Evidence base for a site in a Coastal Change Management Area

A site inside a Coastal Change Management Area is assessed on a different basis from an ordinary flood risk site. The question is not whether the development can be made safe today. It is whether it will still be in a sensible place across the period the local plan and the shoreline management plan cover, which can run to a hundred years. New housing is rarely acceptable in a Coastal Change Management Area, and where something is permitted it often comes with a time limit, a removal obligation, or a relocation commitment. So the evidence base starts with the erosion timeline and works forward from it.

What a Coastal Change Management Area is

Coastal Change Management Areas are identified in local plans for stretches of coast likely to be affected by physical change, whether erosion, landslip, permanent inundation or accretion. They are a planning designation rather than a flood zone, and they come with their own policy framework in the coastal change chapter of the NPPF (August 2026 edition) and in the Planning Practice Guidance on flood risk and coastal change.

Check three things before anything else. Whether your site is inside the designated area, using the local plan's own policies map. What the plan says about acceptable uses within it. And what the mapped erosion prediction says about your site over the relevant periods. The national coastal erosion risk mapping published through the Environment Agency's data service is the usual starting point for the last of those.

The policy position in most plans is that development is only acceptable where it will not be at risk over its planned lifetime, does not require new coastal defences, and provides wider benefits. Vulnerable uses, housing among them, face the highest bar. That constraint is set out further in the note on Coastal Change Management Areas and what they allow.

The shoreline management plan and its epochs

The shoreline management plan for your stretch of coast is the document that determines the answer, and most applicants have never read it.

Shoreline management plans divide the coast into policy units and set a management approach for each across three periods, commonly described as epochs covering roughly the next 20 years, 20 to 50 years and 50 to 100 years. The approaches are to hold the existing defence line, advance the line, manage realignment, or take no active intervention.

Find your policy unit and quote its approach for each epoch in the application. The consequences are direct. A unit with "no active intervention" from the second epoch tells you that defences will not be maintained, which sets the period over which your development can reasonably be expected to survive. A unit with "hold the line" throughout supports a longer lifetime, subject to funding, which is not guaranteed.

Then state the planned lifetime of your proposal and show it sitting inside the period the shoreline management plan supports. A 100-year residential lifetime on a unit with no active intervention after 20 years is the mismatch that refuses applications.

Vulnerability assessment for the proposal

The assessment councils expect covers the site, the proposal and the timeline together.

• The current distance from the erosion edge, measured, with the survey date.
• Predicted erosion for each epoch, taken from the published mapping and any local coastal monitoring data.
• The proposal's planned lifetime, and the basis for it.
• The vulnerability classification of the use, since a caravan pitch and a permanent dwelling are different propositions.
• Access and services over the period, because a road or a sewer lost to erosion makes a surviving building useless.
• What happens at the end of the period: removal, relocation, or abandonment.

Where cliff instability rather than marine erosion drives the risk, a geotechnical appraisal of the slope belongs in the pack, and a Geotechnical Assessment prepared to the relevant ground engineering standards is the document that carries it.

Time limited permissions and rollback

Coastal planning uses two mechanisms that are unusual elsewhere.

A time-limited permission grants the use for a defined period, after which the permission expires and the site must be cleared. It suits uses that can be relocated or that have a short economic life, such as a café, a holiday unit or a car park, and it needs a condition requiring removal and restoration, often backed by a bond or an obligation.

Rollback is the relocation of an existing use inland, away from the eroding edge. Plans that support rollback usually require the original site to be cleared and its permission surrendered, and they may allow a replacement in a location that would otherwise be resisted, such as open countryside. If you are relying on rollback, identify the receiving site early and deal with both sites in one application where the policy allows.

Neither mechanism works retrospectively. A permanent permission granted today cannot be converted into a time-limited one when the cliff reaches the garden.

Flood risk from tidal and wave sources

Coastal change and coastal flooding are different risks, and a site can be exposed to both.

Where the site falls in Flood Zone 2 or 3 on the flood map for planning, a Flood Risk Assessment is required, and it needs to address still water level, wave overtopping where the site is behind a defence, the defence standard and its residual life, and the climate change allowances for sea level rise published by the Environment Agency. Overtopping is the mechanism most often missed, because a site can sit above the still water level and still be inundated by wave action.

The flood risk sequential test applies as it would elsewhere, and a coastal site rarely has an easy answer to it. Where housing is proposed in Zone 3a the exception test follows too. Keep the coastal change case and the flood risk case as separate documents with consistent assumptions, and cross-reference the Sequential Test rather than merging the two arguments.

Coastal processes and any effect on defences

Councils and the Environment Agency will ask whether your proposal interferes with coastal processes, and the answer needs to be more than an assertion.

Cover the sediment transport regime along the frontage, any structure you propose that sits below the high water line, and any effect on neighbouring properties or defences. Works below mean high water springs need a marine licence from the marine regulator, which is a separate consent with its own timescale, and coast protection works may need consent from the coast protection authority.

State clearly whether the development depends on new or improved defences. A proposal that needs a defence to be built or maintained for it to be acceptable is normally refused, because national policy resists development that requires new coastal defences to be viable.

Conditions on relocation and removal

Draft the conditions and obligations you can live with, and expect the council to want the following:

1. A permission expiring on a stated date, with all buildings removed and the site restored.
2. A financial mechanism securing the removal, whether a bond, a charge or an escrow arrangement.
3. A restriction preventing coastal defence works in connection with the development.
4. An occupancy or use restriction matching the vulnerability classification assessed.
5. A monitoring requirement tied to the erosion edge, with a trigger distance at which the use must cease.
6. Where rollback applies, the surrender of the original permission and the clearance of the original site.

Illustrative example: a single dwelling proposed 60 m from a cliff edge on a frontage where the shoreline management plan set no active intervention from the second epoch and the mapping predicted an average retreat consistent with reaching the site within that period. The permanent dwelling was refused. A revised scheme for a relocatable holiday unit, permitted for 15 years with a removal bond and a monitoring trigger at 25 m, was approved.

Enter your postcode on PlanScope to see the flood and coastal constraints recorded at your site before you commission survey work.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.