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Sustainable drainage requirements for planning applications

Sustainable drainage is now a material planning consideration for the Local Planning Authority.

Any new developments or redevelopment should encourage a collaborative approach to ensure that development planning is undertaken to ensure a water sensitive urban design approach which utilises sustainable drainage creating blue infrastructure in order to help create beautiful, successful and resilient places. 

What are sustainable drainage systems?

Approaches to manage surface water that take account of water quantity (flooding), water quality (pollution) and amenity issues are collectively referred to as Sustainable Drainage Systems (SuDS). SuDS mimic nature and typically manage rainfall close to where it falls. SuDS can be designed to slow water down (attenuate) before it enters streams, rivers and other watercourses.

CIRIA's susdrain project has launched a new animation shown below, on Sustainable Drainage Systems (SuDS) that provides an engaging and digestible overview of SuDS.

There are a large variety of drainage options available including green roofs, permeable paving, swales and ponds.  

SuDs information required for major applications

Sustainable drainage systems (SuD's) are now a material planning consideration for major developments (ie developments of 10 dwellings or more and equivalent non-residential schemes).   

All major applications should adopt the approaches, provide the information and meet the standards explained within the Hillingdon SuDs Design and Evaluation Guide.

The Council wish to reduce the need for precommencement conditions, however drainage is critical to be agreed prior to work beginning on site. Therefore to speed up the review of proposals, please ensure that all consultants design to the appropriate standard of detail. An application should as a minimum contain and demonstrate the following points:

  1. Summarise the proposals within the Hillingdon Suds Proforma [396KB].or  SuDs Proforma Excel Spreadsheet [114KB]  Developed by LoDrainage Engineers Group and the GLA so that it is a consistent form across London. Further guidance is contain within the notes.
    • Calculations must adhere to the revised Environment Agency guidance on Climate Change produced in Jan 2016. This requires attenuation to be provided for Commercial 1 in 100year plus 20 percent and residential 1 in 100 year plus 40 percent.
    • Calculations should be provided to demonstrate water is controlled to green field run off rates, at a variety of return periods.
    • A 5l/s rate should not be used as a minimum, as flow control devices have evolved to allow smaller discharge rates.
  2. Plans, drawings and specification of SuD's proposed integrated with landscaping and materials requirements. It is expected design, drainage and landscaping consultants coordinate and integrate plans.
    • Detailed site layout showing SuDs integrated with landscaping proposals. SuDs should contribute to green links and chains as well as accessibility to the Blue Ribbon Network across Hillingdon.
    • Topographical survey of the site currently showing above ground ponding, overland flow routes and proposed levels showing changes manage these risks as well as providing exceedance routes.
  3. Demonstration of the consideration of the spectrum of SuD's in accordance with the SuD's hierarchy, ideally using a variety of options and clear justification provided where the most sustainable solution cannot be provided.
  4. S106 may be considered for off site works where these standards cannot be met.
  5. Information on the receptors of the drainage system. 
    • Where infiltration is proposed a suitable site investigation must be provided including information on groundwater levels, or sizing for a tanked or no infiltration must be assumed.
    • Provide evidence that the proposals connect into a wider functioning Thames Water or private network, ie ie that the point a proposal connects into is part of a wider network, with the appropriate agreements in place.
    • Discuss proposals with Thames Waters free pre planning application service.  Thames Water logo message : This link opens in a new window  This will help identify any potential water and wastewater network reinforcement requirements. Developments which result in the need for off-site upgrades will be subject to conditions to ensure the occupation does not outpace the delivery of necessary infrastructure upgrades. New connection charging information can also be found on the Thames Water website. 
  6. Methods of appropriate water quality control to be provided.
    • Management and maintenance plan for all SuD's to be provided. 
    • To ensure there is ongoing maintenance over the lifetime of the development, a management and maintenance plan will be expected to be provided along with the details of the body legally expected to maintain the system where it is anyone other than a single private land owner.
    • This should also contain details of the standard of operation.
  7. A condition will be added to planning decisions, or developers will be expected to enter into a legal agreement under S106 of the Town and Country Planning Act 1990 (as amended). An example of an appropriate management plan can be found on Susdrain - Useful frameworks and checklists.

Green Roof Lake Farm School  As Hillingdon is in an area where water resources are provided generally from groundwater supplies and these are heavily abstracted. It is expected that drainage proposals should include some at source water collection and water reuse, through the provision of rainwater harvesting tanks or even water butts, or grey water recycling.

This is to minimise water use proportionate with the scale of the proposed development. If this cannot be achieved on site then retrofit more efficient sanitary ware.

Minor applications and householder development Water Pipe Art

Minor development can also cumulatively affect flood risk. There is increasing demand on the capacity of surface water sewers and often the water company will not increase the capacity of the sewer. Small scale development can and should contribute to reducing flood risk by ensuring all hard surfacing is made permeable.

  • All minor development should include plans which shown down pipes are connected to soakaways and or other methods of control and not the sewer.
  • Paving your front garden is not permitted development, if is completely hard surfaced.

For guidance on how to comply with requirements for front gardens the Royal Horticultural Socity has produced a useful booklet 'Gardening Matters - Front gardens' or Hillingdon Council has produced a leaflet on paving front gardens [206KB].

Report non compliance to our planning enforcement team

Please call the Customer Contact Centre on 01895 2506000 or email contact@hillingdon.gov.uk.

If have any other queries regarding the information on this page, please call the Customer Contact Centre and ask to speak to the Flood and Water Management Officer or email flooding@hillingdon.gov.uk.

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Article utilities:  Bookmark and Share Print Print this page Last updated: 13 Mar 2019 at 10:55