Using the analytic hierarchy process and frequency ratio methods for landslide susceptibility mapping in Isparta-Antalya highway (D-685), Turkey

Abstract

The D-685 highway, which connects Isparta to Antalya, has a dense traffic line with a length of 110 km. Landslide and debris flow are common on the road route. In some regions, rehabilitation works have been carried out by the highway commission. However, the clastic, unconsolidated, and high clay content of the lithological units in the road line causes the continuation of landslide and debris flows in different regions. Especially, heavy rain showers increase this effect. Landslide susceptibility maps based on geographical information systems (GIS) were developed to ensure safer driving on the highway and contribute to the planners. Parameters such as lithology, slope, distance from roads, distance from streams, land cover, precipitation, elevation, and aspect were used. Analytic hierarchy process and frequency ratio methods were used to assess these parameters. The obtained susceptibility maps were divided into four classes as low, moderate, high, and very high. There are large areas with high and very high susceptibility in the maps produced by both methods. Some parts of the highway pass through these high and very high susceptibility areas. According to the susceptibility maps, high and very high susceptibility areas are more intense in northern and central areas within the study area. These regions are also the sections with the highest elevation. In the study area, elevation decreases from north to south, and flat areas increase toward the south. For the validation of the maps, 16 of the 81 landslide areas were used for testing purposes. As a result of the analysis, it was found that the obtained maps have a level of reliability of over 90%.