The most recent disaster related to extreme rainfall induced landslides and floods: Petropolis, Rio de janeiro state, SE-Brazil.

In the top of the Serra do Mar, at Rio de Janeiro state, the historic city of Petropolis has a long history of disasters related to extreme rainfall induced landslides and floods, which have become increasingly impactful in association with disorderly urban growth. The last critical event occurred on February 15, 2022, causing 236 deaths and major economic losses. A total number of 149 landslide scars were mapped with the support of a World View 3 satellite image from February 17th. These landslides reached a total area of 37 km², being more concentrated in the central part of the city, especially in the neighborhoods of Alto da Serra (Morro da Oficina), Chácara Flora (Morro do Turco) and Vila Felipe. The critical rains were spatially non-uniform, varying between 100 and 260 mm, in just 3 hours (between 16:00 and 19:00 hours); the highest number of landslides occurred when rainfall exceeded 180 mm (77.2%). Taking into account the geometry of the slopes, it was observed that 52% of these landslide scars occurred on slopes of converging water flows; 37% on divergent slopes and only 17% on planar slopes. Two types of landslide mechanisms prevailed: shallow planar slides and debris flows, which increased flooding in the rivers that drain the city. These rivers were artificially narrowed throughout the city's history, since the 19th century. The forest remnants, although highly degraded, functioned as natural dams for many landslides (45%), reducing the spread of sediment to the valley bottom.