Research

AZ Sunset

A common theme throughout my work is that I develop mathematical and probability theory that describes sediment transport processes and their consequences. I’ve worked on a number of different problems listed below.

A complete and updated C.V. can be found here:
C.V.

Topographic Roughness

Topo Roughness

A) Recent and (B) old tree throw pit-mound couplets. Two slope maps (C) and (D) illustrate topographic roughness created by tree throw.

In soil- and sediment-mantled settings, topographic roughness is created by relatively large stochastic geomorphic processes and is removed by more chronic processes. For example, tree throw is a natural ecogeomorphic disturbance to forests that creates characteristic pit-mound couplets that then degrade through time. Recent work fully develops this idea and uses high resolution topographic data to extract meaningful information about tree throw rates and probabilities. I’ve also extended this idea to other geomorphic processes and settings to include shrub sediment mounds in semi-arid settings, alluvial fans and floodplains that contain abandoned channels by avulsion, and impact craters. As we continue to collect more and higher resolution topographic data (e.g. USGS 3D Elevation Program), work like this will provide meaningful ways to interpret emerging data sets.

Nonlocal Transport

Doane 2018

Figure from Doane et al., 2018 comparing different hillslope sediment transport models.

Nonlocal transport are a relatively new class of models that have recently gained some attention. They differ from more classic, local models in that the sediment flux at a position, x, is a function of conditions around x, weighted by the distance away. The weighting is done b the probability function of particle travel distance which describes the likelihood that a particle travels at least past position x. CLassic, local models only rely on positions at x. So, in steeplands, where particles travel long distances local models do not accurately represent the process. I’ve done work that develops, refines, and explores nonlocal models and the physics of particle motion on surfaces.

Channel Networks and Sediment Yield

Figure from Doane et al., (2021) showing a rilled hillslope in southern Arizona.

Rill networks resemble much larger river networks and represent a relatively rapid sediment transport pathway on hillslopes. I’ve done work that develops a statistical representation of rill networks on hillslopes and the sediment yields that are expected from them. This work contributes towards a better understanding of the statistical moments of watershed shapes and sizes as a whole and explains a long-standing observation of sediment yields on rilled slopes.

Particle Mixing on Hillslopes

Particles on soil-mantled hillslopes take tortuous pathways as they move from bedrock towards the surface. Understanding the statistics of these motions is central to intperpreting natural tracers (e.g. 10Be, OSL) that researchers often use to back out rates of sediment transpport, uplift, or weathering. I’ve contributed towards work that develops theory and numerical simulations of particle motion and how the statistics influence natural tracers.