Analysis of the fundamental differences between dam-forming landslides and all landslides

Abstract

Dam-forming landslides are of significant interest to researchers, as only about 1 % of landslides block rivers, yet these dams can cause extreme flooding when they collapse, with flood flows up to ten times larger than extreme fluvial floods. While regional studies have noted differences in the dimensional characteristics and formation indices between dam-forming and non-dam-forming landslides, a global quantitative comparison has not yet been made. Using open-access global datasets, we conducted a statistical analysis of their morphometric and spatial characteristics, including volume, height/length ratio, and geomorphological factors. Spatial clustering analysis was also performed to determine whether certain landslides are more likely to form dams. The results indicate that dam-forming landslides are a distinct subset: (i) they occur in more upstream areas with higher stream power index values; (ii) they have lower mobility, confined by steeper slopes and shorter hillslope lengths; (iii) shallower landslides with larger surface area and sufficient volume are more likely to form dams; and (iv) they exhibit different spatial clustering patterns compared to general landslides. Despite some data limitations, this global study provides a foundation for quantifying a landslide dam formation index and identifying areas prone to dam formation.