Cost Optimization of Hydraulic and Structural Rehabilitation of Urban Drainage Network

Abstract

Urban drainage systems are prone to symptomatic decay that eventually causes surcharged flows and flooding, with important consequences for the aquatic ecosystems of receiving water bodies in addition to the safety of drinking water and recreational water activities. Rapid urban development and climate change combine with wear and tear along with a lack of network maintenance to accelerate this decay and cause a reduction in the hydraulic system’s capacity. In this context, the need for system rehabilitation becomes more pressing. Cost figures prominently take precedence in the decision-making surrounding the choice of rehabilitation method employed, but models for assessing cost-effectiveness which consider both structural and hydraulic options, in addition to real-world constraints and time-frame conditions, are lacking. This paper proposes an algorithm to maximize the benefits ensuing from the rehabilitation of urban drainage systems. Potential interventions considered in the algorithm include both traditional rehabilitation methods such as the resizing and rebuilding of damaged pipes, in addition to best management practices (BMPs) aimed at reducing runoff rate and volume. A case study from the borough of Verdun is presented, in which the algorithm identifies the best combination of volume retention, pipe rehabilitation, and resizing interventions to optimize the network’s hydraulic performance and minimize operational costs.