Hydrological vs. Mechanical Impacts of Soil Water Repellency on Erosion

Soil erosion is a major concern for both agricultural and natural resources. Soil water repellency (SWR) is known to hinder wetting of soils, decreasing infiltration of water and thus increasing overland flowthe driving force for erosion. The latter, namely the hydrological impacts of SWR on erosion, are quite well established. In contrast, the mechanical impacts of SWR, namely on the resistance to erosion, are poorly understood. Here, we provide a critical review of the current understanding of the combined impacts of SWR on erosion. Analysis of recent experimental data provides contradictory evidence: an increase in erosion with increasing SWR in some cases, versus a decrease in others. We offer a plausible explanation for this contradiction-the interrelated soil mechanical and hydrological impacts of SWR on erosion, which we exemplify by a simple 1D model. We identify research gaps and suggest ways to resolve them.