Soil as the erosion object, its anti-erosion capability reflects the sensitivity degree of soil to erosion and is the inherent factor influencing the process of soil erosion．So researching on the soil erosion mechanism and regulation of regional scale has important significance for building soil erosion prediction model of regional scale and massive work of soil and water conservation and environment construction. Based on involved scientific theory of soil erosion science, soil physics, and hydrodynamics, this research analyzed the character and mechanism of soil erosion progress of four typical soil types through artificial simulation experiments. The objective of our research is to build a comprehensive index which can reflect soil anti-erosion capability, and apply it to the regional soil erosion resrarch. Main results are as follows:
1. Proposition of soil anti-erosion index based on energy consumption theory.
The relationship between the soil detachment and the runoff energy consumption is studied by using the law of conservation energy in this part. The soil erosion rate increases as runoff energy consumption increases, and it also tends to increase with increasing slope gradient under same runoff energy consumption. The soil erosion rate model is built, and a new erosion critical index is put forward. Based on the energy consumption theory of run-off, the concept of soil anti-erosion index (KE, g/J·cm-2·min-1) is proposed. And the expression of mean erosion index value is also built according to mean curve slope. The mean anti-erosion index values of four soils are black soil (0.081) >loess soil (0.062) > purple soil (0.047) > red soil (0.0245).
2. The relationship between soil anti-erosion index and soil erodibility
Under simulated rainfall conditions, soil erodibility K values are diverse, which shows that error will exist when soil erodibility (K-factor) is directly applied to the soil erosion calculation under single rainfall event. Slope erosion quantity showes a linear correlation with rainfall erosivity, slope gradient and slope length. Combined the course of simulated rainfall on many occasions, the K values of red soil, purple soil, black soil and loess soil are 0.0214, 0.0265, 0.0546 and 0.0784, respectively. And the relationship between soil anti-erosion index and soil erodibility is described quantitatively.
3. The relationship between soil anti-erosion index and soil anti-scourability coefficient.
Soil anti-scourability coefficients are evidently different from different parent material, which is due to difference of >0.25 mm water-stable aggregates and soil clay content. Soil anti-scourability ability is red soil > purple soil > loess soil > black soil. Soil anti-erosion index decreases as soil anti-scourability coefficient increases under different slope gradients and flows, and the both show a fine correlation of power.
4. The relationship between soil anti-erosion index and simulated erodibility K values
Simulated erodibility K values of four soil types show a great difference under different models, and simulated K values are generally bigger than that of soil anti-erosion index. There is a fine linear correlation between simulated K values and soil anti-erosion index. A new method is advanced for estimating soil anti-erosion index of the soils in China despite of difference in geographic region and availability of data.
5. The test of soil anti-erosion index on the slope
The observed values of soil erosion quantity is generally bigger than that of simulated values. However, further analysis indicates the significantly positive correlation between the observed values and the simulated values, which shows a line correlation. Coefficients of determination of the observed values and the simulated values reveal the rationality of soil anti-erosion index on the slope.
6. Application of soil anti-erosion index
The erosion index is primarily applied to simulate the sediment yield in July, 1995 during a case study in Yanhe River basin. The results indicate that the simulated sediment amounts are 20 million tons. The simulated results in Yanhe River basin prove that soil anti-erosion index is feasible on the regional scale.
Key Words: soil anti-erosion index; artificial simulation experiments; anti-scourability; erodibility K value; regional soil erosion model；energy consumption theory