Land drainage consent or an environmental permit
The watercourse decides the regime. Main river means an Environment Agency permit; ordinary watercourse means section 23 consent from the lead local flood authority.
The land drainage consent vs environmental permit question is answered by the watercourse, not by the works. If the channel is a main river, the Environment Agency regulates it and you need a flood risk activity permit under the environmental permitting regime. If it is an ordinary watercourse, the lead local flood authority or the internal drainage board regulates it and you need consent under section 23 of the Land Drainage Act 1991. Same culvert, same headwall, two different regulators, two different timescales and two very different fees.
Check the main river map before you draw anything. It takes five minutes and it has reordered more than one programme.
Which body regulates which watercourse
A main river is one shown as such on the statutory main river map, which the Environment Agency maintains and publishes. Everything else that carries water, from a field ditch to a substantial brook, is an ordinary watercourse.
The designation has nothing to do with size. A large drain can be an ordinary watercourse and a modest stream can be a main river, because the map reflects flood risk management responsibilities rather than hydrology. Reaches also change designation along their length, so a channel can be main river downstream of a bridge and ordinary watercourse above it.
Within an internal drainage district, the internal drainage board takes the consenting role for ordinary watercourses in place of the lead local flood authority, and boards often operate byelaws that control works within a set distance of a watercourse as well as works in the channel itself. Check whether the site sits in a drainage district early, because the board's requirements are frequently wider than the county's.
Works caught by each regime
| Regime | Who consents | Works typically caught |
|---|---|---|
| Land Drainage Act 1991, section 23 | Lead local flood authority, or internal drainage board in a drainage district | Culverting a watercourse, altering an existing culvert, building a weir, dam or other obstruction, altering or repairing such a structure, anything that affects the flow |
| Flood risk activity permit under the environmental permitting regime | Environment Agency | Works in, over, under or within a set distance of a main river, works on or near a flood defence structure, and works in a floodplain that could affect flood flows |
| Internal drainage board byelaws | Internal drainage board | Works within a stated distance of a board-maintained watercourse, discharges, and planting |
The Environment Agency's control extends beyond the channel. Permits are needed for activities within a defined distance of the top of the bank of a main river, which is wider for tidal reaches and sea defences, and for works that could affect a flood defence even where the defence is some way from your structure. That distance catches foundations, piling, scaffolding, site compounds and temporary access as well as permanent works.
The permitting regime is tiered. Some activities are excluded altogether, some are exempt but have to be registered, some are covered by standard rules permits, and the rest need a bespoke permit. Working out which tier applies is the first task, because it determines both the cost and the timescale by a wide margin.
The land drainage regime has no such tiering. Either the work needs consent or it does not, and the test is whether it would affect the flow of water in the watercourse.
Application content and timescales
A section 23 consent application is short. It asks for a location plan, a plan and section of the proposed structure, hydraulic calculations showing that the structure passes the design flow without increasing flood risk upstream or downstream, details of the construction method and the maintenance arrangements, and evidence of your interest in the land.
The hydraulic calculations are where applications fail. An authority will want to see the design flow derived by a stated method, the capacity of the proposed structure, the afflux produced upstream, and the effect of a blockage. A culvert sized by eye, or sized to match the pipe the contractor has in stock, gets refused. The practical detail of what a good submission contains is covered in the note on land drainage consent for works to an ordinary watercourse.
A flood risk activity permit application is considerably longer. Expect the Environment Agency to want a description of the activity, drawings, a flood risk assessment addressing the effect on flood flows and flood storage, details of any works affecting a defence, a method statement and a construction environmental management plan, ecological information where protected species or designated sites are engaged, and details of the operator's competence.
Both regimes expect the design to be finished. Neither will consent a principle and leave the detail for later, which is the opposite of how planning permission works and catches developers who assume a condition will cover it.
Fees and typical determination periods
Section 23 consent carries a modest statutory fee per structure, set nationally, and the lead local flood authority publishes the current figure. The Act provides that if the authority does not determine the application within two months, consent is deemed to be granted, which gives the process a hard edge the permitting regime lacks.
Flood risk activity permit charges are set out in the Environment Agency's published charging scheme, which is revised periodically, and they vary by tier. A registered exemption costs nothing or very little. A standard rules permit costs more. A bespoke permit costs considerably more again, and the Agency also offers a chargeable pre-application advice service that is usually worth taking on anything complicated.
Determination periods differ in kind rather than in degree. The Agency publishes service standards for each permit type, and bespoke permits take substantially longer than standard rules permits. Take the current timescales from the Agency's own published information rather than from a programme written for a previous scheme, and build in time for the Agency to ask for further information, which stops the clock.
Two practical points. The two month deemed consent provision in the land drainage regime does not apply to permits, so an Agency application that stalls simply stalls. And neither consent is granted by planning permission: a condition requiring compliance does not obtain the consent for you, and a Grampian condition tying development to obtaining it is common.
Working near a main river without a permit
Carrying out a flood risk activity without a permit, or in breach of one, is an offence under the environmental permitting regime, and the Agency has enforcement powers including notices requiring works to be removed or reinstated.
The commercial consequence is usually worse than the penalty. A contractor who pile-drives a retaining wall within the main river margin without a permit can be required to stop, and the structure may have to come out. On a site with a tight programme that is the kind of event that moves a completion date by a season.
The near misses that cause this are predictable. A site compound placed on the riverside strip because it is the only flat ground. Temporary sheet piling for a basement that happens to sit inside the margin. A crane pad on the floodplain. Scaffolding over the bank. Each of those is an activity in its own right, and the permit has to cover the temporary works as well as the permanent ones. The practical scope of what needs a permit is set out in the note on flood risk activity permits for works near a main river.
Where both are needed on one site
More common than it sounds, and the usual pattern is a drainage outfall.
A site drains to an ordinary watercourse that is culverted beneath the access road. The culvert needs section 23 consent from the lead local flood authority. That watercourse discharges to a main river 80 m downstream, and the new or enlarged outfall structure at the confluence sits within the main river margin, so it needs a permit from the Agency. Two applications, two sets of calculations, and a sequencing problem because each regulator may ask what the other has said.
Other combinations that produce both: a site crossed by a main river and drained by field ditches, a scheme that regrades a floodplain while also culverting a ditch, and a highway improvement that touches a board-maintained drain and a main river bridge.
The way to manage it is a single consents schedule, prepared at the same time as the Drainage Strategy, listing every structure, the watercourse it affects, the regulator, the consent needed, the lead time and the owner of the action. Keep it on one page and review it monthly. Where the site is also in a flood zone, the interaction with the Flood Risk Assessment needs managing so that the two documents use the same levels and the same design events.
Programme risk and when to apply
The sequence that works on most sites:
- Check the main river map and the internal drainage district boundary before the layout is drawn.
- Identify every structure in or near a watercourse, including temporary works, and allocate each to a regime.
- Take pre-application advice from the Agency on anything that may need a bespoke permit, before the planning application is submitted.
- Apply for section 23 consents once the structure design is fixed, which can be after planning permission but before the contractor is appointed.
- Apply for flood risk activity permits as early as the design allows, since they carry the longest lead time.
- Keep the planning drawings, the consent drawings and the permit drawings at matching revisions, because an inconsistency between them will be found.
Why planning permission is not enough on its own, and what that means for the start on site, is set out in the note on ordinary watercourse consent.
This is general guidance, not legal advice; check the position with the relevant regulator or a qualified professional before relying on it. To see which flood and drainage documents a site is likely to need, enter the postcode on PlanScope.
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Frequently asked questions
How do I know whether a watercourse is a main river?
Check the statutory main river map published by the Environment Agency. Designation has nothing to do with channel size, so a large drain can be an ordinary watercourse and a small stream can be a main river. Reaches also change designation along their length, so check the specific location of your structure rather than the watercourse as a whole.
Who consents works to an ordinary watercourse?
The lead local flood authority under section 23 of the Land Drainage Act 1991, or the internal drainage board where the site lies within a drainage district. Boards often operate byelaws controlling works within a set distance of a watercourse as well as works in the channel, so their requirements can be wider.
What happens if the council does not determine a section 23 application?
The Land Drainage Act provides that consent is deemed to be granted if the authority has not determined the application within two months. That gives the land drainage regime a hard edge the permitting regime lacks, since there is no equivalent deemed grant for a flood risk activity permit.
Do temporary works need a flood risk activity permit?
Often yes. Site compounds, temporary sheet piling, crane pads, scaffolding over a bank and temporary access within the main river margin are each activities in their own right. The permit has to cover temporary works as well as permanent ones, and this is the most common source of inadvertent breaches.
Does planning permission cover these consents?
No. Neither section 23 consent nor a flood risk activity permit is granted by planning permission, and a condition requiring compliance does not obtain the consent for you. Expect a Grampian style condition tying the start of development to obtaining the consent, which puts the lead time on the critical path.
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.