Numerical methods for fluvial landscapes

Tracking rivers in landscape evolution models

A simulation of a vertically incising, meandering river.

Sinuous channels abound on planetary surfaces, for example in the form of meandering rivers and delta channels. Such channels often migrate laterally and interact with banks of different strengths due to differences in lithology and sediment grain size. This interplay between the channel and its surroundings shapes many environments, but efforts to explore this interaction with numerical models have been hampered by the evolving, curvilinear geometry of channel boundaries. I developed a novel, vector-based method for land surface- and subsurface-material tracking that overcomes the numerical artifacts inherent in commonly used, grid-based techniques. The vector-based framework provides new opportunities for exploring the long-term co-evolution of sinuous channels and surrounding landscapes.

Mapping channel networks

A visualization of channel network geometry for the Platte River, Nebraska.

Quantitative measures of channel network geometry inform diverse applications in hydrology, sediment transport, ecology, hazard assessment, and stratigraphic prediction. These uses require a clear, objectively defined channel network. Automated techniques for extracting channels from topography are well developed for convergent channel networks and identify flow paths based on land-surface gradients. These techniques—even when they allow multiple flow paths—do not consistently capture channel networks with frequent bifurcations (e.g., in rivers, deltas, and alluvial fans). In practice, channels are commonly mapped using observed inundation extent, and I generalized this approach using a simplified flow model. A case study for the Platte River, Nebraska, revealed that several key descriptors of channel network geometry reach extremal values at a corresponding reference discharge that can be used to compare the geometry of multithread rivers. This approach extends channel network extraction from topography to the full spectrum of channel patterns, with the potential for comparing diverse channel patterns at scales from laboratory experiments to natural landscapes.