Policy information sourced from Hackney Local Plan 2033
LP53 Water and Flooding
All development must have regard to reducing flood risk, both to, and from the site, over its expected lifetime. Potentially vulnerable development must not be located in flood-prone areas as identified by the Council unless it can be suitably demonstrated that flood-risk will be sufficiently mitigated using flood resistance and/or resilience measures.
All development should decrease vulnerability to flooding through appropriate siting, design, and on-, and off-site mitigation.
The following types of development will be expected to submit the appropriate flood risk assessment:
- Developments in fluvial flood zone 2 or 3 including minor development and change of use;
- Developments on sites of 1 hectare (ha) or more in flood zone 1;
- Developments on sites of less than 1 hectare in flood zone 1, including change of use in development type to a more vulnerable class (for example from commercial to residential), where they could be affected by sources of flooding other than rivers and the sea (for example surface water drains, reservoirs);
- All major developments or basement developments in areas with a high risk of surface water flooding, or in an area known to have a potentially elevated risk of groundwater flooding in flood zone 1;
- All development in flood zone 1 located in a critical drainage area
All major developments will be required to submit a Sustainable Drainage Strategy taking into account climate change allowances and supported by a site-specific management and maintenance plan of the drainage proposal. All other developments, particularly for sites located within critical drainage areas, should implement Sustainable Drainage Systems (SuDS) such as water butt, green/blue roof, permeable paving and other above ground green infrastructures.
Development which includes the creation or extension of basements must demonstrate that they will not increase the potential for groundwater flooding to itself or to the surrounding area.
All developments should achieve greenfield runoff rates by attenuating rainwater on site, utilising SuDS and in accordance with the London Plan drainage hierarchy. Where this is shown, through appropriate evidence, to be unfeasible, planning obligations will be expected to reduce the overall flood risk within the site and in the vicinity.
All development should, in liaison with Thames Water, take account of the capacity of existing on and off-site water and sewerage infrastructure and the impact of development proposals on this infrastructure. All major developments will be required to demonstrate that capacity exists on and off-site in the sewerage network to serve the development or that it can be provided ahead of occupation to ensure there is sufficient capacity in the sewerage system to accommodate for the proposed flows.
Where necessary, and as advised by Thames Water, the Council will seek improvements to water and/or sewerage infrastructure related and appropriate to the development so that improvements are completed prior to occupation of development.
All developments should take account of the location, capacity and requirements of, and access to, existing, and need for improved, flood defences, and where needed supporting improvements.
Development must be designed to be water efficient and reduce water consumption. Non-domestic development and refurbishment will be expected to meet the BREEAM excellent standard and, where possible, the maximum BREEAM water-efficiency credits. Residential development must not exceed a maximum water use of 105 litres per head per day (excluding the allowance of up to 5 litres for external water consumption).
New developments are encouraged to incorporate additional water saving, water recycling and water efficiency measures such as smart-metering, rainwater harvesting, greywater recycling, including retrofitting, to help reduce water consumption.
For more information please see the Hackney Local Plan 2033