From Peaks to Prairie: Two Natural Experiments in Decadal Landscape Evolution

Numerical models of landscape evolution play a vital role in geomorphology, but there remains a pressing need to test these models against field data. We are developing two case studies for model-data comparison testing. The two case studies are sites of rapid, decadal landscape change.

The decadal scale is particularly important because:

it is a critical time scale for societal adaptation to rapid environmental change,
it is short enough to take advantage of historical records, and
models of longer-term landscape dynamics should be consistent with shorter-term behavior.

The study pairs two very different environments: a low-relief, semi-arid, soft-rock setting dominated by rapid gully erosion and scarp retreat, and a steep, montane, forested, crystalline-rock setting responding to a 1996 wildfire. The first site, located on the high plains of eastern Colorado, provides a unique opportunity to reconstruct erosion rates and channel growth patterns over a 70-year period. The second site, in the Colorado Front Range, contains an extraordinarily rich 14-year database of post-fire geomorphic response, thanks to intensive monitoring efforts by the U.S. Geological Survey.

The project relies on a variety of methods, including OSL dating, LiDAR DEM analysis (both airborne and terrestrial), and numerical modeling. Modern hydrology and geomorphology are documented with a network of rain gauges and flow sensors, combined with biennial tripod-laser scans to measure rates of channel-head retreat (estimated at ~0.5m/yr). The two data sets are used to test a physically based numerical model of landscape evolution using a Monte Carlo calibration method.

References

Rengers, F.K., McGuire, L.A., Ebel, B.A., & Tucker, G.E. (2018) The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood. Geomorphology, v. 309, p. 121-130, doi:10.1016/j.geomorph.2018.01.003.

Ebel, B.A., Rengers, F.K., Tucker, G. E. (2016) Observed and simulated hydrologic response for a first-order catchment during extreme rainfall three years after wildfire disturbance. Water Resources Research, v. 52, doi: 10.1002/2016WR019110.

Rengers, F.K., Lunacek, M., and Tucker, G.E. (2016) Application of an Evolutionary Algorithm for Parameter Optimization in a Gully Erosion Model. Environmental Modelling and Software, v. 80, p. 297-305.

Rengers, F.K., Tucker, G.E., and Mahan, S. (2016) Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA. Earth Surface Processes and Landforms, doi:10.1002/esp.3929.

Rengers, F.K., Tucker, G.E., Moody, J.A., and Ebel, B. (2016) Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar. Journal of Geophysical Research, v. 121, no. 3, p. 588-608.

Ebel, B., Rengers, F.K., and Tucker, G.E. (2015) Aspect-Dependent Soil Saturation and Insight Into Debris-Flow Initiation During Extreme Rainfall in the Colorado Front Range. Geology, v. 43, no. 8, p. 659-662.

Rengers, F.K., Tucker, G.E. (2015) The evolution of gully headcut morphology: a case study using terrestrial laser scanning and hydrological monitoring. Earth Surface Processes and Landforms, v. 40, no. 10, doi: 10.1002/esp.3721.

Rengers, F.K., and Tucker, G.E. (2014) Analysis and modeling of gully headcut dynamics, North American High Plains. Journal of Geophysical Research, v. 119, p. 983-1003, doi:10.1002/2013JF002962.