Minor Development

The expert flood team at Aegaea can support your minor development planning application with an in-depth look at your project's flood risk against the local and national policy requirements.

You'll need a FRA if your development is within Flood Zone 2, 3 or in a Critical Drainage Area.

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What is a Minor Development and does it require a Flood Risk Assessment?

In England, there are different definitions of Minor Development. The definition is dependent on which type of development you are proposing as the guidance you are referring to provides a different set of criteria, guidance, and policy to be adhered to.
​The approach applied to each development is different depending on environmental conditions, flood zone, type of development, and local policy. This is why it’s important to work with a specialist. You need to make sure you have the right Flood Risk Assessment specific to your development.

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Why is it important to produce a Flood Risk Assessment for a minor development?

Although ‘minor’, there is a risk that if an unregulated development were to occur in a Flood Zone, the new construction – be it a solid building, wall, or even fence – could disrupt the natural flow path of floodwater and in turn increase the risk of flooding elsewhere.

Further minor developments could impede access to flood defence and management facilities. There is also the cumulative impact of minor developments. To provide an example: if each residential property on a street that was in a flood zone constructed an extension of 20m2, the cumulative impact on the displacement could be huge. This is especially true if appropriate mitigation measures have not been incorporated. Areas that previously did not flood could now become susceptible and those areas that did could experience far greater flood levels.

​If you are proposing a minor development and not sure if you require a flood risk assessment or which flood zone you are located in, contact our team by using the form below.

More About Minor Developments

We’ve included an FAQ section below to summarise what you need to understand about your minor development flood risk assessment. If you have any questions not answered here, contact us on info@aegaea.com.

​You may still require a Flood Risk Assessment if minor development is located in Flood Zone 2 or 3 or a Critical Drainage Area.


Flood Risk – Planning Practice Guidance – Minor Development

​A Flood Risk Assessment is required in England when any development is proposed in Flood Zone 2 or 3 or a critical drainage area, regardless of size, any development requires a Flood Risk Assessment.

​More specifically and following the government guidance on flood risk defines a ‘minor development’ as:

  • Minor non-residential extensions: industrial/commercial/leisure etc, extensions with a footprint less than 250 square metres.

  • Alterations: development that does not increase the size of buildings e.g. alterations to external appearance.

  • Householder development (residential): For example; sheds, garages, games rooms, etc within the curtilage of the existing dwelling, in addition to physical extensions to the existing dwelling itself.

This definition excludes any proposed development that would create a separate dwelling within the curtilage of the existing dwelling e.g. subdivision of houses into flats or granny annex.

Should your development meet this criterion, the requirements to achieve planning in a flood zone become more complex and stringent and falls into the national planning guidance/town and country planning definition of minor development. This is discussed in greater detail below.


National Planning Guidance / Town and Country Planning Act – Minor Development

​Following National Planning Guidance, not specific to Flood Risk, Minor Development is classified differently.  Minor Development is viewed as;

  • Commercial developments of less than 1,000 square metres or less than 1ha site area

  • Changes of use of buildings of less than 1,000 square metres or less than 1ha site area

  • Residential development of 1 to 9 dwellings or a site area less than 0.5ha
  • Traveller sites of less than 1,000 square metres or less than 1ha site area
  • Telecommunications equipment proposals
  • Mineral or waste proposals of less than 1,000 square metres or less than 1ha site area

Should you have a project that falls into either definition our team of experts can advise, consult and guide you through what will be expected to meet the requirements of planning.

Flood Risk Experts

Daniel Cook
I’m a Chartered Water and Environment Manager and specialist Flood Risk Consultant, working in the environmental consultancy sector since 2011. Specialist Subject: flood risk policy!
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Christopher Cameron-Hann
I’m a flood risk management, flood modelling and hydrology consultant. Specialist Subject: Flood Forecasting and Economic Analysis.
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Nick Darling-Drewett
Principal Flood Risk Consultant
I’m a Principal Flood Risk Consultant at Aegaea with extensive experience in producing FRAs and drainage strategies. Specialist Subject: FRAs
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Oliver Manston
Flood Risk Analyst
I’m an Analyst starting out my career in the flood management industry with Aegaea. I am currently based in Bristol after having completed a master’s in civil engineering at Swansea University....
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