Exposure to Large Landslides in Cities Outpaces Urban Growth

Abstract

The world's rapidly growing urban population is forcing cities to expand into steeper terrain, increasing the risk of landslides. However, systemic assessments of urban landslide exposure are limited. Across 129 cities and their surrounding commuting areas, we identify 1,085 large (>0.1 km²) landslides that are currently inhabited. Between 1985 and 2015, built-up areas on these landslides have doubled, exceeding the overall urban growth rate. We estimate that at least half a million people are living on landslides and have expanded their total built-up area by 12%, on average, over 30 years. Population trends in adjacent mountain regions increased landslide exposure, with 10% of cities showing disproportionately high exposure. Our study reveals that landslide exposure in mountainous areas around cities grew faster than in commuting areas, regardless of national income. Further model refinements with high-resolution land use data and socio-economic predictors can help quantify the impact of urban zoning policies on global landslide exposure.