Research

Research Summary:

My research in fluvial geomorphology unites modeling and field studies in the larger attempt by geomorphologists to understand the evolution of landscapes over geologic time.

Debris Flows and Landscape Interactions:

Simulations with a landscape model incorporating forest-geomorphic interactions in the Oregon Coast Range indicate that the removal of wood from mountain watersheds would likely result in at least doubling the average runout length of debris flows and increasing the maximum runout length by 400%. These results, part of the Coastal Landscape Analysis and Modeling Study (CLAMS), a collaboration including researchers from OSU's College of Forestry and the USDA Forest Service Pacific Northwest Research Station, suggest that timber harvest could have large consequences for both hazards and aquatic habitat by promoting extension of debris flow impacts into valleys and streams previously unaffected by such catastrophic processes.

The above work spawned studies of debris dams and their effects over geologic time and of where and of sediment storage in headwater valleys.

Questions for ongoing and future research include the following: (1) Can riparian buffers mitigate the effects of forest harvest on aquatic habitat? (2) Given the important role of wood in this system, what might the effects of climate change be? (3) What are the roles of debris flows and wood in the evolution of valley morphology over geologic time? (4) How do sediments deposited by debris flows fit into the sediment budgets of larger basins, e.g., what is the evacuation time distribution of sediments in valleys at the transition between mass-movement and fluvial processes?

Current Projects:

Application of the CHILD model to determine the probability of wood and sediment delivery to a critical reach: This study, funded by the National Council for Air and Stream Improvement (NCASI), will follow up on the above modeling study and examine the effects of forest practices on debris flows and sediment transport, particularly in fish-bearing streams.

Sediment Storage at the Transition Between Debris-Flow and Fluvial Processes: This study, funded by the National Science Foundation (Geomorphology and Land-use Dynamics, EAR-0545768), will use airborne laser-swath mapping (ALSM, aka LiDAR) to measure sediment volumes and radiocarbon dating to estimate evacuation time distributions for sediment stored in mountain stream valleys in the Oregon Coast Range. Results of a pilot study indicate that, while most sediment is evacuated within a few hundred years, some remains for millennia.

Evolution of Landscapes Dominated by Debris Flows: This study, funded by the National Science Foundation (Geomorphology and Land-use Dynamics, EAR-0643353), will use landscape evolution modeling, LiDAR, and field instrumentation and measurement to examine the processes responsible for steepland valley and longitudinal channel profile evolution in the Oregon Coast Range and the Italian Apennines.

shaded relief map of Hoffman Creek tributary colored by soil and deposit thickness

Animation of 3000-year simulation of forest growth, death by fire, storms, soil production and diffusion, landslides, debris flows, and fluvial sediment transport. In the animation and the image (left), the shaded relief map is colored according to soil and sediment thickness. Following debris flow events, thick deposits appear throughout the network. They seem to melt away as the wood constituent decays. Fluvial transport reworks the sediment. The results of this simulation were published in Lancaster et al. (2001).(Download zip-file of animation: zip-file)

River Meandering and Landscape Interactions:

An analysis of historical bank erosion rates of the Willamette River, Oregon, with a model of river meandering recently provided the first quantitative measurement of the erodibilities of different geologic units forming the river's banks. Specifically, we found that modern floodplain deposits are only 2-4 times more erodible than partially cemented sediments likely deposited during the last ice age. While artificial revetments were found to be ten times more resistant than the banks formed of ancient deposits, the lack of revetments on these naturally resistant banks suggests that landowners are actually comfortable with moderate rates of bank erosion such as might be accomplished by replacing revetments with natural vegetation. This research was conducted in collaboration with a project funded by the National Science Foundation's Biocomplexity Intitiative and including researchers in OSU's Departments of Bioengineering and Fisheries and Wildlife and UO's Department of Landscape Architecture.

My interest in channel migration and recent initiatives aimed at restoring the river by removing revetments led me to investigate the gravel migration leaves behind and specifically its effect on stream temperature.

Questions for ongoing and future research include the following: (1) What kinds and amounts of geomorphic change would likely result from removal of revetments? (2) Given that bar formation will likely accompany migration, what are the important hydrologic functions of those bars, especially with respect to the magnitude of hyporheic flow through them and associated cooling effects? (3) What are the mechanisms responsible for these functions? (4) How much and what kind of restoration might achieve cooling that would significantly improve water quality for salmonids?

Current Projects:

Heat Budget in the Hyporheic Zone of a Large, Gravel-Bed River: This pilot study, funded by the National Science Foundation (Hydrological Sciences, EAR-0538075) will use hydrologic and geophysical field techniques and hydrologic modeling to quantify the heat budget of a single gravel bar on the Willamette River, Oregon.

Modeling Meandering in the Landscape: An ongoing study seeks to find the sensitivities of valley morphology to bank and bed material properties with CHILD.

Predicting a Migration Corridor for the Missouri National Recreational River: This study is a collaboration with Robb Jacobson (USGS) and funded by the National Park Service. We will develop a model for predicting the migration of this relatively free-flowing, braided reach of the Missouri River in order to delineate a 100-year migration corridor. The first step will involve use of a calibrated meandering model. Subsequent steps (contingent on funding) will involve incorporation of braiding processes (e.g., bifurcation).

During my thesis work, I developed a new, simple, nonlinear model of river meandering; new analytical tools for identifying inherent length-scales of meandering on channel planforms and the average sinuosity at those length-scales; and used those new analytical tools to compare real meandering streams to those produced by my new model and the more physically-based model of Johannesson and Parker (1989) (Lancaster and Bras, 2002).

In the animation, the model stream flows from top to bottom. Stream coordinates are translated onto a grid. When the channel reaches a pixel, its elevation is set to that of the channel bed. Once the channel vacates a pixel, its elevation is left at the elevation of the channel bed at the bank. The rest of the "landscape" is uplifted at a uniform rate, so pixel elevation is proportional to time since channel occupation.

Pixels are colored by elevation: blue, tan, brown, light green, dark green from lowest to highest.

In the course of the meandering study, I looked at migration of the Ellis River, Maine, with aerial photos.

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stephen lancaster

Last modified: Tue Sep 19 17:36:18 PDT 2006

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Research

Research Summary:

Debris Flows and Landscape Interactions:

Current Projects:

River Meandering and Landscape Interactions:

Current Projects: