Ordinary watercourse consent or a flood risk activity permit

Whether you need ordinary watercourse consent or an environmental permit for a flood risk activity turns on a single question: is the channel a main river. If it is, the Environment Agency regulates works in, over, under or near it under the Environmental Permitting (England and Wales) Regulations 2016. If it is not, it is an ordinary watercourse, and consent for obstructions and culverts comes from the lead local flood authority under section 23 of the Land Drainage Act 1991, or from an internal drainage board where the site sits inside a drainage district.

Neither consent is planning permission, and a planning permission does not authorise the works. On a small residential site that sequencing catches people out more often than the consent itself.

Who regulates which watercourse

Main rivers are designated, and the designation is published. The Environment Agency maintains the main rivers map, and it is the first thing to check at feasibility stage rather than at technical design.

A watercourse that is not on that map is an ordinary watercourse, which covers most brooks, ditches, field drains, streams and some substantial channels. Responsibility for consenting works on them sits with the lead local flood authority, which is the county council or the unitary authority. Inside an internal drainage board district, the board consents instead.

One channel can change status along its length. A stream may be an ordinary watercourse upstream of a confluence and a main river below it, which means two regulators on one site. Check the designation at the location of your works rather than at the nearest bridge.

What each consent covers

The two regimes catch different things, and the overlap is smaller than people assume.

The Environment Agency regime is tiered, which matters for programme. Some low risk activities are exempt and need only a registration. Others are covered by standard rules. Anything that does not fit either needs a bespoke permit, which is a considerably longer exercise with a pre-application discussion, a design and a hydraulic assessment.

Main rivers and ordinary watercourses distinguished

The distinction is administrative rather than physical. Size, flow and name tell you nothing reliable. A designated main river can be a modest channel through a town where the Environment Agency has flood risk management responsibilities, and an undesignated ordinary watercourse can carry a good deal of water through open countryside.

So resist the temptation to judge it on site. Two checks settle it. The main rivers map for designation, and a conversation with the lead local flood authority, who will usually confirm their view in an email that is worth keeping on file.

Culverted and piped watercourses are the awkward category. A watercourse that has been culverted remains a watercourse, and works to an existing culvert commonly need consent even though there is nothing visible on the surface. Historic maps and the drainage searches often reveal a channel that the current site survey does not.

Works that trigger consent

For an ordinary watercourse, the section 23 triggers are obstructions and culverts. In practice that means:

1. A new culvert, including a piped crossing for an access road.
2. Extending, shortening or replacing an existing culvert.
3. A weir, dam, sluice, penstock or flow control structure.
4. A headwall or trash screen where it alters flow.
5. Works that impede flow temporarily, such as a dam for construction in the channel.

A new surface water outfall into an ordinary watercourse is a case to raise with the lead local flood authority even where it may fall outside section 23, because most authorities want to see the discharge rate and the headwall detail anyway. Where surface water is the driver, the Drainage Strategy is the document that carries the design, and national policy expects discharge to a watercourse to sit below the greenfield run-off rate on a previously undeveloped site.

For a main river, the triggers are broader because proximity alone counts. Piling, excavation, fencing, tree planting, a temporary compound or scaffolding within the regulated distance of the bank or a defence can all need a permit.

Timescales, fees and exemptions

Ordinary watercourse consent is determined within two months of a valid application under the Land Drainage Act, and the statutory application fee is modest. Lead local flood authorities publish their current fee and their application form, and several publish local design standards that the application is assessed against. Read those standards before drawing anything, because a culvert diameter or a screen specification that conflicts with them will come back.

Environment Agency exemptions and registrations are quick. Bespoke flood risk activity permits are not. Allow several months from first contact to determination, and treat the pre-application discussion as part of the design process rather than a formality.

Build both routes into the planning programme rather than treating them as post-permission detail. A Flood Risk Assessment that assumes a culverted crossing the regulator will not accept has to be rewritten, and that rewrite lands after the application is already validated.

Enforcement for unconsented works

Doing the works first is expensive. Under the Land Drainage Act the lead local flood authority can require the removal or alteration of an unconsented obstruction, and the cost falls on the person who built it. There is no equivalent of retrospective planning permission that tidies the position up cheaply.

For a main river, carrying out a flood risk activity without the necessary permit is an offence under the Environmental Permitting Regulations, and the Environment Agency has enforcement and civil sanction powers available. Riparian ownership brings duties too, since an owner of land adjoining a watercourse is responsible for maintaining flow and not causing obstruction.

The practical risk on a housing site is the contractor who installs a temporary crossing to get plant onto the site. That is an obstruction, and it needs consent like anything else.

Identifying the right regulator

A five minute routine at feasibility stage avoids nearly all of this.

Check the main rivers map for every channel on or adjacent to the site. Check whether the site falls within an internal drainage board district. Look at the flood map for planning to understand the flood zone and the surface water picture. Then send one email to the lead local flood authority describing the works and asking which consent they consider is needed, and a second to the Environment Agency where any channel is a main river.

Keep both replies. When a case officer asks at validation whether land drainage consent is required, that correspondence is the answer, and it also tells the Foul Sewage Assessment and drainage authors which constraints they are designing to.

If you are working out which documents your scheme needs before commissioning any of them, browse the 66 PlanScope report types and start from the site constraints rather than the report names. This article is general guidance, not legal advice; check the position with your lead local flood authority, the Environment Agency 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.