A risk-based approach to managing wave-induced foreshore erosion in a pit lake

Authors: Bicknell, P; Thomson, M Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2615_112

Cite As:
Bicknell, P & Thomson, M 2026, 'A risk-based approach to managing wave-induced foreshore erosion in a pit lake', 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_112



Abstract:
Pit lakes are a possible post-mining land use for open cut coal mine voids, but their large fetch and deep water can generate locally driven wind-waves that erode the foreshore and threaten shoreline stability. Because pit lake batters and embankments are typically steep and highly modified, wave-induced erosion can create hazards during filling and in the post-filling operational phase, including progressive foreshore retreat, batter instability, and risks to shoreline assets and intended end uses. Erosion risk and treatment needs can vary substantially around the lake perimeter and through time as water levels rise and shoreline exposure changes, yet few established methods exist to quantify these hazards in a pit lake setting or to sequence mitigation efficiently. This work adapts numerical wave-modelling methods used routinely in coastal hazard assessments to large pit lakes. We implement the SWAN wave model in Delft3D to compute random, short-crested wind-generated waves using local wind climate and site-specific bathymetry and shoreline conditions, allowing wave climate to be resolved across the full foreshore perimeter and translated into spatially explicit erosion hazard indicators. Model outputs are integrated with a tailored, risk-based framework to identify erosion-prone sections of foreshore and define when and where erosion control measures are required across filling and post-filling phases. Mitigation options considered include armouring and bank protection, regrading bank angles, and strategic vegetation establishment to dampen wave energy, enabling targeted treatment rather than blanket over-engineering. The paper presents insights from applying this approach to pit lake projects in the Latrobe Valley, Victoria, demonstrating how coastal-grade wave modelling can provide a defensible basis for erosion risk management and closure design in large post-mining lakes.

Keywords: pit lake, wave modelling, foreshore erosion, mitigation, risk

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