Our development flow chart aims to demystify the requirements of a development based on flood zones and if specific uses are acceptable. The types of development that can occur within flood zone 3 is not only controlled by the vulnerability of these usages but also if the site is located within flood zone 3a or 3b.

Areas within flood zone 3 have been shown to be at a 1% or greater probability of flooding from rivers or 0.5% or greater probability of flooding from the sea.įlood zone 3 development needs to submit a flood risk assessment as part of its planning application which determines if the site is classified as flood zone 3a or 3b as well as reviewing flood risk on the site and proposing suitable mitigation. Flood Zone 3įlood zone 3 is actually split into 2 separate zones 3a and 3b by the local planning authorities however the EA do not split the zone and as such their maps only identify a general flood zone 3. The types of development that can occur within flood zone 2 is controlled by the vulnerability of these usages. As the probability of flooding within flood zone 2 sites can vary so much these reports are often the trickiest in terms of analysis and mitigation measures. Flood Zone 2Īreas deemed to be in flood zone 2 have been shown to have between 0.1% – 1% chance of flooding from rivers in any year (between 1:1000 and 1:100 chance) or between 0.1% – 0.5% chance of flooding from the sea in any year (between 1:1000 and 1:200 chance).įlood zone 2 development needs to submit a flood risk assessment as part of its planning application which shows the risk of flooding to the site. There are very few restrictions in terms of flood risk to development on flood zone 1 areas, the exception is for development over 1ha in size which must have a flood risk assessment undertaken as part of a planning application and areas deemed to be at high risk of flooding from rainfall known as Critical Drainage Areas. Areas deemed to be in flood zone 1 have been shown to be at less than 0.1% chance of flooding in any year, this is sometimes known as having a 1:1000 year chance.

Fema flood zones