It is important that your application can demonstrate the site can be sustainably drained; this is a principle of development. This should be demonstrated at the earliest opportunity.
- Craven Local Plan Policies ENV6: Flood Risk, INF4: Parking Provision
- The National Planning Policy Framework (NPPF)
All development including the provision of dwellinghouses where –
(i) the number of dwellinghouses to be provided is 10 or more; or
(ii) the development is to be carried out on a site having an area of 0.5 hectares or more and it is not known whether the development falls within sub-paragraph (c)(i);
(d) the provision of a building or buildings where the floor space to be created by the development is 1,000 square metres or more; or
(e) development carried out on a site having an area of 1 hectare or more
Minor and small developments shall provide details of a practical SuDs scheme and include details on maintenance of scheme. If it is proven that SuDs is not appropriate for the site then the drainage assessment will need to justify why the proposed method has been chosen and gives the best available environmental protection.
The Lead Local Flood Authority (LLFA) for Craven is North Yorkshire County Council. The LLFA will be consulted on planning applications that include the provision of Sustainable Urban Drainage Systems (SuDS).
SuDS are an approach to managing rainwater falling on roofs and other surfaces through a sequence of actions. The key objectives are to manage the flow rate and volume of surface runoff to reduce the risk of flooding and water pollution. SuDS also reduce pressure on the sewage network and can improve biodiversity and local amenity.
SuDS is a departure from the traditional approach to draining sites. There are some key principles that influence the planning and design process enabling SuDS to mimic natural drainage by:
- storing runoff and releasing it slowly (attenuation)
- allowing water to soak into the ground (infiltration)
- slowly transporting (conveying) water on the surface
- filtering out pollutants
- allowing sediments to settle out by controlling the flow of the water
A surface water drainage scheme should include the following information:
- a metric scaled plan of the existing site
- a metric scaled topographical level survey of the area to metres above ordnance datum
- metric scaled plans and drawings of the proposed site layout identifying the footprint of the area being drained (including all buildings, access roads and car parks)
- the existing and proposed controlled discharge rate for a 1 in 1 year event and a 1 in 100 year event (with an allowance for climate change), this should be based on the estimated greenfield runoff rate
- the proposed storage volume (attenuation)
- information on proposed SuDS measures with a design statement describing how the proposed measures manage surface water as close to its source as possible
- geological information including borehole logs, depth to water table and/or infiltration test results
- details of overland flow routes if drainage capacity is exceeded
- a management plan for future maintenance and adoption of drainage system for the lifetime of the development