Roughness measurements of soil surfaces by acoustic backscatter

The measurement of the roughness of soil surfaces on centimeter scales is important to modeling local soil erodibility. An acoustic backscatter technique was examined for its ability to quantify the roughness of porous soil on centimeter scales. Acoustic backscatter offers the possibility of an inexpensive, mobile, and rapid means of estimating statistical properties of soil surfaces. Four soil plots were constructed with varying amounts of roughness. Surface roughness of the four soil plots was measured with the acoustic backscatter technique and a laser microreliefmeter. The roughness power spectra for the surface plots were obtained from surface profiles measured by the laser microreliefmeter and by the acoustic backscatter technique. Statistical values of the RMS (root mean square) height and correlation length of surface roughness for each plot were calculated from the acoustic backscatter power spectra and laser microreliefmeter power spectra and compared. Agreement between the two techniques for estimating roughness statistics was shown to be good (<13% difference) when an adequate amount of data points were used to map out the roughness power spectra. The acoustic backscatter technique appears to be a potential alternative to rapidly and inexpensively quantify the roughness of soil surfaces.