Degree
Doctor of Philosophy (PhD)
Department
Geography and Anthropology
Document Type
Dissertation
Abstract
Artisanal and small-scale gold mining (ASGM) has expanded rapidly across the Madre de Dios (MDD) region of the southwestern Amazon, intensifying erosion, altering river floodplain connectivity, and elevating the transport sediments. While recent studies have documented large-scale landscape disturbance, the underlying hydrodynamic and sediment transport processes remain poorly quantified. This dissertation advances a process-based understanding of mining impacted tropical rivers through an integrated framework combining remote sensing, field measurements, and three-dimensional modeling, organized into three chapters.
Chapter 1 investigates the spatiotemporal variability of suspended sediment concentration (SSC) along a 320 km corridor of the MDD River using harmonized Landsat-Sentinel imagery and complementary field campaigns. Results show that mining impacted reaches, especially between the Colorado and Inambari tributaries, experience large daily-to weekly-scale SSC pulses driven by short hydrologic events and mining activity. Analysis of floodplain oxbow lakes reveals altered connectivity, indicating inflow of mining derived sediment through reactivated drained paths. Vertical profiles show that cohesive fines dominate SSC, emphasizing their importance in downstream mercury transport.
Chapter 2 examines hydrogeomorphological dynamics at a braided-meandering confluence, where the highly disturbed Colorado River joins the MDD. Satellite time series and hydrodynamic measurements reveal that the confluence transitions among three recurring configurations: single-thread, multi-thread, and fully inundated driven by hydrologic stage and mouth bar submerge. Each configuration modifies flow deflection, mixing interface, and sediment routing, creating a broader and more variable interaction zone than typical single-thread confluences. These findings highlight the sensitivity of confluence hydrodynamics to upstream morphological alteration caused by mining.
Chapter 3 employs three-dimensional Reynolds-Averaged Navier-Stokes modeling to quantify how momentum ratio, tributary thread activation, and seasonal bathymetry govern mixing interface behavior. Simulations demonstrate that braided inflow widens and fragments the shear layer, shifts the dominance of secondary flow, and alters downstream recovery patterns. Comparisons between wet- and dry-season bathymetry show how seasonal morphology amplifies or constrains tributary influence.
Together, these chapters provide a multi-scale assessment of how ASGM reshapes sediment transport, confluence dynamics, and SSC pathways in the MDD basin. The findings improve understanding the mercury bearing sediment potential mobility and support more effective monitoring and management of Amazonian river systems.
Date
3-7-2026
Recommended Citation
Guerrero, Leo, "Morphodynamic Response of Meandering Rivers Along Aggressive Gold Mining and Deforestation Activities in the Amazonian Rainforest" (2026). LSU Doctoral Dissertations. 7004.
https://repository.lsu.edu/gradschool_dissertations/7004
Committee Chair
Konsoer, Kory M.
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1