What controls the shape of dunes in alluvial channels?

Abstract:

In big rivers, dunes have complex shapes with low-angle leesides and heights that are much smaller, with respect to flow depth, than previous research has indicated. Despite decades of research concerning alluvial bedforms, we still possess an incomplete understanding of how these complexities link to the controlling mechanisms of formation and dune kinematics, which are influenced by changes in flow dynamics and sediment transport. Recent work suggests several key processes may control the formation of low-angle and complex dune shapes: dune superimposition, sediment suspension, bedform three-dimensionality, and liquefied avalanche flows generated on the dune leeside. These various hypothesized controls require that we focus on the links between the conditions of formation and dune morphology across a wide range of laboratory flows, as well as shallow and deep natural flows. This is essential to fully understand the importance of these processes and their respective dominance in forming the complex shapes typical of natural alluvial dunes.

This talk focuses on investigating dune morphology in big rivers and shallow laboratory flows. This investigation allows the comparison and validation of these possible controlling processes. Then, identifies and discusses the conditions when one process may dominate in creating complex dune shapes. The talk highlights the balance between bedform superimposition and sediment suspension as controls on the formation of low-angle dunes. This balance was inferred through the investigation of dune morphology and kinematics, by using high spatio-temporal resolution bathymetric data obtained from big rivers and shallow laboratory flows.

With the additional time to discuss efforts towards increasing diversity, equity, and inclusion, I will speak about my work creating a Geoscience Camp for Middle School Girls and the Geoscience Learners Initiative. Through engaging with local communities, both are mechanisms towards introducing young BIPOC and Latinx students to Geoscience fields. I will also highlight my participation in GeoLatinas as a leader, mentor, and collaborator.