Research (last update Dec. 2006) Earth Surface Processes Laboratory University of Oregon

On-going projects:

Quantifying hillslope sediment transport using high-resolution topographic data (~1 m spacing) generated via airborne laser altimetry: Oregon Coast Range.

Click HERE to watch 2006 Geological Society of America talk on hillslope evolution models ...click on "Recorded Presentation"

Hillslope morphology in many soil-mantled lanscapes is consistent with erosion by a nonlinear sediment transport model. This model, which addresses soil creep and shallow landsliding, helps to explain the common observation that hillslopes are convex near the crest and become increasingly planar downslope.  We are using the model to predict patterns of sediment yield and constrain the spatial variation of rock uplift in mountainous landscapes.

Documenting patterns of paleo-landslide style and deformation history using statistical analysis of airborne laser altimetry data: New Zealand and Northern California. Hillslopes in most mountainous landscapes are prone to large bedrock landslides. It is difficult to constrain whether pre-historic episodes of slope instability reflect seismic activity, wet climatic periods, increased rates of channel incision, or other mechanisms. Detailed morphologic mapping of paleo-landslides using airborne lidar data reveals a rich suite of surface forms that can be quantified using various statistical analyses. Most generally, recent failures exhibit fresh scarps and deformation features that become increasingly subdued with time. By calibrating our statistical analyses with field-based data constraining landslide age, we hope to generate maps illustrating the timing and style of slope failure across a 300 km2 drainage basin on the North Island of New Zealand. We are proposing to collect additional ALSM data in slide-prone landscapes including: Taiwan and Northern California.  Collaborative project with: Jim McKean (USFS, Boise).

Quantifying biological controls on sediment production and landscape evolution: New Zealand and Eastern Washington. Recent evidence suggests that bioturbation may play a dominant role in the progressive downslope movement of soil on hillslopes.  Because climate change has caused the vegetation assemblage in most hilly and mountainous landscapes to change systematically during the Late Quaternary, rates and mechanisms of sediment transport that drive landscape evolution are likely to have varied significantly.  Thus, the morphology of most landscapes reflects a rich history of forcing by tectonic and climatic processes acting on different temporal and spatial scales. Working with paleo-ecologists and soil scientists, we have gathered preliminary soil and tracer data that allows us to quantify changes in the rate of sediment production through the Late Pleistocene/Holocene transition.  At our study sites in New Zealand and Eastern Washington, we plan to further constrain how ecology regulates surface processes and explore implications for carbon transport and sequestration. Collaborative project with: Cathy Whitlock (U Oregon), Peter Almond (Lincoln Univ, NZ), Alan Busacca (Wash St. Univ), Greg Retallack (U Oregon).

Post-fire erosional response: Oregon Coast Range. Fire fundamentally alters landscape function. Fires often trigger a suite of geomorphic processes that transmit high sediment yields to nearby streams, degrading aquatic habitat and endangering human life.  Preliminary data in the Oregon Coast Range suggest transport by dry ravel dominates geomorphic response to the extent that the soil mantle is preferentially stripped revealing wide swaths of bedrock. Using ALSM data, we plan to develop predictive models for mapping the location and magnitude of sediment delivery following fire events.  In addition, we will use our models to reconcile millennial-scale fluctuations in sediment delivery with long-term fire frequency records documented from lake cores. These studies will enable us to quantitatively link modern process rates with fluctuations revealed in sedimentary deposits. 

Topographic relief limited by the initiation of large landslides: Oregon Coast Range. In the Oregon Coast Range, the location of ancient deep-seated landslides reflects structural and lithologic variation.  Although these inactive landslides possess the potential to: dramatically transform the morphology of landscapes, dam streams, degrade aquatic habitat, and endanger human life, their initiation mechanisms are often poorly constrained.  Quantification of their topographic signature allows us to map their spatial extent, identify structural controls, and predict their influence on landscape evolution. Our preliminary results indicate that topographic relief decreases systematically with increasing landslide density across our 13,000 km2 study area, reflecting regional facies trends in the underlying Eocene sedimentary rocks.

Laboratory simulation of hillslope processes: soil creep and landsliding. Laboratory studies are useful because erosional processes in natural landscapes are often inherently stochastic and difficult to measure.  In our experimental hillslope of granular material, sediment flux varies nonlinearly with hillslope gradient (consistent with the sediment transport model discussed above). Recent experiments have focused on addressing the grain-scale dynamics of unconsolidated sediments subject to disturbances such as freeze-thaw cycles, biogenic activity, or rainsplash.  Experimental profiles of granular displacement are well represented by a model based on rate process theory, wherein energy barriers (neighboring particles) must be overcome in order for grains to dilate and shear downslope.