GEOSPATIAL ANALYSIS AND MODELING OF LANDSLIDE SUSCEPTIBILITY IN COLORADO SPRINGS, COLORADO

Active landslides are one of the most catastrophic natural hazards in the world. They cause thousands of death and loss of the natural environment. In the USA, active landslides cause damage to homes and infrastructures and death of 25-50 people per year. They also disrupt the water supplies and transportation routes in the neighboring areas with an annual cost of about $2-4 billion. Colorado is one of the highly affected states by active landslides, which occur naturally across the Colorado Rockies. According to the 2018 Colorado Hazard Mitigation Plan (CHMP), each county in Colorado has been assigned a landslide risk category, and El Paso County has been assigned an extreme growth risk considering its future population change. Colorado Springs in El Paso County has been selected for this study because it has been experiencing increased landslide activity for 4 decades due to developing new communities on unstable ground. In this investigation, the Ordinary Least Squares (OLS) regression and the Analytical Hierarchy Process (AHP) have been integrated in a Geographic Information System (GIS) to establish a GIS-based model capable of evaluating all factors controlling the landslide activity and investigating the relationship with the recent landslide occurrences to produce a landslide susceptibility map. Fifteen factors have been considered in this study, including four lithological types (shale, gravel, sandstone, and landslide sediments), four soil types (mollisols, entisols/ardisols, alfisols/mollisols, and mixed), three topographical factors (elevation, slope, and aspect), and three landuse/cover types (low developed, developed open space, and shrub-scrub), as well as the precipitation average. The highest precipitation rates, the highest presence of shale units, and the highest slope values combined together are found to be the main trigger of landslides in Colorado Springs. Most landslides are occurring in the western, southwestern, and northwestern parts of the city. Hopefully, the produced landslide susceptibility map can help with the landslide management, hazard mitigation, and future landuse planning in Colorado Springs.