The Karakoram Himalaya is part of the south-central Asian mountain systems. It covers their highest and most rugged terrain and, with some 16,000 km2 of perennial snow and ice, is the most heavily glacierized. Most, if not all, of the Karakoram, was glaciated several times during the Quaternary in some of the most significant glacier expansions of the subtropics. They are recorded in glacially moulded landforms, old lateral-margin deposits, and erratics that lie 1000 m or more above valley floors and hundreds of kilometres beyond modern glaciers (Hewitt 1999). A large number of catastrophic landslides have occurred in these lateral-margin deposits. Occasionally, they have damaged residential buildings, roads, and power grids. Hence, precise identification of future landslides and their extent, volume, and activity is vital for disaster management (Kamiński et al. 2021). Currently, rainfall-induced landslides are dominant in the Karakorum ranges. With the progressive development, landslides and flash floods have caused many casualties and blocked the Karakorum highway several times (Ali et al. 2019). In most events, the landslide movement appears to be linked primarily with the topography and the surge in the bedrock saturation either by groundwater or rainfall. The other important factor is Earthquakes to be considered. As established by new earthquakes, the Karakoram Himalaya ranges are tectonically active (Yousuf et al. 2020). In Karakoram Mountains, there exits mainly deep structural landslides with huge volumes, controlled by the relief and geological strata. One of them is the "Maicher Hill" active landslide.
The first significant toppling event was reported in 1996, and the current appearance of a large crack occurred in 2018. Also, many minor tension fractures are visible, indicating the landslide creep. Significant, semicircular gaps are present at the contact between granitic bedrock and Quaternary deposits. Because of the previous disaster of the Attabad landslide (Gardezi et al. 2021), it was necessary to perform a full-scale investigation of Maicher Hill to prevent future catastrophes and plan mitigation.
The hazard is defined as the likelihood of losses instigated in the event of possible disasters. The primary consideration for landslide hazard assessment is to estimate the landslide probability, collapse pressure, and run-out distance (Fell et al. 2008). Landslides always bring high-density material with them, and its movement path is a hazard for buildings or infrastructure that lies in the run-out path (Huang et al. 2017). To develop a 3D terrain landslide simulation model in the Rapid Mass Movements Simulation (RAMMS), the orthoimage and high-resolution digital elevation model (DEM) is the essential requirement (Bartelt et al. 2017). We performed a detailed airborne survey, and DEM with a 1.2 m resolution was created for the targeted site. The surface movement is evident at the site from geological observations and monitoring sensors installed at the slope. Hence, a time series deformational analysis was performed to understand the deformation level and ultimately identify the landslide's surface boundary. The surface deformation was generated with the Small Baseline Subset Synthetic Aperture Radar Interferometry (SBAS-InSAR) technique. The final deformation map was acquired after processing 47 Sentinel-1 images between 2019 and 2020. This technique delivers precise and affordable tools to identify the surface movement and delineate landslides and their size (Wu et al. 2019). Electrical Resistivity Tomography (ERT) investigations were performed to outline the depth of active landslide materials. The ERT is a commonly used geophysical method to study and estimate the volume of active landslides materials (Huntley et al. 2019).
Initial examination of engineering properties of site topsoil was determined by geological tests and geotechnical reports (Xiansong et al. 2018). Finally, all the calculated parameters were utilized in RAMMS to simulate the high-speed landslide hazard. The study site is an elevated moraines hill body. Several historical events show that moraines have flowed like characteristics and can be categorized as high-speed landslides. Therefore, the RAMMS Debris flow module can simulate high-speed landslides (Bartelt et al. 2017; Huang et al. 2017). The final model shows the movement path, velocity, accumulation thickness, the spatial distribution of the pressure in a 3D terrain. The results are essential for local administration to plan the mitigation to avoid hazards effectively quickly.