Geomorphological Mapping and Erosion of Abandoned Tailings in the Hiendelaencina Mining District (Spain) from Aerial Imagery and LiDAR Data

Abstract

The Hiendelaencina district in Spain was the most important silver producer in Europe during 1844–1925. At the end of the 20th century, with mines having closed, some waste rock dumps were reprocessed, and the sludge from the flotation process was stored in two tailings ponds. When this activity ceased, the residues began to be eroded and disperse. In this study, the state of degradation of both deposits was evaluated using historical mapping and light detection and ranging (LiDAR) data, incorporated into a Geographic Information System. In the aerial images (1946–2018), mine tailings and their main erosive and sedimentary forms were mapped. Geoforms linked to hydrological (channels, gullies, alluvial cones), wind (eolian mantles), hydric–gravitational (colluvium) and anthropic (motorbike tracks) processes which move sludge into the surrounding areas were identified. A net loss of 8849 m3 of sludge, a release of 10.3 t of potentially polluting substances and a high erosion rate of 346 t/ha*year were calculated based on LiDAR data from 2009 and 2014. The ponds show a current high degree of erosion that could increase due to both human activity and the growing frequency of drought and torrential rain periods if stabilization measures are not undertaken.

Static Liquefaction Causes the Flow Failure of a Tailings Dam: A Case Study of El Descargador, Cartagena–La Unión Mining Region, SE Spain (October 1963)

“…This is because the tailings saturate quickly but dry very slowly due to their low permeability and suction [18]. The very low-resistivity values in the vertical profile below the lagoon are consistent with other work [11,18,[29][30][31][32][33][34][35].…”

“…ERI is a non-invasive geophysical method devoted to capture the resistivity distribution in the subsoil by multielectrode schemes [25,40,41]. The moisture content and the hydrochemistry of the pore fluids are probably the dominant factors controlling the bulk resistivity of sediments in many cases [28][29][30][31][32][33][34][35][36]. Mild changes in such parameters cause rough variations in resistivity, which can reach up to several magnitude orders.…”

“…Mild changes in such parameters cause rough variations in resistivity, which can reach up to several magnitude orders. Since tailings typically exhibit significant changes in moisture, hydrochemistry and textural features, ERI is postulated as a useful technique for tailings dam exploration [11,[29][30][31][32][33][34][35].…”

“…Therefore, ERI has strong capabilities to characterize the stratigraphy of the tailings dams, resistivity and the groundwater flow conditions [11,30]. A tailings dam should be considered as a complex multilayer aquifer system, in which there are different hydraulic relationships between the waters stored in the lagoons and the groundwater that flows through sedimentary layers of tailings [11,[28][29][30][31][32][33][34][35][36]. In addition, studies of ERT work on mine tailings dams that assess environmental risk and groundwater flow are relatively abundant [11,[28][29][30][31][32][33][34][35][36].…”

“…A tailings dam should be considered as a complex multilayer aquifer system, in which there are different hydraulic relationships between the waters stored in the lagoons and the groundwater that flows through sedimentary layers of tailings [11,[28][29][30][31][32][33][34][35][36]. In addition, studies of ERT work on mine tailings dams that assess environmental risk and groundwater flow are relatively abundant [11,[28][29][30][31][32][33][34][35][36]. However, combined ERT and geotechnical studies are more limited [18].…”