In the second article in the series “A New Approach to Storm-Water Management and Flood Reduction“, Ed Hill looks at the Sustainable Drainage Systems (SuDS) project in Manor Fields Park, England.
Manor Fields Park is located in the town of Sheffield in Yorkshire, England. It represents the redevelopment of a previously derelict site to manage the stormwater runoff from a 300-unit housing estate in Manor Park, 3km southeast of the city centre.
The park site is 25ha in extent, forming the ‘open space’ component of the housing development, and the outline brief for the site was the “transformation of derelict land into a quality space for wildlife, local residents and visitors”. The design work, with a contract value of £1.5m, was carried out by the Sheffield City Council Landscape Design Team with expertise from the private sector, on behalf of the Sheffield City Council Parks and Countryside Team.
According to the design team, “the defining driver for taking the open space route for managing surface run-off was the considerable costs associated with building a conventional connection of the onsite pipe network to the surface water sewer … This was due to topographic constraints”.
Description of the System
The case study is included on the website of Robert Bray Associates, who provided the expert input for the SuDS component of the development. Since the housing was being redeveloped on a ‘brownfields’ (i.e. previously developed) site, RBA state that source control measures that normally characterise sustainable drainage were not feasible due to the pre-existing layout, and flows were modelled on the basis that no attenuation occurred in the housing area, with the park receiving an “a ‘raw’ product in variable flows”. As a result, stormwater enters the system at one point as is managed via a series of basins following the slope of the site. Silt collection and pollution capture occur mainly in the top basin, with sand filters fitted behind stone walls in the next level of basins. These have gaps between stones in their lower courses to allow water movement, with the flow rate determined by the resistance of the filters and the diameter of the exit pipework. Low flow water passes to the next level down via a shallow channel, but, if the filtering capacity of either of the upper basins is exceeded then water overflows via an alternative grass channel route to the next basin. The third basin level leads out via a volume release control to an existing dry valley leading to the nearby water course. If the capacity of this level is exceeded then it overflows onto a grass arena and exits via an additional control device down to the dry valley.
Wherever possible, materials generated by on-site demolitions were recycled in order to reduce the impact of construction work on the local environment, including a reduction in the need to transport material onto and from the site.
Benefits of SuDS Implementation
According to the Landscape Institute article, use of SuDS “removed the need for engineered below-ground structures and allows natural processes to occur as well as contributing to good design.” It further states that the scheme limited stormwater impact on the River Don during the 2007 floods by containing floodwater, and the park was re-opened shortly afterwards.
RBA states that, by using an alternative approach to stormwater management, the project was able, at no additional cost, to reclaim 2ha of land to improved landscape, construct an events arena in the form of a stormwater basin on difficult terrain, enhance the wetland ecosystem of the site, unlock extra management finance for a public park, an provide an educational opportunity for the wider community and so promote responsible use of facilities.
Overall the scheme delivered many benefits to the park including reclamation of derelict land, revenue for management, recreational space, biodiversity, and community interest.