10Be reproducibility in the Santa Monica Mountains, California, USA: A longitudinal study in a scorched and soaked landscape

Authors

• Eric W. Portenga, Eastern Michigan University
• Kirk F. Townsend, University of Michigan - Ann Arbor
• Lee B. Corbett, University of Vermont
• Paul R. Bierman, University of Vermont
• Marc W. Caffee, Purdue University
• Colin O'Neill*, Eastern Michigan University
• Samantha Skora*, Eastern Michigan University

Document Type

Article

Publication Date

2025

Department/School

Geography and Geology

Publication Title

Geomorphology

Abstract

Since the 1990s, geomorphologists have utilized measurements of cosmogenic ¹⁰Be concentrations from stream sand to quantify erosion rates across landscapes. Few studies employ ¹⁰Be sample collection strategies that specifically test the spatial and temporal reproducibility of ¹⁰Be data. Here, we examine the reproducibility of ¹⁰Be measurements after the 2018 Woolsey Fire, the largest historical wildfire to burn through the Santa Monica Mountains, California, USA. The fire was followed by 13 atmospheric rivers and other high rainfall storms in the subsequent wet season. We present 60 new ¹⁰Be concentration measurements, comprising 3–6 temporal replicate samples of stream sand (and for some samples including different grain-sizes) from seven basins across the Santa Monica Mountains, collected between 2016 and 2021, five of which burned in the fire. We use these data to test whether ¹⁰Be concentrations measured from samples collected after the fire differ from those collected before the fire. Such data test inferences about soil mixing and changing erosion dynamics, specifically depth, in sampled basins. We find that most ¹⁰Be concentrations reproduced within 2σ measurement uncertainties. Only three post-fire ¹⁰Be concentrations from burned basins deviate more than 2σ from pre-fire values. We suggest that ¹⁰Be concentrations of temporal replicates in this study reproduce well because most post-fire erosion in this landscape was shallow. Where deep erosion or erosion at higher elevations occurred, the effects of these processes on ¹⁰Be measurements appear to be transient and would be missed unless sampling occurs closely following a rainstorm or wildfire. Our findings show that ¹⁰Be concentrations generally reproduce well in this steep, tectonically active and rapidly eroding landscape with a Mediterranean climate, despite the presence of wildfires and heavy rainfall events caused by atmospheric rivers.

Link to Published Version

DOI: 10.1016/j.geomorph.2025.109713

Recommended Citation

Portenga, E. W., Townsend, K. F., Corbett, L. B., Bierman, P. R., Caffee, M. W., Bogoski, C., O’Neill, C., & Skora, S. (2025). 10Be reproducibility in the Santa Monica Mountains, California, USA: A longitudinal study in a scorched and soaked landscape. Geomorphology, 478, 109713. https://doi.org/10.1016/j.geomorph.2025.109713