Landslide Hazard Risk Assessment for Los Angeles County, CA

Abstract

Landslides are a natural disaster caused when loose sediment and debris move downhill. Southern California has experienced increasing numbers of landslides in recent years. This is primarily due to high rainfall after long periods of drought, which causes dry soil to be displaced by the high volume of precipitation, runoff, and flooding. Additionally, wildfires in the region have destroyed natural vegetation and root systems that would have held soil in place and prevented erosion. Due to the increased risk of landslides in the region, it is important for residents, government officials, and other local stakeholders to identify high risk areas and take measures to prevent and mitigate the effects of these climatic disasters. The region of focus was Los Angeles County, due to its highly populated residential areas as well as important infrastructure that would be affected by a landslide event. In order to identify high risk regions, a landslide hazard risk assessment was performed in ArcGIS Pro. The main factors used in this assessment were average annual precipitation, slope, aspect, land use/cover, and recent wildfire perimeters. A weighted overlay and visual analysis were used to identify areas that are at high risk of experiencing a landslide. The main at-risk region was determined to be Angeles National Forest and its neighboring communities. To prevent future landslides and mitigate potential damage, it is recommended that the local governments improve drainage routes for runoff, build debris catches along major roads, stabilize slopes by planting vegetation, and regularly update and publicize emergency guidelines for residents.