SSEM: A model for simulating runoff and erosion of saline-sodic soil slopes under coastal reclamation

Current physically based erosion models do not carefully consider the dynamic variations of soil properties during rainfall and are unable to simulate saline-sodic soil slope erosion processes. The aim of this work was to build upon a complete model framework, SSEM, to simulate runoff and erosion processes for saline-sodic soils by coupling dynamic saturated hydraulic conductivity Ks and soil erodibility K-tau. Sixty rainfall simulation rainfall experiments (2 soil textures x 5 sodicity levels x 2 slope gradients x 3 duplicates) provided data for model calibration and validation. SSEM worked very well for simulating the runoff and erosion processes of saline-sodic silty clay. The runoff and erosion processes of saline-sodic silt loam were more complex than those of non-saline soils or soils with higher clay contents; thus, SSEM did not perform very well for some validation events. We further examined the model performances of four concepts: Dynamic Ks and K-tau (Case 1, SSEM), Dynamic Ks and Constant K-tau (Case 2), Constant Ks and Dynamic K-tau (Case 3) and Constant Ks and Constant K-tau (Case 4). The results demonstrated that the model, which considers dynamic variations in soil saturated hydraulic conductivity and soil erodibility, can provide more reasonable runoff and erosion prediction results for saline-sodic soils.