Investigation of topographic thresholds and analysing role of surface materials on gully development in the hillslope of semi arid areas.Case study: Shoorchay

In the surface of semiarid regions, erotion accures severe and rapidly. Liner erosion, specially gully erosion –as a hazardous erosion type, is important factor for delivery materials into runoff and flood plains. This erosion type is formed in semi arid mountains that is not covered by plants. In intensive erosion, many factors are interference, but magnetude of erosion on suitable materials or erosible materials is very high. In shoorchay catchement on Eastern slope of Sahand (located from 36˚ 05́ to37˚ 20́ N and from 46˚ 42́ to 47˚ 15́ E) Big gully is developed on the hillslope of silt and clay. In this article have been effects of factors on studied gully formation and development many indices, such as V and TCI. The results of this study show that in many parts of Shorchay Basin, slope and surface materials have important role on development of gullies