Landslide Hazard Zonation Using Analytical Hierarchy Process and GIS A Case Study of Sardool Chay Basin, Ardabil Province

IntroductionA landslide is a natural phenomenon that often occurs because of falling down or seamless and quick movements of volumes of sediment along the slope. It has such speed and extent that it may influence tens or hundreds of cubic meters of rock and soil together. This phenomenon causes a lot of economic damages to forests and their growth, farmlands, gas and power transmission lines, mines, engineering structures, and buildings. One of the best ways to prevent these damages is preparing a landslide hazard map.
MethodologyThe method used for zoning the Sardool Chay Basin is the Analytical Hierarchy Process. This is one of the most comprehensive multi-criteria decision methods, which was first presented in 1980 by Thomas L. Saati. This method is based on weighing each pair of variables with each other. AHP method consists of three main steps including (1) creating an Analytical Hierarchy, (2) comparing pairs of elements in it, and (3) weighing the criteria. The main feature of this method is the use of expert opinions. In AHP,n paired factors are compared with each other and more weight is given to the layer that has the maximum impact on the target set. The paired comparison of a scale, based on1 to 9, for its two component's relative weighing is hierarchical.
DiscussionIn this study, the landslide hazard zonation was used in the Sardool Chaycatchment in order to identify areas with landslide incidence potential. The main factors contributing to the landslide occurrence in this case study consisted of geology, land use, slope, aspect, rainfall, altitude, distance from faults, and distance from stream. Their layers were prepared in ArcGIS software. An Analytical Hierarchy Process in Expert Choice software was used for paired comparisons of criteria and calculation of final weight. The results indicated that the geology criterion, which weighed 0.343, and the slope criterion, which weighed 0.215, had the most influences on landslide occurrence.
ConclusionLandslide is one of the most common environmental hazards in mountainous areas of the northwest of Iran. Factors such as slope, rainfall, lithology, and earthquakes can trigger them. One of the best ways to deal with this phenomenon, before the implementation of any project, is the zonation mapping of the area. This study was based on the Sardool Chay catchment, located in Khalkhal, the southern part of Ardabil Province.
To this end, 8 factors including geology, land use, slope, aspect, rainfall, altitude, distance from faults, and distance from stream were used. The weighting factors and the Analytical Hierarchy Process (AHP), and the Expert Choice software were used. The results classified the basin into five areas including very high risk of landslides (65 km²), high risk (144 km²), medium risk (202 km²), low risk (142 km²), and very low risk (120 km²). In addition, it indicated that the landslide risk of the Sardool Chay catchment is medium. Comparing the landslide zonation map and points of distribution suggests that the AHP can be a good method of weighing the criteria involved in the happening of the landslide.