Chartered Institute of Water and Environmental Management (CIWEM)              WQR0087


Supplementary written evidence from the Chartered Institute of Water and Environmental Management (CIWEM)

Further to the oral evidence session with the Committee on 26th May 2021, we would like to submit the following recommendations which we did not get the opportunity to make orally during the session.

We strongly consider that sustainable drainage systems (SuDS) have a significant role to play in helping to mitigate the problem of combined sewer overflow discharges in particular, through helping to remove surface water from combined networks.

SuDS in England are currently driven forward through a planning-led approach, focused on delivering them in major new developments (developments of 10 homes or more). Whilst this may be delivering SuDS in most such schemes, these are not necessarily good quality SuDS installations, achieving the full range of benefits that they might. This approach also only stops the present situation (of increasing surface water flood risk and high levels of stormwater overflow discharge) getting worse. It does nothing to ameliorate and improve the situation.

We therefore recommend the following:

1)  Stronger planning policy: It has been improved over recent years but there are still gaps and inadequacies – the planning practice guidance needs updating, the 10 homes threshold is nonsensical in the context of the climate and ecological emergencies, and there are missed opportunities to drive SuDS in the proposals around the National Model Design Codes.

2)  Stronger standards: The Non-Statutory Technical Standards must be updated to reflect the full range of multiple benefits that good, well-planned and implemented SuDS can deliver. They were developed in this form a decade ago and were not taken forward. Again, in the context of the climate and ecological emergencies, let’s not waste another decade and take this forward with renewed zeal.

3)  Give updated standards teeth: Removing the automatic right to connect new development to the sewer. The watchword here is automatic – not the right per se. Make this right conditional on meeting the updated technical standards as far as possible. In other words, impose a sustainable drainage hierarchy on new developments.

4)  Drive adoption: Link all this to adoption and maintenance and back the chosen adoption body or bodies. Regulate them appropriately to deliver that (for example private management companies are not regulated at all). There could be more than one kind of organization e.g. water companies or private management companies. The key thing is that multifunctional SuDS should be being delivered consistently, to good standards, in return for which there is a viable route to adoption and long-term maintenance.



Chartered Institute of Water and Environmental Management (CIWEM)              WQR0087

5)  Support and enable extensive SuDS retrofit: Retrofitting SuDS is the way to harness their ability to make inroads into the problems at the heart of this inquiry. Yet currently retrofit is hard to fund through existing funding mechanisms such as flood defence grant in aid because it is difficult to ascribe the benefits to specific properties. If retrofit SuDS could harness funding streams to deliver flood risk management, air quality, health and wellbeing, nature recovery and water quality outcomes they would be far easier to fund. The criteria and specifics associated with such funding streams are currently prohibitive to this.

The London Strategic SuDS Pilot ( provides evidence of how a distributed retrofit approach can deliver significant benefits across these benefit areas and more through bundling individually small interventions together at more of a catchment scale. Modelling and monetization tools can maximise efficacy and socio-economic benefits. This approach should be taken forward extensively across our towns and cities.



May 2021