Variations in population exposure to landslides within the United States

The 2021 National Landslide Preparedness Act directs the United States Department of the Interior to identify and understand hazards and societal risks posed by landslides across the country. However, a consistent and nationwide understanding of the societal risk posed by landslides does not exist. We attempt to fill this gap by characterizing exposure to landslides across the country using gridded 90-meter resolution landslide susceptibility and population models. The susceptibility model describes where landslides are more and less likely to occur. The LandScan USA population models estimate the number of people in a particular area. Results reveal regional variations in population exposure, such as the disparity in both the total number of people and the proportion of populations exposed to landsliding in different regions. In California, for example, a high number of people are exposed to landslides (> 8 million), but this number comprises only a small proportion of the total population of the entire state (< 30%). In contrast, in West Virginia and Puerto Rico, a low number of people are exposed (< 2 million each), but the proportion of people exposed within the state and territory is relatively high (> 60% and 45% respectively). This example illustrates the utility of a consistent and nationwide understanding of landslide exposure. Decision makers, for example, can use exposure information to inform resource allocation for landslide risk-reduction efforts (e.g., targeted risk communication). Additionally, the information can guide more detailed geologic and demographic investigations in regions where significant societal impacts from landslide events are likely.