Aeolian sediment-trap data from the Colorado River corridor in Grand Canyon National Park, Arizona

SAMPLE COLLECTION: The data file contains sediment-mass data from 16 sites identified by their location with respect to river miles along the Colorado River through Grand Canyon National Park. In that location-naming convention, river miles refer to the distance downstream of Lees Ferry, Arizona (Gushue, 2019), and the designation Left or Right refers to the side of the river when viewed facing downstream. Exact site coordinates are confidential owing to their association with geoarchaeological studies. Samples at each study location were collected using passive Big Spring Number Eight (BSNE) samplers (wedge-shaped, metal traps; Fryrear, 1986) deployed in a vertical array in which four samplers were mounted on a single pole. Trap orifices were set at heights specified in the data files (within 1 meter of the ground surface), for most sites using a set of four samplers situated at 0.1, 0.4, 0.7, and 1.0 meters above the sand surface at the time of installation. Trap heights were adjusted during site visits if they differed substantially from the intended heights due to aeolian inflation or deflation of the ground surface. Each trap is equipped with a vane that turns the trap into the wind. The BSNE design is used widely in agricultural and geologic studies of windblown sediment, in part because its shape allows it to perform nearly isokinetically, causing minimal distortion of air flow at the sampling orifice (Stout and Fryrear, 1989; Nickling and Neuman, 1997; Zobeck and others, 2003). The sampling orifice measures 5 cm tall by 2 cm wide; air flow enters the trap through the orifice and exits through a 60-mesh screen in the upper surface of the trap. Sediment is retained in the lower half of the trap after falling through a wider (18-mesh) screen. Wind-tunnel studies (Goossens and others, 2000) indicate an efficiency range of 70 to 130 percent for BSNE sand traps for the wind velocities and sediment grain sizes encountered in Grand Canyon (typically fine to medium sand). Efficiency less than 100 percent indicates that air flow is directed away from the orifice, such that the trap undersamples windblown sediment, whereas efficiency greater than 100 percent indicates that air flow is directed into the trap, oversampling windblown sediment. An efficiency range of 70 to 130 percent was used in previous reports to estimate sand-transport values from these study sites (refer to reports linked to under Related External Resources tab in this data release page). The same previous reports (under Related External Resources) presented weather data collected from sites adjacent to the sand-trap locations with which this data release is concerned.

SEDIMENT MASS ANALYSIS: Sand traps were emptied and the sediment from each trap collected during maintenance visits days to months apart. Sediment was brought to the laboratory at the U.S. Geological Survey (USGS) Grand Canyon Monitoring and Research Center in Flagstaff, Arizona, to be weighed. Organic material was removed from the sediment by treating the samples with hydrogen peroxide. Samples were dried overnight in an oven at 80 degrees C, allowed to cool in a desiccant chamber, and weighed on a scale with precision to 0.0001 g.