Policy information sourced from the Islington Local Plan
S9 Integrated Water Management and Sustainable Drainage
- All development proposals must adopt an integrated approach to water management which considers sustainable drainage, water efficiency, water quality and biodiversity holistically across a site and in the context of links with wider-than-site level plans. Water management must be considered as early as possible in the design process.
- All development proposals must ensure that surface water run-off is managed as close to its source as possible in line with the London Plan drainage hierarchy (repeated below), with priority given to green features over grey features:
- rainwater use as a resource (for example rainwater harvesting, blue roofs).
- rainwater infiltration to ground at or close to source.
- rainwater attenuation in green infrastructure features for gradual release (for example green roofs, rain gardens).
- rainwater discharge direct to a watercourse (unless not appropriate).
- controlled rainwater discharge to a surface water sewer or drain.
- controlled rainwater discharge to a combined sewer.
- Development proposals for impermeable paving will be resisted, including on small surfaces such as front gardens and driveways, unless they can demonstrate that the level of run-off will not exacerbate flood risk in the area, both direct and cumulative risk.
- Drainage must be designed and implemented in ways that promote multiple benefits including increased water use efficiency, improved water quality, and enhanced biodiversity, urban greening, amenity and recreation.
- All developments are required to demonstrate that appropriate SUDS have been implemented in accordance with the drainage hierarchy to ensure that surface water run-off rates and volumes entering open space are predictable and water at the surface is clean and safe. All developments must identify how the initial run off from a site following a rainfall event will be dealt with; and demonstrate that an appropriate maintenance plan will be put in place providing details of how the SUDS will be maintained after implementation to ensure their continued effectiveness.
- Major developments creating new floorspace, and major changes of use that will result in an intensification of water use, must be designed to achieve the following standards:
- Surface water flows from the site must be reduced to a greenfield run-off rate (8 litres/second/hectare for Islington), where feasible. Where it is demonstrated that achieving a greenfield run-off rate is not feasible due to the site conditions, run-off rates must be minimised to as close to the greenfield rate as possible.
- The volume of run-off that must be stored on-site must be calculated based on the nationally agreed return period value of a 1 in 100-year storm event plus a 40% allowance for climate change for the worst storm duration. Where the site-specific FRA indicates that an additional volume of run-off must be stored above and beyond the amount calculated based on the method above, this must be provided on site.
- Major developments involving works to an existing building should reduce run-off rates for the site as a whole, rather than focusing solely on new buildings.
- All major developments must submit a Surface Water Drainage Pro-forma to ensure surface water drainage proposals meet policy requirements.
- All minor new build developments of one unit or more are required to reduce existing run-off levels as far as possible. Where this is demonstrated not to be possible, existing run-off levels must be maintained as a minimum.
- SUDS must be designed and implemented as a central part of the SDCS, using an integrated approach which maximises biodiversity and water use efficiency alongside other benefits including, where appropriate and practical, amenity and recreation. All developments must maximise areas of soft landscaping and other permeable surfaces to support this, in accordance with Policy G4.
- All developments must demonstrate that they have minimised the use of mains water and have been designed to be water efficient, through the SDCS. Water use must be minimised as part of all developments by reducing water demand in the first instance through the installation of water efficient fittings and appliances, and the use of water saving measures. Developments must use smart metering, and retrofitting of water efficiency measures is encouraged where feasible.
- Where feasible, developments located adjacent to a waterway, such as a canal, must utilise the waterway to supply non-potable water for on-site needs, including landscape irrigation.
- Residential development must minimise water consumption in accordance with the Optional Requirement of the Building Regulations, achieving mains water consumption of 105 litres or less per head per day (excluding allowance of up to five litres for external water consumption). Non-residential developments, including refurbishments, must minimise water consumption by achieving all credits on Water consumption (Wat 01) under the relevant BREEAM scheme, in accordance with the requirements of Parts E and G of Policy S3.
- Major developments and/or developments with high/intense water usage - including hotels, hostels, and student housing - are required to incorporate a rainwater and greywater recycling system. Minor developments must incorporate rainwater recycling, where feasible and practical.
- The development of land affected by contamination must not create unacceptable risks to human health and the wider environment, including local water resources. Assessment and remediation of any contaminated land must be carried out before any development commences on site.
- All developments are required to protect water quality and demonstrate that there will be no negative impacts on the quality of local water resources as a result of the development. All developments must assess and mitigate any potential impact on groundwater; only appropriate land uses should be located within groundwater Source Protection Zones (SPZs).
- All development proposals located adjacent to the New River or Regent’s Canal are required to protect and improve the benefits provided by the water environment to help to ensure that these waterways can reach and maintain good ecological status, in accordance with the recommendations of the Thames River Basin Management Plan (TRBMP).
For more information please see the Islington Local Plan