2020 CSDMS meeting-028
Variability in regolith characteristics as a proxy to model the seasonal evolution of the Draix CZO badland catchments.
The morphology of the Earth’s surface is continuously evolving under multiple factors (tectonics, climatic, etc). As the interface between the lithosphere and the atmosphere, the critical zone provides the prime record of these changes and can be directly monitored. Understanding the physical processes that control temporal changes is important to quantify and predict them.
In this context, we aim to constrain the effect of physical rock weathering on erosion rates and their variation over seasonal cycles. We focus our studies on marly badland catchments in the southeast of France. The Draix-Bléone Critical Zone Observatory allowed data collection and experiments over the last 35 years and represents an ideal environment for this project (Mathys et al, 2005). The marly badland of Draix are subject strong weathering and erosion processes, caused by a variety of physical processes, resulting in the formation of a spatially and temporally variable regolith layer. Significant production of regolith is observed during the winter and rapid washing of slopes during the spring and early summer (Bechet et al., 2016). Based on regolith characteristics from the field we will build a 1D model of the dynamic of the regolith. Characterizing the seasonal variability and climatic dependence of regolith production is a prerequisite to predict yearly variations in sediment flux and its evolution under changing climate conditions.
We sampled the upper part of the regolith in the Draix catchment, in four targeted places, to obtain grain size distributions and water contents. Characteristics of the detrital cover that affect the rate of weathering. High-resolution photogrammetry records will enable comparing surface changes (roughness, thickness, grain size) over the seasons. Furthermore, we cleaned a 1m² surface on a ridge of regolith to monitor weathering processes and estimate regolith production during each season. We aim to repeat this exercise at the end of each season; the resulting difference in thickness removed should represent the new regolith formed
Two years of field campaigns are scheduled. We will use our field observations on the temporal variation of regolith characteristics to inform a 1D model of regolith dynamics. In parallel, the second goal of the project will be to spatialize and implement the latter description into a landscape evolution model based on Landlab (Hobleyet al., 2017) to simulate the effects of regolith dynamics on catchment-scale erosion. The development of this new module will be helpful to follow critical-zone evolution in different soil cover contexts.
Bechet, J., J. Duc, A. Loye, M. Jaboyedoff, N. Mathys, J.-P. Malet, S. Klotz, C. Le Bouteiller, B. Rudaz, and J. Travelletti (2016), Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs), Earth Surf. Dynam., 4, 781–798, doi: 10.5194/esurf-4-781-2016.
Hobley, D. E. J., J. M. Adams, S. S. Nudurupati, E. W. H. Hutton, N. M. Gasparini, E. Istanbulluoglu, and G. E. Tucker (2017), Creative computing with Landlab: an open-source toolkit for building, coupling, and exploring two-dimensional numerical models of Earth-surface dynamics, Earth Surf. Dynam., 5, 21–46, doi: 10.5194/esurf-5-21-2017.Mathys, N., S. Klotz, M. Esteves, L. Descroix, and J. M. Lapetite (2005), Runoff and erosion in the Black Marls of the French Alps: Observations and measurements at the plot scale, Catena, 63, 261–281, doi: 10.1016/j.catena.2005.06.010.