Development below mean high water and marine licensing

If any part of your scheme sits below mean high water springs, you need a marine licence as well as planning permission, and neither consent substitutes for the other. The marine licence comes from the Marine Management Organisation under Part 4 of the Marine and Coastal Access Act 2009. Planning permission comes from the local planning authority, whose area generally runs out to the low water mark. Between those two lines sits a strip of foreshore where both regimes apply at once, and that is where most coastal projects get into difficulty.

The practical consequence for a developer is budget and programme. A marine licence is a separate application, with its own fee, its own consultees, its own environmental assessment regime and its own determination period. Treat it as a parallel track from day one rather than as a condition to be discharged later.

Where planning jurisdiction ends and marine licensing begins

Mean high water springs is the landward edge of the UK marine area. Seaward of that line, and in estuaries and tidal rivers for as far as the tide reaches at mean high water springs, the Marine and Coastal Access Act 2009 regime applies.

Local authority boundaries, by contrast, generally extend to the low water mark. So the ordinary planning system reaches further seaward than many developers expect, and the marine regime reaches further inland than most expect, particularly up tidal creeks and rivers.

A slipway, a pontoon, an outfall, a revetment or a jetty on a tidal river twenty kilometres from the open coast can be a licensable marine activity. The test is the tidal limit, not the look of the water.

Activities that need a marine licence

Section 66 of the 2009 Act lists the licensable activities. The ones that catch development schemes are the deposit of any substance or object in the sea or on the sea bed, the construction, alteration or improvement of any works in or over the sea or on the sea bed, dredging, and the removal of substances or objects from the sea bed.

Those categories are broader than they sound:

• Piling for a pontoon or a jetty is construction of works on the sea bed.
• Laying a pipe or cable across the foreshore is both deposit and construction.
• A rock armour revetment is deposit of substances.
• Scour protection, even a few tonnes of rock placed round an existing pile, is deposit.
• Capital and maintenance dredging to keep a berth usable needs its own licence and its own disposal site.

There is an exempted activities order which takes a list of minor and low-risk operations outside the licensing requirement, usually subject to notification or registration rather than a full application. Check the current text against your specific operation rather than assuming a small job is exempt, because the exemptions are tightly drawn by quantity, location and method.

The overlap zone where both consents bite

Between mean high water springs and the low water mark, works can need planning permission and a marine licence together. This is the normal position for slipways, steps, outfalls, sea walls and most access structures.

Two points follow. First, a scheme that straddles the line needs its drawings to show which elements sit where, because the two authorities will each only consent their own part. Second, where works sit wholly below low water, there is often no planning application at all, which surprises applicants who assume the council has a view. It may still be consulted, but it is not the decision maker.

Harbour authorities add a third layer inside their statutory limits. Works inside a harbour can need a harbour works licence or the harbour authority's consent under its own local Act or harbour revision order, and that consent is separate again from the marine licence.

Fixing the tidal boundary on a specific site

The mean high water springs line printed on Ordnance Survey mapping is a cartographic record of a surveyed position, not a legal boundary fixed for all time. The real boundary is physical and it moves as the foreshore accretes or erodes.

For a scheme close to the line, three steps settle the position:

1. Order the large-scale mapping and note the surveyed mean high water springs and mean low water lines across the site.
2. Commission a topographic survey tied to Ordnance Datum, with the tideline picked up on the ground and tidal levels taken from published Admiralty data for the nearest standard or secondary port.
3. Put the result to both the Marine Management Organisation and the local planning authority in a pre-application enquiry, with the drawing, and ask each to confirm what it considers to be within its remit.

That third step is worth the delay. An applicant who assumes the line and designs around it can lose a season if the licensing authority takes a different view of where the tide reaches.

Illustrative example. A developer proposes twelve waterside apartments with a shared pontoon on a tidal creek. The building platform sits above mean high water springs, so it needs planning permission alone. The pontoon, its piles and the access gangway sit below that line, so they need a marine licence as well, and the gangway abutment straddles the boundary and appears on both applications. The dredging needed to keep the berth usable is a third licensable activity with its own disposal arrangements. The figures and arrangement here are illustrative only.

Application content and determination

A marine licence application is evidence-led. Expect to provide the works description with quantities, coordinates in a recognised projection, drawings, a method statement, a navigational risk assessment where vessels are affected, and an assessment against the marine plan for the relevant area and the UK Marine Policy Statement.

Environmental assessment runs on a separate track from the terrestrial system. Marine works have their own environmental impact assessment regulations, and a scheme can need a marine environmental statement without triggering terrestrial screening at all. Where terrestrial screening is triggered as well, an Environmental Impact Assessment must be prepared by competent experts under the 2017 Regulations, and an AI-assisted draft is a starting point for those experts rather than a replacement for them.

Habitats and designated site duties apply on both sides of the line. The Marine Management Organisation acts as competent authority for its own decision, and the council does the same for the planning application, so the same marine protected area can generate two assessments with different scopes.

Determination periods depend on complexity and consultation. The licensing authority publishes service standards and fee scales, and both change, so check the current published schedule when you build the programme rather than relying on a figure from a past project.

Sequencing the consents and the property interest

Neither consent is a legal prerequisite for the other, so you can run them in parallel. Most developers do, because the surveys overlap heavily: bathymetry, sediment sampling, benthic survey and navigational data feed both applications.

There is a property layer too. The sea bed and much of the foreshore belong to the Crown Estate, so works will need a lease or licence from the landowner on top of the regulatory consents. That is a commercial negotiation with its own timescale, and it is entirely separate from the statutory process. The same principle applies on land where third party rights exist over the surface, as with registered common rights and who holds them.

Flood risk consents can be a fourth strand. Works within 16 metres of a tidal main river bank or a sea defence generally need a flood risk activity permit from the Environment Agency, and on sites in the tidal floodplain the Flood Risk Assessment supporting the planning application should be written in the knowledge of what the permit will require. Abstraction and discharge add yet more, in the same way that groundwater abstraction points and the 50 metre rule can constrain an inland site.

Enforcement for unlicensed works

Carrying out a licensable marine activity without a licence is a criminal offence under the 2009 Act. The licensing authority can serve notices requiring works to stop, be removed or be remediated, and it can prosecute.

Unlike planning enforcement, there is no immunity period that converts unlicensed marine works into lawful ones through the passage of time. A pontoon installed without a licence stays unlicensed. That is the single most important difference for anyone used to the terrestrial system, and it means retrospective regularisation is the only route back.

Enter your postcode on PlanScope to see which planning reports a coastal or waterside site is likely to need alongside the marine consents.

This is general guidance, not legal advice. Marine licensing turns on the precise works and their position, so check the current legislation and the position with the licensing authority, 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.