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ORIGINAL RESEARCH

Estimating the Fine Soil Fraction of Desert Pavements Using Ground Penetrating Radar

^a Desert Research Institute, Nevada System of Higher Education, 755 E. Flamingo Rd., Las Vegas, NV 89119
^b Desert Research Institute, Nevada System of Higher Education, 2215 Raggio Parkway, Reno, NV 89512
^* Corresponding author (Darren{at}dri.edu)

Received 29 July 2005.

A reconnaissance tool that can estimate the clay content and saturated hydraulic conductivity (K_s) of well-developed desert pavements has immediate applications for researchers and practitioners who work in arid environments. We examined the use of surface-based ground penetrating radar (GPR) to rapidly approximate these properties on six, 100-m-long transects for two different aged (100 000 vs. 4000 yr) desert pavement surfaces. We determined early-time amplitudes from GPR transects, ground electrical conductivity, hydraulic properties, clay content, water content, and soil salinity at regular intervals along each transect. Both surfaces were low in water content and salinity; however, the older pavement contained substantial amounts of silt and clay in the surficial soil horizon. Using multivariate linear regression, which included GPR amplitude and a nominal measure of soil structure ascertained by visual field inspection, we show significant correlations between measured and predicted values of both silt plus clay content (r = 0.84, P < 0.0001) and K_s (r = 0.73, P < 0.0001) for the older surface. No significant correlations were found on the younger surface. This is probably due to the low concentrations of clays in the young soil. Including the metric of soil structure improved the predictive capabilities on the older surface. The GPR method provides higher spatial resolution than electromagnetic measurements. The results suggest that, at this location, the approach is not influenced by heterogeneities in lower soil horizons. The method can be used for reconnaissance surveys as a means of estimating the clay content, and in some cases K_s, of surficial soils on certain well-developed desert pavements.

Abbreviations: EC, electrical conductivity • EM, electromagnetic • GPR, ground penetrating radar • TDR, time domain reflectometry