Commissioning the project
The Environment Agency in Luton commissioned Groundwork East to develop a Sustainable Urban Drainage Scheme (SuDS) at Lewsey Park, in partnership with Luton Borough Council and Thames Water.
This was as a result of the successful river improvement project that was carried out two years earlier on the brook at its source. The initial reprofiling works increased capacity for flow of the brook at peak flow and reinstated a drinking pond for historic cattle.
The SuDS project was commissioned to prevent pollution and to reduce the quantity of flooding, as during periods of high rainfall, surface water caused flooding to the park. Groundwork carried out a topographic survey as well as a site investigation survey, in order to identify the soil type and permeability. The topographic survey gathered data about the ground profile in Lewsey Park and presented them as contours on a plan. This allowed us to collect data about the natural and man-made features of the land, including its elevations, to help us identify potential flood spots. A site investigation survey identified any contaminants in the soil and collected data to recognise any potential risks.
There were several SuDS features that were taken into consideration, including the installation of hydrodynamic separators, and introduction of permeable paving. The hydrodynamic separators were designed to be installed on the three main surface water sewers entering the brook at its source, with an associated water quality monitoring system. The separator was chosen as it removes silt and other particles from the water, meaning they can no longer enter the river; this prevents a build-up of sediments and debris, which could otherwise lead to downstream flooding and erosion.
The park edge along the front of the main road was hard, with kerbs and raised planters restricting the flow of water off the highway. The highway and park interface was redesigned so that the water flow was not restricted, with the planters and kerbs removed, and permeable paving incorporated to parking areas. Swales were also designed to reduce the water entering the sewer system.
Design work has now moved on to improvements to another tributary of the River Lea, called ‘Houghton Brook’, where wet woodland areas and rain gardens are being investigated. The rain garden at the source would be a retrofit SuDS feature, ideal for an educational resource when accompanied by interpretation panels. The panels will provide a combination of text and visuals to tell a story about Houghton Brook.