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The Sequential Test for commercial development - Christchurch

Planning Policy Statement 25 (PPS25) requires local planning authorities to follow a risk-based approach in their consideration of applications for new development. The first stage of this approach is the Sequential Test which aims to steer new development to areas with the lowest probability of flooding. Only when there are no reasonably available alternative sites within zone 1 (low probability) can development within zone 2 (medium probability) or zone 3 (high probability) be considered.

Christchurch Borough Council has produced a Strategic Flood Risk Assessment that shows Flood Zones 1, 2 and 3 in the years 2086 and 2126. This has been done to meet the requirements of PPS25 which states that development must be safe for its full design life; 60 years in the case of commercial developments and 100 years for housing. The Sequential Test must be based on these future Flood Zones.

This page explains the process of conducting the Sequential Test for commercial (non domestic) applications. Advice for housing developments can be found on the sequential test for new housing development in Christchurch page.

Reasonably available alternative sites

Before development within a flood zone can be considered, a Sequential Test must demonstrate that no 'reasonably available alternative sites' exist within zone 1 (low probability) which could be developed instead. The geographic area over which the test for commercial uses must be carried out will vary with the use proposed. For example A1 retail uses are most suitable within town centres, district centres and local shopping parades, while B8 warehouse uses might be appropriate for any number of industrial estates.

Applicants are advised to identify locations across the Borough which may be suitable for the commercial use being proposed and consider whether or not they are 'reasonably available alternative sites'. Applicants should peak with Christchurch planning officers prior to submitting any application for a development affected by flood risk.

Which Flood Zones to use?

The Sequential Test must always be carried out using the 'undefended' flood zones which do not factor in the protection afforded by existing defences - maps are provided on the Christchurch Strategic Flood Risk Assessment page. These zones show the extent of flooding should a defence be overtopped or breached during a flood. The 'defended' zones can only be considered as part of the Exception Test, and only once the Sequential Test has been passed.

New buildings exist for many years and must be safe throughout their 'design life'; for non-domestic uses this is taken to be 60 years. Consequently a new commercial premises built in 2010 must be safe from flooding until 2070. The Christchurch Strategic Flood Risk Assessment provides flood maps for the year 2086 which indicate whether a site is likely to be affected in that time.

To accurately determine the risk, a site-specific Flood Risk Assessment will be required for all applications affected by current or future flood zones.

Environment Agency Standing Advice

Planning applicants and their agents should refer to the Environment Agency Flood Risk Standing Advice for England (opens in a new window) for guidance on what to do when submitting a planning application. 

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