Increasing urbanization is a dominant global trend of the past few decades. For cities to become more sustainable, however, the infrastructure on which they rely must also become more efficient and resilient. Urban infrastructure systems are analogous to ecological systems because they are interconnected, complex and adaptive, are comprised of interconnected components, and exhibit characteristic scaling properties. Analyzing them together as a whole, as one would do for an ecological system, provides a better understanding about their dynamics and interactions, and enables system-level optimization. The adoption of this “infrastructure ecology” approach will result in urban development that costs less to build and maintain, is more sustainable (e.g. uses less materials and energy) and resilient, and enables a greater and more equitable creation of wealth and comfort. Resilience, or the capacity of a system to absorb shocks and perform under perturbations, can serve as an appropriate indicator of functional sustainability for dynamic adaptive systems like Urban Water Systems. This research developed an index of resilience (R-Index) to quantify the “full-spectrum” resilience of urban water systems. It developed five separate indices, namely (i) Index of Water Scarcity (IWS), (ii) Relative Dependency Index (RDI), (iii) Water Quality Index (WQI), (iv) Index of Network Resilience (INR), and (v) Relative Criticality Index (RCI), to address the criticalities inherent to urban water systems and then combines them to develop the R-Index through a multi-criteria decision analysis method. The research further developed a theoretical construct to quantify the temporal aspect of resilience, i.e. how quickly the system can return back to its original performance level. While there is a growing impetus of incorporating sustainability in decision making, frequently it comes at the cost of resilience. This is attributable to the fact that the decision-makers often lack a life-cycle perspective and a proven, consistent and robust approach to understand the tradeoff between increased resilience and its impact on sustainability. This research developed an approach to identify the sustainable and resilient (SuRe) zone of urban infrastructure planning and design where both sustainability and resilience can be pursued together.

The overall goal of this research is to develop an integrated system dynamics framework for sustainable management of municipal water and wastewater systems. Canadian municipalities have traditionally relied on grants received from senior levels of government to finance construction of water supply and wastewater collection infrastructure. User fees for water and wastewater services were determined so as to recover only the operating expenditures with no allowance to recoup the capital costs of infrastructure. As the infrastructure assets started approaching the end of their service life, investments needed to rehabilitate these assets were deferred in the expectation of receiving further grants for this purpose. Hence, a significant backlog of deteriorated infrastructure has accumulated over the years. Recently enacted regulations require that all expenditures incurred on provision of water and wastewater services should ultimately be financed from user fee based revenues. Another piece of legislation provides for establishment of service performance standards. Urban water and wastewater systems involve interconnections among physical infrastructure, financial, and socio-political factors. Several interacting feedback loops are formed due to these interconnections and render the management of water and wastewater infrastructure as a complex, dynamic problem. Existing asset management tools in the literature are found inadequate to capture the influence of feedback loops. A novel system dynamics approach is used to develop a demonstration model for water and wastewater network management. Model results for a case study show significance of feedback loops for financial sustainability of the system. For example, user fees have to be substantially increased to achieve financial sustainability, especially when price elasticity of water demand is considered. A detailed causal loop diagram for management of wastewater collection networks is presented. The causal loop diagram lays out qualitative causal relationships among system components and identifies multiple interacting feedback loops. Based on this causal loop diagram, a system dynamics model comprised of a wastewater pipes sector, a finance sector, and a consumers sector, is developed. Policy levers are included in the model to facilitate formulation of different financing and rehabilitation strategies for the wastewater collection network. Financial and service performance indicators included in the model allow comparison of different financing and rehabilitation strategies. Data requirements for implementation of the model are discussed. The wastewater collection network model is implemented for a case study of a medium-sized Canadian municipality with a substantial backlog of deteriorated pipes. A methodology for parameterization of the model using existing data sources is presented. Simulation results indicate that different financing strategies ranging from no borrowing to full utilization of debt capacity can achieve similar total life-cycle costs but with significantly varying impacts for consumers in terms of service performance and financial burden. A detailed causal loop diagram for management of a watermain distribution network is employed to identify feedback loops. The causal loop diagram is then developed into a system dynamics model comprised of watermain pipes, financial, and consumer sectors. Data requirements for implementation of the model are discussed.