Policy information sourced from Wandsworth Development Planning Management Policies Document
DMS 5 Flood risk management
If applicants can demonstrate through a site specific FRA that their site would be unaffected by all forms of flood risk including tidal, groundwater, fluvial and pluvial flood risk, the development restrictions set out in this table do not apply. Exceptions to this are some basement developments in flood zone 3b (see table 2.2).
Applications for minor development (See NPPG for definition of minor development) and changes of use are not subject to the Sequential or Exception Test.
A site specific FRA will be required for all development within flood zone 2, 3a and 3b, development over 1 hectare in area within flood zone 1, or where development may be subject to other sources of flooding. The FRA should examine the flood risk both to and from the proposed development for all sources of flood risk including tidal, fluvial, surface water, groundwater, sewer and artificial sources whilst accounting for the impacts of climate change for the lifetime of the development.
The FRA will be required to consider how the development will remain safe during a flood and how development would recover from a flood. Developers will be required to make future tenants or freeholders aware of the likelihood and possible impact of flooding on the property, how to receive flood warnings and what action should be taken should a warning be received or a flood occur. In some cases it may be necessary to develop a capability within the property for affected people to stay in a safe place for 72 hours whilst the area is flooded. This information should be contained within a flood evacuation plan.
Development in flood zones 1, 2 , 3a and 3b will be permitted subject to meeting the criteria in the following table:
| Flood Zone | Land use and Development Restrictions |
|---|---|
| Flood zone 3b (Functional Floodplain) | On undeveloped sites, planning permission will not be permitted unless it is for:
classification will not be permitted. Safe refuge is required above the 1 in 200 year tidal flood level (including climate change) (or appropriate extreme water level as advised by the Environment Agency) or the 1 in 100 year fluvial flood level (including climate change). Safe access and egress (must be low hazard in accordance with FD2320) is required for all sites. Conversions of basements to a higher vulnerability classification or self contained units will not be permitted. Habitable rooms will not be permitted in basements. All basements, basement extensions and basement conversions must have safe access threshold levels and internal staircases provided to access floors above the 1 in 200 year tidal flood level (including climate change) (or appropriate extreme water level as advised by the Environment Agency) or the 1 in 100 year fluvial flood level (including climate change). Where basements are proposed they should also include storage for surface water and/or other SuDS proposals as set out in Policy DMS6. See DMPD Policy DMH5 for the policy on garden development Sequential Test Required for all development, except if the site and its proposed use has already passed the sequential Test informed by the SFRA as completed by the Council, and/or the site is located within the Nine Elms Opportunity Area. Exception Test Required for all development except water compatible development. Flood Risk Assessment Required for all development proposals. |
| Flood zone 3a (High Probability) | Acceptable Land uses are:
extreme water level as advised by the Environment Agency. Depending on the flood level and comparison of site levels, this may not preclude ground floor residential use subject to the inclusion of satisfactory flood risk mitigation measures to be agreed in consultation with the Environment Agency. B. Safe refuge above the 1 in 200 year tidal flood level (including climate change) (or appropriate extreme water level as advised by the Environment Agency) or safe access and egress (must be low hazard in accordance with FD2320) is required for all sites to enable the evacuation of people from the development, provide the emergency services with access to the development during times of flood and enable flood defence authorities to carry out any necessary duties during periods of flood. C. All basements, basement extensions and basement conversions must have safe access threshold levels and internal staircases provided to access floors above the 1 in 200 year tidal flood level (including climate change) or appropriate extreme water level as advised by the Environment Agency. D. Self-contained residential basements and bedrooms at basement level will not be permitted. For development in undefended fluvial areas (River Wandle and Beverley Brook) E. Floor levels for more vulnerable development with a sleeping element are required to be raised over the 1 in 100 year fluvial flood level (including climate change) plus an additional 300mm freeboard depending on the source of flood risk to be agreed with the Environment Agency Depending on the flood level and comparison of site levels, this may not preclude ground floor residential use subject to the inclusion of satisfactory flood risk mitigation measures to be agreed in consultation with the Environment Agency. Floor levels for undefended less vulnerable developments should also be raised in accordance with this standard. F. Safe refuge above the 1 in 100 year fluvial flood level (including climate change) or safe access and egress (must be low hazard in accordance with FD2320) is required for all sites to enable the evacuation of people from the development, provide the emergency services with access to the development during times of flood and enable flood defence authorities to carry our any necessary duties during periods of flood. G. All basements, basement extensions and basement conversions must have safe access threshold levels and internal staircases provided to access floors above the 1 in 100 year fluvial flood level (including climate change). H. Self-contained residential basements and bedrooms at basement level will not be permitted. Where basements are proposed surface water flooding should be considered with potential mitigation to include raising access floor level thresholds, providing storage for surface water and/or other SuDS proposals as set out in Policy DMS6. See DMPD Policy DMH5 for the policy on garden development. Sequential Test Required for all development, except if the site and its proposed use has already passed the Sequential Test informed by the SFRA as completed by the Council, and/or the site is located within the Nine Elms Opportunity Area. Exception Test Required for more vulnerable development. Flood Risk Assessment Required for all development proposals. |
| Flood zone 2 (Medium probability) | No land use restrictions.
For development in defended tidal areas (River Thames and Wandle Delta area)
A. Floor levels for more vulnerable development with a sleeping element are required to be raised above the 1 in 200 year tidal flood level (including climate change) or appropriate extreme water level as advised by the Environment Agency’s Flood Risk Standing Advice. Depending on the flood level and comparison of site levels, this may not preclude ground floor residential use subject to the inclusion of satisfactory flood risk mitigation measures to be agreed in consultation with the Environment Agency. B. Safe refuge above the 1 in 200 year tidal flood level (including climate change) (or appropriate extreme water level as advised by the Environment Agency’s Flood Risk Standing Advice), or safe access and egress (must be low hazard in accordance with FD2320) is required for all sites to enable the evacuation of people from the development, provide the emergency services with access to the development during times of flood and enable flood defence authorities to carry out any necessary duties during periods of flood. C. All basements, basement extensions and basement conversions must have safe access threshold levels and internal staircases provided to access floors above the 1 in 200 year tidal flood level (including climate change) or appropriate extreme water level as advised by the Environment Agency’s Flood Risk Standing Advice. D. Self-contained residential basements and bedrooms at basement level will not be permitted. For development in undefended fluvial areas (River Wandle and Beverley Brook) E. Floor levels for more vulnerable development with a sleeping element are required to be raised above the 1 in 100 year fluvial flood level (including climate change) plus an additional 300mm freeboard depending on the source of flood risk to be agreed with the Environment Agency’s Flood Risk Standing Advice. Depending on the flood level and comparison of site levels, this may not preclude ground floor residential use subject to the inclusion of satisfactory flood risk mitigation measures to be agreed in consultation with the Environment Agency. Floor levels for undefended less vulnerable developments should also be raised in accordance with this standard. F. Safe refuge above the 1 in 100 year fluvial flood level (including climate change) or safe access and egress (must be low hazard in accordance with FD2320) is required for all sites to enable the evacuation of people from the development, provide the emergency services with access to the development during times of flood and enable flood defence authorities to carry G. out any necessary duties during periods of flood. All basements, basement extensions and basement conversions must have safe access threshold levels and internal staircases provided to access floors above the 1 in 100 year (including climate change) fluvial flood level. H. Self-contained residential basements and bedrooms at basement level will not be permitted. Where basements are proposed surface water flooding should be considered with potential mitigation to include raising access floor level thresholds, providing storage for surface water and/or other SuDS proposals as set out in Policy DMS6. See DMPD Policy DMH5 for the policy on garden development. Sequential Test Required for all development, except if the site and its proposed use has already passed the Sequential Test informed by the SFRA as completed by the Council, and/or the site is located within the Nine Elms Opportunity Area. Exception Test Required for all highly vulnerable development. Flood Risk Assessment Required for all development proposals. |
| Flood zone 1 (low probability) | No land use restrictions.
Where basements are proposed surface water, groundwater and sewer flooding should be considered with potential mitigation to include raising access floor level thresholds, providing storage for surface water and/or other SuDS proposals as set out in Policy DMS6.
See DMPD Policy DMH5 for policy on garden development.
Sequential Test
Not applicable
Exception Test
Not applicable
Flood Risk Assessment
Required for sites greater than 1 hectare in area.
Required for all other development proposals where there is evidence of a risk from other sources of flooding, including surface water, groundwater and sewer and artificial sources. For the purposes of considering the risk of surface water flooding, Flood Risk Assessments should be undertaken for all sites where flooding in a 1 in 30 event is predicted to result in flood depths exceeding 300mm. |
For more information please see the Development Planning Management Policies Document