Driveways, raingardens and soakaways
When talking to a member of a community that had recently flooded, the conversation moved on to a disagreement he and his wife were having. The couple wanted to landscape the front area of their property so they could park their cars there. One of them just wanted to dig up the front lawn and garden to install a tarmac driveway, the other was aware that doing this would reduce the ability of their property to naturally drain surface water.
The discussion turned to how the couple could ‘do their bit’ to manage surface water (created by the property), within the property boundary and not contribute to potential surface water problems in the wider area in future.
There were a few things that the gentleman and his wife were unaware of, and so will not have considered.
Depending on the scale of work they would like to undertake, there may be planning rules to consider. The following rules apply to the front gardens of houses only:
- If the surface area of the planned surfacing is more than 5m², planning permission will be needed for laying traditional, impermeable driveways that do not allow for the water to run to a permeable area.
- Planning permission is not required if a new or replacement driveway of any size uses permeable (or porous) surfacing which allows water to drain through, or if the rainwater is directed to a lawn or border to drain naturally.
Points to consider
- How much surface water may need to be managed? SuSDRAIN, one of the leading providers on Sustainable Drainage Systems resources and information, calculate that during a heavy storm enough rainwater could fall on an average driveway to fill 3 baths (this could be as much as 500+ litres).
- By using a method that provides a slow release of infiltration, the paving could filter out pollutants, help recharge groundwater and therefore help reduce the risk of flooding.
These options allow surface water to penetrate the surfacing, through the sub base and either be held in an attenuation system or feed into a soakaway (see below) to infiltrate slowly into the ground.
Using traditional surfacing materials such as concrete or asphalt to surface an area could be done in such a way as to use the fall of the driveway to direct surface water into a
Channel or French drain which could then empty into a;
Soak away – lined with a membrane and filled with either rocks, gravel or drainage crates which provide a void for water to attenuate.
Rain garden – these can be created with plants, shrubs or bushes planted in a depression in the ground which may be dry for long periods of time. The rain garden will collect surface water and allow it to either infiltrate, evaporate or both.
Water from roofs could also be channelled into these systems by making alterations to drainpipes. This will reduce the demand on sewers during heavy downpours.
Water companies charge for dealing with rainwater from properties which enters the sewer network. This is through a;
- Fee in the standing charge.
- Charge based on the rateable value of your property.
- Charge related to the type of property you live in.
If no rainwater from your property enters the sewer system at all, you may be entitled to a surface water drainage rebate from your water company. If you can make a case for the rebate you will not be charged for surface water drainage on future bills and some of the amount you have paid previously may be refunded.
For more information with good links and tips on this subject visit Guidance on the permeable surfacing of front gardens.