Alaska Capital Declares Disaster Over ‘Catastrophic Flooding’ Threat from Glacial Lake

Alaska Governor Mike Dunleavy has issued a disaster declaration in response to an “imminent threat of catastrophic flooding” from a glacial lake outburst flood (GLOF) tied to Suicide Basin, a side basin of the Mendenhall Glacier. The move follows a joint local disaster declaration by the City and Borough of Juneau and the Central Council of the Tlingit and Haida Indian Tribes of Alaska.

According to officials, “Hydrologic monitoring by the National Weather Service (NWS) and US Geological Survey (USGS) confirms that the volume of water currently impounded in Suicide Basin has reached or exceeded levels observed during prior flood-of-record events. A release is expected at any time.” Flooding could impact the Mendenhall River and surrounding neighborhoods in the Mendenhall Valley.

This year’s conditions follow two consecutive years of severe flooding, including the August 2024 GLOF, which caused widespread damage and prompted both state and federal disaster declarations. Dunleavy said, “By issuing this declaration before the flood occurs, we can position state resources and personnel in advance… Our goal is to act early to reduce impacts and preserve community safety.”

City Manager Katie Koester emphasized readiness: “The HESCO barriers are in place, and we believe they will perform as designed… This proactive emergency declaration gives us the tools to act swiftly and decisively.”

The NWS confirmed that Suicide Basin is at full capacity and beginning to overtop, urging residents to finalize preparations. Evacuation notices are being distributed to all homes within the 17-foot inundation zone as authorities prepare for a possible historic flood event.