content@managingwater.co.uk Drainage Systems - SuDS
The Lamb Drove SuDS Monitoring Programme
- Quantifying the benefits Richard Stevens, Royal HaskoningDHV
The multiple benefits of SuDS are widely recognised; however quantification of these benefits is rarely undertaken. The Lamb Drove Sustainable Drainage Systems monitoring programme has done just that and is providing a vital contribution to the SuDS evidence base.
The Lamb Drove site was completed in 2006 and comprises a one hectare residential development with 35 properties in Cambourne, Cambridgeshire. The site was selected to showcase SuDS as part of the FLOWS (Living with Flood Risk in a Changing Climate) programme funded by the European Regional Development Fund (ERDF) through the INTERREG IIIB North Sea Region programme. Royal HaskoningDHV, working with Robert Bray Associates, were commissioned by Cambridgeshire County Council to retrofit SuDS and property flood-proofing measures into the design of the Lamb Drove development site. The design followed three guiding principles of simplicity, visibility and easy maintainability.
Through an integrated system of sustainable drainage features, the site brings environmental, ecological and social benefits to residents. The SuDS management train at this site includes the use of ‘source control’ measures including a green roof, permeable pavements, under-drained swales and water butts, ‘site control’ measures including bio-retention swales, detention basins and wetlands,
Figure 1
and a final ‘regional control’ retention pond. The ground conditions on the site offer little potential for infiltration so the system operates through attenuation of flows through the network of features.
Royal HaskoningDHV was commissioned to undertake monitoring of the performance and benefits of the implemented SuDS over a period of two years which began in October 2008. This was extended until the end of 2011 with the final report published in 2012. Flows are monitored across the site as they move along the treatment train. A control site of similar size and development density, but with traditional drainage, is also monitored. Water quality samples were collected on a quarterly basis at both the SUDS site and the control site. The environmental benefits of the scheme were assessed through habitat surveys and the local residents were surveyed to assess their views on the scheme. The results from the Lamb Drove site were compared to results from the control site.
The SuDS system has attenuated surface water flows; significantly reduced peak flows have been observed when compared to the Control Site (Figure 1). The monitoring programme has clearly shown the successive attenuation and reduction of both flow and volume through each stage of the SuDS management train.
The SuDS system has improved the quality of water discharged from the Study
Site when compared to the Control Site. Results have shown that the Study Site has observed reductions in concentrations of a variety of pollutants and other water quality indicators including hydrocarbons, heavy metals and suspended solids.
In addition the Study Site has shown a higher number and diversity of species present over the three habitat surveys than the Control Site, demonstrating that the Study Site represents a more natural management regime.
The resident surveys found that they regard the open space around their homes more aesthetically pleasing when compared to other parts of Cambourne. It is apparent that the residents of Study Site have a high regard for the aesthetics and visual appearance of the open spaces within the SuDS scheme. This agrees favourably with findings from some other SuDS sites, where the positive impact on the immediate areas had transformed into locally higher property values.
These results are already being used at the national level to promote the benefits of SuDS and overcome the lack of confidence on their actual performance. By providing significant evidence base on the performance of SuDS compared to conventional systems, this study takes the industry a long way in providing scientific information on the performance of SuDS systems.
More information about this SuDS project can be accessed at
http://www.cambridgeshire.gov.uk/environment/planning/drainagesystems/monitoring.htm or by contacting
richard.stevens@
rhdhv.com.
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