Rogan, A, Kim, V & Rastogi, S 2026, 'A risk-based framework for hydrologic design decision-making under non-stationary climate conditions', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-19, https://doi.org/10.36487/ACG_repo/2615_141
(https://papers.acg.uwa.edu.au/p/2615_141_Rogan/)
Abstract: The annual exceedance probability (AEP) of a surface water event has traditionally been used to convey the design aim for a hydrologic assessment. This conventional method has begun to lose its utility due to the introduction of non-stationary aspects, such as climate change. For example, to assess a design flow for a closure surface water infrastructure element, a climate scenario (shared socio-economic pathway) and a prediction year may need to be selected to determine a design flow. Further, there have been significant updates to the prediction approaches over the past decade, such as global warming predictions [e.g. updated Coupled Model Intercomparison Project Phase 6 (CIMP6) predictions] and the hydrologic design approaches (e.g. Version 4.2 of Australian Rainfall and Runoff), with more updates likely to occur over the coming decades. Additionally, other non-stationary aspects, like evolution of a closure landform (e.g. pre- and post-pit lake formation), can provide varying risks in different phases of the mine closure period that require differing mitigations.
The implication of this is that the use of AEP can become less meaningful as a means of communicating likelihood and the associated level of design risk control. This paper presents a framework to aid decision-making in the selection of surface water design events within a more traditional risk-based process, represented by the likelihoods and consequences. By using common recommendations for design life and AEP for a range of surface water infrastructures, the equivalent likelihood can be estimated, allowing a design screening chart to be developed that is linked to typical industry risk acceptance levels. This is then further linked to economic, environmental and loss of life consequence metrics to support determination of a consequence category, and then an associated design likelihood band for hydrologic design event screening.
An illustrative example is presented of the risk-based framework for a conceptualised mine void peripheral catchment in Victoria.