Ordinary watercourses land drainage consent

Gwynedd Council are responsible for authorising consent to individuals, companies, group of individuals and public bodies, who wish to carry out changes to an ordinary watercourse that may affect flow or flood risk. This consent is called an Ordinary Watercourse Consent.

Under Section 23 and 25 of the Land Drainage Act 1991 the erection or alteration of any mill dam, culvert, weir or other like obstruction to the flow of an ordinary watercourse requires consent from the Lead Local Flood Authority (LLFA). Main rivers are regulated by Natural Resources Wales. 

The regulation consists of two elements:

  • the issuing of consents for any changes to ordinary watercourses that might obstruct or alter the flow of an ordinary watercourse;
  • enforcement action to rectify unlawful and potentially damaging work to a watercourse.


A consent will be required for activities on an ordinary watercourse that’s likely to stop or limit the quantity of water stored within a watercourse, including culverting, bridges, weirs etc.

This would therefore mean that any excavation for land drainage, culvert or other passage for water in, into or out of any watercourse or in or through any bank of any watercourse would need consent.

Consent will be required under the above legislation for both permanent and temporary works. Even if you have planning permission or any other development permissions, you will still require consent from us to work on ordinary watercourses.


An authorised consent from us for any such changes to the watercourse is important, as any changes have the potential to increase flood risk to people and property, either those upstream or downstream and often unconnected to the works in question. 

You are encouraged to contact us in advance of applying for consent so that we can discuss your requirements, provide advice and ensure that your application is completed correctly. Before completing your application please review the application guidance notes about ordinary watercourse land drainage consents. 

Upon receipt of an application, there is a time limit of two months to grant or refuse consent. The application isn’t approved until you receive formal consent. 

Contact us by email at FCRMU@gwynedd.llyw.cymru  

Terms and conditions

You are responsible for ensuring any works are carried out in accordance with the consent and any other associated legislation. You must ensure the contractors carrying out the works are fully aware of the consent and its conditions. 

Apply for ordinary watercourse land drainage consent by downloading and completing an ordinary watercourse land drainage consent application form. 

You can email your completed applications form to FCRMU@gwynedd.llyw.cymru or post to: 

Flood and Coastal Erosion Risk Management
Gwynedd Council
Shirehall Street
LL55 1SH


Enforcement action against unconsented works

In the case of works undertaken without consent, and where we deem that consent would have been required, works cannot be retrospectively consented. 

Under section 24 of the Act enforcement action may be taken where damaging or potentially damaging works on ordinary watercourses have been undertaken without the necessary consent. Enforcement action may also be taken where consented works have been undertaken in a manner contravening the consent. Where such works have been carried out enforcement powers are available to the LLFA, which include: 

  • an advice letter to the individual reminding them of the requirements of their consent
  • a letter to warn the individual that their actions are in breach of the consenting legislation
  • a notice enforcing remedial action or prohibiting an activity from being carried out
  • direct remedial action, plus a recharge or the costs of such actions and possible prosecution 

On April 1st, 2019 under Section 66 of the Land Drainage Act 1991, Gwynedd Council established the Land Drainage (Gwynedd Council) Bylaws 2019. The purposes of these bylaws are:

a)    securing the efficient working of a drainage system in the Council’s area;

b)    regulating the effects on the environment in the Council’s area of a drainage system;

c)    securing the effectiveness of flood risk management work within the meaning of Section 14A of that Act, or

d)    securing the effectiveness of works done in reliance on Section 38 or 39 of the Flood and Water Management Act 2010 (incidental flooding or coastal erosion).

Consent will be required for maintenance works within 8 metres of an ordinary watercourse. These works would include tree planting, depositing or storing objects or matters, lighting a fire, construct a building etc. Common activities which may require bylaw consent from the Council are shown on the attached information sheet, although this list is not exhaustive.

These bylaws are in place to prevent third parties undertaking unconsented activities which may increase the risk of flooding. They will however not stop anyone who has already a right or a duty under any other legislation such as an Act or Regulation or permit to act accordingly.

If you are planning to undertake any activity managed under the bylaw powers, you are asked to contact us for advice beforehand by either calling 01341 424421 or by emailing FCRMU@gwynedd.llyw.cymru