Purpose

The influence of slope gradient on interrill erosion processes is a key scientific problem in the decision-making process regarding soil erosion control in Loess Plateau. The relationship of time to runoff (RT), flow velocity (V), runoff rate (RR) and interrill erosion rate (IER) with slope gradient was investigated to derive accurate experimental model to evaluate and quantify the influence of slopes on interrill erosion processes.

Materials and methods

The experimental soil was collected from Ansai County of Shaanxi Province, China. The average diameter of the test soil was 0.041 mm. The experiment was conducted at slopes of 8.74%, 17.62%, 26.78%, 36.38%, 46.6%, 57.70% and 69.97% under I of 90, 120 and 150 mm h⁻¹, respectively, using indoor simulated rainfall. Time to runoff, flow velocity, runoff rate and interrill erosion rate were measured for each combination.

Results and discussion

Results showed that the time to runoff decreased as a linear function with increasing slope gradient. Slope gradient was a good predictor of time to runoff for different rainfall intensities with NSE from 0.90 to 0.97 and MSE from 0.1 to 0.25 and R² from 0.90 to 0.97. The flow velocity increased as a power function with increasing slope gradients. Slope gradient was a good predictor of flow velocity for different rainfall intensities with NSE from 0.91 to 0.93 and MSE from 0.01 to 0.015 and R² from 0.95 to 0.98. The runoff rate increased as a power function with increasing slope gradients. Slope gradient was a good predictor of runoff rate for different rainfall intensities with NSE from 0.90 to 0.95 and MSE from 0.000000024 to 0.000000044 and R² from 0.94 to 0.97. The interrill erosion rate increased as a power function with increasing slope gradients. Slope gradient was a good predictor of interrill erosion rate for different rainfall intensities with NSE from 0.98 to 0.99 and MSE from 0.00022 to 0.00055 and R² from 0.98 to 0.99.

Conclusions

By performing the controlled simulated rainfall experiments, this study showed that slopes strongly influenced interrill erosion processes for different rainfall intensities.