PLT26 - Quantifying Hazard Potential in Dams: Integrating In-Situ Condition Analysis and Failure Mechanisms.

Abstract Description: In compliance with the South African National Water Act No 36 of 1998, dam owners are required to conduct dam safety evaluations on dams with a safety risk on a 5-year basis. The main purpose of these evaluations is to consider whether the safety norms pertaining to the design, construction, monitoring, operation, performance, and maintenance of the dam satisfy acceptable dam engineering practices. A critical deliverable for these assessments is the declaration of the hazard potential of the dam and whether its overall condition classifies it as a dam that with a safety risk. Practitioners in this instance consider several metrics to determine the appropriateness of the hazard rating assigned during the last registration of a dam as that which poses a safety risk. The most prevalent methodology considered for this purpose is dam breach assessment and flood inundation modelling, as a fundamental tool for risk-based dam safety analyses. This paper presents a comprehensive overview for quantifying the risk potential of particularly earth embankment dams based on the prevalent failure modes exhibited by the dam under consideration. To determine the latter, the design of the dam, in-situ condition and freeboard analysis are evaluated. A risk factor (low, medium and extreme) that quantifies the hazard potential as a function of both the impact within the inundation boundary and the potential failure mechanism is presented. Two case study dams in the Limpopo Province are presented to demonstrate the methodology. Findings from the study indicate that a more robust approach based on analysis should be followed to determine more site-specific risk metrics.