The landscapes that we live in are continually shaped by water. On geologic timescales, water-driven processes redistribute mass and energy across the surface of the Earth. On yearly to decadal timescales, they create natural hazards that threaten human life and infrastructure. My research seeks to develop a better mechanistic understanding of these surface processes, their connection to landscape form, and the threats that they pose. I utilize a variety of quantitative techniques to accomplish these goals, but my approach generally focuses on integrating numerical modeling with field and remote sensing data. Below, you will find a few examples of the types of problems that I have been focusing on recently.
Post-Wildfire Sediment Transport and Debris Flows
Recently burned watersheds experience large increases in runoff due to a lack of rainfall interception and fire-induced reductions in the infiltration capacity of the soil, making them prone to high rates of erosion and debris flows. I am interested in using numerical models, often in combination with high-resolution topographic datasets and field measurements, to better understand connections between wildfire-induced changes to soil properties, runoff generation, the effectiveness of different sediment transport mechanisms, and debris flow initiation. Results will help will lead to improved predictions of the magnitude of post-wildfire erosion and related hazards.
Check out a great video of a debris flood in the San Gabriel Mountains occuring several months after the 2016 Fish Fire! Along with colleagues from the USGS Landslide Hazards Group, we are continuing to study how the landscape recovers from the fire.
Recent Papers: McGuire et al. (2017); McGuire et al. (2016); Rengers et al. (2016); Kean et al. (2016)
Understanding how feedback among climate, vegetation cover, soil development, and sediment transport shape hillslopes is central to geomorphology. Slope aspect influences the amount of solar radiation received by a hillslope and can drive differences in moisture and energy balances that ultimately influence the hydrologic, ecologic, and geomorphic processes that shape hillslopes. Therefore, by examining variations in geomorphic processes across gradients in slope aspect, it is possible to isolate interactions between climate and hillslope morphology in a setting where non-climatic variables are relatively uniform. The development of asymmetry (e.g. differing slope gradient as function of aspect) on cinder cones, for example, can be used to examine connections between aspect-driven changes to microclimate and hillslope evolution over geologic time.
Recent Papers: Rasmussen et al. (2017); McGuire et al. (2014)
Shallow Landslides in the Colorado Front Range
A historic amount of rainfall fell on the Colorado Front Range during a five day period in September, 2013. More than 1100 debris flows were mobilized from shallow landslides during the storm, with more than 78% occurring on south-facing hillslopes. There are a number of potential explanations for this trend, including aspect-driven variations in soil thickness, soil hydraulic properties, apparent root cohesion, and rainfall interception by vegetation. Because the spatial extent of the rainfall extended over a vast elevation range (1800-4000 m) containing different ecological zones with distinct soil and vegetation properties, and because of the strong aspect-dependent response, this event created a natural experiment to study the impact of vegetation and soil properties on debris flow initiation.
Recent Papers: McGuire et al. (2016); Rengers et al. (2016)
I am generally interested in using landscape evolution modeling to quantitatively connect observed patterns in landscapes with the underlying processes responsible for their formation. For instance, even in rapidly evolving landscapes drainage network can become organized to have a parallel structure with a periodic spacing between channels. An example of this is alluvial terraces subject to rapid changes in base-level elevation. Understanding these patterns provides insight into the how sediment is transported over geologic timescales in different settings.
Recent Papers: McGuire et al. (2015); McGuire et al. (2014); McGuire et al. (2013); Pelletier et al. (2011)