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How Is a Flood Risk Assessment Formed?

Flood Risk Assessments (FRA) are used to analyze a proposed development to determine the likelihood of flooding. The risk does not just come from groundwater sources or sources of rivers (fluvial), it will also consider sources such as coastal and estuary sources (tidal) or surface water sources (pluvial).

Flood Risk Assessments are required before making plans. If a project is located in an area that is a Flood Zone, or another vulnerable area, it is probable that approval is not granted without one.

What is an Flood Risk Assessment?

The Environment Agency in England and Wales requires that an expert Flood Risk Assessment be submitted with planning applications for zones at danger of flooding. You will also need A Flood Risk Assessment if the proposed development takes place within 20 meters of the Environment Agency main river.

You can use on the website to determine if your location is in a flood area or in which flood zone it is.

As per the Environment Agency,

For the majority of developments within flood zones, you will need to perform a flood risk assessment.

This includes developments:

Flood zone 2 or 3, including minor development and changes of use.

More than 1 hectare (ha) in flood zone 1

less than 1 ha within flood zone 1, including the possibility of changing development type to a more vulnerable category (for example , changing from commercial to residential), where they could be affected by flood sources other than sea and rivers (for example surface reservoirs, drains); and

Flood zone 1 is a region that was notified by Environment Agency as having critical drainage problems.

It is also advisable to contact your local planning authority to check if the site is located within an area that has been identified as having drainage issues that are critical.

How is an Flood Risk Assessment Formed?

A Flood Risk Assessment is compiled with the help of third party data sources. The sources of these data could be from the Environment Agency modelling or data obtained by consultants on their own. A study of the data sets will be undertaken to get a full picture of the location and any flood-related dangers discovered.

What are the factors that can affect flooding?

Flooding can be influenced by a variety of factors, including:

Surface water run-off

Local Topography

proximity to rivers and coasts



current land usage

existing drainage




vegetation cover

rainfall levels

What is Drainage Strategy/Design, and what can it do?

Flood Risk Assessments usually require that you demonstrate (and demonstrate) that the proposed development will not increase the risk of flooding elsewhere.

In this scenario the need for it is likely that a Drainage Strategy could be requested by the Local Planning Authority.

They can be found anyplace in the world that is not a floodplain (river or coastal).

It is recommended to ensure that any subsequent run-off due to the proposed development will be controlled.

What could we do to help?

We are able to provide the Level 1 and Level 2 Flood Risk Assessments that:

Identify whether any flooding caused by the development site merit more investigation;

Determine if the area is in danger of flooding.

Determine if the location could increase the risk of flooding due to increased run-off;

Confirm possible sources of flooding;

Examine the quality and availability of information that is available;

Assess the flood risk to an area and the effect of flood risk elsewhere;

Review the scope of the development design, and scope any additional work as necessary.

How we are qualified to help you

People who aren’t experts or have been trained in Flood Risk Assessments may produce them. However the nature of the Flood Risk Assessments make them a complex evaluation. Authorities might reject assessments which do not cover all flooding scenarios. This can lead to lengthy delays between the approval of plans and the beginning of work.

If there is a major flood event, an insufficient Flood Risk Assessment could even cause a claim for negligence against the developer.