You cannot talk about the application of sustainable drainage without some reference to real life situations and this collection of SuDS guidance on these web pages are no exception.
I cannot talk the talk without walking the walk and the following examples include components installed at my own home.
A common and useful application of the retrofitting of SuDS (or the addition of SuDS to an existing drainage system can be demonstrated by the following example.
In a typical street it is common to have paved footways and tarmaced highway. When traffic calming is added, this can be done by building out the footway into the highway to create a narrowing or chicane.
The first element to consider is why create the build out in paved surfaces? Why not have the chicane as a grassed feature. This will reduce the runoff by replacing hard surfaces. The first principle of SuDS. The use of vegetation also adds an element of “interception” to runoff (i.e losses are added to the system where evaporation and transvaporation are encouraged).
The first element to consider is why create the build out in paved surfaces? Why not have the chicane as a grassed feature. This will reduce the runoff by replacing hard surfaces. The first principle of SuDS. The use of vegetation also adds an element of “interception” to runoff (i.e losses are added to the system where evaporation and transvaporation are encouraged).
The first element to consider is why create the build out in paved surfaces? Why not have the chicane as a grassed feature. This will reduce the runoff by replacing hard surfaces. The first principle of SuDS. The use of vegetation also adds an element of “interception” to runoff (i.e losses are added to the system where evaporation and transvaporation are encouraged).
In order to attenuate and deal with an increased roof area from an extension building control were seeking the inclusion of a soakaway in the garden adjacent to the extension. However, in this case, the shape of the garden and the existence of foul drainage and other structures prevented suitable off-sets to any soakaway (5m).
The alternative, was to introduce a rain garden such that it intercepted roof drainage, provided attenuation, take up by the plants and evaporation with any remaining runoff then directed to an overflow and a perforated pipe distributing this within areas of the garden away from structures.
In this case the rain garden was a prefabricated tank system with a void within the lower half to provide the storage and the upper half available for planning and soil.
The tank was provided by SuDS Planter (https://www.sudsplanter.com/)
The tank is lined with a water roof membrane as well as a felt layer to minmise damage to the structure prior to filling with a sand loam soil.
A layer of soil is added and an overflow pipe (for when the runoff exceeds the filtration of the soil)
The down pipe could be entirely disconnected and diverted to the rain garden, or in this case, a diverter added to the downpipe.
The rain garden is planted with a selectionof water and drought resiliant plants (a selection is based on the specification given in the UK Rain Garden Guide - https://raingardens.info/wp-content/uploads/2012/07/UKRainGarden-Guide.pdf)
Part of the extension included additional parking areas. In keeping with permitted development and the Governments encouragement to only increase paved areas if they were permeable I installed a gravel based permeable pavement.
In my case the underlying soil is predominately Chalk and a good soil to allow infiltration. As the paving is only taking its own rainfall it does not need to be 5m away from any structure.
As with all SuDS (and any drainage etc) utilities have to be considered.
Existing manholes and accesses need to be considered.
Try to minimise the compaction of the soils as this will reduce the permeability
A layer of at least 100mm of Type 3 (no-fines granular sub-base) is laid on a geo-textile to provide the load bearing part of the driveway
To keep the surface gravel layer in place I usded a geo-grid laied over the Type 3 (again with a geo-textile layer to prevent mixing of the gravel layers)
The geo-grid is filled with stone and raked over to produce the final surface. Overall the whole structure is competely pervious and allows rain to infiltrate through with no connection to the main drains.
