Reconstructing the Spill Propagation of the Aznalcóllar Mine Disaster

Abstract The mine pond failure of Los Frailes (Aznalcóllar, Spain) was one of the most catastrophic mining-related disasters worldwide. Despite having been analysed from different disciplines, there have been only two attempts to simulate the propagation of the spill. In both cases, the spill was reconstructed using poor or incorrect topographical data, assuming a spilled hydrograph at the breaking point, and considering the fluid as water. In this research, new pre-failure topographical data were obtained combining field data with remote sensing techniques. These data were used to estimate the spilled hydrograph at the breaking point utilising a two-dimensional hydrodynamic numerical tool. Finally, due to the nature of the spilled fluid, two different attempts of reconstructing the spill propagation process of the Aznalcóllar mine disaster were performed. First, the fluid was considered as water with a suspended sediment load (26–660 g/L), i.e. assuming Newtonian fluid flow. Then the fluid was assumed to be mud-like (non-Newtonian fluid flow). These new simulations revealed that using a Newtonian fluid model, such as water with or without sediment, produced the best results in matching observed and simulated data. The non-Newtonian approach (muds) performed poorly. This suggests the spill behaved more like a concentrated sediment-laden flow than a mud-like one, possibly due to changes in fluid behaviour caused by the mine tailings in the pond after the failure.