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4 situations when you will need a flood risk assessment


You may need to conduct or commission a flood risk assessment as part of a planning application.


There are three flood zones that cover risks from river or sea flooding. These run from the lowest risk, flood zone 1, to the highest, flood zone 3.


You can find out what flood zone your development is in here.


The 4 main situations when you will need a flood risk assessment are when your development:

  • is in flood zone 2 or 3 - even for small developments

  • is more than 1 hectare in size (that's about 2.5 acres) - even if it's in flood zone 1

  • involves a change of use to a more vulnerable class (for example from commercial to residential), where it could be affected by surface water drains, reservoirs etc - even if it is in flood zone 1

  • has critical drainage problems as notified by the Environment Agency - even if it is within flood zone 1

If your developed is covered by any of the 4 situations above, a written flood risk assessment will be needed. Normally, a flood risk specialist will need to be hired to carry out the flood risk assessment, but it could be possible to do it yourself if it’s for a simple, low-risk development, for example a house extension.


If you’re unsure you can find out more here or you can contact Planix.uk Planning Consultants for advice using advice@planix.uk or 0845 170 8050.