Temporal Analysis of Forest Cover Change and Landslides Susceptibility Mapping along Karakoram Highway Using Geographic Information System and Remote Sensing

Abstract

Landslides is considered as the most dangerous natural hazards in the mountainous region caused by deforestation, heavy rainfall and earthquake. The objectives of this study were to map the deforestation and use an Analytical Hierarchy Process (AHP) along with Weighted Linear Combination and Scoops 3D model to map the Landslides susceptible areas along the Karakoram Highway (KKH). The study area includes a part of Karakoram Highway which is included in the China-Pakistan Economic Corridor (CPEC) within Pakistan. This research incorporated the geomatics techniques for monitoring the forest cover change and assessing landslide susceptibility along Karakoram Highway, Pakistan. Supervised image classification was performed in ArcMap ver. 10.5 to identify changes in the forest cover along KKH. In order to study the slope stability of the area, the Analytical Hierarchy Process along with Weighted Linear Combination and Scoops 3D was used. The causative parameters for running AHP comprises of the lithology, presence of thrust, land use land cover, precipitation, and Digital Elevation Model (DEM) derived variables (slope, curvature, aspect, and elevation). Scoops 3D model incorporated the 3D properties of subsurface and the earthquake loading data. The study used Landsat 4, 5 TM, Landsat 7 ETM and Landsat 8 OLI imagery for 1990, 2000, 2010 and 2016, respectively. The results categorized the region into five major land use land/cover classes i.e., forest, vegetation, urban, open land and snow cover. Results from post classification forest cover change maps illustrated remarkable decrease (26 %) in forest cover in the last two and a half decades. The primary cause of the forest cover dynamics is the shift of native forest towards urbanization and urban vegetation. Nonetheless, there is no significant change in the reserved forested area which makes i only 2.97% of the total forest cover. The results from AHP and WLC identified four landslide susceptibility zones, i.e. low, moderate, high and extremely high susceptible zones. Almost 73% of the total area fall in moderate to high susceptible zones. The results of limit equilibrium analysis using Scoops 3D categorized the area into 4 groups of slope failures volume, i.e., low, moderate, high and extremely high mass. The validation of outputs from AHP and Scoops 3D were validated using landslides inventory produced by Geological Survey of Pakistan. The results from both the techniques showed similar output that coincides with the known landslides areas. However, Scoops 3D provide not only the susceptible zones but also the range of volume of the potential slope failures. The intense forest degradation and risk-prone topography of the studied region has amplified the risk of landslides. Henceforth, effective policies and forest management are needed to protect not only the environmental and aesthetic benefits of the forest cover of this area but also to manage the disaster risks. The results of this research will help in comprehending the deforestation and forest degradation patterns. This is expected to serve in efficient forest conservation and management plans and policies.