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Hill / Bryn

Glossary and Frequently Asked Questions


  • TAN 15

    TAN 15 is a technical advice note produced to provide technical guidance to supplement the policy set out in Planning Policy Wales (PPW), in relation to development and flooding. TAN 15 advises on development and flood risk, and provides a framework within risks arising from both river and coastal flooding, and from additional run-off from development in any location, can be assessed.

  • Flood Consequence Assessment (FCA)

    As defined in Appendix 1 of TAN 15, an FCA is an assessment undertaken to develop a full appreciation of the following:
    - The consequences of flooding on a development.
    - The consequences (i.e. overall impacts) of the development of flood risk elsewhere within the catchment for a range of potential flooding scenarios up to that flood having a probability of 0.1%.
    - To establish whether appropriate mitigation measures can be incorporated within the design of the development to ensure that development minimises risk to life, damage to property and disruption to people living and working on the site or elsewhere in the floodplain.

Frequently Asked Questions

  • When do I need to produce a Flood Consequence Assessment (FCA)*?

    If a development proposal is in zone C1, zone C2 (if it is defined as being of low vulnerability) or zone B (if flooding has been identified in those parts as being a material consideration) meets the justification tests outlined in section 6 of TAN 15, a FCA will need to be produced in order to assess whether the consequences of flooding of that development can be managed down to an acceptable level. There may be certain instances (e.g. some minor alterations / extensions to existing properties), where a FCA may not be required and it is recommend that guidance is sought from the Environment Agency (EA) before undertaking a FCA.

    (* - the flood zones referred to in the answer are references to the TAN 15 development zones; please refer to the 'Development Advice' section of this website for further information)

  • Can I use the information contained in the Conwy Tidal Flood Risk Study in producing an FCA?

    Yes, much of the information contained in the Conwy Tidal Flood Risk Study can be used as part of the production of a FCA for developments within the flood risk study areas. For example the information may be used when considering the following requirement that are listed in A1.5 of TAN15:
    - The likely sources of flooding.
    - The depths of flooding throughout the site.
    - The speed of inundation of the site.
    - The rate of rise of floodwaters throughout the site.
    - Velocities of floodwaters across the site.

  • Where can I gain further information and guidance in relation to producing a FCA?

    In the first instance the Environment Agency should be contacted in relation to obtaining guidance in relation to producing a FCA.

    Specific guidance and information is given in Section 7 and Appendix 1 of TAN 15.

  • Do the Conwy Tidal Flood Risk Study (CTFRS) maps replace the Development Advice Maps (DAM) given in TAN 15?

    No, however, Environment Agency Wales (EAW) and Conwy County Borough Council's Planning Department have agreed that the CTFRS maps are more up to date and provide more accurate flood risk information to assist in the production of FCAs.

  • Do I need to produce a Flood Consequence Assessment for a conservatory or extension to an existing property?

    Section 11.19 of TAN 15 states that 'applications for minor extensions or alterations should not raise significant issues unless they are likely to have a direct and adverse effect on a watercourse or its flood defences, would impede access to flood defence and management facilities or where the cumulative impact of such developments could have a significant effect on flood storage capacity or flood flows'.

    Before undertaking a FCA advice and guidance should be sought from the Environment Agency.


Conwy County Borough Council, Bodlondeb, Conwy, North Wales, LL32 8DU.
Telephone: 01492 574000. Fax: 01492 574559. E-mail:
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