Investigation on effects of lithology on soil erosion and sediment yield in Sangerd Drainage Basin

On areas with highly eroded soils, where vegetation is absent or negligible, runoff generation and erosion processes can greatly be affected by the nature of parent material. This research was carried out to investigate the effects of lithology and soil parent material on erosion and soil loss, using rainfall simulator in Sangerd Drainage Basin which is located in Khorasan Razavi Province. To do this research, 11 homogeneous soil units (map units) with the same slope (20%), land use (rangeland), different lithology (marls and conglomerate) and erosion facies (sheet-rill, rill and rill-gully) were selected. A rainfall simulator producing 36 mm h-1 rainfall intensity and 30 minute duration was used at 33 locations over soil erosion plots. The amount of sediments was measured. In order to investigate factors affecting on soil erosion and sediment yield, soil was sampled from 0-15 cm depth of plot adjacent areas. For statistical analysis, SPSS 22 was used. Results showed that soil erosion and sediment yield have meaningful differences in different lithologies. Eem-RG and Plc-SR soil units with 260.9 and 45.1 gr m-2 have the most and the least sediment yield, respectively. It was found that the sediment yield had positive correlation with some soil properties such as silt, Ec, pH, SAR and antecedent soil moisture and negative correlation with sand, OC, NPV, vegetation and rock fragment cover.