Shoreline Management Plans Explained: Hold the Line, Managed Realignment and No Active Intervention

England's coast runs to roughly 6,000km, and nearly all of it is covered by a shoreline management plan: the document that decides whether a stretch of shoreline gets defended, left alone, or allowed to move. A shoreline management plan (SMP) sets a policy for how a section of coast will be managed against flooding and erosion out to 2105, choosing between four options: hold the line, advance the line, managed realignment and no active intervention. Twenty SMPs, prepared by seven coastal groups between 2006 and 2012, cover the English coast between them, and each of the four policies decides, in practice, whether a town keeps its sea wall, whether a site gets moved back from an eroding cliff, or whether a marsh is allowed to flood on purpose.

For planning consultants and their clients, a shoreline management plan is more than background reading. Planning Practice Guidance expects local planning authorities to use SMPs as the evidence base for designating Coastal Change Management Areas and deciding coastal applications. A striking number of local plans, it turns out, do not show that evidence at all.

Under the Environment Agency's most recent modelling, dropping shoreline management plan delivery altogether would put an estimated 65,100 properties at coastal erosion risk by 2105, more than six times the roughly 10,100 at risk if current SMP policies are delivered in full.

What is a shoreline management plan?

A shoreline management plan is a non-statutory policy document that sets out how a length of coast will be managed against flooding and erosion, split into three time periods running out to 2105. Twenty SMPs cover the English coast, prepared jointly by the Environment Agency and local authorities through seven coastal groups, and each one sets a distinct policy for every stretch it covers.

• Non-statutory but authoritative. SMPs carry no legal force of their own, but Planning Practice Guidance directs local planning authorities to treat them as the evidence base for coastal planning decisions.
• Twenty plans, seven coastal groups. Prepared collaboratively by the Environment Agency, local authorities and other coastal bodies between roughly 2006 and 2012, covering approximately 6,000km of open coast.
• Three time periods. Each policy unit is assessed across the short term (to 2025), medium term (to 2055) and long term (to 2105).
• Refreshed, not static. The Environment Agency ran a nationwide SMP refresh between 2019 and 2023, producing health checks on all twenty plans, modernised action plans, and the map-based SMP Explorer, launched in January 2024.
• Independently reviewed. A 2023 peer review recommended stronger governance, clearer deliverability, closer integration with the planning system and better climate adaptation.

The four shoreline management policies: hold the line, advance the line, managed realignment and no active intervention

Every stretch of coast covered by an SMP is assigned one of four management policies for each of the three time periods, and government guidance defines each precisely. Hold the line means to “maintain or upgrade protection from flooding or erosion by holding the shoreline in broadly the same position.” Advance the line means to “actively move shoreline defences significantly seawards”, rare outside land reclamation and port schemes. Managed realignment means to “change the position of the shoreline in a controlled way, such as by slowing erosion or creating areas of habitat.” No active intervention means to “maintain or encourage a more natural coastline”, which in practice means adaptation rather than defence.

Policy commonly changes between the three epochs: hold the line now, managed realignment or no active intervention later, to give affected communities lead-in time before a harder decision arrives. The transition between one epoch's policy and the next is where most of the difficulty happens on the ground. A policy of hold the line to 2055 followed by no active intervention to 2105 effectively puts an expiry date on a community's existing defences, and that is a harder conversation than the plan itself usually lets on.

How do shoreline management plans feed into planning decisions?

Planning Practice Guidance gives shoreline management plans a defined role in plan-making. Local planning authorities are expected to draw on SMP policies as their evidence base when deciding whether to designate a Coastal Change Management Area, and when assessing whether a proposed development can be considered safe for its expected lifetime, a minimum of 100 years for residential development.

1. The SMP sets a policy. Each policy unit gets a hold the line, advance the line, managed realignment or no active intervention policy for each of the three epochs.
2. The local plan uses it as evidence. Planning Practice Guidance directs local planning authorities to draw on the relevant SMP when designating a Coastal Change Management Area and setting local development policy.
3. Planning decisions account for the SMP's direction. An application is assessed against how the shoreline is expected to be managed across the development's whole lifetime, not its likely condition on the day it is built.

How often do local plans actually reflect their shoreline management plan?

Not consistently, and Parliament's own scrutiny committee has said so in the plainest terms. In its 2026 report on coastal erosion, the Environment, Food and Rural Affairs Committee cited a 2018 Climate Change Committee finding that up to a third of local plans for coastal locations showed no evidence of using their SMP as the required evidence base. The Committee looked again in 2026 and found the gap had still not closed.

A 2018 Climate Change Committee report found that up to a third of local plans for coastal locations showed no evidence of using their shoreline management plan as the required evidence base, a gap MPs revisited in 2026 and found had still not been closed.

The Committee's own findings sharpen the point further. Sixteen of England's 94 coastal authorities had no active local plan at all at the time of its inquiry, and no coastal local plan currently extends beyond 2036: only ten years into the second epoch that most SMPs run to 2055. That mismatch matters in practice. A scheme approved today under a plan that stops looking ten years ahead can sit for decades under a shoreline policy the plan never accounted for. The Committee recommended making SMP incorporation a statutory requirement for coastal planning authorities, with compliance checked at Local Plan examination, and called on Defra and MHCLG to publish a fully costed roadmap for delivering it by December 2026.

For anyone bringing forward a coastal planning application, that is a due-diligence point as much as a policy debate. A flood risk assessment or planning statement that cites only the local plan's own policies, without checking the underlying SMP and how it addresses vulnerability classification and development lifetime, may be working from an evidence base the local plan itself has never properly absorbed.

What NCERM2 shows happens with and without SMP delivery

The Environment Agency's second National Coastal Erosion Risk Map (NCERM2), published in January 2025, models coastal erosion exposure under contrasting management scenarios: current SMP policies delivered, and no active intervention applied everywhere. The gap between them is stark.

Roughly half of the properties at risk are residential, and the infrastructure exposure by 2105 includes around 10km of major roads, 173km of minor roads and 6km of railway. One in six of the properties at risk by 2100 sits in one of England's most deprived areas. That gap between the delivered and undelivered scenarios widens further under higher sea-level-rise projections, which is why Unda treats the sea-level allowance used in a coastal flood risk assessment as a policy question as much as a modelling one. The Agency is careful about how the mapping should be read: it shows areas of land likely to be at erosion risk, not the precise future position of the shoreline, and it cannot be used to assess an individual property.

Where are shoreline management policies already reshaping England's coast?

The policy choices above are already visible at named places on the map, and a few examples show why the policy chosen for a stretch of coast matters as much to a planning application as any other site constraint.

• Jaywick, Essex. A 1953 storm surge broke over the sea defences here and killed 37 people, around 5% of the village's population at the time. The Environment Agency has since completed a £12m scheme to raise and strengthen the sea wall, protecting roughly 3,000 homes and businesses. Flood risk assessment in Jaywick.
• Pevensey Bay, East Sussex. The whole settlement sits behind a shingle wall on low ground the sea would otherwise reclaim, and almost all of it is mapped in Flood Zone 3. Flood risk assessment in Pevensey Bay.
• Mablethorpe, Lincolnshire. On the open North Sea coast, defended by a concrete sea wall, a recharged sandy beach and pumping stations, this is a place where it is the sea and its tides, not a river, that set the terms for any development. Flood risk assessment in Mablethorpe.
• Winchelsea Beach, East Sussex. Reclaimed marshland behind a shingle bank, kept dry by groynes and a secondary embankment, with most of the village in Flood Zone 3. Flood risk assessment in Winchelsea Beach.
• Hastings, East Sussex. A steep coastal town where flooding can arrive from several directions at once: rain off the High Weald, watercourses backing up at Bulverhythe, and the sea held off the seafront by a line of defences. Flood risk assessment in Hastings.
• Great Yarmouth, Norfolk. Standing on a narrow spit with the North Sea on one side and the tidal Yare and Bure, opening into Breydon Water, on the other, so its defences have to hold on two fronts at once. Flood risk assessment in Great Yarmouth.
• Lowestoft, Suffolk. Britain's most easterly town, built around the tidal Lake Lothing where it meets the North Sea. Flood risk assessment in Lowestoft.
• Dawlish, Devon. A coastal town where the sea, a small but flashy stream and the surrounding hills all shape flood risk at the same time. Flood risk assessment in Dawlish.

If you are bringing forward a planning application on or near the coast, the starting point is establishing exactly what your site's shoreline management plan policy says, and whether the local plan you are relying on has actually kept pace with it. Unda's flood risk assessments for planning draw on the current SMP, NPPF and Planning Practice Guidance directly, rather than assuming a local plan's own wording is up to date.