International Journal of Sediment Research 23 (2008) 130-137 Methodologies of preparing erosion features map by using RS and GIS Mohammadi Torkashvand Ali 1 and Nikkami, Davood 2 Abstract The erosion features map is one of the basic maps in erosion and sediment studies and watershed management programs. Some methodologies of preparing erosion features map by using RS and GIS were compared in research which took place in the Jajrood sub-basin in north-east Tehran, Iran. In the first phase, four working units' maps were prepared by integration a) plant cover, geology and slope b) land use, geology and slope c) land use, rocks sensitivity to erosion and slope and d) land use, rocks sensitivity to erosion and land units’ layers. In addition to these four working units' maps, three more maps were also evaluated in separating erosion features including e) land units f) sensitivity of rocks to erosion and g) image photomorphic units. The efficiency of these seven working units' maps was evaluated by 314 control points. For this purpose, by using erosion features of control points regarding field views, surface, rill, gully and channel erosion maps were prepared and compared by crossing them with working units' maps. Results showed that method "d" was better than "a", "b" and "c" in providing soil erosion features regarding economic and executive considerations. The accuracy of methods "e" and "f" was 53.0 and 42.9% and their Root Mean Squared Error was more than method "g" and methods "a" to "d". The coefficient of variation was highest for methods "e" and "f" and the least for method "e" and the greatest precision was related to image interpretation. Key Words: Map of soil erosion, Remote sensing, GIS, Jajrood river basin, Iran 1 Introduction The erosion features map is one of the most important and basic maps in erosion and sediment yield studies (Mohammadi, 2006). In erosion features mapping, field studies and aerial photo-interpretation are perhaps the most precise methods but time consuming and expensive ones (Nejabat, 2003). Rahnama (2003) investigated the possibility of providing an erosion features map for Iran, using aerial photographs in the Isfahan province. He concluded that preparing this map by using aerial photo-interpretation for the total area of Iran would be very difficult because photo-interpretation and field practices are time consuming and expensive. Therefore, in this research, methodologies of preparing this map are investigated by integrating effective data layers in the environment of Geographic Information Systems (GIS) and processing Remotely Sensed (RS) satellite images and data. More erosion and sediment studies have been carried out to provide a quantitative erosion map (Singh et al., 1992; Martinez, 2003; Ygarden, 2003; Essa, 2004; Mohamed Rions, 2005) and less to preparing an erosion features map. Limited studies have been done in providing erosion features maps like Global Assessment Soil Degradation (GLASOD) studies that divided erosion into 4 categories: water, wind, physical and chemical and prepared a world erosion map of scale 1:5,000,000 (Oldeman et al., 1988). Noble and Fletcher (1984) provided a New Zealand erosion features map of scale 1:250,000. Working units had been established by the integration of lithology, soil, slope, erosion, vegetation cover, climate 1 Assis. Prof., Islamic Azad University-Rasht branch, Rasht, Iran, E-mail: Mohammadit_a@yahoo.com 2 Assis. Prof., Soil Conservation and Watershed Management Research Institute, Tehran, Iran Note: The original manuscript of this paper was received in May 2007. The revised version was received in Jan. 2008. Discussion open until June 2009. - 130 - International Journal of Sediment Research, Vol. 23, No. 2, 2008, pp. 130-137