Territorial expansion and hydroclimatic change as drivers of landslide risk in Brazil

Landslides are among the most damaging natural hazards in Brazil. While impacts have long been concentrated in steep coastal mountain ranges, particularly in the Southeast, recent extreme rainfall events and expanding human occupation point to a broader and more complex national risk landscape. Because landslide occurrence is shaped by both hydro-meteorological forcing and land-use and settlement dynamics, a key question is how hydroclimatic shifts and territorial expansion interact with pre-existing susceptibility to shape hazard, exposure, vulnerability, and overall risk at the country scale.

Here we present a national-level assessment integrating: (i) landslide-susceptible terrain, (ii) geomorphometric controls, (iii) a spatial classification of hydrological-cycle tendencies, and (iv) population characteristics derived from census-based spatial units, together with indicators of spatial expansion. Susceptibility is represented through a nationalized interpretation of an existing global framework that combines topographic factors with proxies for geology, vegetation disturbance, and infrastructure. Terrain attributes are derived from elevation-based products, and hydroclimatic tendencies are summarized using a nationwide synthesis describing contrasting modes of hydrological-cycle change. All datasets are integrated at the census-tract scale, enabling direct comparisons among susceptibility patterns, hydroclimatic tendencies, and population distribution and expansion.

Results show that areas mapped as more susceptible often coincide with zones of higher human presence, indicating that exposure remains elevated where terrain conditions are unfavorable. In addition, vectors of population expansion frequently point toward more susceptible areas, which commonly include settlements with higher vulnerability. When hydroclimatic tendencies are intersected with the higher susceptibility classes, “drying” conditions appear more widespread, whereas “acceleration” occupies a smaller, yet still meaningful, portion of susceptible terrain. These patterns motivate two working hypotheses. First, in regions tending toward drying, a potential reduction in rainfall frequency or totals may lower landslide occurrence in typical years, but could also create conditions for larger responses during rare, high-intensity storms. Second, in regions tending toward hydrological acceleration, increases in rainfall intensity and/or event clustering are expected to promote more frequent triggering, consistent with observed behavior in well-known Brazilian hotspots.

Overall, this synthesis suggests that hydroclimatic tendencies may steer landslide regimes in different directions across Brazil, while continued settlement expansion increases exposure in susceptible terrain.