An Evaluation of Stormwater Treatment Efficiency of Sustainable Drainage Systems (SuDS)

Natural pathways and processes of dealing with drainage in each location or catchment have continued to be distorted by developments necessitated by increased urbanization in response to factors such as increased population, migration (internal and external) as well as infrastructural and industrialization expansions. These developments have led to increased imperviousness resulting in flooding incidents and pollution of rivers. The initial response to the drainage problems was to view stormwater as a nuisance which must be removed from the catchments as quickly as possible by engineering pathways of removal to natural water courses. Also, it is noteworthy that stormwater runoff can contain diverse pollution (including nutrients, toxins, hydrocarbons and metals) depending on its source and pathways that it travels. Whilst the conventional drainage approach required construction and maintenance of channels which are capital intensive, it also created environmental problems such as pollution of surface and groundwaters as well as distortion of ecosystem of receiving waters. In other to deal with these challenges and respond to stringent environmental legislations, there was need to apply more sustainable approaches to stormwater management and eliminate or reduce the problem of conveyance by dealing with drainage at source. Sustainable drainage system (SuDS) (also widely known as Best Management Practice (BMP) and Low Impact Development (LID) have revolutionalised the way and manner stormwater is managed particularly in developed nations such as UK, USA, New Zealand, Australia and European Union member States. SuDS employ an array of techniques aimed at delivering the three main paradigms of sustainable drainage: quantity, quality and amenity (QQA). LID seeks to mimic a site’s natural drainage processes and pathways by incorporating them in development of the site. SuDS employ technique (s) to deal with drainage at source. One of the main drivers of SuDS is the multi benefits which it offers alongside sustainable drainage at source. SUDS techniques include permeable paving, porous concrete/ asphalt, green roofs, wetlands, bioretention ponds, French drains, infiltration trenches, swales and basins, etc. This chapter evaluates treatment efficiencies of wide range of SuDS devices under different conditions and discusses some of the challenges to evaluating and comparing their stormwater treatment efficiencies. It is proposed that guidance in the application and evaluation of performance of these systems will support effective assessment of their performance and help to provide solution to some of the challenges highlighted.