10May 2019

Government’s latest review of sustainable drainage: a box-ticking exercise reinforcing a suboptimal state of affairs?

Dr Tudorel Vilcan and Dr Karen Potter, Urban Flood Resilience


The Ministry of Housing, Communities and Local Government’s (MHCLG) review of current planning policy for sustainable drainage (SuDS) in England has recently been published – but we question whether this exercise could have had more to do with validating the Government’s current policy approach, rather than an accurate and critical review of the application and effectiveness of planning policy for sustainable drainage systems.


Planning policy was strengthened in 2015 to make SuDS a requirement in all new major developments and encourage greater uptake. The original intentions of Schedule 3 of the Flood and Water Management Act (FWMA) 2010 were to bring about new arrangements, including to make the requirement for SuDS mandatory on new developments, complying with new National Standards on SuDS and answerable to a SuDS approval body (SAB). The question of the effectiveness and performance of the ‘strengthened’ planning system to implement SuDS is therefore a crucial one, particularly in terms of future policy design choices to support key stakeholders.


The MHCLG review examined how national planning policies for SuDS are reflected in local plans, finding that more than 80% of the adopted local plans contained policies reflecting the requirements of the National Planning Policy Framework (NPPF) 2012. It examined the uptake of SuDS in new developments (commercial/mixed-use, major and minor housing), finding they are implemented at rates of 80 to 90%. The review concluded that it has shown that current arrangements for SuDS in planning have been successful in encouraging the take-up of sustainable drainage systems (p12).


In the absence of a specific definition of SuDS (not employed by the review in order to avoid ruling out any novel applications), we are concerned as to what has been considered and captured as constituting a SuDS feature. For example, the review noted heavily engineered components such as underground tanks were viewed unfavourably and that only ‘generally’ were ‘‘traditional’ drains and sewers, gullies and catchment pits identified as falling outside the scope of acceptable SuDS’ (p10). Whilst some will consider such features SuDS because they deal with water quantity, we lack the detail on how successful local planning authorities have been in ensuring that sustainable drainage is prioritised as vegetated features (e.g. swales, rain gardens, green roofs) in order to conserve and enhance biodiversity as called for by the NPPF (DCLG, 2012).


The review’s methodology also raises concerns in relation to the representativeness and robustness of the report’s findings. In using a ‘nested design’, non-randomly picking 12 local authorities from the total of 338, and then selecting (again, non-randomly) 13 applications in each of the 12 local authorities, we have 156 applications in total. The combination of this non-probabilistic design and small sample size means the statistical uncertainty cannot be estimated, that is, to provide an indication of the reliability of the report’s findings. Ultimately the assertion that ‘80 to 90% of planning applications have SuDS’ could have a variability of +5 % or -50%.


Due to issues of representativeness and robustness we remain somewhat sceptical regarding the uptake rates of SuDS reported by MHCLG (2018). Although it is acknowledged that there is potential for industry bodies to address skills and knowledge gaps, and that more emphasis by applicants is required on SuDS adoption and maintenance arrangements, overall MHCLG have also missed the opportunity for genuine engagement and critical reflection in the interpretation of their data. The recommendations of this report would appear to have influenced the latest version of the NPPF (2018), for which we are concerned will not offer the substantial improvement and support to stakeholders required when it comes to the future uptake of sustainable drainage and its maintenance in England.


For a longer, more detailed version of this blog, please visit this webpage:


MHCLG (2018) A review of the application and effectiveness of planning policy for Sustainable Drainage Systems (SuDS), Ministry of Housing, Communities and Local Government, London.


DCLG (2012) National Planning Policy Framework. Available at:–2 Accessed (15.01.18).

Our Partners