Pirouz, B, Javadi Rudd, S & Seddon, KD 2026, 'Geomorphology of thickened tailings beaches: insights from field deposition and full-scale trials', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-13, https://doi.org/10.36487/ACG_repo/2655_61 (https://papers.acg.uwa.edu.au/p/2655_61_Pirouz/) Abstract: The tailings beach slope and profile are undoubtedly the most critical design parameters for thickened tailings schemes. The storage capacity, initial embankment and subsequent raise heights, water pond size and location, tailings storage facility (TSF) footprint and the long-term operational costs all depend on the actual achieved beach slope. Realistic and accurate beach slope prediction would not be possible without a full understanding of the mechanisms governing the formation and development of thickened tailings beaches. Observations from large-scale field deposition trials and full-scale TSFs across various mine sites have been used to develop a descriptive model that outlines the key processes and mechanisms involved in thickened tailings beach formation, their interactions, and their effects on the resulting overall beach slope. The model presented in this paper highlights the relative significance of sheet flow and self-formed channel flow in the formation and evolution of the beach. The model is set in the context of the overall picture of thickened tailings beach development over time, and describes different stages of beach formation, the development of a plunge pool, flow mechanisms from the plunge pool, sheet flow and formation of channel flow, the progressive extension of self-formed channels over time, flow behaviour at the downstream end of self-formed channels, the interaction between sheet flow and channel flow that form and expand the overall stack footprint and beach slope. Keywords: thickened tailings, beach slope, sheet flow, self-formed channel, plunge pool