Analysis and determination of optimum risk factors to prioritize illegal discharge potential in urban catchments.

Illegal discharges into stormwater drainage systems have significant adverse impact on water quality in urban watercourses, human health, and ecosystem sustainability. The objective of this paper was to search for optimum risk factors based on existing data to determine the potential severity of illegal discharge within selected two catchments, and identify which areas merit priority investigation. The methods used in the investigation included risk factors metric ranking, spatial analysis, multi criteria evaluation, and composite risk map production. Results from the study indicated that many land use, hydraulic, and hydrologic factors affect the location of illegal discharges. Risk factors were ranked in terms of their performance to predict locations of illegal discharge potential. The performance ranking enabled composite risk map to be produced, prioritizing each catchment into low, medium and high risk areas of illegal discharge potential. • Many land use, hydraulic, and hydrologic characteristics affect the location of illegal discharges. • Risk mapping is an effective tool to structure the implementation of illegal discharge control program. • The tool provides a framework for a tiered approach which may result in program-wide cost savings. [ABSTRACT FROM AUTHOR]