Feasibility of soil erosion measurement using time domain reflectometry.

• Soil erosion was measured by detecting changes in air–soil interface of TDR probe. • Feasibility of TDR-based soil erosion measurement was evaluated by experiments. • Soil erosion can be effectively measured within a wide soil moisture range. • Simultaneous measurement of soil moisture content can ensure reliability. Scientific research and control technology of soil erosion both rely on accurate and efficient soil erosion measurements. Based on the principles of locating interfaces in layered media and measuring dielectric properties by time domain reflectometry (TDR), we developed TDR-based measurement of changes in the air–soil interface along the TDR probe for soil erosion measurement, and simultaneously measuring volumetric soil moisture content (θ v). Part of a three-rod TDR probe was inserted in the soil and the rest exposed to air, so changes in the air–soil interface could be denoted by changes in the length of exposed probe (L air). TDR waveforms were analyzed using a combination of tangent line method and second-order bounded mean oscillation methods to identify time points at positions of impedance discontinuity in electromagnetic propagation, then converting these data to L air and θ v by calibrated equations. According to the laboratory experiment using sandy loam and silt loam, L air could be effectively measured within a wide soil moisture range by the calibrated equation and the thickness of the eroded soil layer could thus be determined. The RMSE of θ v measurement ranged between 0.003 and 0.025 cm3 cm−3, which enabled the identification of the appropriate soil moisture range for measuring L air , and achieve reliable simultaneous measurement of soil erosion and soil moisture content. The simulated rainfall experiment using sandy loam and silt loam and field scouring experiment conducted in loam also indicated that the proposed method could achieve high measurement accuracy in erosion environments, for which L air with the RMSE from 1.8 to 2.1 mm and θ v with the RMSE from 0.007 to 0.024 cm3 cm−3. The proposed method has various advantages, including versatility, minimal disturbance, easy automation of measurement at multiple positions, etc., could serve as a new technical option for soil erosion measurement, and extend the utilization of TDR. [ABSTRACT FROM AUTHOR]