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New website improves Juneau flood preparedness

A new flood preparedness website for Juneau residents is now live.

The was developed by the University of 911���� Southeast and the 911���� Climate Adaptation Science Center.

The first-of-its-kind, publicly accessible website shares interactive flood inundation maps and provides valuable flood forecasting information for the Mendenhall Valley under different glacial lake outburst flood scenarios. The online maps, which were contracted by the City and Borough of Juneau, allow users to view inundation areas and associated water depths.

“The Juneau Flood Dashboard provides a new way to visualize flood inundation maps,” said Eran Hood, a hydrologist and professor at UAS who led the development of the website. “Making the maps easily accessible and viewable will increase residents’ ability to make informed decisions and protect themselves and their property.” 

An August 2024 glacial lake outburst flood, the 14th in as many years in Juneau, was also one of the most devastating. Millions of dollars of property were inundated within a few hours when the Mendenhall River flooded.

The floods originate in Suicide Basin, which each winter slowly fills with rain and meltwater. In the spring and summer, as Suicide Glacier retreats amidst warmer conditions, the basin begins to fill more rapidly. The Mendenhall Glacier itself serves as an ice dam that holds this water back until a weak spot forms and a channel flows through it — releasing a burst of water into the Mendenhall River and valley below, typically in early August. 

Using the new website, residents can search individual addresses and toggle through inundation maps at different flood levels — including those showing how flooding will change when barriers are operational. 

To help prepare for potential evacuations, color-coded flood stages show roads that may become inundated during an outburst flood. Residents can also find answers to frequently asked questions, explore the definitions of flood stages, access historical flood data and learn more about the science behind the Mendenhall Glacier and Suicide Basin.

Mendenhall Lake gage readings collected by the U.S. Geological Survey and alerts issued by the National Weather Service refresh on the website every 15 minutes. 

Much of what is known about Juneau’s annual flood is the result of more than a decade of AK CASC research. Since the first flood in 2011, before the annual floods became a major public safety issue, the center invested in myriad projects dedicated to understanding Suicide Basin. 

In 2018, the AK CASC funded a that remains a critical source of data for ensuring the accuracy of the annual flood forecasts issued by the National Weather Service. The continuation of this program will allow researchers to track changes in the basin and accurately forecast flood volumes from annual outburst floods. 

Flood preparedness and communications matter a great deal to Juneau’s residents. Data back to 2004 indicate that Google searches in Juneau containing the keywords “flood,” “glacier,” “Mendenhall” and “insurance” reached their highest levels in the past two years. 

According to Aaron Jacobs, a meteorologist with the NWS, the regularly receives close to a million page visits annually. The new Juneau Glacial Flood Dashboard complements the site for Suicide Basin and allows interactive access to the new flood inundation maps for the Mendenhall Valley.

The annual glacial lake outburst flood forecasts continue to be an existential challenge for the capital. 

“In the future, depending on how the basin evolves, the flood could get bigger,” Hood said. “We know that this event will last for several decades, which is why studying it and improving our understanding of how it will evolve is critical.”

ADDITIONAL CONTACT: Eran Hood, 907-796-6244, ewhood@alaska.edu

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