Planning Policy concerning Development and Flood Risk, applies to all new developments under PPS 25 in England. Flood zone categories have been identified by the Environment Agency on published Flood Maps. The flood zone categories are as follows:
The Flood Risk Zones are 1, 2, 3a and 3b. Zones 2, 3a and 3b are the "at risk" categories. Zone 2 is based on the extreme flood outline at 0.1% (1 in 1000) or greater risk. Zone 3a is at greater risk (1% for river or 0.5% for sea). "Functional Floodplain" at 5% risk (1 in 20).
"More Vulnerable" development (which includes dwellings) should not be permitted in Zone 3b. The exception test is required in Zone 3a.
In order to pass the PPS25 Exception test all of the following must be demonstrated:
- the development makes a positive contribution to sustainable communities, and to sustainable development objectives of the relevant LDD;
- the development is on developable brownfield land or where there are no reasonable alternative options on developable brownfield land;
- a flood risk assessment demonstrates that the residual risks of flooding to people and property (including the likely effects of climate change) are acceptable and can be satisfactorily managed; and
- the development makes a positive contribution to reducing or managing flood risk
A Flood Risk Assessment Report is likely to be required for all development in Zones 2, 3a and 3b.
Appendix E of PPS25 provides a checklist of the Environment Agency Requirements.
The flood risk assessment may depend on EA site-specific requirements. It needs to include the technical means of reducing the risk of flood damage to an acceptable level. The assessment includes the following:
- Relationship of site levels to potential flood levels (AOD)
- Historical data research on past flooding incidents
- Obtaining data from the EA
- Calculating 1 in 100 and 1 in 1000 year flood levels
- Modelling using MIKE FLOOD or HECRAS as appropriate
- Assessing existing flood defences
- Breach Assessment if required
- Identifying emergency plans and warning systems
- Recommending development solutions
The FRA report details what conditions should be imposed on the development to ensure no additional risk to life and minimal damage or disruption to people, property and the natural environment.
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