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

We present six years of data collection from the Arroyo de los Pinos, an ephemeral channel in central New Mexico. The Pinos is home to a state-of-the-art sampling station with a large array of sensors to measure hydrologic and sediment data during flash floods. Hydrologic related data include water depth, velocity, and discharge, rainfall rates, and upstream flow patterns. Sediment related data include bed- and suspended load transport rates and grain size distributions. Some sediment related data was also collected using surrogate equipment, instruments that collect data related to the transport of sediment using acoustic and vibration methods while significantly reducing the cost of operation.

Instantaneous bedload fluxes were as high as 12 kg s^-1 m^-1. Suspended sediment concentration was also high, as large as 100,000 mg L^-1, with evidence of clockwise hysteresis. Flow events last 3 hours and typical peak flow discharges were 14 m³ s^-1. The Pinos averages 3 – 5 flow events per year but some years (two of the six years thus far) record no flow. These values depict a highly active system with significant sediment transport. Through physical, direct measurements and an extended record using surrogate instruments we estimate that the Pinos transports 0 – 3,400,000 kg of sediment as bedload per year. Total mass transported in suspension is 8x higher, on average.

Our vision for the Arroyo de los Pinos monitoring station is to provide the highest quality direct, physical measurements alongside novel ways to measure sediment in transport. By selecting the Pinos as our observatory, we aim to advance sediment monitoring in rivers with a wide range of grain sizes in transport. Further understanding of sediment transport processes will aid regional decision makers that manage sediment in arid lands.