Navigating the Risks of Flood Zone 3: A Comprehensive Guide (2023)
What are flood zones?
Flood zones are areas along the river in which water flows. Depending on how often water flows in these areas, then there is a level of risk given to them. For instance, in England, areas where water constantly flows are flood zone 3. Areas in which water is less likely to flow are flood zone 2.
The role of the Environment Agency
The Environment Agency, which is a public body responsible for the enhancement and protection of the environment in England, created a flood risk map to show the different types of flooding across England.
This tool was developed to help councils, developers, and the community in planning with respect to the flood risk in the areas concerned.
Flood Zone Classification
To specify the risk of flooding in different areas, the Environment Agency classifies the flood zones into 4 parts.
Flood Zone 1
Flood Zone 2
Flood Zone 3a
Flood Zone 3b
Flood Zone 1 - Flood probability is low
The areas that fall under this category have less than a 0.1% probability of flooding in a given year. There are very few restrictions on flood risk for areas in this category and there is an exception for the below-mentioned case.
The flood risk assessment must be undertaken for a planning application for development greater than 1 hectare in size and Critical Drainage Areas which are the areas that are considered to be at high risk of flooding due to rainfall.
Flood Zone 2 - Flood probability is medium
The areas that fall under this category have between 0.1% to 1.0% probability of river flooding and between 0.1% to 0.5% probability of sea flooding in a given year.
Development in flood zone 2 is required to submit a flood risk assessment as part of the planning application.
Flood Zone 3a - Flood probability is high
Flood zone 3a is the area that has between 3% and 1% or greater probability of river flooding and 0.5% or greater probability of sea flooding in a given year.
Flood zone 3b - The functional food plain
Areas that are at considerable risk of flooding from rivers or the sea are classified as flood zone 3b. Flood zone 3b has a probability of flooding of up to 3%.
This area is made up of land where water must flow or be kept during floods.
If you would like to know the flood risk for an area in England, you might check the Environment Agency’s flood map here.
Under the surface water section, you will be able to find out the Lead Local Flood Authority (LLFA) for the explored area.
For Northern Ireland, Scotland, and Wales, use the links below.
How flood zone 3 fits the planning process?
To carry out the flood risk assessment as part of the planning application, keep in mind the following points.
Research the development site - Contact the Lead Local Flood Authority, the Internal Drainage Board, and the Environment Agency for possible flood risk information on the area.
Sequential test -You might require a sequential test if it has not been conducted for the proposed development. In some cases, you might also need an exception test. More information here
Location plan - A location plan consisting of street names, any bodies of water, and other geographical features such as railway lines, etc would be needed.
Site plan - A site plan consisting of the development proposal, the existing site, and structures that could possibly affect the water flow must be provided.
Surveys - You need to indicate the existing site levels, levels of the proposed development, a cross-section of the site indicating road levels, and any other levels informing flood risk.
Assessments - Consider the following in your flood risk assessment.
Flood risk
Surface water runoff
Flood risk management
Developments on or near main rivers
Sites within the functional floodplain
For more information, visit the link - https://www.gov.uk/guidance/flood-risk-assessment-in-flood-zones-2-and-3#plans.
What developments are permitted in flood zone 3?
Flood zone 3a
Less vulnerable developments and water-compatible developments are considered acceptable.
Developments like emergency service stations, park homes, and basement flats, which are highly vulnerable, are not permitted.
Developments like hotels, hospitals, houses, and essential infrastructure like substations should pass the exception test.
Flood zone 3b
As far as essential infrastructure and water-compatible developments are concerned, they will have to pass the exception test to be accepted in flood zone 3b.
In flood zone 3b, which is considered as the functional floodplain, developments like caravans, basement flats, etc are highly vulnerable, houses, hospitals, etc are considered more vulnerable, and commercial developments, churches, etc are considered less vulnerable are not permitted.
Techniques for designing structures to withstand flooding in Flood Zone 3
Any water-compatible and essential infrastructure developments must be designed in such a way that
It stays operational and safe during a flood
It does not increase flood risk in some other areas or block water flows
It does not lead to loss of floodplain storage
Best practices for siting and elevating structures in Flood Zone 3
When the depth of the water is up to 0.3m, the development must be as water-tight as possible. Use materials with limited permeability to do this, such as impermeable concrete.
When the depth of the water is between 0.3m and 0.6m, the development must be created in such a way that will keep water out (barring structural issues) by:
employing flood-resistant materials (such as lime plaster) and design with low permeability to at least 0.3m
ensuring that all areas are accessible to facilitate drying and cleaning
When the depth of the water is greater than 0.6m, the building or development must be designed to allow water to pass through the property in order to prevent structural damage by
ensuring that water can drain away easily after flooding
ensuring that there is access to every room to facilitate drying and cleaning
utilizing materials with low permeability to at least 0.3m
FAQs
How do I know if I live in a flood risk area UK?
The risk of various types of flooding where you live and in the neighbourhood can be shown with the use of maps.
The Environment Agency has created the following maps:
A map detailing the long-term danger of flooding for a property and the probable extent of flooding to houses from surface water, rivers, or reservoirs across the UK. You may discover who your Lead Local Flood Authority (LLFA) is by providing your postcode here, choosing your property, and then clicking through to the map to discover more about your flood risk.
This flood map for planning is employed in planning and design to determine whether a location is likely to flood and to show which flood zone it is.
Should you buy a house that floods?
There is no reason not to purchase a home constructed on a floodplain if you are prepared to do your research and are completely aware of the hazards involved. But you should still perhaps take some safety precautions. For further information, visit the National Flood Forum's page on property protection.
Can I get a mortgage on a flood-risk property?
It is possible, but it is not a given. The fact is that certain properties are situated in flood-prone zones. As a result, there are lenders willing to offer mortgages in these high-risk areas.
Your best chance of getting a mortgage is to speak with a broker who deals in flood risk areas and is well-versed in these regions. They can still assist in locating the ideal solution for your circumstances even if you have previously been rejected.