The glacial lake outburst flood (GLOF) from Suicide Basin occurred on August 13th, exactly a year after last year’s flood. Water levels on the Mendenhall River remained slightly below predictions and below the previous record with a crest of 14.7 feet at the Auke Bay gage. The 2025 GLOF crested at 16.6 feet.
This year’s event was again forecast in detail by the NWS based on the extensive monitoring system in place at Suicide Basin. Despite the installation of extensive flood barriers, about 5000 residents of Juneau’s Mendenhall Valley were advised to evacuate ahead of the flood in case due to the possibility of barriers failing. Juneau officials declared the flood threat over on late Thursday (August 13) afternoon.
Although the river crested above “major flood” stage the 2026 event was less damaging than previous GLOFs with only minor damage reported to homes and other infrastructure. The HESCO barriers held with minimal seepage.
Flood preparation measures, in particular the HESCO barriers, and extensive monitoring of Suicide Basin have proved successful in minimising GLOF damage in 2025 and 2026 after very destructive events in 2023 and 2024. However, it remains difficult to predict the long-term evolution of the glacial and hydrological systems that contribute to the annual overtopping and outflow of the lake in Suicide Basin.
Further information can be found on the overview page of the Suicide Basin monitoring network (weather.gov/ajk/suicidebasin) and the Juneau Glacial Flood dashboard.
