Ryan-Reid, E, Perrigo, R & Atkinson, S 2026, 'A risk-based approach to hydraulic modelling for the design of mine closure flood management structures', 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. 1-13, https://doi.org/10.36487/ACG_repo/2615_95
(https://papers.acg.uwa.edu.au/p/2615_95_Ryan-Reid/)
Abstract: Maintenance or reinstatement of surface water flows through the post-mining landscape is often required to sustain sensitive environmental and cultural heritage receptors over the long term. The design of flood management controls requires selection of an appropriate rainfall annual exceedance probability (AEP) event for hydraulic modelling.
In Western Australia, there is an absence of regulatory guidance or industry standard for the selection of the design AEP rainfall event, resulting in a range of AEP events being adopted for closure at different mines, often within the same catchment. Example design AEP events adopted for closure design range from the probable maximum flood (PMF) to the 1:1,000 AEP event, reflecting the high variability in interpretation of site-specific risk considerations by mining companies.
This paper proposes a risk-based approach for selecting design AEP rainfall events for hydraulic modelling, which is undertaken to inform surface water management design through the post-mining landscape. Key aspects of this approach include establishing the intended design life of the surface water control measures, evaluation of risk to downstream receptors, assessment of available materials required to construct controls as well as constructability and feasibility considerations. 
The paper also presents a structured risk-based framework for the development of a sustainable surface water strategy, including phases of modelling, iterative assessments and scenario modelling. These proposed approaches aim to provide improved consistency of approach and clarity for closure planners, hydrologists, regulators and other key stakeholders to understand the factors influencing the surface water closure strategy.