Flood risk and surface water drainage - information for a valid application
Most information regarding flooding and surface drainage that should be submitted with a planning application is required by national legislation.
For ease of use by applicants, Waverley’s Local Validation List includes National and Local Validation requirements/ See Item 11 of the adopted Local Validation List.
Flood Risk Assessments
Helpful advice on Flood Risk Assessments has been provided by the Government :
Flood Risk Assessments for Householder and small commercial extensions
A simplified Flood Risk assessment using this form is acceptable for domestic extensions, outbuildings and commercial extensions under 250sqM.
Surface Water Drainage System
Surface water drainage information, when required, should be provided including the completion of the Waverley SuDS Proforma.
A safe means of access and egress must be provided for any new development within Flood Zones 2 and 3. Advice in the form of a Guidance Statement from the Environment Agency dated October 2015 to Local Authorities includes the following;-
The applicant should demonstrate that a safe access and egress route with a ‘very low’ hazard rating in accordance with the ‘Framework and Guidance for Assessing and Managing Flood Risk for New Development’ (FD2320/TR2) and the National Planning Policy Framework (NPPF) can be provided from the development to an area wholly outside of the 1% annual exceedence probability (AEP) plus an appropriate allowance for climate change flood extent. Any other classification of route, for example ‘danger for some’ or ‘danger for most’, will place future occupants of the development, including vulnerable people, at risk from potential flood water depths and flows. Vulnerable occupants include children, the infirm and the elderly.
It should be noted that during a prolonged flood event, safe refuge in the development may not be suitable due to lack of supplies (i.e. fresh drinking water and food), power supply or sanitary provision and these issues should be considered. Generally in previous flood events some foul sewage networks have not been functioning correctly due to capacity issues and/or their outlets/pumping stations being offline….
Therefore, it is essential that a safe route of access and egress can be provided and maintained during flood events up to and including the 1% AEP plus an allowance for climate change flood event. If a safe route cannot be provided your authority should consider refusing the application in accordance with paragraph 103 of the NPPF and your local flood risk planning policy. Please note, safe access and egress applies to all forms of development and not solely those which are required to pass the exception test.
Where a route with a ‘very low’ hazard rating is not possible the local authority may deem an evacuation plan a suitable approach to mitigate the risk posed. Paragraph ID 7-057-20140306 of the National Planning Practice Guidance (NPPG) states that those proposing developments should take advice from the emergency services when producing an evacuation plan for the development as part of the flood risk assessment.
The Council will therefore, require the submission of a topographical survey which identifies the AOD (Above Ordnance Datum) covering the entire safe means of access and egress and details of flood levels and velocities of flood water in affected areas.
Page owner: Ben Hammond. Last updated: 22/09/2020 20:12