Doctor of Philosophy
Civil and Environmental Engineering
Simonovic, Slobodan P.
Dam systems are arrangements of interacting components that store and convey water for beneficial purposes. Dam failures are associated with extreme consequences to human life, the environment and the economy. Existing techniques for dam safety analysis tend to focus on verifying system performance at the edge of the design envelope. In analyzing the events which occur within the design envelope, linear chain-of-events models are often used to analyze the potential outcomes for the system. These chain-of-events models require that combinations of conditions are identified at the outset of the analysis, which can be very cumbersome given the number of physically possible combinations. Additional complications arising from feedback behaviour and time are not easily overcome using existing tools. Recent work in the industry has begun to focus on systems approaches to the problem, especially stochastic simulation. Given current computational abilities, stochastic simulation may not be capable of analyzing combinations of events that have a low combined probability but potentially extreme consequences. This research focuses on developing and implementing a methodology that dynamically characterizes combinations of component operating states and their potential impacts on dam safety. Automated generation of scenarios is achieved through the use of a component operating states database that defines all possible combinations of component states (scenarios) using combinatorics. A Deterministic Monte Carlo simulation framework systematically characterizes each scenario through a number of iterations that vary adverse operating state timing, impacts and inflows. Component interactions and feedbacks are represented within the system dynamics simulation model. Simulation outcomes provide useful indicators for dam operators including conditional failure rates, times to failure, failure inflow thresholds, and reservoir level exceedance frequencies. Dynamic system response can be assessed directly from the simulation outcomes. The scenario results may be useful to dam owners in emergency decision-making to inform response timelines and to justify the allocation of resources. Results may also help inform the development of improved operating strategies or upgrade alternatives that can reduce the impacts of these extreme events. This work offers a significant improvement in the ability to systematically characterize the potential combinations of events and their consequences.
Summary for Lay Audience
This research presents a novel approach to define and characterize potential combinations of events that can impact the ability to safely manage water flow in dam systems. Dam systems consist of infrastructure whose primary purpose is to store and convey water for beneficial purposes, such as power production, water supply, flood control and recreation. The water barrier is the dam itself, and water passages may include gated or ungated spillway systems that release excess flows, diversions, tunnels or penstocks (pipelines) that convey water to power-generating turbines. Another key part of a dam system is the system operator(s). Operators can be a single person or an organization. In some cases the operation of the dam may be automated. Operators make decisions on how to adjust water flow through the dam based on available information, with the goal to safely and economically manage the reservoir. The failure of a dam can cause a major flood, potentially having catastrophic consequences to human life, the environment and the economy. One possible way in which a dam can fail is through the inadequate control of water flow. For example, should the outflow passages fail to function, inflows into the reservoir can cause the water level to rise to critical levels that may result in failure of the dam. This research focuses on the analysis of flow-control in dam systems. A dam system and the interactions amongst its components are modelled in detail and an exhaustive list of possible combinations of events is developed. Each of these combinations is simulated many times to characterize the potential outcomes that may occur. The simulation model calculates the water levels and flow releases as they change over time. Parameters were developed to provide some indication about the potential impacts of a scenario. The result is a systematic characterization of these unlikely, yet potentially hazardous, combinations of events that can affect the ability to safely operate a dam system. The information produced through this methodology may be useful in developing operating strategies and emergency response plans that could occur over the course of a dam’s lifetime.
King, Leanna M., "Using a systems approach to analyze the operational safety of dams" (2020). Electronic Thesis and Dissertation Repository. 6880.
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