Three storms test a decade of multi-hazard warning in south-eastern Bangladesh

Abstract Landslides and flash floods in south-eastern Bangladesh share their storms but are warned for separately. This study compares the compound events of June 2017, August 2023 and July 2026 on the same slopes, using gauge-corrected rainfall, a date-checked landslide inventory, river records and situation reports. In 2017 the lower of two published rainfall thresholds for landslides was crossed 17 to 25 hours before the first failures and the higher one two to eight hours before, and gauges existed for both hazards but dedicated warnings for neither. By 2026 numbered landslide bulletins were issued for each sub-district under a draft national protocol and 38,422 people were sheltered. In Rangamati, where the district gauge recorded 343 mm in 24 hours in 2017 and 287 mm in 2026, deaths fell from 121 to one. A slope-stability model shows that the 2026 storm was no gentler on the slopes than that of 2017. The lower threshold is exceeded on 14 to 19 days of an average monsoon even at the region's two long-running gauges, while the higher one missed most dated landslides. The heaviest monsoon rain showed no detectable trend since 1950, but 3 °C of warming at about 7 % more rain per degree would make the higher threshold fire about 60 % more often. In 2026 the remaining landslide deaths concentrated in refugee camps on cut slopes despite warnings, suggesting that the missing part of the warning system lies between the warning and the people it reaches.