عنوان مقاله [English]
Landslides are natural geological processes that have revolutionized ground clearance, re-form. Landslide is one of the most remarkable phenomena in environmental issues, watershed and natural resources. Landslide importance can be discussed and analyzed from various perspectives. The most important reason for the importance of this phenomenon, caused by the occurrence of damage to life and property it is. Iran, with vast mountainous areas, which make up half of the breadth of the country, having risen from active tectonic morphology, fracture and fragmentation of many, there are other reasons including lithology sensitive and vulnerable countries in terms of landslides are is. Nowadays people change the land use and expansion of communication networks, sensitive to the Earth's surface landslides, especially in mountainous areas has intensified. In the twentieth century, Asia has the highest incident of landslides (220 reported cases) to be allocated. America continent has the largest number of casualties (more than 2,500) and Europe has experienced the highest losses. Iran is some of the damage caused by landslides. If the damage caused by the 4900 landslide recorded (from 1372 to September 1386) in the country is estimated 126,893 billion rials. In this regard, landslide, relative probability of this phenomenon in a regional event, based on the specific environmental features of the area limits. In this way, the virtual ground level and degree of actual or potential risk to specific areas (low - high) is divided. Yayijilu catchment area in this study is that the basin and in the southwestern city of Ahar in East Azerbaijan province, and is one of Ahar Chai is a sub-basin. Given that one of the most consistent ways to reduce the effects of landslides in the basin, to identify areas prone to natural disaster and zoning of these areas based on their susceptibility to landslide. Landslide to benefiting from the capabilities of geographic information system (GIS) and a model (AHP) is sent.
Yaijelo basin is in east Azarbaijan and southwest region Ahar. And is subbasin of the Ahar chai. The study area lies between the latitude of 38° 21΄ N to 38° 27΄N and longitudes of 46° 48΄ E to 46° 57΄E. At first , study area was investigated and determined its extent using satellite images of spot 2008 and 1:25000 topographic maps. In order to consider and landslide hazard zonation in the basin, the maps and data layers such as, lithology, slope, aspect, distance to basian drainage, the distance to the fault, elevation , land use and precipitation were prepared in the geographic information system (GIS). Then identified landslide in the study area by using, satellite images and field data. Then affecting factors were binary compared using analytical method by indicating the weight of each factor as indicator for their effects in occurrence of landslide. Accordingly, the landslide zonation hazard map was prepared to the use of weighed information layer and weighted coefficient of each factor. In the end , the presented model and zonation map were compared with observed landslide , and landslide index values and model accuracy were calculated .
Discussion and Results
The landslide phenomenon is one of environmental hazards which occur in yaijilo basin in southwest region Ahar. Therefore , creation of one regional strategy is very necessary to reduce its damages and maintains natural and human resourses, furthermore , landslide hazard zonation map can help research centers in environmental management and planning. In this study , GIS technique and AHP model have been used to achive goals. The result showed that integration of GIS technique and AHP model is a mighty method for preparation of landslide hazard zonation map in study area.
To determine the factors influencing landslide, data layers of elevation, slope, aspect, lithology, distance to fault, distance to river, land use were rainfall analyzed through overlaying the dispersion map of landslide. The results showed that elevation of 1900-2100 meters, slope 25- 45 percents, the east direction, Limestone, marl, sandston Formation, distance of higher 3000 meters from fault, distance of 200- 400 meters from river and finally land use agriculture lands are appropriate to landslide. The results are shown as table and landslide susceptibility maps.
In this study, Prioritization of landslide Effective Factors using AHP Model showed that slope, lithology, land use, distance to river, rainfall, distance to fault, elevation and aspect were found to be the most important factors affecting landslide. According to effective factors in landslide occurrence, the study area was zoned as various layers. Finally, landslide occurrence zones were recognized from very low risk to very high risk. The results are shown as five classes of landslide susceptibility. The result shown is about 2.36% of Yayjelo basin area very high probability of landslides in the area.. Also on 21.93 % probability of high, 45.38% of the average probability, 28.14 % at least and 3.21 % probability of occurrence is very low.