High-Resolution Landslide Susceptibility Assessment along a Mountain Road Corridor in Carbonate Terrains Using Handheld SLAM LiDAR and GIS-Based AHP: Northeastern Iraq

Abstract

Corridor landslides in road networks as well as rock slope instabilities on mountains roads represent hazards for transport systems in many areas, especially in karst terrains where slope behavior depends on discontinuities, bedding structure, and stress changes due to the removal of material during excavation. Slope instabilities on roads cuts occur often in northeast Iraq; nevertheless, their corridor vulnerability assessment is still limited due to the absence of topographic datasets for steep slopes. The present research has developed a methodology for evaluation of landslide risk along the Dokan-Topzawa road route (1.8 km) employing portable handheld Simultaneous Localization and Mapping (SLAM) Light Detection and Ranging (LiDAR) system coupled with Analytical Hierarchy Process (AHP) analysis utilizing GIS. LiDAR data (~ 400 million point cloud) have been processed to construct the Digital Elevation Model (DEM) from which nine conditioning factors related to geomorphology, geology, and environment have been extracted. The weight values of the factors have been obtained using AHP technique with an acceptable consistency ratio (CR = 0.02), which further have been combined into Landslide Susceptibility Index (LSI) with a weighted linear combination technique at 10 meter resolution. The resultant susceptibility map categorized the area into four susceptibility categories namely very low, low, moderate and high susceptibility zones. High susceptibility zones comprised 37.4% of the study area whereas zones having moderate and high susceptibility constituted 51.9% of the area. The landslide site investigations revealed that observed sites of landslides were situated in zones of moderate to high susceptibility. Profile interpretation through LiDAR and site investigations confirmed that factors influencing slope instability were mainly fractured limestone, unfavorable beddings towards the road, steepness of slope and seepage through discontinuities.