New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

Ephemeral channels that characterize a large part of New Mexico are a result of powerful, short-duration floods driven by storms largely during the monsoon season of July and August. Due to the nature of these floods and the channels through which they flow, large amounts of sediment are transported as bedload. These large bedload fluxes, combined with erratic storms and fast-rising flows, make quantifying bedload transport challenging and hazardous. Systems designed to directly monitor and sample bedload flux are effective, but only until samplers reach capacity. Additionally, any equipment placed in-channel is subject to damage and maintenance requirements resulting from bedload transport. Since bedload transport involves impacts of rolling, sliding, and saltating grains with the bed, seismic instruments have emerged in recent years as a potential means with which to study bedload transport without hazardous or expensive measurements. Although some work has been done to characterize seismic signals generated by bedload transport in perennial alpine streams, fine-grained gravel bed arroyos have remained largely unexplored.

To investigate seismic signals generated by floods in these arroyos, 5 broadband seismometers and 66 seismic nodes have been deployed at the Arroyo de los Pinos, an ephemeral watershed in central New Mexico, over multiple monsoon seasons encompassing numerous flash flood events. To isolate signals generated by bedload transport, outside sources of seismic noise including rainfall and human activity have been characterized. Additionally, seismic signals emanating from a hydraulic jump have been characterized for the purpose of ruling out its interference with bedload-generated signals. Ongoing research involving both seismic and hydrologic instruments has determined that with outside noise sources characterized and avoided, elevated seismic power at an appropriate range of frequencies is well explained by bedload transport rates. Findings suggest that seismic instruments may be an effective complement to traditional water and sediment-monitoring instruments when these instruments are deemed impractical, insufficient, too expensive, or too invasive to install.