A Review of the Factors Affecting the Biodiversity of Constructed Stormwater Management Systems along Roads

Sammanfattning: Constructed Stormwater Management Systems (CSMSs) are usually designed to treat urban runoff, but can act as artificial habitats that support relatively diverse aquatic ecosystems. However, in order to manage these systems in an environmentally friendly way, more knowledge of the factors affecting the biodiversity within these CSMSs is required. The aim of this thesis was to deduce the main factors that affect the biodiversity within CSMSs. The report is split into two main sections: the first part consisting of a literature review and the second containing data analysis. Following the literature review, the factors that appeared to have the greatest impact on the biodiversity within CSMSs were: salinity; pond size and shape; vegetation; nitrogen oxide concentrations; noise; and PAHs and heavy metal concentrations. However, it is apparent that nature is a complex system, with many of these factors interlinked and interrelated; therefore, no factors should be neglected. Furthermore, different species have various tolerance and lethal concentration levels for each harmful factor. Following the data analysis, it became clear that pond age and CSMSs substrate type also have a statistically significant effect on the biodiversity within CSMSs. Pond age may form a polynomial relationship, with biodiversity increasing in the short-term, peaking and then decreasing in the long-term when heavy metal accumulations become lethal. Clay (naturally) based ponds seem to support the highest biodiversity, with PEHD bases slightly negatively correlated and concrete bases very negatively correlated with biodiversity. Future design and management of CSMSs should consider the potential aquatic habitats that these systems have to offer, as well as being primarily designed to limit pollution to the wider environment. To increase the regional biodiversity, the design of CSMSs should be personalised, at a family level, to satisfy the different needs of Fish, Amphibians and Invertebrates, and to move away from homogeneity and towards heterogeneity.