Drainage

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4.1.43 The Council is committed to the concept of sustainable development. One aspect of this is Sustainable Urban Drainage Systems (SuDS), a method for treating and disposing of surface water run off from new developments, in an environmentally sustainable manner.

4.1.44 The conventional method of draining excess surface water from built-up areas has been via underground pipe systems. In most cases, these deliver surface water to watercourses much more quickly than the original or greenfield site. They also convey potential harmful pollutants to the watercourses without treatment. This method of drainage may lead to flooding and other environmental damage.

4.1.45 The Scottish Executive’s Scottish Planning Policy (SPP) 7 ‘Planning and Flooding’ states the primary role of SuDS is to manage the flow of rainwater run-off from a new development site to mitigate peak flows to water courses and reduce flood risk. SuDS can also treat run-off so as to improve water quality and can incorporate landscape and habitat features to the benefit of amenity and biodiversity. Scottish Executive Advice on the issue is contained in Planning Advice Note (PAN) 61 ‘Planning and Sustainable Urban Drainage Systems’.

4.1.46 Drainage issues are material planning consideration in the determination of planning applications. The Council will require SuDS to be incorporated in development proposals at the earliest stages in project design, prior to a formal planning application. The Council will require drainage measures in new development proposals to have a neutral or better effect on the risk of flooding both on and off the site. An ecological approach to surface water management will be encouraged by, for example forming wetlands or ponds. The Council will consult Scottish Water and SEPA on appropriate planning applications. However, it is recommended that applicants, as part of the information in support of a planning application, show that the drainage is acceptable to Scottish Water and SEPA.

4.1.47 The ‘Sustainable Urban Drainage Systems design manual for Scotland and Northern Ireland’ published by CIRIA includes the following 4 general methods of control by SuDS:

a) filter strips and swales

b) filter drains and permeable surfaces

c) infiltration devices, and

d) basins, ponds and wetlands

which should be constructed as close as possible to the source of the water.

4.1.48 Other important methods include minimising the area of hard surfaces such as car parks, driveways and footpaths and encouraging the reuse of rainwater (e.g. provision of water storage butts), particularly at the household level.

4.1.50 The Council will encourage developers to submit a Drainage Impact Assessment (DIA) along with SuDS as part of significant new development proposals and for all proposals in areas where there is flood risk. An assessment takes into consideration the impact of a proposed development on its catchment areas especially with regard to flood risk and pollution. At the time of adopting the Local Plan there was no national policy framework available for DIA. Until such a policy framework is available, Policy DQ 12B provides guidance on this matter.

DQ 12A Sustainable Urban Drainage Systems

Whenever practicable, development proposals must be accompanied by a Sustainable Urban Drainage Scheme at the time of submitting a planning application. The Council will encourage proposals to adopt an ecological approach to surface water management through habitat creation or enhancement by, for example forming wetlands or ponds and opening up culverted watercourses.

Developers should refer to the ‘SuDS Design Manual’ published by CIRIA for further guidance on selecting and designing SuDS.

The Council will require arrangements to be made for maintenance of all parts of a proposed Sustainable Urban Drainage System.

DQ 12B Drainage Impact Assessment

The Council will generally require developers to submit Drainage Impact Assessments with the following categories of development:

a. development of ten or more new dwelling houses,

b. non-householder extensions measuring 100 square metres or more, and

c. other non-householder developments involving new buildings, significant hardsurfacing or alterations to landform.

Developments excluded from the above three categories might require a DIA when affecting sensitive areas such as areas affected by flooding, contamination or wildlife interest.

In all cases the Council will encourage the use of the best sustainable options for waste and surface water drainage.