Flooding: Some key considerations for developers

Authors: Julie Vaughan, Senior Associate, Environment and John Buttanshaw, Associate, Environment, London

In the aftermath of the extreme flooding of winter 2015/16 the government is currently undertaking a 'National Flood Resilience Review'. This will assess how the country can be better protected from future floods and increasingly extreme weather events.  In this post we look at how to find out if your development is in a flood zone, what is needed for a flood risk assessment, and some of the other permissions, permits and consents which are required when considering flood risk. 

From a development perspective, flood risk assessment already forms a key component of many planning applications. At present, development within flood zones 2 or 3 (broadly, zones where there is a more than a 1 in 1000 annual probability of river or sea flooding) must carry out an assessment and submit it with their planning application. Certain developments in flood zone 1  (generally where the area is greater than 1 acre or where there are particular drainage issues) will also need to provide an assessment. The flood zone of a development can be checked using this Environment Agency map.  

A flood risk assessment is a substantial document. It considers flood hazards and their probability, the impacts the development may have and any necessary measures to address these. In addition, the assessment needs to consider how flood risk at the site is likely to be affected by climate change. The Environment Agency recently published revised climate change allowances which should be incorporated into future assessments (see the guidance here).

In addition to planning permission, if the development involves works on, over, under or near a main river, flood or sea defence, or changes to any structure that helps control floods, an environmental permit for flood risk activities from the Environment Agency may be required. Note that these permits have replaced the previous 'flood defence consent' regime from 6 April 2016 (most previously existing flood defence consents will be automatically 'converted' into an environmental permit, but certain activities are now exempt or excluded from the regime so this should be checked). Works on or near watercourses that are not main rivers may still need permission from either the lead local flood authority or the Internal Drainage Board in the area.

There are a myriad of other issues that need to be considered in terms of flood risk caused by developments, including the availability of insurance, and the potential for nuisance claims where the development risks causing flooding to a neighbouring property. In addition, the interface with the contaminated land regime may need to be considered given flooding can lead to the migration of contamination to or from the development.

For more information please contact: