This year’s glacial lake outburst flood originating from the glacier damned lake in Suicide Basin occurred on August 13. The water level of the Mendenhall River at Auke Bay reached 16.65 feet, a new record that tops even the previous records set in 2023 and 2024.
The water level of the crest was predicted almost exactly by the NWS. Extensive monitoring and warning systems in Suicide Basin and along Mendenhall River are in place to support forecasters, borough officials, and residents. See here for an overview and further information.
Compared to the previous two years, damage from flooding in the Mendenhall Valley was minor. After the severe impacts in previous years, extensive flood protection barriers were installed along the river to create a levee. The barriers mostly held, preventing widespread damage. Nonetheless, several streets flooded and some residents suffered flooding of their homes for the third year in a row.
The levee consists of so called HESCO barriers, a box construction made from collapsible wire frames that can be filled with sand or other materials. The barriers are generally considered a stopgap measure that was put in place after the damaging 2023 and 2024 events. Longer term response measures are still a matter of discussion.
Although the sensors and cameras in Suicide Basin allow near-real time monitoring of conditions, it is difficult to predict how the GLOFs will develop over the coming years and decades. The glacial and hydrological systems that control the overtopping of the glacial lake and the subsequent outflow are complex and influenced by multiple, interconnected factors. 2023, 2024, and 2025 have been exceptional in the time series to date in terms of the amount of water that was released from the basin.