Laser scanner technology in the assessment of mining tailings surface changes and rehabilitation interventions after the Fundão dam rupture, Brazil

In this work, we evaluated the changes that occurred by the deposition of the tailings, and the consequences after the implementation of rehabilitation procedures, in a stretch of the Gualaxo do Norte River, Brazil. The deposition occurred after the largest environmental disaster in the history of Brazil, the rupture of the Fundão dam, which dumped tons of ore tailings into the environment, producing several losses in the Doce River Basin. We carried out three surveys with laser scanner in the area: the first with airborne laser scanner in 2011, before the dam collapse; and two with terrestrial laser scanner after the disaster, in 2016 and 2018. The cloud points were aligned and evaluated regarding their positional accuracy using Global Navigation Satellite System control points. The changes in sediment volume as well as the material gains or losses among the periods were assessed according to differences in the coordinate Z. The siltation affected both the Gualaxo do Norte channel and the river terraces, with the study area suffering a deposition of almost 40 thousand m 3 of sediments. It was also possible to identify zones where the deposition of sediments predominated over removal/erosion, with 68% of the study area in 2016 recording accumulation of tailing layers in relation to the pre-rupture situation. In 2018, the deposition zones corresponded to almost 80% of the study area (in relation to the situation in 2016), and the most material accumulated was associated with topsoil deposition through rehabilitation interventions. Laser scanner technology proved to be promising to estimate the volume of tailings and identify areas with accretion or removal of sediments, being a great tool to direct environmental recovery initiatives in the Fundão dam most affected areas.