Validation of the Use of Synthetic Colour-Contrast Aggregates for Estimating Splash and Surface Erosion

Introduction and Goal:

Soil erosion is one of the most important environmental, natural resource and agricultural issues in the world. Soil splash is the initial stage following the impact of raindrops on the soil surface, leading to the breakdown of the soil aggregates and the detachment of soil particles, ultimately cousing splash erosion. This process is followed by a decrease in soil permibeality, an increase in runoff, and consequently, surface erosion. Therefore, the accurate estimation of splash and surface erosion is necessary for the success of soil conservation erosion control and reduction of natural hazards. In this regard, innovative methods have been developed that utilize photography and image processing techniques to estimate splash and surface erosion. The aim of this research was to  validate the splash and surface erosion estimates using synthetic colour-contrast aggregates.

Synthetic colour-contrast aggregates were initially prepared using mineral pumice particles and yellow concrete colour. Then, soil with a silty-clay-loamy texture was sampled from the Marzanabad-Kandalus road bank, and natural and synthetic colour-contrast aggregates with diameters of 1.77, 2.89 and 4.05 mm were separated. Surface erosion was then measured in 20×40 cm plots. Additionally, splash erosion was measured using the splash cup method under a rainfall intensity of 60 mm hr-1 lasting 10 min in three repetitions.

The results showed that the average rates of net splash for different soil aggregate diameters of 1.77, 2.89 and 4.05 mm, were 73.72, 38.73 and 20.68 g m-2, respectively, and also the average rates of total splash were 192.61, 73.97, and 44.46 g m-2, respectively. These results indicate a decrease in the average amount of net and total splash with increasing in the soil aggregate diameter. The results showed that synthetic colour-contrast aggregates demonstrate an acceptable efficiency in measuring net splash, total splash and surface erosion with coefficients of determination of 82, 70 and 82%, respectively. The results also showed that the average soil loss for different soil aggregate diameters of 1.77, 2.89, and 4.05 mm, was 94.69, 83.22, and 42.20 g m-2, respectively. in other words, surface erosion decreased with an increase in the diameter of soil aggregates on the soil surface.

Conclusion and Suggestions:

The results of this study indicate that using synthetic colour-contrast aggregates allows for a quicker and reasonably accurate estimation of splash and surface erosion at the plot scale. As this method does not require sampling runoff and sediment from the plot, it reduces the cost of erosion and sediment research. Additionally, the synthetic colour-contrast aggregates do not disturb the soil surface and are environmentally friendly. Therefore, it is recommended to use this method for indirect estimation of splash and surface erosion in field and laboratory studies.