Fish pass planning permission in England

 

A fish pass sounds like the sort of project planning should simply wave through. The whole point is normally to improve a river by helping fish move past a weir, sluice or other obstruction.

In practice, fish pass planning permission can bring several separate regimes together at once. The works may be an engineering operation requiring planning permission, the Environment Agency may need to approve or permit works in the river, biodiversity net gain may need to be addressed, and a historic weir can introduce listed building, archaeology or scheduled monument issues as well.

That does not make fish passes difficult in principle. It does mean the consents need to be identified early, preferably while the type and position of the pass can still change.

 

Do you need planning permission for a fish pass?

 

Usually the first planning question is whether the proposed works amount to development. Under section 55 of the Town and Country Planning Act 1990, development includes the carrying out of engineering operations in, on, over or under land. A permanent fish pass involving concrete, stonework, excavation, a bypass channel or alteration of an existing weir can readily fall within that description.

That does not automatically mean a full planning application is required. Planning permission can also be granted nationally through the General Permitted Development Order, so any relevant permitted development right should be checked before an application is prepared.

Planning permission is only one part of the picture. Even where the planning works are permitted development, separate river, fisheries and heritage consents can still be required.

 

Council-owned land and Part 12 of the GPDO

 

Fish passes are quite often promoted by local authorities, river trusts or the Environment Agency on council-owned land. Where the local authority is carrying out the works, or they are being carried out on its behalf, Part 12 Class A of the GPDO is worth checking.

Class A permits the erection, construction, maintenance, improvement or alteration by or on behalf of a local authority of small ancillary buildings, works or equipment on land belonging to or maintained by it, where they are required for the purposes of a function exercised by the authority on that land otherwise than as a statutory undertaker. For this purpose, the ancillary building, works or equipment must not exceed 4 metres in height or 200 cubic metres in capacity.

Ownership alone is not enough. The identity of the developer, the function being exercised, the relationship of the fish pass to that function and the physical limits all need to fit the wording of Class A.

If Part 12 does apply, the project is permitted development. That has an important knock-on effect: development granted planning permission by a development order is exempt from mandatory biodiversity net gain. Ecology, protected species and habitat policy still matter, but the statutory 10% BNG condition does not apply.

 

Environment Agency approval is a separate consent stream

 

A planning permission does not authorise works in a river. The Environment Agency should normally be involved early where a fish pass is proposed, both because of fish passage and because of the physical effect of the works on the watercourse.

The Environment Agency has a specific fish pass approval process. For salmon and migratory trout, the statutory regime sits principally in sections 9 to 11 of the Salmon and Freshwater Fisheries Act 1975; eel passage is also dealt with under the Eels (England and Wales) Regulations 2009. The fish-pass rules apply in particular where a new obstruction is created, an existing obstruction is materially altered or fish passage is made more difficult. Even where a project is intended to improve an existing barrier, early agreement with the local fisheries team is sensible because the type, gradient, attraction flow and location of the pass need to suit the fish species using the river.

Depending on the works, the project may also need:

• a flood risk activity environmental permit for works in, over, under or close to a main river
• registration of a flood risk activity exemption where a very specific exemption fits the proposal
• Ordinary Watercourse Consent from the lead local flood authority or internal drainage board where it is an ordinary watercourse rather than a main river
• an impoundment or abstraction licence, or reliance on a current regulatory position statement, where the design changes how water is held back, diverted or abstracted
• measures for safe eel passage under the eel passage rules
• a Water Framework Directive assessment where required for the relevant flood risk activity permit

There are specific flood risk activity exemptions for some eel-pass devices and for fish-passage notches in an existing impounding structure. They are tightly defined, so a larger technical fish pass or bypass channel should not be assumed to qualify merely because its purpose is fish passage.

 

BNG: the 0.2 hectare exemption is not the de minimis rule

 

This is an easy area to muddle because there are now two different small-development exemptions.

For planning applications made on or after 6th August 2026, mandatory BNG does not apply where the development site within the red line is 0.2 hectares or less, provided the development does not impact any onsite priority habitat.

The older de minimis exemption is different. It applies where the development does not impact onsite priority habitat and impacts less than 25 square metres of onsite habitat and less than 5 metres of onsite linear habitat. A watercourse is a linear habitat for biodiversity metric purposes, so a very small red-line site does not automatically satisfy de minimis where works extend along a river.

For a fish pass, it is therefore worth asking the questions in this order:

• is the development already exempt because it is permitted development
• if a planning application is required, is the red-line site 0.2 hectares or less
• does the development negatively impact any onsite priority habitat
• if the 0.2 hectare exemption does not apply, can the separate de minimis test be met

The exemption should be evidenced rather than simply asserted on the application form.

 

Is a man-made weir itself priority habitat?

 

This is where fish-pass schemes on chalk streams and other priority rivers need careful analysis.

A concrete or masonry weir is plainly an artificial structure. That does not mean the structure itself has to be treated as valuable river habitat. Equally, the fact that part of a river has been physically modified does not automatically mean the surrounding watercourse has lost its status as priority habitat.

The legal BNG exemption test is narrower and more useful: does the development impact onsite priority habitat by decreasing its biodiversity value?

That is an ecological evidence question. On a chalk stream, the application should distinguish the artificial weir structure from the river habitat around it, identify any temporary and permanent impacts, and explain whether the works degrade or instead improve the priority habitat.

Drawing the red line tightly around concrete does not by itself answer the habitat question if construction, access, dewatering, bank works or flow changes affect the river beyond it. Conversely, a project that replaces or modifies an artificial barrier specifically to restore fish migration may have a strong factual basis for saying the priority habitat is being enhanced rather than negatively impacted.

 

A fish pass can help the biodiversity metric

 

If BNG does apply, do not assume a fish pass simply creates another 10% problem. The statutory biodiversity metric contains a separate watercourse module and its current guidance expressly recognises fish-passage improvements.

Weirs are normally treated as major watercourse encroachment because they interrupt the natural channel. However, the June 2026 statutory metric guidance says that features introduced to restore natural river function or improve migratory pathways should not themselves be recorded as encroachment. It gives an in-river fish pass such as a rock ramp as an example.

The guidance also deals with a technical fish pass attached to an existing weir. Where that is the only feasible enhancement option, the existing weir’s watercourse encroachment multiplier may be reduced from major to minor in the enhancement calculation.

That can make a substantial difference to the watercourse units. A qualified River Condition Assessment assessor should be involved where the statutory metric requires a condition assessment, and the watercourse calculation should be designed alongside the engineering rather than added at the end.

See the statutory biodiversity metric tools and guidance for the current metric documents.

 

Historic weirs can create several heritage issues

 

Many weirs survive because they once served a mill, estate, water meadow, navigation or industrial use. The surviving structure can therefore be part of the historic environment even where its original function has disappeared.

Before a design is fixed, check whether the weir or adjoining land is:

• part of, attached to or within the curtilage of a listed building
• within the setting of a listed building
• inside a scheduled monument, where Scheduled Monument Consent may be required
• within a registered park and garden
• a non-designated heritage asset in its own right
• within an archaeological priority area or a site with archaeological potential

Listed Building Consent is separate from planning permission. Works merely affecting the setting of a listed building do not themselves require Listed Building Consent, but the setting remains a planning consideration. Where the weir is itself part of the listed building or a qualifying curtilage structure, alteration can require consent.

A historic mill site may also justify an archaeological desk-based assessment, building or structure recording, or archaeological investigation. Our guide to archaeology and planning applications explains the planning side in more detail.

 

Flood risk and river hydraulics still matter

 

A fish pass is intended to improve ecological connectivity, but it can also alter the way water moves through a weir. Changes to crest levels, openings, bypass flows, channel roughness or the control structure can affect upstream water levels and downstream velocities.

That means the planning and permitting evidence may need to demonstrate that the scheme will not increase flood risk elsewhere. Depending on scale and location, this can require hydraulic modelling or information equivalent to a Flood Risk Assessment.

Temporary works matter too. Cofferdams, dewatering, working platforms, sediment disturbance and machinery access can all create flood and pollution risks even where the completed pass is beneficial.

 

What should accompany a fish pass planning application?

 

The exact validation list varies by authority and site, but a well-prepared fish pass application may need:

• a location plan, block plan and detailed general arrangement drawings
• long sections and cross sections showing existing and proposed river and weir levels
• a planning statement explaining the need for the project and the consent route
• an ecological appraisal and any species surveys required for the site
• a BNG exemption statement, or a completed statutory metric and supporting habitat plans where BNG applies
• a River Condition Assessment and watercourse metric work where required
• a heritage statement where a historic weir, listed building or registered landscape is affected
• an archaeological assessment where the site has archaeological potential
• a Flood Risk Assessment or hydraulic note/model where water levels or conveyance could change
• a Water Framework Directive assessment where required by the Environment Agency
• a construction environmental management plan covering pollution prevention, sediment, timing, dewatering and fish rescue where appropriate
• details of Environment Agency fisheries consultation, fish pass approval and the flood risk activity permit or exemption route
• tree information where access or construction could affect protected or important trees

For a sensitive river and heritage site, the strongest application is normally one where the planning, ecology, river engineering and heritage evidence all describe the same design and the same construction method.

 

A sensible route through the consents

 

1. confirm land ownership, riparian rights and who will actually carry out the works
2. check whether a permitted development right such as Part 12 Class A could grant planning permission
3. confirm whether the watercourse is main river or ordinary watercourse and engage the correct regulator
4. involve the Environment Agency fisheries team while the fish-pass type and location can still change
5. map every heritage designation and establish whether the weir itself is designated, curtilage listed or a non-designated heritage asset
6. ask the ecologist to settle the priority-habitat and BNG exemption position before relying on a small red line
7. coordinate the ecology, hydraulic and heritage requirements into the final engineering design
8. submit the planning and regulatory applications in a sequence that avoids one consent requiring a redesign of another

A project that opens kilometres of river to fish migration can have a very strong planning and ecological case. The trick is not to mistake a worthwhile environmental objective for an exemption from the normal consent process.

 

Key legislation and official fish pass guidance

 

• Town and Country Planning Act 1990, section 55 – meaning of development
• GPDO 2015, Schedule 2 Part 12 – development by local authorities
• Biodiversity Gain Requirements (Exemptions) Regulations 2024
• Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026
• Salmon and Freshwater Fisheries Act 1975, sections 9 to 11 – fish passes for salmon and migratory trout
• Eels (England and Wales) Regulations 2009, regulation 14 – eel passes and alterations to existing fish passes
• GOV.UK BNG exempt development guidance
• Environment Agency fish pass approval
• Flood risk activity environmental permits
• Exempt flood risk activities
• Low risk impounding activities: RPS 302 – includes fish easements and fish passes on existing impounding works where its conditions are met
• Low risk abstraction for nature recovery actions and fish or eel passage: RPS 374
• Safe passage for eels
• Water Framework Directive assessment for a flood risk activity
• Statutory biodiversity metric tools and guides

Conservation, Heritage & Protected Sites

 

Fish Pass Planning Permission Page Created: 8th September 2026