An anthropogenic flow type gravitational mass movement: the Corrego do Feijao tailings dam disaster, Brumadinho, Brazil

Tailing dam failures are most common worldwide that should be. The recent disasters of Fundao dam (2015) and Corrego do Feijao dam (2019) are among the worst of these disasters in terms of human, social, environmental, and economic costs. The Corrego do Feijao dam collapsed at 12:28 p.m. on Jan. 25, 2019, killing 272 people, with 11 still missing. The dam had 76 m high, with a crest of 720 m. It stored 12 Mt iron ore tailings, mostly composed by sand to silt-sized hematite, goethite, and quartz. Its sudden collapse provoked (a) a rotational slide which destroyed the complete dam structure; (b) a debris avalanche; (c) a debris flow; and (d) a mudflow, composed by a mixture between tailings material and the soil. The debris flow velocity is estimated to be at least 90 km/h in the first 500 m downstream of the dam. CENACID team subdivided into the affected area into zones of destructive capability (ZDC), from ZDC1 to ZDC4, in order of increasing destructivity. The ZDC4 comprises both a debris avalanche and an extremely high-energy debris flow, where basal and lateral erosion predominates. In the ZCD3, the material is transitioning from low-energy debris flow to mud flow because of the increase of soil mixed with the tailings. The ZDC2 comprises high-energy mudflow, with predominance of deposition over erosion. The ZDC1 is a low-energy mudflow that is deposited in the Paraopeba River. In the river channel, the finer sediment has been carried downwards either as a bedload or as a suspension load. The qualitative preliminary analysis of this anthropogenic gravitational mass movement enhances our understanding of this type of disaster. This initial quantitative analysis is important to improve the risk analysis in tailings dam failure events.