Lessons learned from the five SuDS projects

Two of the projects experienced potential issues with construction. There is a risk that contractors with no previous experience of SuDS measure installation may be unable to install the measures correctly. This can reduce SuDS function and lead to costly future maintenance and/or repair.

For large and complex projects, contractors must have previous experience of SuDS installation (as with the Priory Road project). Alternatively, the design team must be on site to supervise construction (as with the Bridget Joyce Square project).

Green roofs generally need an expert to identify whether the building can cope with the extra structural loading of the roof. However, as the Lost Effra project showed, community green roof building is possible with a willing contractor. It can also encourage wider take-up of green roofs across the community.

Smaller schemes, such as de-paves and downpipe disconnection into a swale or raingarden, may not need experts or specialist contractors. Instead, they can be done by local people (subject to planning permission, if necessary).

One of the strongest themes running through the five retrofit projects has been the importance of engaging local people from concept and design to installation and maintenance. This is not an ‘optional extra’ but a crucial part of any successful SuDS project. If done well, it can:

• result in better-designed and multi-functional SuDS measures
• raise awareness of climate change, potentially leading to behaviour change
• encourage community ownership and maintenance of SuDS measures
• encourage additional SuDS measures to be installed in the neighbourhood.

Monitoring water quality and quantity can be challenging. It needs to be factored into SuDS design, and requires specialist equipment and expert analysis. In addition, the monitoring industry is not yet set up to undertake all the different types of monitoring required for SuDS schemes (flow, weather, moisture, pressure, etc.) Many companies specialise in just one type of monitoring. This can make SuDS monitoring expensive.

Because of this, comprehensive monitoring was only included in two projects - Bridget Joyce Square and the Climate-Proofing Social Housing Landscapes project. However the Dale Court rain gardens at Priory Road were designed so that monitoring equipment could be installed in future. Monitoring can provide invaluable data to support the use of SuDS across London.

Other SuDS projects including monitoring are Renfrew Close rain gardens in Newham and the Ruislip London Underground depot green roof.

As technology improves and gets cheaper, and as SuDS take-up increases, we anticipate more monitoring will be included as standard in new SuDS projects.

The experience of the five demonstrator projects suggests that maintenance of new SuDS measures doesn't need to be costly. For example:

• the Alma Road project shows that maintenance costs are balanced, if not outweighed, by the benefits of the SuDS measures
• the Bridget Joyce Square project demonstrates that the maintenance costs of SuDS measures can be reduced through careful design
• the Climate-Proofing Social Housing Landscapes project’s maintenance costs are similar to the costs before the project began
• the costs of maintaining the landscaping at the front of Dale Court at Priory Road actually decreased as a result of the SuDS installation
• the Lost Effra projects are being maintained by the local community.