PPS 15: Planning and Flood Risk
Development Control Considerations
7.1 The susceptibility of all land to flooding is a material consideration in determining planning applications. Development proposals may be directly at risk from flooding and/or may increase the risk elsewhere. The consequences for occupiers in such cases, both in terms of personal safety and damage to property, can be serious. Where a flood risk is known to exist, the Department will pay particular regard to these considerations when determining planning applications. It should be noted however that the Department's responsibility in this respect does not affect the liability position of developers or owners.
7.2 Climate change is also a material planning consideration and its impact on flood risk over the expected lifetime of the proposed development will be assessed. All planning applications, including those for the renewal of planning permission, will be determined with reference to the most up to date flood risk information available to the Department.
7.3 Planning Service will consult Rivers Agency for advice on the nature and extent of flood risks where the circumstances are appropriate. Such circumstances will include:
- where, exceptionally, development is considered appropriate within riverine or coastal floodplains;
- beyond floodplains on land with a known history of flooding;
- proposals which may affect a flood bank or other flood control structure;
- where a proposal is likely to involve the alteration or diversion of a watercourse; and
- where a proposal is of a size or nature that could significantly increase surface water run-off. These will normally be developments of ten or more dwellings;where buildings or hardsurfacings exceed 1000 square metres; or where the application site comprises an area of 1 hectare or more.
7.4 Planning Service will also consult the Environment and Heritage Service where the circumstances set out in the final two bullet points prevail.
7.5 Water impounding structures such as reservoirs or other man made ponds and lakes may constitute a source of flood risk and serious flooding can occur if they are overwhelmed or if a dam or bank fails. This type of flood event can also trigger ground stability problems, for example landslides in adjacent areas. Where development is proposed near a reservoir, man made pond or lake it will be necessary for the applicant to provide up to date information on the integrity of the impounding structure concerned.
7.6 Generally, it is unlikely that applications to extend or alter individual buildings will raise flood related issues unless it is anticipated that a proposal may have a direct adverse effect on a watercourse, a flood defence structure or impede their maintenance or management. It may however be necessary to consider flood risk where changes of use involve intensification or could have implications for the safe evacuation of people from the development.
7.7 For large development schemes (i.e. those that require an assessment of flood risk or the submission of a drainage assessment), it may be necessary to consider the removal of permitted development rights. This may also be appropriate where run-off carries the potential to adversely affect a sensitive area5 . Guidance on the assessment of flood risk and the preparation of a drainage assessment is set out in Annex D.
7.8 Where the risk of flooding is a material consideration good practice dictates that applicants should identify potential flood risk and/or run-off issues as early in the development process as possible. To facilitate the identification and consideration of flooding or drainage issues and enable proper scoping of potential risks, early consultation with the Planning Service and Rivers Agency is recommended.
Environmental Impact Assessment
7.9 For certain types of project an Environmental Assessment determination will be made under the Planning (Environmental Impact Assessment) Regulations (Northern Ireland)1999. In such cases the Department will expect flood risk assessment and drainage assessment to be addressed in the Environmental Statement.
5 Sensitive areas will include areas within, or upstream of, a conservation site designated under national or international legislation, for example Areas of Special Scientific Interest.