SuDS design and delivery

When Covid-19 affected our plans for the SuDS in Sutton’s Schools project, the South East Rivers Trust shifted its focus from Education and Engagement to Design and Delivery – increasing the expertise we are able to give on future sustainable drainage systems (SuDS) projects.

The primary objective of any SuDS scheme is to alleviate flood risk – capturing and storing rainwater, reducing pressure on the drainage system.

We worked with schools to deliver clear benefits, whether it be for wildlife, as calm spaces or to enhance the work of particular lessons.

The SuDS in Sutton’s Schools project was managed by the London Borough of Sutton council and our role has been to deliver education and engagement to help schools meet flood relief targets. The primary aim has been to alleviate flood risk in the Hackbridge area – known as Critical Drainage Area 33.

The SuDS in Sutton’s Schools project was delivered in schools in two phases – using the summer holidays to deliver the bulk of the work. The first phase was completed in 2019 and, because of delays caused by Covid-19, the second phase was completed in 2021.

Clear benefits to schools

Producing SuDS that had clear benefits for the schools presented a range of challenges.

Schools are busy sites, so some features that aim to provide benefits – such as a rain garden installed to green a grey area of the playground – may cause an obstruction.

It was vital to ensure the SuDS were valued by the schools. Our expertise in engaging schools helped us to get crucial input from site users and incorporate their views into the final designs.

We had hoped to add rain gardens too, but no suitable locations could be found. Instead we focused on planters, finding ways of tailoring them to individual schools’ needs.

By trialling different options, we have been able to develop a clear methodology for delivering a range of school-friendly SuDS planters.

In total, we have built 10 SuDS planters – one trial planter at Sutton Council offices and a further nine planters at three schools.

Children planting for the SuDS in Schools project © South East Rivers Trust

Trial Planter

A trial planter provided us with the opportunity to practice installation, ironing out the kinks before going into schools.

It enabled us to develop a strategy for various aspects of the build: for example, how to add cross-braces that bear the load of a saturated planter while keeping it water tight so no leaks occur.

In addition, we trialled the use of a geocellular storage layer rather than gravel which is usually used. The amount of void space in geocellular storage is more than triple that in a gravel storage layer (depending on the gravel).

Therefore, by utilising geocellular storage we could increase the contribution our planters were making to the overall flood alleviation targets of the project.

We also developed our own method of distributing the runoff more evenly throughout the three-metre-long planters.

Geocellular storage for SuDS in Schools

Carshalton High School for Girls

At Carshalton High School for Girls, we delivered planters in two areas.

One area had two planters – one with a gravel storage layer and one with a geocellular storage layer. Monitoring equipment was added to each to gather data on the effectiveness of the different storage layers in reducing runoff. Data could also be shared with pupils in geography lessons. Features that could be used in these lessons was a priority for the school.

A further three planters were added to an outdoor lunch area. Already equipped with recycled plastic picnic benches, we used recycled plastic for the planters and matched them to the existing furniture.

To increase the amount of seating available, we designed planters with integrated benches.

Planters for SuDS in Schools © South East Rivers Trust

Holy Trinity Church of England Junior School

We worked directly with the school’s Eco Council before the lockdown, to gain input from pupils on the designs.

Again, they had a preference for recycled plastic because they liked the idea of saving waste from landfill.

Features to attract wildlife was another priority. The staff requested the planters reflect the school colours – black and red.

The planters allow access on all sides – so a full class of pupils can fit around the pair. Galvanised metal arches will be added to direct the water from the downpipes to the planters.

The landscape designs include one bee, butterfly and bird friendly planter and one mini-beast planter. A range of wildlife features will be added including nectar rich planting, a perching branch, birdfeeders, a bird bath, a bug hotel, log piles and beetle refuges – places where bugs can retreat to when the planter becomes saturated.

Our aim was to make these planters not just a visual enhancement to the front of the school but a useable educational feature that will be valued by pupils and teachers.

Planters to match school colours. SuDS in Schools

Wandle Valley Academy

At Wandle Valley Academy, the remit was very different. Their primary concern was creating features that were robust. For this reason, we installed planters made out of metal troughs that could not be dismantled or broken. The planters are sited in an underused part of the school.

This enabled the school to use the SuDS as a calm place where pupils can go to escape the rest of the busy school.

The landscaping scheme that will be added later includes plants with various textures, smells and colours.

WandleValleyAcademy

Summary

Covid-19 has meant we haven’t been able to carry out all the education activities we had planned, but by shifting our focus to delivering school-friendly SuDS features we have found a way to keep the schools engaged. We delivered these smaller features during term time so that the schools did not have to wait until the summer holidays to have SuDS installed on site.

The hope is, that we will be able to involve pupils with the planting. If this is not possible, follow up activity ideas will be provided for the schools so that pupils and staff are aware of their new SuDS features and the benefits they provide.

Plants with benches © South East Rivers Trust