Sustainable Drainage System (SuDS)

From 07 January 2019, all new and significant developments will have to implement some kind of sustainable drainage system (SuDS) as part of its design and build.

These SuDS must be designed and built in accordance with standards published by Welsh Government and approved by the local authority acting in its role as a SuDS approval body (SAB). The SAB will then have the duty to adopt any compliant systems; serving multiple properties.


Coronavirus Update 

Due to the impact of the Coronavirus Pandemic, the Vale of Glamorgan Council’s SuDS team has adapted the way they work. Most staff are working from home and contactable by their normal contact details.


For general enquiries please contact:

  • 07764 967 034


Please note that it may take longer than normal to respond to enquiries during this time and we thank you for your patience.


We will continue to accept new SAB applications and requests for pre-application advice, and determine these applications where possible. However, we will not offer face-to-face meetings at this time.


We would also urge our customers to use email to submit information at this time to manage workload efficiently.


We will continue to undertake enforcement work, monitoring compliance with SAB conditions and taking action against breaches of SuDS control.


If you have a specific enquiry about a case, please contact the case officer directly but copy in to all emails.


Why have these regulations come into force?

Welsh Government has been looking to move away from traditional drainage solutions for some time as these techniques are designed to remove water away from developed areas with no regard for the drainage regime downstream or the quality of the water. What SuDS aim to do is mimic the natural drainage patterns of the area, which reduce the chance of flooding and pollution on the surrounding water bodies.


Schedule 3 of the  Flood and Water Management Act (FWMA) 2010 is the legislation that is driving the introduction of SuDS throughout Wales. All new developments will have to have approved surface water drainage systems on developments of 2 or more properties or that have a construction area of over 100m2 


SuDS - Welsh Government



If you would like more information about this process, please contact the SAB team:



SuDS application fee calculator


Please note: There is currently no fee for a SuDS Pre-Application. This tool is to only provide an approximate fee. 


  • Commuted Sums

    Securing a sustainable funding mechanism for the lifetime of development is a key objective of the SuDS Approving Body (SAB). The SAB has a responsibility for the management and maintenance of SuDS assets after they have been adopted. Commuted sums ensure that the SAB has the resources to cover the upkeep and (where appropriate) the replacement of the assets they have adopted. The effectiveness of SuDS and the associated multiple benefits will rely on appropriate maintenance.


    In order to ensure consistency throughout Wales, the methodology identified in “Commuted Sums for Maintaining Infrastructure Assets” prepared by the CSS (County Surveyors Society), will be used to calculate commuted sums for all drainage assets being adopted by the SAB, whether through a S38 agreement or a bespoke legal agreement for the life of the development.


    The calculation of a commuted sum includes consideration of:


    • The estimated periodic maintenance cost of the asset to be adopted e.g. silt clearance. The SuDs manual provides useful information on this element and sums will be in accordance with agreed maintenance schedules.
    • The future cost of renewal or replacement (e.g. permeable paving has design life of 20 years, over the lifetime of the development this could lead to 3 or more replacements).
    • The duration over which the sum is required. Commuted sums for SuDS features serving residential developments will be calculated over a 100yr period.  Non-residential developments will be calculated using the proposed lifetime of the development, usually 75 years or less if agreed with the SAB on a case-by-case basis.  The Association of Directors of Planning and Transport recommends commuted sums for highway structures should be calculated to cover a 120 year period.  Commuted sums for SuDS features, other than those classified as structures, solely serving the adopted highway will be calculated over a 60 year period.
    • The effective annual interest rate that will provide a return on the sum invested prior to its expenditure after the effects of inflation have been taken into account. The discount rate is usually recalculated on an annual basis, based on the long-term neutral base rate and retail price index excluding mortgages, and applied from 1st April each year. Based on a LTNBR of 4.5% and RPIX inflation of 7.7% the discount rate for 2021/22 is -3.0%. We appreciate the current rate of inflation will significantly increase the commuted sums required for new applications. as such we will undertake an interim review quarterly to consider whether an increase in the discount rate - thereby reducing commuted sums - is appropriate