Flood risk and new developments
Contents
- Flood risk and new developments
- Flood risks for planners
- Flood risks for developers
- Landowners and consenting
Flood risks for developers
Developers will need to demonstrate that:
- within the site, the most vulnerable development (e.g. an electricity substation, homes, etc) are in areas of lowest flood risk unless there are overriding reasons to use a different location and they can be properly protected against flood risk
- the development is appropriately flood resilient and resistant, including safe access and escape routes where required, and that any residual risk can be safely managed, including emergency planning situations; and it gives priority to the use of sustainable drainage systems
- the availability of water and water infrastructure has been considered for the lifetime of the development including water efficiency measures and the protection of water quality - find more guidance on water supply, wastewater and water quality
Site-Specific Flood Risk Assessments
Site-specific Flood Risk Assessments (FRAs) are undertaken by applicants when a planning application is submitted where flood risk is an issue. The National Planning Policy Framework (NPPF) states that FRAs should identify and assess the risks of all forms of flooding to and from the development and demonstrate how these flood risks will be managed so that the development remains safe throughout its lifetime, taking climate change into account.
A Site-Specific Flood Risk Assessment Checklist can be used to help prepare a Site-Specific Flood Risk Assessment.
During the planning process, the best outcomes are secured through more proactive working and early, pre-application discussions between developers and development control planners. In this way the management of surface water can be carried out effectively and contribute towards place making and good urban design.
| Do | Don't |
|---|---|
| Start as early as possible thinking about surface water and how to manage it properly | Assume a standard format and cost for all Site-Specific Flood Risk Assessments |
| Undertake pre-application discussions | Use a Site-Specific Flood Risk Assessment to justify preconceived land allocations and housing targets |
| Ensure geographical scope suitable for the sequential and exception tests (if needed) | Assume that the Environment Agency will produce a Site-Specific Flood Risk Assessment for you or has all the information |
| Consider all sources of flooding | Assume on is not needed if there is no history of flooding |
| Consider current and future flood risk |
Surface Water Drainage Assessments
We have published local guidance intended to inform developers of our expectations relating to the completion of Drainage Assessments.
Although Site-Specific Flood Risk Assessments may not be required for sites not identified as being at risk of flooding, there may still be a requirement to provide a Drainage Assessment in order to consider the impact the development may have on surface water management.
Groundwater Flood Risk Assessments
If properties have been affected by groundwater flooding or where the local planning authority has highlighted a potential groundwater flooding issue related to a potential development, this source of flood risk should be included within the Site-Specific Flood Risk Assessment.
A conceptual model of the groundwater on site is often required to enable the risk to be assessed and to provide a basis for designing any required mitigation measures.
Data on the geology, topography, historical land use and hydrology of the site should also be incorporated into the detailed groundwater flooding assessment.
Standards of protection – local requirements
Following the significant flooding to Northampton town centre in Easter 1998, improvements were made to the defences along the River Nene. To secure the level of protection afforded by the new defence, the standard set for new developments goes beyond the approved industry standards.
All new development in the Upper Nene catchment must be designed for a flood with a 0.5% probability of occurring in any one year, including an appropriate allowance for climate change.
Residual flood risk
In any development there could be residual flood risk, which is the flood risk after all measures of risk avoidance, reduction and mitigation have been taken. Measures should be in place to manage and plan for the residual risk, including evacuation procedures.
Last updated 08 March 2024