SUDS IN SCOTLAND - THE MONITORING PROGRAMME OF THE SCOTTISH UNIVERSITIES SUDS MONITORING GROUP
SR(02)51
March 2004

EXECUTIVE SUMMARY

1. Background and purpose of the research

Sustainable Urban Drainage Systems (SUDS) are storm or surface water drainage facilities designed to address three essential issues: water quality, water quantity, and amenity (including biodiversity). The purpose of this research was to provide a substantial body of knowledge on the performance of SUDS (in terms of water quality, hydrology and amenity) and the factors that affect performance. The project involved the continuation of a five year programme of monitoring and assessment of SUDS performance. Two principal categories of SUDS system were monitored: source control and site/regional control systems. Assessments of the quantity and quality of sediments, biodiversity at ponds and public perception have been investigated.

The project draws together results from the work of the ongoing Scottish Universities SUDS Monitoring Programme which was supported and encouraged by the Sustainable Urban Drainage Scotland Working Party (SUDSWP). This research project was funded by SNIFFER, Environment Agency and SEPA. The monitoring programme was supported by the Sustainable Urban Drainage Scotland Working Party (SUDSWP), and received financial support from the Environment Agency, SNIFFER, Scottish Water, the Scottish Environment Protection Agency (SEPA), Wilcon Homes, Formpave Ltd., Yorkshire Water and Dundee City Council.

2. Structure of the report

The report has two sections.

Part A contains detailed monitoring and performance information on most of the types of SUDS encountered in Scotland, including ponds, detention basins, swales, filter drains and infiltration trenches and porous paving.

Further sections provide the results of analysis of public perception, of pond sediments, and of surveys of aquatic and riparian vegetation and macroinvertebrates.

Part B comprises fourteen Site Summary Sheets including details of results from five ponds, two detention basins, two porous paving installations, three filter drains and two swales. The purpose of these sheets is to give a 'snapshot' of all aspects of behaviour of the SUDS systems.

3. Key findings

The implementation of SUDS in Scotland has been a great success in achieving the water quality and flow control objectives for which they were planned. A wide range of systems has been monitored, and although many examples of poor practice have been found and highlighted, it is clearly demonstrated that the systems are all producing at least the hydrological and water quality benefits desired.

The research demonstrates that:

• most source control SUDS in Scotland serve contributing areas which have relatively low levels of contamination;
• source control systems investigated operate primarily hydrologically, and have been found to effectively control rates of surface runoff and these SUDS localise and treat contaminants;
• only exceptionally will SUDS not mitigate against pollution or lead to contamination problems themselves;
• site/regional control systems provide significant hydrological benefits, but in addition they attenuate peak concentrations of pollutants.

Maintenance is an absolute necessity for all drainage systems and SUDS are no exception. Observations on maintenance are an underlying theme of the report.

The local acceptability of SUDS depends on their appearance, and some of systems monitored have an entirely unsatisfactory appearance. However, a number SUDS which were in need of maintenance to improve their appearance also afforded excellent performance.

Below ground assets were generally found to be in poor condition and those monitored did not perform well.

A number of discrepancies between design and installations were found although more recent examples have been designed to a better standard than earlier systems.

4. Implementation and dissemination

This report is intended to be of interest to several stakeholder groups including environmental regulators, water service providers, local government, developers, national government, environmental consultancies, non-governmental organisations; and researchers.

Research findings have been incorporated into CIRIA publications and the studies reported here can be expected to inform design guides through information details such as: treatment volume, percentage runoff, changes in water qualities, inlet and outlet design.

KEY WORDS

Sustainable Urban Drainage Systems; SUDS; Best Management Practice (BMP); Surface Water; Storm Water; Source Control; Scotland; Amenity; Maintenance; Hydrology; Water Quality; Diffuse Pollution; Performance.

Copies of this report are available from the Foundation, in electronic format on CDRom at £20.00 + VAT or hard copy at £35.00, less 20% to FWR members.