CSDMS 2018 annual meeting - Geoprocesses, geohazards

Modeling blocky hillslope evolution in layered landscapes

Rachel Glade
University of Colorado, Boulder, United States

Landscapes developed in rock layers of differing erodibility are common on Earth, as well as on other planets. Hillslopes carved into the soft rock are typically characterized by steep, linear-to-concave up slopes or “ramps” mantled with material derived from the resistant layers above, often in the form of large blocks. To better understand the role of sediment size in hillslope evolution, we developed a 1-D numerical model of a hogback. The hybrid continuum-discrete model uses a traditional continuum treatment of soil transport while allowing for discrete, rules-based motion of large blocks of rocks. Our results show that feedbacks between weathering and transport of the blocks and underlying soft rock can create relief over time and lead to the development of concave-up slope profiles in the absence of rilling processes. In addition, the model reaches a quasi-steady state in which the topographic form and length of the ramp remains constant through time. We use an analytic approach to explore the mechanisms by which our model self-organizes to this state, including adjustment of soil depth, erosion rates, and block velocities along the ramp. An agreement of analytic solutions with the model shows that we understand its behavior well, and can carefully explore implications for hillslope evolution in the field. Current work explores the interactions between blocky hillslopes and channels in a 2-D numerical model built in Landlab. Our models provide a framework for exploring the evolution of layered landscapes and pinpoint the processes for which we require a more thorough understanding to predict their evolution over time.

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Of interest for:
  • Terrestrial Working Group