Study and Morpho-Climatic Classification of Gullies in Ardabil Province

Gully erosion is a serious problem of many watersheds in Iran, and the particularly in Ardabil province, because of climate, lithology, morphology, and land use and land cover characteristics. This research has been focus on gully morpho-climatic classification as a first step in evaluating gully processes for control of gully erosion in Ardabil province. For this purpose, on the first step, these affected areas were found base on available previous data, aerial photographs, satellite pictures and field investigation. Areas over than 500 hectares and their dominant climates were specified with usage of climate map (in widespread Domartan method). Then for the following study, a couple of the area, if it was possible, was chosen from each climate. From each region, one representative gully and two repeated ones were chosen on which experiments such as measuring the characteristics of morphology; soil sampling and other related studies were performed. Consequently, according to the main characteristics, which exist among the gullies of different areas, such as climates, view plan, these gully areas have been classified base on cluster analysis. Ardabil province with 17953 km2 area is located in northwest of Iran, there are 8 climates in which more than 55 percent is under influence of ultracold semi-arid and Cold-arid. Also totally 7 areas, which were affected by gully erosion, were found, covering an area, which amounts to 46500 hectares and have 2 different types of climates. Most of the gullies are located on hills and some on plains; they belong to discontinued gullies group. In the gully areas, surface and subsurface soil textures are usually clay, clay-loam, loam and sand clay-loam and in some cases is silty-loam. The view plan of gullies is dendretic and linear. The head cuts of gullies are rounded, notched and pointed, the vertical plan of head cuts are generally vertical and cave. The width section of these gullies are U-shaped in northern areas and V-shaped in southern areas. In view point of their depth, they are in the intermediate gullies (1-10m). The gullies are formed in rangeland and in dry land farming's. In Ardabil, the appearance and characteristic of gullies encouraged by some local factors, such as erodible lithology and soils, heavy rainfall in some areas and mainly the anthropic influence, represented by land use changes, degradation of vegetation cover, overgrazing and trampling by cattle on the pastures, leaking the water of irrigation from the lower agricultural area,the road network and up-and-down hill farming which supports flow concenteration. The gullies damages in the studied area have occurred on rangelands, cultivate lands and roads. These areas, which are classified base on cluster analysis, are in 2 classes (one with ultracold semi-arid climate and the other with Cold-arid). The first class consist of Hashtjin, Kandiraq, Qezaz and Mersht-Bodalalu area and the other Mogan 1, 2 and 3. The results of this research show that gully erosion can look dramatic in some area of Ardabil region, but if the gully have satbilised it may be better to leave it alone. Gullies can be prevented in the studied area by maintaining ground cover, prevention of surface runoff concentration, land rehabilitation, controlling over grazing by livestocks and improper road constructions.