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Palu Colostate 0053A 15347.Pdf DISSERTATION FLOODWAVE AND SEDIMENT TRANSPORT ASSESSMENT ALONG THE DOCE RIVER AFTER THE FUNDÃO TAILINGS DAM COLLAPSE (BRAZIL) Submitted by Marcos Cristiano Palu Department of Civil and Environmental Engineering In partial fulfillment of the requirements For the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Spring 2019 Doctoral Committee: Advisor: Pierre Julien Christopher Thornton Robert Ettema Sara Rathburn Copyright by Marcos Cristiano Palu 2019 All Rights Reserved ABSTRACT FLOODWAVE AND SEDIMENT TRANSPORT ASSESSMENT ALONG THE DOCE RIVER AFTER THE FUNDÃO TAILINGS DAM COLLAPSE (BRAZIL) The collapse of the Fundão Tailings Dam in November 2015 spilled 32 Mm3 of mine waste, causing a substantial socio-economic and environmental damage within the Doce River basin in Brazil. Approximately 90% of the spilled volume deposited over 118 km downstream of Fundão Dam on floodplains. Nevertheless, high concentration of suspended sediment (≈ 400,000 mg/l) reached the Doce River, where the floodwave and sediment wave traveled at different velocities over 550 km to the Atlantic Ocean. The one-dimensional advection- dispersion equation with sediment settling was solved to determine, for tailing sediment, the longitudinal dispersion coefficient and the settling rate along the river and in the reservoirs (Baguari, Aimorés and Mascarenhas). The values found for the longitudinal dispersion coefficient ranged from 30 to 120 m2/s, which are consistent with those in the literature. Moreover, the sediment settling rate along the whole extension of the river corresponds to the deposition of finer material stored in Fundão Dam, which particle size ranged from 1.1 to 2 . The simulation of the flashy hydrographs on the Doce River after the dam collapse was initially carried out with several widespread one-dimensional flood routing methods, including the Modified Puls, Muskingum-Cunge, Preissmann, Crank Nicolson and QUICKEST. All of these methods presented unsatisfactory results, with prediction errors in peak discharge up to 44%, and differences in timing to peak up to 5 hours. ii A new and more accurate one-dimensional flood routing approach was then used, solving the full dynamic equation into an equivalent diffusive wave format and reformulating the hydraulic diffusion coefficient in terms of the Froude number and floodwave celerity. The numerical solution to this new approach was implemented using Crank Nicolson and QUICKEST schemes. The error in predicted peak discharge along the Doce River was reduced to 2%, and the maximum difference found in time to peak was about 1 hour. Regarding sediment transport, a comprehensive one-dimensional numerical model is developed, coupling the new floodwave propagation algorithm with the numerical solution for advective sediment transport and settling. One of the main features of this model is the ability to simulate the propagation of the floodwave and sediment through the entire Doce River extension with or without reservoirs. A sensitivity analysis showed that a hypothetical decrease in water temperature from 30°C to 5°C would have resulted in a concentration 13 times higher at the outlet. In addition, without the presence of hydropower reservoirs on the Doce River, the sediment concentration at the basin outlet would have been 70,000 mg/l instead of the observed 1,600 mg/l. Finally, a simplified numerical model based on the Doce River measurements can simulate the hypothetical collapse of 56 tailings dams in the Doce River basin to estimate the potential impact on the water supply for the towns along the river. Those simulation results show that tailings dams located in the Piracicaba basin, a Doce River sub-basin, have the highest potential to adversely impact the water supply of the downstream towns due the volume stored and proximity with populated towns. Ultimately, the collapse of the biggest dams in this sub-basin could affect approximately 1,000,000 people for several days. iii ACKNOWLEDGEMENTS I believe in God and I believe in Jesus Christ. I thank God for giving me life, strength, courage, faith, peace, perseverance and especially for surrounding me with amazing people. My goal is to help and support others, doing this perhaps I can reflect at least a spark of the love, gentleness and goodness of Jesus Christ, who has a perfect and inspiring life. I would like to thank Dr Pierre Julien for his priceless assistance in my studies and also for his constant enthusiasm, good mood and his friendship. I am grateful with my committee members: Dr. Robert Ettema, Dr. Christopher Thornton, and Dr. Sara Rathburn for their valuable contribution for my research. I also thank Linda Hinshaw for always being willing to help me. I would like to thank CNPq (National Council for Scientific and Technological Development - Brazil) for the financial support and for given me the wonderful opportunity to study in U.S. I am also thankful for all friends I made along this academic journey. I am grateful to the Rising Stars team: Chun-Yao Yang, Jai Hong Lee, Weimin Li, Woochul Kang, Neil Andika, Susan Cundiff, Sydney Doidge, Kristin LaForge, José Anderson do Nascimento Batista and Hwa Young Kim. I really appreciated their fellowship and contribution given during the seminars. Thanks also to Prof. Ernesto Sagás for helping me a lot when I just arrived in U.S. Thanks for Randy and Jan Babcock, Steve and Edie Eckles, Tim and Lorna Green, Mel and Bonnie Crane, John and Susan Morse, and all the members of International Student Incorporated - Fort Collins for giving outstanding assistance to international students like me. iv I also really appreciate the constant support and friendship of Wade and Carol, Cameron and Shanni Pacheco and all our friends of Christian Challenge - Fort Collins. I am also thankful for Pastor Bill and Priscila Prater, Mr. Bill Prater (in memoriam), Rev. Kimberly Salico-Diehl, John and Diana Finley, Mr. Lee and LauraLee and all the Carter’s family, Don and Fran Lambert, Joe and Sandy Martinez, Jeff and Sandy Lindberg and all our friends of American Baptist Church, especially for receiving us like members of their family. I am grateful for the support of all our family in Brazil, specially my parents José Carlos Palu and Maria Ilda Palu, my aunt Divanir Pallu and my parents-in-law Carlos Alfredo Kock and Luiza Kiyoko Fujita Kock. I am thankful for their patience and understanding during our absence. We missed you so much! Finally, my deepest thank to my amazing and dedicated wife Susan. I am very grateful for her smile, for her help every day, unceasing support, encouragement and steadfast love. I love you so much! v DEDICATION To Susan, my beloved wife vi TABLE OF CONTENTS ABSTRACT ................................................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................................ iv DEDICATION ............................................................................................................................... vi LIST OF TABLES .......................................................................................................................... x LIST OF FIGURES ..................................................................................................................... xii LIST OF SYMBOLS ................................................................................................................... xvii 1. INTRODUCTION ................................................................................................................ 1 1.1 The Fundão Dam Collapse ................................................................................................ 1 1.2 Data Availability .................................................................................................................. 3 1.3 Problem Statement and Opportunity .................................................................................. 4 1.4 Research Objectives .......................................................................................................... 4 2. LITERATURE REVIEW ...................................................................................................... 6 2.1 Tailings Dam Failure .......................................................................................................... 6 2.2 Tailings Dams in Brazil ....................................................................................................... 8 2.3 Modeling of Tailings Dam Failures ................................................................................... 12 2.4 Steady Flow in Channels ................................................................................................. 15 2.5 Unsteady Flow in Channels ............................................................................................. 16 2.5.1 Governing Equations .................................................................................................... 16 2.5.2 Full Dynamic Wave ....................................................................................................... 18 2.5.3 Diffusive Wave Approximation ...................................................................................... 19 2.5.4 Numerical Methods ....................................................................................................... 21 2.6 Flood Routing in Reservoirs ............................................................................................
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