The relationship between drainage density and soil erosion rate: a study of five watersheds in Ardebil Province, Iran

Abstract

Drainage density is one of the parameters that can be considered as an indicator of erosion rate. This study analysed the relationship between drainage density and soil erosion in five watersheds in Iran. The drainage density was measured using satellite images, aerial photos, and topographic maps by Geographic Information Systems (GIS) technologies. MPSIAC model was employed in a GIS environment to create soil erosion maps using data from meteorological stations, soil surveys, topographic maps, satellite images and results of other relevant studies. Then the correlation between drainage density and erosion rate was measured. The mean soil loss rate in the study areas were 1 to 6.43 t.h-1.y-1 and drainage density values varied 1.44 to 5.43 Km Km-1.The results indicate that the relationship between these two factors improved when the types of sheet erosion, mechanical erosion and mass erosion was ignored because these types of erosion were not mainly influenced by the power of runoff. There was a high correlation between drainage density and erosion in most of the watersheds. Finally a significant relationship was seen between drainage density and erosion in all watersheds. Based on the results obtained, the present method for distinguishing soil erosion was effective and can be used for operational erosion monitoring in other watersheds with the same climate characteristics in Iran.