Climate-proofing social housing landscapes

This project has installed retrofit SuDS measures on three social housing estates in the London Borough of Hammersmith & Fulham:

• Queen Caroline Estate
• Cheeseman’s Terrace
• Cyril Thatcher, Eric MacDonald and Richard Knight Houses

Together, the three estates cover an area of five hectares and are home to 700 deprived households.

All three of the housing estates are in Critical Drainage Areas (identified as contributing to surface water flood risk). Before the project started, most surface water from these estates drained directly into the combined sewer system via gullies. This increased the risk of localised surface water flooding.

This large project was also funded by the Life + Programme of the European Commission, Hammersmith & Fulham Council, and Groundwork London.

The housing estates were assessed to identify the most appropriate and effective mix of SuDS measures. A wide variety of measures were installed across the three estates. Some features, such as green roofs on pram sheds and small rain gardens in soft landscape areas, were installed across all three estates. Others, such as the trench tree pit at Richard Knight House and the Schotterrasen at Queen Caroline Estate, were specific to an estate because of their particular constraints, like space restrictions.

Installing the green roof on Richard Knight House was planned to coincide with new waterproofing and insulation upgrades as part of the council’s repairs programme. Co-ordinating the work helped to reduce costs. This is a good example of how the London Sustainable Drainage Action Plan is intended to work.

The sites will be maintained (at similar cost to before the project) by Hammersmith & Fulham Council’s contractors. The Groundwork team gave them training on how to take care of the SuDS measures.

A key part of the project was performance monitoring. This was led by the Sustainability Research Institute at the University of East London, and included:

• Time lapse cameras to capture performance of measures during rain events and vegetation development
• Weather stations to monitor environmental conditions, including the timings and size of rain events
• Flowmeters and pressure sensors to monitor water accumulation and infiltration times
• Thermal monitoring using a thermal imaging camera
• Biodiversity monitoring on the green roofs, using vegetation surveys
• Photographic monitoring to monitor biodiversity
• Storm simulation tests to monitor SuDS measure performance in extreme weather events

Environmental improvements

The monitoring has shown how effective SuDS measures are at reducing surface water runoff. For example, the capacity of the ground level SuDS (like the swales and basins) hasn’t yet been breached. That means 100 per cent of the rain falling on 3,160m² of impermeable surfaces and collected by these SuDS measures has been diverted away from the drainage system. The pressure sensor in the Queen Caroline Estate’s Beatrice House basin shows surface water collecting very quickly in the basin. However it has been shown to quickly infiltrate into the ground for all rain events monitored.

Flowmeters show up to 98% drop in peak water flow for Queen Caroline Estate’s retrofit pram shed green roofs compared to nearby, non-vegetated roofs. They also showed substantial delays in water leaving the roofs. This has helped to reduce peak flows into the local drainage systems. Here's a short video of the Queen Caroline Estate’s green roofs at work.

Infrared imaging of a hot day in July 2016 (32.6^oC) revealed the large temperature difference between non-vegetated roofs (more than 49^oC) and vegetated green roofs (approximately 34^oC). This shows the potential for using vegetation to aid local urban cooling.

This project has also helped increase biodiversity. For example, the green roofs have been colonised by plant species typical of London green roofs. Just the green roof on Richard Knight House supports 64 species. In turn, these have attracted a range of insect pollinators, including bees and hoverflies.

As time goes by, monitoring data will help assess the long-term value and impact of SuDS measures.

Community engagement

Groundwork London worked with residents throughout the project, giving them the chance to shape the improvements on their estates. This helped raise awareness of the implications of climate change for London. It also highlighted what steps residents themselves can take to help with climate adaptation and resilience.

Engagement activities included:

• Resident meetings, for example with Tenants & Residents Associations and other interested resident groups on the estates
• Consultation events during the earlier phases of the project (before and after the start of design work);
• Community mapping, to identify areas of under-used space, and areas prone to water pooling and overheating
• Workshops, events and training
• Input to local adaptation plans, setting out what residents value the most about their estates, what they would like to look after, and the support needed from others in to do this

Raised timber planting beds or other planting areas were installed at all three estates, with gardening clubs set up by Groundwork London. Residents are now managing these beds, and are continuing to grow food and plants. Informal play features have also been installed alongside the green infrastructure features, to encourage residents to use the green spaces.

Reducing inequality

Rainwater often pooled outside the entrance to Richard Knight House. This was awkward for most residents, and made it difficult for one resident who uses a walking frame to leave their flat.

The surfacing outside the entrance was re-laid to drain into a small rain garden in the nearby grass area. This small, low-cost SuDS measure hugely improved residents’ experience of the space. In turn, this helped build support for larger SuDS measures across the estate.

Education and training

Much of the topsoiling, turfing and planting of the SuDS measures was done by Groundwork London’s ‘Green Teams’. The Green Team programme helps unemployed young people into work by training them in horticulture, landscaping and maintenance activities. This allows them to complete a Level 1 City & Guilds Award in Practical Horticulture Skills. The project supported 22 trainees, more than half of whom live locally. The project also helped to train Hammersmith & Fulham Council’s staff and maintenance contractors. This gave them an understanding of the local impacts of climate change and meant they could identify and maintain suitable SuDS retrofit measures.

Awards

This project won an Urban Greening Award at the 2015 Sustainable Water Industry Group (SWIG) Awards. It was Highly Commended in the Landscape Institute's 2016 Awards, in the Adding Value through Landscape/ Environmental Improvement category and won the Landscape Institute's 2016 College of Fellow’s Award for Climate Change Adaptation.

There were no major challenges to the project. Small challenges were addressed as they emerged including:

• It was hard to engage some residents in the climate change agenda at first as it wasn’t seen as an immediate problem for the estates. The project overcame this by linking wider threats to local issues, such as water pooling and overheating.
• Several open spaces on the estates were fenced off and rarely used. Some residents were concerned that opening up the spaces might encourage anti-social behaviour. In reality, the opposite has happened, with the spaces now more widely used and valued.
• Even with utility company drawings and radar surveys for underground services, not all services were identified. That meant some design changes were needed during construction.
• Construction works close to residents’ homes and altering access routes were a concern for some residents. This was expected and managed through Groundwork London’s Community Projects Officer and relevant council teams.
• The scheduling of works at Cheeseman’s Terrace reduced the time available for monitoring. This was solved by using storm simulation tests. The aim is to extend the monitoring period by up to a year (subject to funding) to better understand the longer-term performance of the SuDS measures.