Entrainment and Transport of Sand and Tailings along the Paraopeba River, after the Collapse of a Tailings Dam, Minas Gerais, Brazil

A Warren Distinguished Lecture with
Marcelo H. Garcia, PhD, NAE

ABSTRACT
In this presentation, Marcelo Garcia discusses some of the tools needed to assess the spatial-temporal evolution of tailings discharged into a river following a dam breach. As global demand for minerals increases, accidental releases of mine tailings into rivers are likely to persist, oftentimes generating large pulses of dense granular material that interact with ambient sediment and alter river hydraulics, sediment transport, and bed aggradation. To better predict the evolution of sand–tailings mixtures, we derived a density-based active-layer formulation for mass conservation (Exner equation) that uses sediment density as a surrogate tracer for iron tailings. This formulation was implemented in a 1D hydraulic and sediment transport model developed for the Paraopeba River in Minas Gerais, Brazil, which was impacted by a tailings dam collapse in January 2019. Model results show that tailings continuously mix with ambient sand and become trapped in the substrate, particularly upstream of hydraulic structures, whose backwater effects extend for a few kilometers. The second part of the talk focuses on tailings entrainment into suspension—the dominant transport mode in the Paraopeba River—and evaluates whether near-bed concentrations (Ca), could be predicted using existing formulations for sediment entrainment rates (Es) under equilibrium conditions. Laboratory experiments performed in an annular flume indicate that Ca can be reproduced reasonably well with existing equations when tailings are treated as well-sorted material, but poorly-sorted materials require additional dimensionless parameters representing relative bed roughness and viscous-sublayer effects to obtain reasonable predictions of sediment entrainment into suspension.

SPEAKER
Marcelo Garcia holds the M.T. Geoffrey Yeh Endowed Chair in Civil Engineering and is Director of the Ven Te Chow Hydrosystems Laboratory at the University of Illinois at Urbana-Champaign. Before UIUC, Garcia was a Research Fellow at St. Anthony Falls Hydraulic Laboratory and completed his graduate studies in Civil Engineering (MSCE’85, PhD’89) at the University of Minnesota. His undergraduate education in Water Resources Engineering took place at Universidad Nacional de Litoral in Santa Fe, Argentina. Garcia served as Editor-in-Chief of the International Journal of Hydraulic Research (IAHR) as well as the Manual of Engineering Practice No 110 "Sedimentation Engineering," published by ASCE. Garcia has worked with more than one hundred graduate students, including 45 PhD candidates, 65 M.S. students and several post-doctoral research associates. Four of his doctoral graduate students have received the International Lorenz G. Straub Award for most meritorious PhD dissertation in hydraulics and related fields. His honors include IAHR’s Arthur Thomas Ippen Award and M.S. Yalin Lifetime Achievement Award, as well as ASCE’s Walter Huber Research Prize, Hilgard Hydraulics Prize (twice), Hunter Rouse Award, Wesley Horner Award and the Hans Albert Einstein Award in Sedimentation Engineering. Co-shared the Chandler-Misener Award for most notable paper published in Journal of Great Lakes Research, International Great Lakes Association. Garcia is a Fellow of the American Geophysical Union (AGU), a Fellow of EWRI, a Distinguished Member of ASCE, and an Honorary Member of IAHR. Garcia was also awarded an Honorary Doctorate by the National University of Cordoba, Argentina. Garcia was co-leader for the Sedimentation Studies Task Working Group for the St. Clair River International Great Lakes Commission (Canada-USA) and was a member of the International Scientific Committee to reduce the risk of flooding in Florence, Italy. Garcia serves on the Board of Consultants for the Miami Conservancy District (MCD) in Dayton, Ohio, and on several international boards. Marcelo Garcia is a Member of the US National Academy of Engineering and a Corresponding Member of the National Academy of Engineering of Argentina.