E3S Web of Conferences 415, 05018 (2023)
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https://doi.org/10.1051/e3sconf/202341505018

Anthropogenic gravitational mass movements and the fluvial
geomorphological changes: the Vale (2019) and Samarco (2015)
tailing dam disasters, Brazil
Jefferson Picanço1,2*, Maria José Mesquita1, and Renato Eugenio de Lima2
1Institute of Geosciences, University of Campinas (UNICAMP), Department of Geology and Natural Resources (DGRN), Rua CarlosGomes, 250 CEP 13083-855, Campinas, SP. Brazil.
2Center for Scientific Support in Disasters (CENACID-UFPR)

Abstract. Major tailings dam failures have caused death, pain, and disruption to a community's activities.
These dam ruptures mobilize millions of tonnes of tailings, which move with gravity and can therefore becalled anthropogenic mass movements. A survey of the typology of the damage caused is a necessity toassess the damage caused, especially to riverside populations. This work describes the mass movements inthe 2015 Samarco/Mariana and 2019 Vale/Brumadinho tailing dam disasters. Mass movements have been
described as avalanches, high and low-energy debris flows, and mud flows. The regions where the tailings
dispersion was active were also verified, where it caused substantial changes in the landscape. On the otherhand, it has been verified in areas where this dispersion was passive, carried out only within the fluvial
dynamics. The Vale/Brumadinho disaster, which resulted in 270 deaths, was of tremendous energy anddestructive power, while the Samarco/Mariana disaster, which resulted in 19 deaths, was catastrophic overthousands of kilometers. A careful evaluation of these modifications is a first step toward mitigating theaffected territories and bringing social justice to the affected populations.

1 Introduction
The major disasters associated with ore tailings dam
failures have caused many losses in human lives,material damage, and a sizeable environmental liability[1], not to mention the pain and suffering of the people
who inhabit these territories [2]. These disasters occur
due to several causes 3, mainly dam failures due totorrential rains or problems in the massif or liquefaction
process [3]. In general, accidents with ore tailings dams
arise during economic crises, when the commodity
prices drop, and the exploration companies cut the ore
dam safety protocols [4]In Brazil, two devastating disasters have caused
uncountable death and endless mourning anddestruction. Both occurred at iron ore tailing dams in theIron Quadrangle region, near the Minas Gerais state
capital Belo Horizonte (Figure 1). Brazil is the second
iron producer in the world, with reserves of 34 billion
tonnages [5].
The first disaster occurred in the Fundão Dam, inthe Bento Rodrigues district, municipality of Mariana(Figure 1). It was operated by the company Samarco. It
caused 19 deaths and extreme environmental impacts in
Barra Longa municipality and other cities of the Rio
Doce basin, reaching the Atlantic Ocean in the city ofLinhares, 600 km away (Figure 1) [6,7]). The second
disaster occurred at Dam B1 of the Córrego do Feijão
mine in the municipality of Brumadinho, operated by

the mining company Vale. It was responsible for 270
deaths and significant social and environmental damage[8, 9].

Fig. 1. Main localities in the text related to the tailings dam
disasters of Vale (2019) at Brumadinho municipality andSamarco (2015) at Bento Rodrigues Village.

Even though these disasters are of anthropogenic origin,
there are many similarities with gravitational mass
movements, at least in the first moments when thepotential energy was high [10]). There are many
similarities to avalanches, debris flows, and mudflows,
where channel erosion is extreme, causing numerous* Corresponding author: jeffepi@unicamp.br© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0(https://creativecommons.org/licenses/by/4.0/).

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changes in river morphology. After losing strength,
these materials are passively transported along the river
channel as bottom sediments or suspended [11]. In thesestretches, the material can silt up the river and change
the dynamics of the channel. With the presence oftailings materials in the order of 106 m³, these changes
reach large scales. On the other hand, the characteristics
of each tailing material are very different from naturaldeposits, which depend on the mining and beneficiation
process and the obstacles that the material encountersalong the pathway.
The present work shows some of these aspects, theirsimilarities and differences, and the changes made along
the river channel during the failure of significant tailings
dam episodes in the 2015 Fundão tailings dam Samarco and 2019 Córrego Feijão Mine - Vale disasters.
Fig. 2. Initial flow path, near the village of Bento Rodrigues,at the confluence of the Santarém stream and the Gualacho do
Norte River. The blue bar shows the geomorphological dam of
the channel, and the arrows show the tailings path, bothbreaking the dam and remounting the Gualacho do Norte
River.

2 Anthropogenic flow characteristics
2.1 The 2015 Samarco/Mariana Disaster
The Fundão and the Santarém dam are in the Germano
mine complex, comprising numerous dams with sandysilty and silty-sandy tailings [12]. The dam was built in2005 by the upstream method from an earth dike.
According to the authors, the ore tailings dam presented
several structural problems in 2009, 2012, and 2014.
The Fundão mine disaster occurred at 3:42 pm on
5/Nov/2015 and involved the release of 32 million m³ oftailings [12]. The tailings overtop the Santarém dam andenters at Santarem stream talweg. The tailings spreadbeyond the small stream, destroyed the village of BentoRodrigues (Figure 2) and caused 19 deaths [13]. A
geomorphological trap in the mouth of the Santarem
stream over the Gualacho do Norte River blocked theflux. Most of the flux overcame the barrier andcontinued downstream, whereas the flux rose upstreamof the river (Figure 2). Afterward, the material continued
flowing down the Gualacho do Norte River until itreached the Carmo River and invaded part of BarraLonga city, 40 km from the ruptured dam. The marginal
and basal erosion slowed down as the flux lost strength.
At this point, the deposition rate was higher than theerosion rate, forming central sand bars at the channel ofthe Carmo River (Figure 3) [13]. The material flew
down from the Carmo River, reaching the Doce River.
Most of the material was retained in the hydroelectrical
Candonga dam (Figure 4). Around 22 million m³ oftailing were accumulated in the Santarém stream,
Gualacho do Norte, and Rio do Carmo rivers upstream
to Candonga dam, while 10 million m³ were drained
through the Doce river channel [12]. The fine-grain
fraction took only 17 days to pass Linhares city, in theEspírito Santo state, and reach the ocean, where it wasdispersed (Figure 1) [13].

Fig. 3. Carmo River above before the disaster and beyond
silted up after the passage of the flow, showing the channelbars formed by the tailings.

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fluid [10]. In these places, the more minor drainages,
such as the Ferro-Carvão stream in Brumadinho and theSantarém stream valley in Bento Rodrigues, werecompletely buried, with drainage avulsion and intense
basal undermining in their upper portions [10, 13]. In theFerro-Carvão stream, an avalanche and a flow of highenergy dense debris reached speeds of more than 90km/h [10] and devastated the downstream areas. This
material was entrained into the stream channel througha channeled debris flow. The regolith eroded by thebasal and lateral erosion was incorporated into thetailings.

Fig. 4. Candonga hydroelectric dam, on Doce River,completely silted up after the passage of the flow.

2.2 Córrego do Feijão Mine Disaster
The B1 dam at the Córrego do Feijão Mine was built
between 1974 and 1976 and was operated until
2015[14]. The tailings dam has had ten expansion works
during this period, reaching 720 m of crest length, 86 mheight, an area of 249.5 thousand m², and a volume of
11.7 million m³. The tailing comprised hematite andgoethite minerals containing quartz and kaolinite [8]. 'It
consisted of poorly graded silty sand with densities
between 4.02 and 5.11 [8]The failure occurred by liquefaction inside thetailings, resulting in a sudden rupture at 12:28 pm on
January 25, 2019 [8]. The material flew along the FerroCarvão stream until it was deposited in the Paraopeba
river, causing a sudden block [10]. The dam collapse led
to several types of gravitational movements, such asdebris avalanches, debris flows, and mudflows,covering 8.4 km in about 45 minutes. This disaster
caused 270 casualties, most of them in Vale facilities,
which were in the ore tailings path.
There is a relationship between energy and massmovement types in the tailings path (figure 5), depicting
four zones of destructive capacity from ZDC4 (thehighest) to ZDC1 (the lowest) [10]. At the beginning of
the rupture, the dam's driest material behaved as a debris
avalanche, with speeds of up to 100 km/h, measured inimages from security cameras [10]. Whereas the wet
tailing material behaved as high-energy debris flow,eroding the ground and destroying most of the mine
facilities in its path. The resulting wet materials consistof tailings and eroded soil mixture. In the lowerdeclivities, the material behaves like a low-energy
mudflow, deposited in the Paraopeba River andpassively dispersed by fluvial dynamics.

Fig. 5. Schematic visualization of the Córrego do Feijão dam1, ranging from a debris avalanche in the most proximal area
to low energy mudflow in the Paraopeba river [10]. After thefailure, a high-energy debris flow developed in the tailings,destroying the Vale Headquarters. The zones of destructivecapability (ZDCs) discussed in the text are indicated as ZDC1(medium or low destructive capability), ZDC2 (highdestructive capability), ZDC3 (very high destructivecapability), and ZDC4 (extreme destructive capability)

The tailings material from the Fundão Dam Disasterwas slightly thinner and in greater quantity, composedof silty-sandy and silty material with high fluidity.
Initially, this material caused basal undermining anderosion of the margins of the Santarém stream. Thetailings were often dammed and remounted up in small
streams when finding gorges and more funneled relieffeatures.
A thick regolith contributes significantly to materials
to the flux. Mudflows with Plasticity index (PI) valuesof more than 5% cult reach areas with slight declivity[15].

3 Discussion
The tailings dam failures damages are associatedwith the potential energy, the channel declivity andformat, and the presence or absence of regolith. The
regions of most significant damage were upstream,
where the material behaved like a dense, high-energy
fluid. Trees and regolith blocks floated in the denser

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The curves in the streams contribute to slowingdown the direction due to the higher frictional energy.
In downstream areas, the declivity and the material
behaved like a mudflow, with less energy being
deposited, blocking the Paraopeba River 40 minutes
after the dam rupture. In the Paraopeba River, thematerial flow was predominantly passive, governed by
the river's fluvial regime (11). The same behavior could
be attributed to the tailing's material downs at theCandonga Hydroelectric dam in the Doce River.
The extensive formations of sand bars in theChannels of Carmo River are not verified in theParaopeba River. The Carmo River had bars in the same
area before the disaster. After the disaster, the mostsignificant difference was the extensive silt up of thechannel. On the other hand, the Paraopeba river does nothave significant material to form bars in its channel.

4. M. Davies, T. Martin Mining market cycles andtailings dam incidents. In: 13th International
Conference on Tailings and Mine Waste, Banff,
AB. (2009)http://www.infomine.com/publications/docs/Davies
2009.pdf. Accessed July 27, 2019
5. Brazilian Mineral Summary, Iron, Nacional Mining
Agency (2018) https://www.gov.br/anm/ptbr/centrais-de-conteudo/publicacoes/serieestatisticas-e-economia-mineral/sumariomineral/pasta-sumario-brasileiro-mineral2018/ferro_sm_2018
6. M. C. Cordeiro, G. D. Garcia, A. M. Rocha, D. A.
Tschoeke, M. E. Campeão, L. R. Appolinario, A. C.
Soares, L. Leomil, A. Froes, L. Bahiense, C. E.
Rezende. Sci Total Environ 654,1209–1217 (2019)
7. G. W. Fernandes, F. F. Goulart, B. D. Ranieri, M.
S. Coelho, K. Dales, N. Boesche, M. Bustamante,
F. A. Carvalho, D. C. Carvalho, R. Dirzo, S.
Fernandes. Nat. Conserv. 14(2), 35–45 (2016)
8. P. K. Robertson, L. Melo, D. J. Wiliams, G. W.
Wilson. Report of the Expert Panel on theTechnical Causes of the Failure of Feijão Dam I.
December 12, 2019.
http://www.b1technicalinvestigation.com/pt/.
Accessed December 29, 2019
9. CPRM (SERVIÇO GEOLÓGICO DO BRASIL.
Monitoramento especial da bacia do rio
Paraopeba. Relatório 01:
https://www.cprm.gov.br/sace/conteudo/paraopeba/
RT_01_2019_PARAOPEBA.pdf. Accessed July29, 2019
10. R. E de Lima, J. L. Picanço, A. F., da Silva, & F.
A. Acordes. Land.,17(12), 2895-2906. (2020).
11. M. G. Macklin, P. A. Brewer, K. A. HudsonEdwards, G.Bird, T. J. Coulthard, I. A. Dennis, & J.
N. Turner. Geomorph. 79(3-4), 423-447, (2006)
12. N. R. Morgenstern, S. G. Vick, C. B. Viotti, B. D.
Watts. Report on the immediate causes of thefailure of the Fundão dam. Commissioned by BHP
Billiton Brasil Ltda., Vale S.A., and Samarco
Mineração S.A. (2016)
13. L. C. Mendes, M. F. Felippe. Rev. Geogr.-PPGEOUFJF, 6(4) (2016).
14. W. P. D. Silva, R. C. Gomes. Soils Rocks 36(1),37–53 (2013)
15. O. Hungr, F.S. Leroueil, L. Picarelli. Lands. 11(2),167–194 (2014)

4 Conclusions
The2015
Samarco/Marianaand2019
Vale/Brumadinho disasters show the occurrence ofgravitational mass movements of an anthropogenic
nature, with many similarities and differences between
them. When reaching water courses, the flow of thesematerials was very significant, on the order of 8.4 km in
the Corrego Ferro-Carvão in Brumadinho and more than
40 km in the case of the Gualacho Carmo and DoceRivers. The Vale/Brumadinho disaster had higher
energy, with avalanches and debris flows with great
destructive power. On the other hand, theSamarco/Mariana disaster had less energy but, with thelarge volume of spilled material, showed remarkable
fluidity and behaved like a high-density mudflow fortens of kilometers.
Major disasters involving mining tailings dam
failures in Brazil are still a disaster in the process. By
violently destroying the riverbanks and silting thechannels with tailings mud, the mining companies took
away the landscape and the memory of all the people
who inhabited their territory. In addition to deaths,
mourning, damage to the economy, and environmental
destruction, the destruction of riverbanks meant a
profound change in the lives of people who lived on
their banks, not just fishers and farmers. Therefore, aninventory of this destruction and the means to remedy it
is necessary so that the rivers can return to theirtraditional uses.

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