Southampton has approximately 35km of tidal frontage including the River Test and River Itchen, which join to form Southampton Water. The tidal influence of these rivers extends through the administrative boundary of the city. Southampton also has a number of rivers within its boundaries, namely Tanners Brook, Holly Brook, Rolles Brook, Monks Brook, Jurds Lake and Bligmont Crescent Stream. Approximately 10% of the city is identified as currently at high or medium risk of flooding from these sources.
Due to the urban nature of Southampton, the city is also at risk of surface water flooding where rainfall is unable to soak into the ground or enter the drainage systems. Other sources of flooding which are less predictable and pose less of a risk within Southampton include groundwater and artificial sources such as reservoirs. Any future development within areas of flood risk will need to be designed for any flooding over the lifetime of the development and be able to manage the effects of flooding ensuring the development is safe.
The documents below set out detailed information on the relevant sources of flood risk which face Southampton now and in the future.
Partnership for Urban South Hampshire Strategic Flood Risk Assessment (PUSH SFRA)
The Partnership for Urban South Hampshire (PUSH) commissioned a joint Strategic Flood Risk Assessment (SFRA)for the sub-region which was prepared in accordance with Planning Policy Statement 25: Development and Flood Risk (PPS25). The SFRA is a critical part of the evidence base for the sub region and enables the Local Planning Authorities within the PUSH sub region to make informed decisions on the allocation of land for development in their Local Development Frameworks. The SFRA was completed in December 2007. The final report and series of maps can be accessed via the PUSH SFRA web link below.
Level 2 Strategic Flood Risk Assessment (SFRA)
The Level 2 SFRA, which progresses and updates the PUSH SFRA, was completed in partnership with the Environment Agency. The series of documents provide detailed information on the nature of the risk, both current and future, from all sources of flooding in the city, which includes coastal, river, surface water and ground water. The principle objective of the Level 2 SFRA is to provide Southampton City Council with sufficient information to comprehensively apply the requirements of Planning Policy Statement 25 (PPS25): Development and Flood Risk, to satisfactorily inform the relevant Local Development Documents of the Local Development Framework. The Level 2 SFRA also identifies a range of potential strategies to manage flood risk and adapt to climate change on the major development sites located within flood risk areas. The Level 2 SFRA, completed in September 2010, is available to download at the bottom of the page.
Flood Risk Assessment Guidance – More Vulnerable Development
The Flood Risk Assessment (FRA) guidance for more vulnerable development (as defined by PPS25) was produced to assist developers/applicants when dealing with the control and mitigation elements of the flood risk management hierarchy (as outlined in the PPS25 Practice Guide) in order to manage flood risk and ensure new development is safe. The guidance document is available to download at the bottom of the page.
Site Flood Plan – Guidance & Templates
Complementary to the FRA guidance, the Emergency Planning team have produced the Site Flood Plan (SFP) overview and template documents. A SFP will be required where it is not feasible to achieve safe access/egress to the development site. The SFP must outline how users of the site can avoid the danger from hazards in flood events. The guidance and template documents are available to download at the bottom of the page.
Sustainable Drainage Systems (SUDS)
In order to manage surface water developers are encouraged to implement sustainable drainage into new development. ‘It will always be much more effective to manage surface water flooding at and from new development early in the land acquisition and design process rather than to resolve problems after development’ (Annex F, PPS25). The management of surface water should be demonstrated as part of the Site Specific Flood Risk Assessment ensuring the proposed drainage system will reduce flood risk to the site itself and elsewhere, taking climate change into account. A guide for developers on achieving sustainable drainage is available to download at the bottom of the page. Further information on the implementation of SUDS can be accessed via the CIRIA web link below.
Southampton City Council
