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Geography Colloquium - Jose Constantine

Friday, March 15, 2019
12:20pm – 1:15pm

Storrs Campus
AUST 445

Jose Constantine Department of Geosciences Williams College

Tropical Insights into Meandering Rivers: From the Self-Deforming Rivers of the Amazon to the Frozen Rivers of Borneo

Meandering rivers abound the globe and have fascinated artists and scientists for centuries. Recent decades of research led to important progress in our ability to explain why straightened rivers end up returning back to their meandering selves. But much of this research was focused on how the individual forms of meanders could force water to dig out the sides of river channels. Although it is true that the curved form of meanders drive an erosive behavour in river flow, recent observations from across tropical river systems have revealed new insights into the ways that meandering rivers can evolve. The meandering rivers of the Amazon Basin provide perhaps the last opportunity to study undisturbed river systems, with satellite imagery revealing an important role of sand grains. Sediment eroded from the Andean Mountains ends up moving through and eventually depositing within many of the rivers draining the Amazon. These sediment deposits end up deforming the riverbeds of meanders, helping to drive the erosive potential of river flow. The paradox is that the more Andean sediment supplied to these rivers, the more sediment they end up excavating from their valley floors. On the other side of the globe, the meandering rivers of Borneo could not be more different in terms of their behavour. Although they looks incredibly similar to their Amazonian counterparts, Bornean rivers appear frozen in place, with some of the lowest migration rates reported in scientific literature. Their valley floors are empty of features we expect to see in meandering rivers, and their response to widespread deforestation has been surprising. Palm oil plantations are replacing ancient tropical forest at rates that are unrivaled, but Bornean rivers have only gradually responded. Migration rates have increased somewhat, and there is some evidence that the mechanisms driving riverbank erosion have changed. However, there is no doubt that the response of Bornean rivers has been muted. This talk will summarize these new research findings, placing them in context with our ever evolving theory explaining the origin and evolution of the most dynamic of riverscapes.

Contact:

Scott Stephenson [stephenson@uconn.edu]

Geography Department (primary), Center for Environmental Science and Engineering, College of Agriculture, Health and Natural Resources, Geosciences, UConn Master Calendar

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