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safety management action in the surveillance process is to verify that the motor does indeed rotate as intended during the inspection and testing process. The failure modes of the various components of the spillway gate module can then be derived by taking the compliment of the operational mode of the component. Thus, if the operational modes of the components (or higher levels of the system) are known, then the operational failure modes can be derived directly. The derivation of failure modes from operational modes is of crucial importance, because it contributes greatly to overcoming the problem of a failure modes analysis (of any type) not having the analytical power to reveal the modes. In Failure Modes and Effects Analysis (and its variants), the analysis depends heavily on the ability and expertise of the analyst for finding all necessary modes. [12] 3.2 OPERATIONAL MODES BASED OR FAILURE MODES BASED SURVEILLANCE? None of the above provides direct answers to the questions that motivated this paper: 1. To what extent should dam owners rely on risk assessment to guide their surveillance activities? And, 2. Which approach to risk assessment should they use and to what extent? But then, perhaps these are the wrong questions from the perspective of dam safety assurance, where the overriding objective is to demonstrate that the dam and its various subsystems, modules and components are functioning properly and are available to be brought into service as required. Of course, the definitions of what constitutes an “operational mode” and a “failure mode” are vitally important. It is a somewhat straightforward matter if failure modes are derived from operational modes, although it must be recognised that this derivation is not “cut and dried”, as the operational function may not be achieved exactly as intended. Rather than considering failure modes in dam surveillance as forming the basis of real-time dam safety assessment, we suggest that it is more appropriate to consider operational modes as the basis of surveillance for risk management and failure modes as being derived from the loss of the operational modes and from design knowledge. This also means that from a dam surveillance perspective, the effort should be focused on the performance attribute that can be determined in the most efficient and effective way. This said, visual (and now remote via drones etc.) inspections, monitoring and testing all target deviations from the expected performance state of the dam and it various sub-systems, one of which is the failed state (in principle there can be unexpected performance states that are not failed states). Thus, understanding of and focus on the operational modes of a dam, which can be assessed continually in time if necessary, thereby providing the capacity to capture functional and non- functional (failed) states all of which can be validated and verified objectively, provide the foundational basis of a robust dam safety assurance program. 1559