using aerial photos and gis capabilities to estimate gullyhead advancement (case study: samal watershed, bushehr province)

gully erosion is one of the most severe types of water erosion that inclusive and global model to represent its development under different environmental circumstances is difficult. moreover, having knowledge about history behaviors of a gully and its advancement requires direct annual monitoring that is not possible in iran conditions because of cost and time. gis and remote sensing with providing spatial data in a large scale have an important role in such evaluation. in this study aerial photos of two periods (1967-1995) were used to estimate the gully head advancement based on frames geometry (using dispositive and camera calibration data of aerial photos) and rigorous procedure. digital topographic layers (contour line, point elevation, rocks, and water body and stream line) of digital topographic maps were used to generate a digital model with high accuracy (7×7 m cell size) by pci geomatica 9.1 software. the results indicated that the mean of gully head advancement in 1967-2008 period was 1.3 my - . the results of this study showed that the gully head advancement can be obtained with acceptable accuracy using of aerial photo and gis techniques. further regression analysis showed that there was significant relationship between the gully contribution area, distance from ridge, height of gully head and sar with gully head advancement.