Suicide Basin, a glacial side basin of icy water along the Mendenhall Glacier near Juneau, is rapidly filling and is expected to reach capacity by mid-August, prompting heightened monitoring and flood preparedness by local and state officials and families in the Mendenhall Valley areas prone to flooding.
According to the latest update from Aug. 4, the basin’s water level has risen nearly 27 feet in the past week, climbing at an average rate of about 3 feet per day. The current water elevation stands at 1,340 feet — 28 feet below its estimated spillover point of 1,368 feet. The water elevation was 1,337 on Sunday.
View the USGS timelapse camera images at this link.
The spillway threshold has been recalculated this summer due to a change in ice conditions. A recent drone survey conducted by the University of Alaska Southeast revealed that the elevation of the basin’s natural ice dam that holds the water back is 3 feet lower than it was last year.
Suicide Basin has produced annual glacier lake outburst floods since 2011, sending torrents of water down the Mendenhall River. The most destructive flood occurred on Aug. 6, 2024, damaging homes, parks, and infrastructure in the Mendenhall Valley. That historic event happened when the basin reached its capacity at 1,357 feet.
The last release event from Suicide Basin occurred on Oct. 20, 2024.
The timing and intensity of the next outburst flood depend on several dynamic factors, including temperature fluctuations over the Juneau Icefield and precipitation from possible late-summer storm systems. If current trends continue, an overflow event could begin as early as the second week of August.
Residents in flood-prone areas near Mendenhall Lake and River have been urged to stay informed through updates from the National Weather Service and the City and Borough of Juneau. Emergency managers are preparing early-warning protocols and updating response plans in anticipation of another potential flood.