Optimization of the restructuring cost of an urban drainage network

Urban drainage networks are subjected to increased runoff caused by urbanization and climate change. Wear and tear, coupled with a lack of network maintenance, reduces the hydraulic capacity of these networks and results in surcharged flows, discharges and overflows calling for the need to institute effective restructuring strategies. The purpose of this study was to develop an optimization model for the optimal selection and placement of structural best management practices (BMPs). In this research, four types of structural BMPs were being considered (i.e., retention pond, green roofs, infiltration trenches and vegetated depressions). The objective function was to minimize the total cost of BMPs, within the constraints of (1) draining infrequent heavy rainfall without surcharging the conduits and (2) driving frequent small rainfall into the water-treatment plant without overflows. The model was tested on a case study in the Greater Montreal Area and the results obtained from the model effectively demonstrated its capacity to improve the hydraulic and environmental performances by adopting optimal BMPs placement strategies.