Have you had a Planning Application refused due to failing the Sequential or Exception Test? Has the Environment Agency advised that you need to satisfy these tests before continuing with a Flood Risk Assessment?
Increasing numbers of Planning Applications are being rejected on Sequential / Exception test grounds. The Environment Agency advises that the Sequential Test is carried out at an early stage of the planning application determination process:
‘Failure to apply the test at an early stage in the determination process can result in a waste of resources for all parties in the completion and assessment of FRA’s for development that is later refused planning permission on Sequential Test grounds.’
The Sequential Test and parts 1 and 2 of the Exception Test should be satisfied before the commencement of a FRA to prevent wasted time and money.
Flood Response Plans for existing and proposed developments.
Proposed Developments
The Environment Agency is increasingly requesting that Flood Response Plans be prepared to support
Flood Risk Assessments for new development in Flood Zones. Future occupiers should be aware of the flood risk and know what to do before, during and after a flood.
Existing Developments
Have you been flooded in the past? Is your
house or business at risk of flooding? Would you like to have property-specific information on how to be prepared and
deal with flooding when it happens?
In 2004 national flood maps were created by the Environment Agency to support the planning documents PPS 25 and TAN15. The maps published are based on Digital Terrain Modelling (DTM).
The flood maps give a general picture and are not site specific. Structures such as bridges and embankments, which may affect the flood plain locally, have not generally been taken into account in producing the flood maps. The EA will consider challenges to the maps submitted and make amendments as appropriate. It is possible to successfully challenged the EA flood map in a number of locations with an example being Wepre Park, Connah’s Quay.
In order to change the Flood Zone outlines, revised flood extents must be produced by detailed site specific flood modelling and assessment, in accordance with EA guidance.
Environment Agency flood risk maps have been published showing areas which are considered to have a 1 in 100 (1%) chance of flooding. Some Insurance Companies also produce their own flood maps. Properties at significant risk may be refused full insurance cover or asked to pay higher premiums. The sale value of the property can also be seriously affected. A Flood Risk Assessment (FRA) for an existing property details the practical measures that could be implemented to reduce risk to life and minimise damage or disruption to people and property. The key benefits include improvements to insurance cover, reduced premiums, and improved saleability of property.
Produce comprehensive 1D and 2D hydrodynamic modelling of watercourses, rivers, culverts and floodplain areas using a range of industry standard hydrodynamic software packages e.g. MIKEFlood, Isis, TuFlow and Hec-Ras.
Flood Risk Assessments, on Environment Agency advice, increasingly have to be accompanied by such hydrodynamic models. Depending on which flood zone category a development is located, both PPS25 and TAN15 suggest the watercourses and structures potentially affecting the flooding of a site be modelled to confirm or provide more detail than is available within the existing EA flood maps. This often involves a Flood Map Challenge.
Use site specific models to predict flood depths, velocities, inundation rates and flood hazard ratings to support a number of flood risk scenarios.
Hydrological studies also providing specialist hydrology advice utilising the latest software, WINFAP-FEH 3. These studies often provide the input for flood risk assessments and hydraulic models.
Identify and evaluate the existing water environment, take into account any constraints and assess the impact of the development on the water environment.
Make hydrology calculations during detailed design for varies structures, advising on capacity requirements and design considerations.
Increasingly the Environment Agency (EA) requires breaches of coastal and river defences to be investigated as part of the flood risk assessment process.
This service investigates and advises on the most appropriate drainage solutions and provides a written report to demonstrate to the Planning Authority that the site drainage can be adequately dealt with in order to gain Planning Permission. Alternatively the report can be used to assess the viability of purchasing/developing a site.
Following a Preliminary Drainage Assessment, detailed drainage solutions should be provided, including calculations, design drawings and packages for submission for adoption (Section 104 Applications)
For new developments, connection to an existing sewerage system is not always practical or possible. An on-site treatment plant may be more cost effective than pumping to an existing system.
Aim: To design housing developments which avoid, reduce and delay the discharge of rainfall to public sewers and watercourses. This will protect watercourses and reduce the risk of localised flooding, pollution and other environmental damage.
Assessment Criteria: Mandatory Elements must be achieved i.e. showing that the peak rate of run-off does not increase following development. Up to 2 credits are available for using SUDS to improve water quality of the rainwater discharged or for protecting the quality of the receiving waters.
Aim: To encourage housing development in low flood risk areas, or to take measures to reduce the impact of flooding on houses built in areas with a medium or high risk of flooding.
Initial Bid Designs, used to give initial budget indications and Complete Detailed Designs which includes design approval by the water company.
The Security and Emergency Measures (Water and Sewerage Undertakers) Direction 1998 and subsequent guidance issued by DEFRA require plans to ensure the provision of essential water supply and to endeavour to maintain a piped water supply.