Variation in soil saturated hydraulic conductivity along the hillslope of collapsing granite gullies

Saturated hydraulic conductivity (K-s) affects the soil hydrological process and is influenced by many factors that exhibit strong spatial variations. To accurately measure K-s and its scale, spatial variability and relationship with collapsing gullies, we analysed four double-ring infiltrometer diameters in three soil layers during in situ experiments designed to measure K-s in two typical collapsing gullies (three slope sites) in Tongcheng County of China. The results showed that K-s increased with increasing inner ring diameter, but no significant difference existed between inner diameters of 30 and 40 cm. The K-s in red soil layers was higher than that in sandy soil layers, the transition layers had the lowest values. K-s also varied with slope position, gradually decreasing with distance from the gully head. The suggestion is that the spatial variation in K-s is affected not only by the intrinsic soil properties but also by the interaction with the collapsing gully.