Ordinary watercourse consent and when it is needed
Planning permission does not authorise works in a ditch. Ordinary watercourse consent comes from the lead local flood authority under the Land Drainage Act 1991, and it is usually applied for too late.
Ordinary watercourse consent is a separate consent from planning permission, issued under section 23 of the Land Drainage Act 1991 by the lead local flood authority, and it is needed before you build any structure that obstructs or alters the flow of a watercourse that is not a main river. Culverting a ditch, putting in a headwall, installing a piped crossing for an access road, or building a weir all need it.
The point that catches developers is timing. A planning permission granted with a drainage condition does not authorise the works in the watercourse, and the consent is often applied for months too late, after the access design is fixed.
What counts as an ordinary watercourse
An ordinary watercourse is any watercourse that is not designated a main river. The definition in the Land Drainage Act is wide: rivers, streams, ditches, drains, cuts, dykes, sluices, sewers other than public sewers, and any passage through which water flows.
Wide enough that the roadside ditch nobody has thought about for thirty years is one. So is a field drain that only carries water after rain. The absence of water on the day of your site visit proves nothing, because the test is whether water flows through it, not whether it is flowing now.
Main rivers sit under a different regime. Works in, over, under or within 8 metres of a main river need a flood risk activity permit from the Environment Agency rather than a consent from the lead local flood authority, and the two are frequently confused on sites where a main river and an ordinary watercourse meet. Check the main river map before you decide which body to approach.
The works that require consent
Consent is needed for any mill dam, weir or other like obstruction to the flow, and for any culvert or alteration to a culvert that would affect the flow.
In practice that covers:
- piping or culverting any length of open ditch
- a new headwall, outfall or inlet structure
- a vehicle or pedestrian crossing over the watercourse
- a weir, dam, penstock or flow control structure
- raising or lowering the bed or banks in a way that affects the flow
- a temporary dam or over-pumping arrangement during construction
Temporary works count. A contractor damming a ditch for a fortnight to lay a pipe needs consent for that too, and the fact that it comes out again afterwards is not a defence.
Who issues the consent
The lead local flood authority, which is the county council or the unitary authority, took over the consenting role for ordinary watercourses from the Environment Agency under the Flood and Water Management Act 2010. Where the site lies within an internal drainage board district, that board is the consenting body instead.
So on a two-tier site the district council grants the planning permission and the county council grants the watercourse consent. They are different teams with different timetables and, on a bad day, different views. The lead local flood authority is also a statutory consultee on surface water drainage for major development, which means the same authority may comment on your planning application and consent the works, but the two decisions remain separate.
| Consent | Body | Legislation |
|---|---|---|
| Ordinary watercourse consent | Lead local flood authority or internal drainage board | Land Drainage Act 1991, section 23 |
| Flood risk activity permit | Environment Agency | Environmental permitting regime |
| Planning permission | Local planning authority | Town and Country Planning Act 1990 |
How it relates to planning permission
Neither consent grants the other. You can hold planning permission for a housing scheme whose access crosses a ditch and have no lawful means of building the crossing.
Two habits avoid the problem. Identify every watercourse on and adjoining the site at the earliest layout stage, including the ones that appear only on historic mapping, and mark them on the drawings you submit. Then ask the lead local flood authority, at pre-application stage, whether the crossings shown will be consented in principle. An authority that will not culvert a length of ditch will say so, and the layout can change while changing it is still free.
Where the drainage strategy relies on a discharge to an ordinary watercourse, the riparian position also needs checking. You need a right to discharge, which is a legal question about the land rather than a matter for the consent, and the consent does not supply it.
Culverting and the presumption against it
Expect to be refused consent to culvert unless there is no reasonable alternative. National policy and the Environment Agency's long-standing position both favour keeping watercourses open, on flood risk, ecology, maintenance and amenity grounds, and lead local flood authorities apply the same approach.
What tends to be accepted is a short culvert for an access crossing where no other access is achievable, designed with an adequate hydraulic capacity, a natural bed, headwalls that allow maintenance access, and a trash screen only where it can actually be maintained. What tends to be refused is culverting a length of ditch to gain developable area, which is the application most often made.
Where a site already has a culvert in poor condition, de-culverting as part of the scheme is worth raising early. It buys goodwill on the drainage strategy, and on some sites it releases enough attenuation to change the wider design.
Application content and timescales
The application goes to the lead local flood authority with location and detailed drawings, hydraulic calculations showing that the structure passes the design flow without increasing flood risk, construction details and a method statement, and a plan showing land ownership and the riparian interests affected.
The authority has two months to determine an application under section 23, and the Act provides for consent to be treated as given where the authority fails to determine within that period, which is a mechanism worth knowing about and a poor thing to rely on. It works rather differently from the way deemed planning permission arises in the planning system, so do not assume the two behave the same way.
A statutory fee is payable per structure. It is set in legislation and is small relative to the design work, so confirm the current figure with the authority rather than working from a figure quoted on an earlier project.
Enforcement for unconsented works
Carrying out works without consent is an offence, and the authority can require the works to be altered or removed, or carry out that work itself and recover the cost from the person responsible. There is no immunity period of the kind that applies to planning breaches, so an unconsented culvert installed years ago remains a live liability and shows up in due diligence.
That matters most on acquisitions. Where a site has an existing culvert, ask for the consent. If nobody can produce it, price the risk before exchange rather than after.
For the wider surface water evidence base, the 66 report types by category show which drainage and flood documents usually travel together on a scheme of this kind.
This is general guidance, not legal advice; check the position with your lead local flood authority, your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.
Enter your postcode on PlanScope to see which reports your site is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
What is an ordinary watercourse?
Any watercourse that is not designated a main river. The Land Drainage Act definition covers rivers, streams, ditches, drains, cuts, dykes, sluices, sewers other than public sewers, and any passage through which water flows. A dry roadside ditch that carries water after rain still counts, so the absence of flow on the day of a site visit proves nothing.
Who issues ordinary watercourse consent?
The lead local flood authority, which is the county council or unitary authority, following the transfer of the role from the Environment Agency under the Flood and Water Management Act 2010. Where the site sits within an internal drainage board district, that board consents instead. Works affecting a main river need an Environment Agency permit rather than this consent.
Does planning permission cover works in a ditch?
No. The two consents are independent, so a permission for a scheme whose access crosses a ditch does not authorise building the crossing. Identify every watercourse at layout stage, show them on the submitted drawings, and ask the lead local flood authority at pre-application stage whether the crossings will be consented in principle.
Will consent to culvert a ditch be granted?
Usually only where there is no reasonable alternative. National policy and drainage authority practice favour keeping watercourses open on flood risk, ecology, maintenance and amenity grounds. A short access crossing with adequate capacity, a natural bed and maintainable headwalls is often accepted. Culverting a length of ditch to gain developable area usually is not.
How long does a consent application take?
The authority has two months to determine an application under section 23, and the Act provides for consent to be treated as given if it fails to determine within that period. Do not plan around that mechanism. Submit the hydraulic calculations, construction details and method statement with the application so the clock is not stopped for missing information.
What happens if works were done without consent?
Carrying out the works is an offence, and the authority can require alteration or removal, or do the work itself and recover the cost. There is no immunity period equivalent to the planning one, so an old unconsented culvert remains a live liability. On acquisitions, ask for the consent and price the risk if none exists.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.