Gerard Salter Defends PhD: Controls on the Flux Distribution of Delta Networks

Ph.D candidate Gerard Salter successfully defended his Ph.D in Earth Sciences on August 30th, 2019. He is advised by Chris Paola of the St. Anthony Falls Laboratory and Department of Earth and Environmental Sciences at the University of Minnesota. 

Congratulations Dr. Salter!

Controls on the Flux Distribution of Delta Networks
Gerard Salter, PhD Candidate in Earth Sciences
Advisor: Chris Paola, Gibson Chair of Geoscience, CSE Distinguished Professor, and affiliated faculty at the St. Anthony Falls Laboratory

Distributary networks are the arteries of river deltas, controlling how fluxes such as water, sediment, and nutrients are delivered to different parts of the delta. Deltas are home to an estimated 500 million people worldwide. Understanding 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 drown. In this talk, I focus on the controls governing flux partitioning at delta bifurcations. Using numerical modeling and laboratory experiments, I argue that the interplay between bifurcation instability and downstream deposition leads to a rich spectrum of flux partitioning dynamics. This work shows that sediment bypass (the portion of supplied sediment that is passed offshore) is a key control on delta dynamics. Next, I show that coupling between upstream and downstream bifurcations in a network can lead to chaos. This implies that in the long-term, delta “weather” (precise configuration) may be unpredictable, although we could still hope to predict delta “climate” (statistical description). Finally, my overall conclusion is that the interplay between upstream and downstream controls results in complex flux partitioning dynamics.