Climate Stress, Infrastructure Limits, and Urban Landslide Risk

Landslides are among the deadliest natural hazards. Their impact is the highest in urban areas, where human exposure peaks. However, in addition to increasing exposure, multiple human-induced landscape alterations may also increase the probability of landslide occurrence. Hence, when we consider landslide risk in urban areas, not only does elevated exposure increase risk, but the exposed elements may also alter the frequency and intensity of the hazard.

This relationship between exposure and hazard has already been demonstrated in physics-based hazard models that explore landslide potential in informal neighbourhoods. There is also ample evidence of landslides along intercity roads, linking hillslope modification to landslide occurrences. However, the number of observations is limited in urban areas. Here, we discuss the Granizal Landslide that occurred in June 2025, killing 27 people in the Metropolitan Area of the Aburrá Valley, Colombia. The rainfall-induced Granizal Landslide occurred in the steepest section of the urban zone, as could be expected. However, the landslide’s source area coincides with a road and a potentially malfunctioning sewage system, indicating that the exposed elements may have contributed to the landslide^[1].

The Granizal Landslide is alarming, as such incidents may increase as climate change intensifies. Especially in the tropical urban centres, more extreme rainfall events may overburden water infrastructure, not only informal infrastructure but also infrastructure that complies with the design standards. The statistical thresholds used to design the infrastructure may become inadequate due to shifts in rainfall patterns. Hence, we could broadly argue that climate change may be eroding the knowledge base that we used to design infrastructure. Perhaps not in the Aburrá Valley, but in other places we have already observed landslides in locations with little or no prior experience and risk awareness. This poses an additional risk due to the lack of knowledge among the newly exposed population about effective behavioural responses^[2].

^[1] Ozturk, U., Braun, A., Gómez-Zapata, J. C., and Aristizábal, E.: Urban poor are the most endangered by socio-natural hazards, but not exclusively: the 2025 Granizal Landslide case, Landslides, https://doi.org/10.1007/s10346-025-02680-y, 2025.

^[2] Bubeck, P., Ozturk, U., Aristizabal, E., Thieken, A. H., and Wagener, T.: Mortality reduction despite changing climate extremes requires better understanding of human behavioral response to warnings, Environmental Research Letters, 20, 101004, https://doi.org/10.1088/1748-9326/ae034f, 2025.