North Warwickshire Borough Council

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Climate Change and Global Warming - Sustainability

Surface Water Run-off

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Surface water drain

Our changing climate is leading to a higher frequency of storm events - times where high volumes of rain fall in a short period. This water can lead to flooding in the vicinity or further downstream if allowed to flow directly to storm sewers and watercourses. The Council, along with the Environment Agency, seeks to minimise the risk from flooding by ensuring all new development is sustainably drained where possible, or at least that surface water is retained on site with a restricted discharge to sewers or watercourses.

Householder Developments and Driveways

The most common form of development enhancing surface water run-off is from resurfacing or extending driveways. From 1st October 2008, permitted development rights for dwellings changed such that you will now require planning permission if you wish to lay non-permeable surfacing or sub-base material, or wish to direct surface water directly to the sewer, from a cumulative area of 5m2 or greater.

There is a range of materials which are permeable. These include pea gravel or similar (although the design of the driveway should not allow extraneous material to be carried by wheels onto the highway), block paving with raised edges to ensure a percolation gap between blocks, and permeable tarmac. Permeable sub-base materials, such as 4/20 and Type 3 sub-base are also suitable.

Where you wish to use a non-permeable surface, there is the further option to direct surface water to a permeable area of your property. This could be wheel tracks with water directed to grass in-between or either side, reinforced grass and gravel, or a soak away installed for this purpose.

You can get further guidance on the above and the permeable surfacing of front gardens here. These restrictions are likely to extend to commercial property in the near future.

Surface Water in Other Development

The Council will assess whether there is an increase in surface water run-off arising from the development. This could arise from buildings, parking areas, roads or other such development. Where this occurs, we will seek information on how the development will be sustainably drained, and in larger developments, look to see how such drainage can be used in conjunction with open spaces and biodiversity gain.

  • Small to medium developments - permeable paving, soak away and subterranean storage/attenuation chambers are likely to be most suitable for such developments. These should be clearly indicated on the site plan provided with your application, along with the routes of any piping. Details of the construction method and materials for permeable paving should also be included (such as a cross section diagram), and details of flow restriction chambers and proposed discharge rates in the case of subterranean storage/attenuation chambers. Planted areas can also reduce run-off on such sites.
  • Medium to large developments - although the above drainage methods may also be appropriate here, the use of Sustainable Urban Drainage Systems (SUDS) is likely to be sought. Examples include ponds, wetlands and swales, and design proposals should be shaped around these to incorporate them and give them a functional use (such as forming part of the open spaces and landscaping). These should be clearly indicated on the site plan provided with your application, along with the routes of any piping. Where swales are proposed, details of the construction method should be included (such as a cross section diagram). As storm sewers may lead to or run from such proposals, you are advised to contact Severn Trent Water and the Environment Agency at an early stage of drafting your proposals.

Please contact the Planning Control team should you require further advice.

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