What is a Flood Risk Assessment?

A Flood Risk Assessment (FRA) reviews a proposal of development in order to assess its risk for flooding. This risk is not only from groundwater sources and river sources (fluvial), it will also take into account sources including sewer sources, estuary/coastal (tidal) or surface water (pluvial).

Flood Risk Assessments are often required prior to planning – if a development is located in a Flood Zone or other at-risk area, it is likely that planning permission will not be validated without one.

When Is a Flood Risk Assessment Required?

In England and Wales, the Environment Agency requires a professional Flood Risk Assessment (FRA) to be submitted alongside planning applications in areas that are known to be at risk of flooding. You will also need A Flood Risk Assessment if the proposed development is taking place within 20 metres of an Environment Agency main river.

To find out if you are in a flood zone or which flood zone you are in, you can use the gov.uk online search facility which allows you to search by place name or postcode, National Grid Reference (NGR) or by Easting and Northing. This can be found here https://flood-map-for-planning.service.gov.uk/

The Environment Agency states that:

You need to do a flood risk assessment for most developments within one of the flood zones.

This includes developments:

  • In flood zone 2 or 3 including minor development and change of use;
  • More than 1 hectare (ha) in flood zone 1;
  • Less than 1 ha in flood zone 1, including a change of use in development type to a more vulnerable class (for example from commercial to residential), where they could be affected by sources of flooding other than rivers and the sea (for example surface water drains, reservoirs); and
  • In an area within flood zone 1 which has critical drainage problems as notified by the Environment Agency.

[source gov.uk here] https://www.gov.uk/guidance/flood-risk-assessment-for-planning-applications

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

How Is a Flood Risk Assessment Formed?

A Flood Risk Assessment is compiled using third party data sources. These can include data from the Environment Agency modelling, or independent data collected by the consultant or EMS Geotech. An analysis of the data sets will be undertaken to get a full overview of the site and any associated flood related risks identified.


What Factors can Influence Flooding?

Flooding can be influenced by various factors including:

  • surface water run-off
  • local topography
  • proximity to rivers and coasts
  • geology
  • groundwater
  • current land usage
  • existing drainage
  • mines
  • quarries
  • hardstanding
  • vegetation cover
  • rainfall levels



What is Drainage Design/Strategy?

Often, one of the most important requirements of the Flood Risk Assessment is to ensure (and be able to demonstrate) that the proposed development will not lead to an increase in flood risk elsewhere.

In this situation, a Drainage Strategy is likely to be requested by the Local Planning Authority.

This can include sites which are not located in a floodplain (river or coastal).

It is requested to ensure that subsequent run-off from the proposed development will be mitigated.

How can EMS Geotech help?

EMS Geotech can provide Level 1 and Level 2 Flood Risk Assessments that:

  • Identify whether any flooding related to the development site warrant further investigation;
  • Identify whether the area is at risk of flooding;
  • Identify whether the site may increase the flood risk due to increased run-off;
  • Confirm possible sources of flooding;
  • Assess the availability and adequacy of existing information;
  • Qualitatively assess the flood risk to a site and the impact of flood risk elsewhere;
  • Assess the possible scope for appropriate development design and scope additional work where required.

How We Are Qualified To Help you

‘Non-Professional’ Flood Risk Assessments can be produced by individuals who are not specifically trained or professionally qualified in this field. However, the nature of Flood Risk Assessments make them a complex evaluation. Evaluations which do not cover all flooding eventualities have the potential to be rejected by Authorities during the planning stage, which can cause lengthy delays to the validation of planning and commencement of the project.

In the event of a catastrophic flood event, an insufficient Flood Risk Assessment could even result in a claim of negligence being made against the developer.

EMS Geotech provide Flood Risk Assessments undertaken by our experienced Geo-Environmental Engineering Consultants, allowing you peace of mind.