Paraná River Project - Background: Introduction

Living with the river Downstream view of the Paraná River

Project Introduction

The drainage basins of the World’s ten largest rivers amount to 17% of the global continental drainage area and deliver ~33% of the sediment load transported into the oceans. The way this vast sediment load moves through km-wide rivers is hugely important in determining flooding, bank failure, infrastructure collapse and ultimately creates the deposits that host some of the most lucrative mineral and hydrocarbon reserves. Despite the global importance of these rivers, our present knowledge-base relating to the morphology, dynamics and sedimentology of large rivers is wholly inadequate. A central weakness relates to how evidence derived from small rivers has been applied uncritically to rivers many orders of magnitude larger. We have good theoretical reason to question this transfer, since force balance considerations suggest a dependence on width-depth ratio that does not scale linearly with flow discharge. Furthermore, evidence is now emerging that the dominant processes and deposits of large rivers may be fundamentally different to currently accepted wisdom.

It is therefore clear that a major re-evaluation of how the World’s largest rivers operate is long overdue. This requires two major efforts. The first needs to quantify the morphodynamics and hydrodynamics of large rivers in order to identify the dominant processes and controls on channel evolution. The second needs to assess the implications of these findings for how we interpret the sedimentary record of large rivers. Up until very recently, it has been impossible to obtain representative high-resolution measurements in large rivers of either bed topography, flow structure and sediment transport or bar subsurface sedimentology. This proposal will use new technological advances in Multi-Beam Echo Sounding (MBES) and Ground Penetrating Radar (GPR) to obtain the World’s first comprehensive database on channel dynamics, bar deposition and alluvial architecture in large braided rivers. This will be combined with development and application of innovative numerical modelling methods (both Computational Fluid Dynamics (CFD) and Reduced-Complexity (RC) approaches). In combination, these data and models will provide new quantitative understanding of the form and functioning of the World’s largest rivers and will allow us to evaluate existing, and develop new, interpretations of their alluvial architecture.