The Use of GIS and RS analysis for soil erosion MappingCase study: Kalat-e-Sadat watershed of Sabzevar

The rate of technology and advance of human in field data collection is the cause of using aerial and spatial information of the earth and geographic information system (GIS). In the other hand, one of the basic study in soil conservation and watershed management is soil erosion assessment, which this technology tend to low cost and high speed. The main objective of present study is, the use of GIS and Remote Sensing (RS) analysis for soil erosion mapping. In order to meet this general objective: - The Terrain Mapping Units or TMUُ s are delineated by using slop map, land evaluation, and rock sensibility to erosion maps of the study area. - Bureau of land management (B.L.M) formُ s have been used and during the fieldwork were completed for each TMUُ s. Erosion map made with this method caalled BLM erosion map. - Aerial photographs at scale of 1:40000 have been used and erosion map of the study area was derived, by photo-interpretation and field observations for details of the erosion process - Satellite imagery of land sat TM-29 April 1987 have also been used and erosion map of the study area was prepared, by using interpretation. For this, the false color composite of RGB731 have been used. To test of the validity of the erosion map made with the RGB731 applied for erosion assessment in this study, the erosion map made by B.L.M method was selected, as real erosion map. This map is probably the most efficient way of deriving the spatial distribution of the erosion in this research. The results of accuracy assessment between aerial photo-interpretation map, satellite image erosion map and real erosion map (B.L.M) shows: In 63.61% of the area, erosion map using satellite imagery is conform to real erosion map and in 57.26% of the study area, map made with aerial photo-interpretation is too. The accuracy for points which have BLM formُ s is %54.54 for map using satellite imagery and 45/45% for map made with aerial photo-interpretation. Also the results of accuracy assessment between aerial photo-interpretation map and erosion map made with using RGB731 shows that in 51.94% of the area, and 45.45% of points which have BLM's form, the result is the same.