Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Earth Surface
Arid and semi-arid landscapes, including deserts, grasslands, and rangelands, comprise roughly 40% of Earth’s land surface, and are inhabited 2.2 billion people – nearly one-third of the global population. Hillslopes in arid landscapes are often characterized by rocky slopes below vertical cliffs, which are formed by relatively weak erodible rock capped by a stronger rock more resistant to erosion. The absence of vegetation on these dry hillslopes means that there are no tree or plant roots to stabilize the soil.
These hillslopes are very sensitive to changes in climate, such as increasing rainfall intensity, which causes a rapid runoff response and results in flash flooding, along with mud or debris flows, with devastating consequences for communities in these regions. Despite the global importance of drylands, we do not have a clear understanding of how these landscapes evolve in response to a changing climate.
In a new study, Shmilovitz et al. [2024] demonstrate exactly how dryland hillslopes respond to the intensity of rain storms, and how the shape of hillslope escarpments changes over time as a result of erosion and movement of rock debris down slope. The authors developed a mathematical model and conducted model experiments to test the effects of the number of rainstorms, frequency of rainstorms, and intensity of rainstorms on the erosion rate, movement of rock debris, and the resulting shape of an escarpment. Results from these experiments show that repeated short and intense rainstorms lead to higher erosion rates that enhance the horizontal retreat of the cliffs. The runoff generated by these storms can effectively transport rock debris down slope and undermine the vertical cliffs.
While previous research on landscape evolution in drylands has considered only long-term average rainfall rates, this new work shows that it is essential to simulate the effects of individual rainstorms to accurately predict how these landscapes will evolve, especially under changing climatic regimes.
Citation: Shmilovitz, Y., Tucker, G. E., Rossi, M. W., Morin, E., Armon, M., Pederson, J., et al. (2024). Impacts of rainstorm intensity and temporal pattern on caprock cliff persistence and hillslope morphology in drylands. Journal of Geophysical Research: Earth Surface, 129, e2023JF007478. https://doi.org/10.1029/2023JF007478
—Marisa Repasch, Associate Editor, JGR: Earth Surface