Flood Risk Assessment

What is a Flood Risk Assessment?

A flood risk assessment is a report that considers a proposed development, its proposed layout, form and construction etc. in order to assess the likelihood and the associated risk of flooding. The risk of flooding that is to be assessed as part of the flood risk assessment could be from groundwater, surface water, a water source such as a river or stream, coastal or tidal flooding, and/or flooding from sewer sources. The flood risk assessment should also take into consideration adjacent land uses and surrounding areas to assess the likelihood of whether a development poses a flood risk to these nearby areas.

The flood risk assessment will take into consideration and analyse data sources from third parties such as the Environment Agency, Local Authorities, water company and/or data obtained/held by private companies. The floors risk assessment will likely use a combination of this data to enable production of the flood risk assessment.

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What is included in a Flood Risk Assessment?

The requirements for what is to be included within a flood risk assessment is set out and defined within the National Planning Policy Framework. This sets out the guidance which needs to be followed in order to determine the viability of a development in terms of the flood risk. The key part of the National Planning Policy Framework which needs to be followed when producing a flood risk assessment is paragraph 164. The flood risk assessment should determine whether a proposed development is safe for its intended lifetime and whether it provides sustainable benefits to the area.

The majority of flood risk assessments will include the following information:

The site address;
The description of the proposed development;
The assessment of the flood risk in relation to the various sources of flooding relevant to the development, including contingency allowance for climate change;
The estimated flood level of the proposed development, including;
- a river flood level with a 1 in 100 or greater annual probability;
- the tidal flood level with a 1 in 200 or greater annual probability;
- plus an allowance for climate change;
Details of flood resistance, mitigation and resilience plans;
Supporting plans and drawings relevant to the proposed development;
Any other information as required by the relevant guidance.

The estimated floor level may be able to be obtained from the Environmental Agency or the Local Planning Authority in order to include within the flood risk assessment. If this is not available then a specialist assessment will need to be undertaken to calculate this.

The flood risk assessment does not need to be issued in a specific format, although will need to contain relevant surveys, plans and assessments. Some local authorities may require specific information and this should be checked prior to submitting the flood risk assessment.

Why do I need a Flood Risk Assessment?

A flood risk assessment is a requirement under the National Planning Policy Framework and Environment Agency guidance for any development which is located within a flood risk zone 2 or 3, a critical drainage area, or where located in flood risk 1, the site in question is equal to or greater than 1 hectare in size. A flood risk assessment will also be required where the development is being constructed within 20 meters of a main river as classed by the Environment Agency.

A flood risk assessment should be undertaken at the earliest possible opportunity to ensure that the findings and recommendations can be taken into consideration as part of the early design and as part of the planning process.