Government policy on flood and water management has been strengthened in recent years to respond to recent flooding events and increased public concern over the impacts of climate change, human safety and property damage. Key policy for England is currently set out in Planning Policy Statement 25 (PPS25) – Development and Flood Risk (2006) and for Wales and Scotland in other similar government documents (links below).
Local planning authorities have a duty to ensure that flood risk and the potential impacts of flooding from a variety of sources are considered for all development proposals in high flood risk zones and proposals over one hectare in lower flood risk areas. Flood risk zones are mapped out on the Environment Agency website.
Authorities exercise this duty by requiring developers to undertake flood risk assessments geared to the scale of their proposals using PPS25 guidelines (England) and consulting with the Environment Agency where necessary.
We can offer technical and regulator liaison services to suit the needs of your site.
Click on the following headings to find out more:
Scoping study
A scoping study will identify flood sources and likely flooding scenarios.
Available flood level data from the Environment Agency, planning authority, waterways and drainage boards on historical and predicted future events will be identified. Where this information is not available, particularly in rural areas, this stage will highlight the need for new hydrological models to assess flood levels, characteristics and overall risk.
The application of the PPS25 sequential test is of primary consideration at this stage. To pass this test, it must be demonstrated that there are no alternative sites with a lower probability of flooding, appropriate and available for the same type of development. Applicants are advised to engage with planning authorities on sequential testing early on in the planning process to avoid project delays.
If the site lies within a medium or high flood risk zone and the sequential test has been satisfied, it may also be necessary to apply the exception test. To pass this test, it must be further demonstrated that the development provides wider community benefits that outweigh the flood risk.
Full flood risk assessment
By undertaking a selection of the following additional tasks, the results from a flood risk scoping study can be incorporated into a full flood risk assessment and report.
- Application of the sequential and exception tests.
- Review of site drainage, geology, groundwater levels, fluvial and tidal features and flood management structures.
- Consultation with the Environment Agency, local planning authority, waterways and internal drainage boards.
- Assessment of ground levels through land surveying techniques or examination of existing ordnance survey data.
- Assessment of future flood levels taking into consideration climate change forecasts employing hydrological modelling where required.
- Estimation of surface water run-off.
- Source-pathway-receptor flood risk assessment.
- Recommendations for flood mitigation building design and sustainable urban drainage systems (SUDS).
The scale of the assessment will be proportionate to the scale of the development proposals.
Flood modelling
Depending on available data, drainage, fluvial or coastal modelling may be required to fully assess flood risk. Applications can be varied and require the use of extensive land survey data.
Typical applications include river channel simulation, tidal flood defence breach or overtopping modelling.
We can manage delivery of the full range of flood risk assessment services, including drainage design. Services are designed to meet the scale and type of the development and the assumed risk and impact of flooding.
Useful links
Department for Environment, Food and Rural Affairs
www.defra.gov.uk
Environment Agency
www.environment-agency.gov.uk
Department for Communities and Local Government
www.communities.gov.uk
Welsh Assembly Government Technical Advice Note 15 (TAN 15) – Development and flood risk (July 2004)
http://wales.gov.uk
Scottish Planning Policy 7 (SPP7) – Planning and flooding (February 2004)
http://www.scotland.gov.uk/Resource/Doc/47210/0026394.pdf
Scottish Environmental Protection Agency
http://www.sepa.org.uk/flooding/flood_risk.aspx
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