Monitoring and modelling suds retention ponds: Case studies from Scotland

SUDS (Sustainable Drainage Systems) retention ponds are an important part of Blue Green Infrastructure and provide multiple benefits, including flood risk alleviation, water quality improvements, recreation, amenity and biodiversity value. Characterisation of sediments and suspended particulate matter (SPM) is important for assessing SUDS functioning and understanding patterns of ecosystem dynamics because of its key role in pollutant adsorption, biogeochemical cycling and influencing light penetration. This paper gives an overview of our research on nine ponds, all of which represent important components of Blue Green Infrastructure. Most of the ponds have been specially designed as SUDS ponds, whilst the rest are used for comparative purposes. An important part of the presented research is analysis of SPM and particle size distribution. Water quality is assessed both by physico-chemical analysis and by regular sampling of aquatic invertebrates. Further current and planned ecological surveys include phyto- and zooplankton, vegetation, fungi, lichens and vertebrate animals. Modelling of the sites’ hydrology and the responses to storm events is currently being undertaken using CityCat, and more programming effort is planned to interpret the patterns observed. The results show that SPM in these ponds includes particles of both biological and abiotic origin; considerable proportion of SPM is smaller than 100 microns. The preliminary analysis indicates that the biological community is instrumental for water quality improvements, but may be experiencing both physical and chemical limitations. Although biodiversity of the SUDS ponds studied appears to be lower than that of natural ponds, their species richness constitutes up to 60-80% of that observed at the control sites. In particular, some of the ponds studied proved to have healthy amphibian populations, thus providing conservation value among other SUDS multiple benefits.