Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Water Resources Research
Understanding the connections between topography, soils, bedrock lithology, and hydrologic function of catchments is critical for improving our models for future environmental change and deciphering the topographic imprints of past climates. Previous landscape evolution modeling (LEM) studies that explored the co-evolution of catchment topography and runoff generation processes found remarkable controls of subsurface runoff generation on hillslope length and drainage density (see figure above). However, experimental evidence supporting these model-based findings has been lacking.
In their new study, Litwin and Harman [2024] select watersheds with similar humid climatology and tectonic histories but with contrasting lithologies, and combine measurements of precipitation, streamflow, and ground saturation. They find that hillslope lengths were shorter and the landscape experienced more widespread and frequent saturation at their site with low subsurface flow transmissivity. These observations suggest a dynamic link between topography, lithology and variable source area for runoff generation over storm time scales.
The authors further explore if these lithology-controlled hydrologic response dynamics have an imprint on hillslope morphology over landscape evolution time scales. To investigate, they use their LEM, coupling subsurface hydrology with geomorphic transport laws. Parameterized for each site’s conditions, model experiments underscore the role of subsurface controls, suggesting that hydrologic characterization of subsurface flow differences are necessary to explain the observed differences in runoff and topography.
Citation: Litwin, D. G., & Harman, C. J. (2024). Evidence of subsurface control on the coevolution of hillslope morphology and runoff generation. Water Resources Research, 60, e2024WR037301. https://doi.org/10.1029/2024WR037301
—Erkan Istanbulluoglu, Associate Editor, Water Resources Research
