Policy FRD4 Sustainable Drainage (SuDS)
A sustainable drainage solution (hard or soft SuDS) for the management of surface water run-off will be required for any development proposal that triggers the requirement for a Drainage Assessment (DA) under Policy FRD3 Management of Development in regard to Surface Water Flood Risk. An exception will be applied where it is clearly demonstrated through the DA that the site is fundamentally unsuitable for a SuDS solution.
A ‘soft SuDS’ solution may also be required for particular zonings for housing and economic development to be identified through the LDP Local Policies Plan.
Management and Maintenance
Planning permission will not be granted until the applicant has satisfied the Council that suitable arrangements will be put in place for the future management and maintenance, in perpetuity, of SuDS required under this policy. A Section 76 planning agreement may also be sought.
Justification and Amplification
This policy seeks to further the Executive’s long term goal of delivering a sustainable water sector in Northern Ireland. The RDS, ‘A Long-Term Water Strategy for Northern Ireland (2015-2040)’, and the SPPS all promote SuDS as an important part of the delivery mechanism in contributing to attaining this goal.
Council will not only promote SuDS through this policy, but also through key site requirements on specific zonings at Local Policies Plan stage where appropriate. In this way, the LDP will influence developers to use SuDS as the preferred drainage solution, particularly in areas susceptible to surface water flooding and also for relatively large developments where the benefits are likely to be greater and SuDS easier to facilitate. Lands susceptible to surface water flooding are identified on the Strategic Flood Maps NI website at https://www.infrastructure-ni.gov.uk/topics/rivers-and-flooding/flood-maps-ni.
SuDS are defined as management practices and control systems designed to drain surface water in a more sustainable way than conventional piped systems. Reducing the amount of surface water run-off to watercourses, or slowing down the rate of discharge, helps to reduce flood risk. There can also be significant amenity benefits for local communities when SuDS schemes are integrated into the wider green/blue infrastructure network.
SuDS can vary in size and composition. The appropriateness of a SuDS solution will be determined by the local characteristics of each site including its size, topography, geology, hydrogeology, flood risk and the available discharge points (rivers, drains or sewers). They can vary in size and composition and are often classified as ‘hard’ or ‘soft’ SuDS.
The integration of a variety of different techniques usually provides the best solution, however it is acknowledged that in most cases ‘hard SuDS’ will be the preferred drainage solution for developers as these are currently adopted by NI Water. Examples of ‘hard’ SuDS are solutions such as attenuation tanks, permeable paving, and oversized pipes for storm water that are separated from the wastewater system.
‘Soft’ SuDS are usually in the form of swales, ponds, wetlands and infiltration beds carved into the landscape to collect water and let it soak naturally down into the ground where it replenishes the water table. These types of SuDS have a role in improving the quality of the run-off from a development and in enhancing nature conservation and biodiversity. Other SuDS include rainwater harvesting and green roofs (see Appendix I Part B for more detail on SuDS).
SuDS measures to reduce surface water runoff alone may not be enough – stormwater separation also needs to take place so that rainwater is prevented from entering combined sewers. Applicants should therefore include drainage systems to reduce the amount of rainwater in the combined wastewater system by providing separate drains and by reducing sewer infiltration which will also help improve water quality. New storm connections to the combined sewer system should be avoided as NI Water will not permit a new combined sewer to enter its system without the inclusion of a SuDS system.
An appropriate maintenance and management plan for SuDS will be required to be submitted with the planning application to ensure continuity in the future operation of SuDS by, for example, a property management company or for adoption by Council or another public authority. This plan will be required to be agreed with the Council and may involve a S76 planning agreement where necessary to ensure effective ongoing maintenance.
Where an applicant considers a site to be fundamentally unsuitable for SuDS, the reasons for this must be set out in the Drainage Assessment and supported by a suitable qualified engineer.
The Water and Sewerage Services Act (Northern Ireland) 2016 includes proposals to ensure that SuDS systems are constructed to the appropriate standard. NI Water also now have the power to refuse a surface water connection on the grounds that suitable alternatives to connection to the public sewer exist, or could reasonably be provided (this includes SuDS). The range of SuDS solutions currently considered for adoption by NI Water are identified in Article 161 guidance on the NI Water website https://www.niwater.com/sewers/.