Operational Safety of Dams and Reservoirs

Using system dynamics simulation for assessment of hydropower system safety

“…A small group of researchers have noted the following shortcomings associated with traditional risk assessment approaches in the dams industry and other industries [ Regan , ; Hartford et al ., ; King et al ., ]. The focus of traditional risk analysis tends to be on extreme events at the edge of the design envelope in terms of structural loads and inflows, while failures may occur well within the design envelope due to a combination of events which individually may not be uncommon [ Komey et al ., ; Hartford et al ., ] Selection of events and failure modes, as well as assigning probabilities to events can be a very subjective process due to the lack of data relating to dam failures and the variety of infrastructure components and other contributing factors involved in each incident [ Hartford and Baecher , ; Leveson , ] Events are often assumed to be completely independent of one another, despite the fact that common cause events are possible [ Putcha and Patev , ; Leveson , ; Komey et al ., ] Traditional analysis techniques such as fault trees and event trees often assume a linear progression of events, ignoring component interactions that can lead to nonlinear system behavior [ Regan , ; Leveson , ; Thomas , ] Systems are decomposed into more manageable subsystems for analysis and the interactions between them are completely ignored or simplified [ Regan , ; Leveson , ; Thomas , ] Traditional risk assessment tends to focus on the generation of singular values representing the probability of event occurrence and the consequence, when in reality probabilities are subjective and consequences are dynamic as the level of reduced performance can vary in time before the system recovers fully [ Leveson , ; Simonovic , ; Simonovic and Arunkumar , ]. …”

“…In an effort to address the aforementioned shortcomings, researchers in the dams industry have pointed to a systems approach [ Regan , ; Komey , ; Komey et al ., ; Hartford et al ., ; King et al ., ] along the lines of what is implemented in the nuclear and aerospace industries as well [ Leveson , ; Song , ; Thomas , ]. One of the major techniques that can be used in the analysis of systems is simulation, which involves a “what if” assessment of the various inputs to a system where outputs are determined in response to a particular set of inputs.…”

“…Hartford et al . [] suggest that traditional methods of dam safety focus on extreme earthquakes, erosion, and flood events but are not equipped to deal with flow control failures (operational failures) that occur well within the system's design envelope. Regan [] and Baecher et al .…”

“…The research of Regan [] and Hartford et al . [] advocate for the consideration of surface water flow‐control dams as systems and using the systems approach for assessment of dam safety risk. Regan [] and Hartford et al .…”

“…Regan [] and Hartford et al . [] point to control systems theory as a potential path forward for the development of a new tool for risk assessment of engineering infrastructure systems. Control systems theory is an interdisciplinary approach that involves the use of feedback to determine how systems behave in response to inputs and as a result of system structure [ Leveson , ].…”