2023 CSDMS meeting-102
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The Impact of Streambed Mobilization on Fine Sediment and Organic Carbon Hysteresis in Mountain Rivers
Nicole Hucke,
(She/Her),University of Idaho Boise Idaho, United States. nicoleuthalia@gmail.com
Elowyn Yager, University of Idaho Boise Idaho, United States. eyager@uidaho.edu
Andrew Tranmer, University of Idaho Boise Idaho, United States. andyt@uidaho.edu
Rachel Watts, Utah State University Logan Utah, United States. miss.rachelwatts@gmail.com
Janice Brahney, Utah State University Logan Utah, United States. janice.brahney@usu.edu
Joel Rowland, Los Alamos National Laboratory Los Alamos New Mexico, United States. jrowland@lanl.gov
George Perkins, Los Alamos National Laboratory Los Alamos New Mexico, United States. gperkins@lanl.gov
Rose Harris, Los Alamos National Laboratory Los Alamos New Mexico, United States. rosejhar@lanl.gov
Rivers exhibit high temporal variability in their constituent concentrations, which can result in distinct hysteresis patterns of suspended sediment (SS), particulate organic carbon (POC), and dissolved organic carbon (DOC) during various high-flow events. In mountain rivers, this variability may be controlled by the mobilization of streambed sediment, which is enriched with organic carbon and other nutrients and can be evaluated by the entrainment of the armor layer, a group of coarser particles that act as a protective layer to finer sediment. In this study, we test if resulting hysteresis patterns could be controlled by the extent to which the armor layer was mobilized by analyzing POC, DOC and SS patterns during monsoon-driven flow events in two river reaches at the Valles Caldera National Preserve, New Mexico. We collected continuous water samples over numerous flood hydrographs using automated ISCO samplers while also monitoring flow depth, turbidity, and fluorescent dissolved organic matter (fDOM) using YSI EXO2 sondes. Turbidity and fDOM were included because they can be used as proxies for SS and DOC, respectively. To quantify armor mobilization, we deployed tracer particles of different sizes and mapped their location before and after each event. We found that constituent hysteresis changes between clockwise and counterclockwise for different flow events, each with their own streambed mobilization characteristics. Opposite hysteresis occurred for DOC and fDOM than for POC, SS, and turbidity. Additionally, there were poor correlations between DOC and SS, while POC and SS were found to be well correlated. Our results imply that DOC hysteresis might not be related to the release of fines from the streambed, whereas POC is. These findings suggest that the temporal variability of SS and POC can be partly understood by the mobilization and suspension of fine sediment not only seasonally, but also over individual high-flow events. We show how the mobilization of the armor layer can be an important contributor to this variability.
