There are three types of solutions to creating a permeable driveway:
- Using gravel or a mainly green, vegetated area.
- Directing water from an impermeable surfaces to a bordering rain garden or soakaway.
- Using permeable block paving, porous asphalt or porous concrete.
Permeable paving works by permeable surfaces allowing water to soak through the surface into the ground below.
These webpages have been produced in collaboration with Interpave, the Environment Agency and Warwickshire Wildlife Trust.
What are the Council doing?
There is a city-wide interest in installing Sustainable Drainage Systems. This presents an opportunity for the Council to collaborate with partners, including the Environment Agency and Severn Trent Water. We are integrating permeable paving into Coventry, within the city centre. The company Interpave have produced several case studies to showcase great examples of how permeable paving can be used successfully.
Case study: White Hart Lane, North Tottenham, London
This case study was an approach taken to reduce flooding and pollution of the hidden Moselle River, through the use of bioretention gardens to collect and treat polluted road run off. Permeable paving was used to further reduce run off.
Case study: Bridget Joyce Square, Australia Road, White City, London
This is a SuDS (Sustainable Drainage System) park with the community at its heart, and an example for future urban landscapes.
It celebrates roof water collection with sculptural gutters, downpipes and twisted steel halyards bringing water into rain gardens.
Concrete block permeable paving overlays a tarmac road and filters water into the rain gardens.
These webpages have been produced in collaboration with Interpave, the Environment Agency and Warwickshire Wildlife Trust.
Types of permeable paving
Loose gravel
Loose gravel is the simplest type of permeable paving to construct, and it is cost-effective. The driveway sub-base is covered in a layer of gravel/shingle. A strip of block paving or asphalt at the entrance to the driveway helps to limit the loss of the gravel/shingle.
Wheel tracks
These are paved tracks that align with car wheel tracks, with permeable material between the tracks to allow any run off to soak away.
Reinforced grass and gravel
This system strengthens the grass, allowing cars to drive over it causing minimal damage. Manufacturers are able to advise on the best material for individual locations. The Council uses this system in some residential areas.
Hard permeable and porous surfaces
This is a type of hard surfacing which allows water to soak into it. It can include porous concrete blocks and porous clay block paving. The material has gaps between the blocks which allows the water to soak away. It has a permeable sub-base.
Rain gardens and soakaways
Water can be directed towards a border, rain garden or soakaway. A rain garden is a depression in the garden to collect and store rainwater before allowing it to soak away into the ground or flow to the drains.
Soakaways are a similar idea where water is piped into a gravel-filled trench or geocellular box and allowed to soak into the ground.
Rainwater harvesting
Water butts or underground rainwater tanks can be used to complement all drainage methods to reduce run off. The water can then be reused for numerous purposes. Specialist rainwater harvesting companies can help.
These webpages have been produced in collaboration with Interpave, the Environment Agency and Warwickshire Wildlife Trust.