Draft Regulation 18 Sandwell Local Plan
Sustainable drainage and surface water management (SuDS)
5.51 As a heavily urbanised and industrial borough, much of the land in Sandwell is covered in impervious surfaces (such as roads, pavements, hardstanding, and rooftops), which are water-resistant and prevent rainwater from soaking away into the ground. This has led to a high dependence on hard engineering solutions to manage rainwater run-off, storage and drainage, and has increased the risk of isolated surface water flooding.
5.52 Policy SCC5 sets out the requirements for new development to incorporate sustainable drainage and surface water management solutions (SuDS), to increase the amount of rainwater that is drained in sustainable ways.
Policy SCC5 - Sustainable drainage and surface water management
- All new developments in Sandwell should incorporate Sustainable Drainage Systems (SuDS); development proposals should provide details of adoption, ongoing maintenance and management of SuDS.
- SuDS shall be designed in line with the Black Country Local Standards for SUDS. Preference will be given to systems that also contribute to the conservation and enhancement of biodiversity and green infrastructure in the wider area.
- For all major developments, surface water flows must be reduced back to equivalent greenfield rates. If greenfield runoff rates are not considered to be feasible for viability or other reasons, the developer must submit evidence demonstrating what the constraints are and how the development will accommodate runoff rates that are as close as possible to greenfield rates.
- For all minor developments, a minimum reduction of 30% over pre-development runoff rates will be required. Under no circumstances will post-development runoff rates that are greater than pre-development runoff rates be permitted. Surface water run-off should be managed as close to its source as possible.
- Surface water drainage strategies are required for all major developments, regardless of their size and the flood zone and catchment they are in to meet the requirements of the Lead Local Flood Authority. These should consider all sources of flooding to ensure that future development is resilient to flood risk and does not increase flood risk elsewhere and should look to provide wider betterment.
- A hydrogeological risk assessment is required where infiltration SuDS is proposed for anything other than clean roof drainage in a Source Protection Zone 1[104].
Justification
5.53 The incorporation of Sustainable Drainage Systems (SuDS) into new developments helps to manage and minimise surface water. SuDS are generally landscaped facilities such as wetlands, retention ponds, soakaways, swales and /or permeable surfaces. Their primary function is to reduce the volume and peak rates of water run-off from new development, but they should also be designed to fulfil their potential to provide new wildlife habitats and amenity spaces in new developments; they should be multifunctional.
5.54 SuDS can also improve water quality by increasing the filtration of pollutants and will thereby help to support the objectives of the Water Framework Directive. They allow the management of diffuse pollution generated in urban areas by treating water and reducing the level of pollutants that enter rivers and other watercourses therefore resulting in less wastewater requiring treatment.
5.55 The NPPF makes it clear that:
Major developments should incorporate sustainable drainage systems unless there is clear evidence that this would be inappropriate[105].
5.56 Due to the legacy of contaminated land created by heavy industry and extractive activities in Sandwell, there is a risk of polluting groundwater and /or surface water if SuDs are not properly designed. The presence of contaminated land needs to be considered when planning SuDS; national guidance such as the CIRIA SuDS Manual C753 provides guidance for the use of SuDS on contaminated land.
[104] Source Protection Zones are designed to control activities close to water supplies intended for human consumption. These water sources include wells, boreholes and springs, all of which are used for public drinking. Zone 1, defined as the inner zone, is the most sensitive part of an area within a zone.
[105] NPPF (2021) paragraph 169 or later iteration