Topographic characteristics of ephemeral gully erosion in loess hilly and gully region based on RS and GIS

A series of ephemeral gullies and their topographic parameters were extracted from high resolution remote sensing image Quickbird and Digital Elevation Model (DEM), and analyzed by statistical methods in order to realize the topographic characteristics of ephemeral gully erosion on hill slope in the Loess Plateau. The results showed that the number of ephemeral gully within hill slope was mainly influenced by slope steepness, slope length, aspects and upslope length. The topographic characteristics of ephemeral gully erosion depended on slope steepness, slope length, upslope length and upslope drainage area. The average length of ephemeral gullies within hill slope was linearly correlated with slope length significantly. There was a quadratic curve relation between slope steepness and frequency of ephemeral gully, slope steepness of ephemeral gully and its upslope length. The upper limit of critical slope steepness of ephemeral gully erosion was between 26° and 27°, and the lower limit was between 15° and 20°. In addition, the critical slope length ranged from 50 to 80 m. The critical curve of ephemeral gully distribution was determined based on the sine value of slope steepness of ephemeral gully and upslope drainage area of ephemeral gully. The average length of ephemeral gullies within sunny slope was less than that within shady slope. This study provides an effectual technological support for water and soil conservation on hill slop in loess area.