Sustainable Drainage Systems

The aim of Sustainable Drainage Systems (SuDS) is to manage rainwater in a way that is similar to natural processes, using the natural landscape and vegetation to manage the flow and volume of surface water where possible.

SuDS manages water on the surface or close to it, and as closely to its source as possible; it manages the flow and provides a variety of additional advantages, which include;

  • Managing flood risk;
  • Improving water quality;
  • Creating habitats and improving biodiversity;
  • Supporting wellbeing by bringing people closer to green and blue communal areas.

In Wales every new development of more than one house or where the construction area is 100m2 or more, will be subject to mandatory sustainable drainage systems to manage surface water. Drainage systems for every new development must be planned and constructed in accordance with statutory SuDS standards published by Welsh Government.

From the 7th of January, 2019 onwards, Schedule 3 of the Flood and Water Management Act 2010 will become operational. This means that all new developments of more than 1 house, or where the construction area is 100m2 or more, will need to provide sustainable drainage systems (SuDS) for managing surface water. The construction area is defined as any part of the site which has drainage implications, including buildings, parking areas etc. 

SuDS plans must be approved by the Gwynedd Council in their role as the SuDS Approval Body (SAB), prior to the commencement of construction work. All applications will be considered against the national standards published by Welsh Government.

Whilst the process of approving drainage schemes is separate to need to obtain planning approval we would encourage developers to consider these two elements concurrently, as each can influence the other. It is important to note that construction work can not begin without both Planning and SAB approval in place.

The SAB will have a duty to adopt SuDS which serve more than one property, provided that its functions correspond with the approved proposals, including any SAB approving conditions.

We would like to encourage developers to contact the SuDS Approval Body (SAB) as soon as possible whilst developing their project, to discuss specific requirements and to receive guidance about what will be expected when submitting a full application.

The first hour of the pre-application service will be offered to developers free of charge. A fee will be chargeable for any further feedback, at cost to the Council. The fee amount and level of feedback expected will be agreed between the Council and developer prior to the preparation of the feedback.

A pre-application service form is available here. Or for an informal discussion, the SAB can be contacted. Please see the bottom of this page for contact information.

If you are ready to submit a full application to the SuDS Approval Body (SAB), the application form together with guidance notes on how to complete, is available here. We would encourage applicants to complete the from electronically if possible and return via email to The application will then be validated, and if complete, the fee will be processed. In order for the SAB to verify an application it must contain:

  • a plan detailing the construction area and drainage system,
  • information to demonstrate how the work will comply with the SuDS Standards;
  • the information requested in the application form checklist;
  • the appropriate fee.

The SAB is granted a statutory 7 week period for determining a regular application, with 11 weeks granted for developments which require an Environmental Impact Assessment as part of the Planning application. We will endeavour to determine each application as soon as possible.

All applications will be considered  against the National standards which have been published by Welsh Government. A link to the National standards, and other useful information, is provided below.

Statutory standards for sustainable drainage systems - designing, constructing, operating and maintaining surface water drainage systems 

SuDS Wales

SUS Drain

The fee charged by the SuDS Approval Body (SAB) for a full application has been determined by Welsh Government and included in The Sustainable Drainage (Application for Approval Fees) Regulations 2018.

The fee for a full application is dependant on the size of the construction area, as noted below;

(a) £350 for each application, and

(b) an additional amount up to a maximum of £7,500 calculated by reference to the size of the construction area as follows—

(i) £70 for each 0.1 hectare or fraction of 0.1 of a hectare, for the first 0.5 hectare;

(ii) £50 for each 0.1 hectare or fraction of 0.1 of a hectare, from 0.5 hectare up to and including 1.0 hectare;

(iii) £20 for each 0.1 hectare or fraction of 0.1 of a hectare, from 1.0 hectare up to and including 5.0 hectares;

(iv) £10 for each additional 0.1 hectare or fraction of 0.1 of a hectare in excess of 5.0 hectares.

If the applicant is a Community Council, the fee charged will be halved.

It is important to note that there could be a need for other payments in addition to the application fee, such as:

  • inspection fees
  • temporary bonds that may be required to secure the construction work
  • a funded maintenance plan for the drainage system. 

These costs will be dependant on the nature and scale of the work, with the applicant being made aware of the requirements as part of the approval process.  If you are unsure of any aspect of the fees contact us directly (details below).


Useful information

Useful information from Welsh Water about Sustainable Drainage Systems

Welsh Water Sustainable Drainage Systems


Contact us


Phone: 01286 679 355 / 01286 679 501

Post: Gwynedd SAB, YGC, Cyngor Gwynedd, Penrallt,Caernarfon, Gwynedd, LL55 1BN