Laboratory and Statistical Methods for Estimating Soil Erosion on Al-Jabal Alkhdar Slopes

The study applied some dynamic laboratory methods to estimate soil susceptibility to water erosion. Non-dynamic laboratory methods such as statistical methods were also applied. Tests were carried out on topsoil samples (0-10 cm) collected from five sites located on the semi-arid southern slopes of Al-Jabal Alkhdar: Meseliba (Taknes); Marawa; Sirat Alia (Gandulah), Grehat (Gandulah), and Qasar Mestashi (Salantah). The results showed compatibility between the results of all the dynamic methods, which showed that the soil of Qasar Mestashi is the most susceptible to erosion, which corresponds to the deterioration of its physical and hydraulic properties and the low content of organic matter. It was also found that the soil of the Sirat Alia area was the least erosive, which corresponds to the high content of clay, organic matter, and soil water-stable aggregates. On the other hand, the statistical method using the K-USLE nomograph (diagram) did not succeed in producing results consistent with the dynamic laboratory methods, the K-USLE nomograph results unexpectedly showed that the soil of Grehat is relatively the most susceptible to erosion, although these soils have a good content of clay, organic matter, and soil water-stable aggregates. The high content of silt at Grehat soils could be the reason for the high susceptibility estimation when the statistical method is applied. Accordingly, the variance in the results of statistical methods is expected due to the slight changes in the soil fractions, which raises doubts about the efficiency of statistical methods in providing a reliable characterization of soil susceptibility to water erosion. Dynamic laboratory methods were the closest to soil characteristics and field conditions, which could make them more realistic and reliable indicators as low-cost and easy-to-apply methods, and contribute to more efficient erosion measurement at Al-Jabal Alkhdar region.