CATEGORISING FLOOD RISK

There’s a scale of three categories that identify if an area is at risk of flooding, where a higher number shows a greater level of danger:

Flood zone 1 These areas are considered to be at very low risk, with less than a 1 in 1,000 chance of flooding. There aren’t many planning restrictions here, except for in the case of large developments.

Flood zone 2 There’s a moderate chance of flooding here; annual probabilities are between 1:1,000 and 1:100. The local planners will ask for a flood risk assessment (known as a flood consequence assessment in Wales) which usually means you’ll have to commission a report. The results will analyse the risks, indicate the impact of the new building on potential flooding and identify the ways that the threat will be tackled in the design.

Flood zone 3 This means the area is at a high risk of flooding – a chance of 1:100 near rivers and 1:200 by the sea. Planning applications in these zones need a more detailed assessment. Local authorities have their own subdivision of this category into 3a and 3b. The latter identifies a 1:20 possibility, so the restrictions on new development are the most stringent.