South East Rivers Trust (& the Wandle Trust)

SuDS Design and Delivery


While Covid-19 has affected our plans for the SuDS in Sutton’s Schools project, at the South East Rivers Trust we have used this opportunity to shift our focus from Education and Engagement to Design and Delivery – increasing the expertise we are able to give on future SuDS projects. 

Background to the project

The primary objective of any SuDS (sustainable drainage systems) scheme is to alleviate flood risk in the local area.  Adding features that capture and store rainwater or allow it to infiltrate reduces pressure on the drainage system so it doesn’t become overwhelmed.  However, there must also be clear onsite benefits for site users to commit to the project.

The SuDS in Suttons’s Schools project is a partnership project between the London Borough of Sutton and the South East Rivers Trust.  The primary aim of the project is to alleviate flood risk in Critical Drainage Area 33 – the Hackbridge area of Sutton.  The main project has been managed by the council while the role of the South East Rivers Trust has been to add value for schools.  This partnership has been crucial for securing buy-in from schools so that flood relief targets could be met.

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 due to delays caused by Covid-19, the second phase is due to be completed in 2021. 

During the first phase of the project, SERT’s primary role was to add value for schools by delivering education and engagement activities. 

Pupils adding plants to their SuDS in 2019

School-Friendly SuDS

SERT has shifted its focus on to designing and installing SuDS features that have clear benefits for the schools involved.  This can present a range of difficulties.  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 is important to work closely with a school to ensure the benefits provided from a SuDS scheme are actually valued by the school and outweigh any disadvantages or disruption the scheme might cause. 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 both SuDS planters and rain gardens to the school sites but no suitable location for a rain garden 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 – 1 trial planter installed at Sutton Council offices and a further 9 planters spread across 3 school sites. 

Trial Planter

The 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 3-metre-long planters

The threaded bar cross brace
Geocellular storage layer

The trial planter has been built, connected and planting has been added.  

All the planters in the schools have now been built but they have not yet been finished off. The aim is to have all planters completed by the end of March 2021.

Carshalton High School for Girls

At Carshalton High School for Girls, we delivered planters in two areas of the school.  In one area, two planters were installed – one with a gravel storage layer and one with a geocellular storage layer. Monitoring equipment was added to each planter to gather data on the effectiveness of the different storage layers in attenuating runoff.  Not only was this included to help us evaluate the success of the geocellular storage layer design,  but it also meant data could be shared with the Geography pupils of the school.  SuDS is part of the Geography scheme of work and having features on site that can be integrated into lessons was a priority for the school.

Planters with monitoring equipment
Lunch area planter that matches existing furniture
Connecting the planter to a cast irion downpipe

A further three planters were added to an outdoor lunch area of the school.  This area was already equipped with recycled plastic picnic benches so, at the school’s request, 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 with benches to provide extra seating

Holy Trinity Church of England Junior School

At Holy Trinity Church of England Junior School we were able to work directly with the Eco Council before the lockdown.  These sessions enabled us to get input from pupils on what they would like to see in the final designs.  Again, they had a preference for recycled plastic because they liked the idea of saving waste from landfill.  Another priority for them was to include features to attract wildlife.  The staff requested the planters reflect the school colours – black and red. 

The planters have been positioned to allow access on all sides – so a full class of pupils can fit around the two planters.  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 with these designs, 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. 

Black and red planters reflect the school colours

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 in any way.  The location where the planters are sited is an underused part of the school.  By turning these into sensory planters it enables the school to use this as a calm place where pupils can come to escape the busyness of the rest of the school.  The landscaping scheme that will be added later includes plants with various textures, smells and colours.

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 with project.  We were able to deliver 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.