Current Research in EEPS Seminar – Gerard Salter – Department Earth Sciences, University of Minnesota
Dynamics of flux partitioning in delta bifurcations
Bifurcations are the gatekeepers of delta networks, controlling the distribution of fluxes such as water, sediment, and nutrients to different parts of the delta. Deltas are home to an estimated 500 million people worldwide. They are naturally low-lying, making them vulnerable to relative sea-level rise. Understanding of how fluxes are partitioned among the branches of delta networks could help us predict which parts of a delta will receive enough sediment for land-building to keep up with relative sea-level rise, versus which parts of a delta are likely to face inundation. In this talk, using numerical modeling and laboratory experiments, I argue that the interplay between bifurcation instability and downstream deposition leads to a rich spectrum of avulsion dynamics. Next, I demonstrate that angle asymmetry acts as an additional control on flux partitioning. Finally, I show that coupling between upstream and downstream bifurcations in a network leads to chaos. This implies that in the long-term, delta “weather” (precise configuration) is unpredictable, although we could still hope to predict delta “climate” (statistical description). I conclude by describing my proposed research at Rice, in which I will explore the feedbacks between delta networks and their floodplains, and quantify the implications for floodplain sequestration of carbon and contaminants.