Juneau in Alaska is using real time flood forecasting and public information tools to help residents prepare for recurring glacial outburst floods linked to meltwater and rainfall around the Mendenhall Glacier.
The US city has experienced repeated flooding from the basin beside the Mendenhall Glacier since 2011. The floods remained relatively limited for years, but the river reached record levels in 2023, followed by new benchmarks in 2024 and 2025. Scientists expect similar floods to continue occurring in the coming decades.
The recurring floods have caused significant damage to homes and infrastructure. In one case, a resident home was inundated by a roughly 3-foot wave, causing damage estimated at $150,000. Another resident reported 16 inches of water in a garage and seven months of repairs costing about $35,000.
Glacier basin creates sudden flood risk
The flooding is associated with a basin beside the Mendenhall Glacier known as Suicide Basin. Meltwater and rain accumulate in the basin until increasing water pressure lifts part of the glacier and creates a drainage pathway releasing a large volume of water toward the Mendenhall River.
During major outburst floods the basin can release more than 15 billion gallons of water, according to scientists cited in the report.
In 2023 flooding inundated around two dozen homes and caused millions of dollars in damage. The following year, another event damaged nearly 300 homes increasing concern among residents and officials about the recurring nature of the hazard.
Juneau’s location adds to the challenge. The city has around 32,000 residents while neighbourhoods in the Mendenhall Valley lie directly in the potential path of floodwaters.
Forecast dashboard gives residents more time
Researchers from the University of Alaska Southeast and the Alaska Climate Adaptation Science Center worked with Juneau officials to develop an online flood dashboard. Introduced in 2025, the tool translates glacier, hydrology and flood data into forecasts that residents can use to prepare for rising water.
The dashboard provides flood maps forecasts and information explaining how glacial outburst floods develop. In 2025, more than 15,000 people accessed it for real time flood information.
Researchers say the forecasts can predict the height of glacial floods within hours giving residents additional time to move belongings, protect entrances or leave threatened areas.
The tool has also helped residents understand why flooding occurs and how rainfall glacier conditions and water accumulation in the basin can influence the timing and scale of an event.
The information is being used by Juneau officials to plan physical flood defences. After analysing flood data authorities began studying where temporary barriers should be installed along the Mendenhall River.
The city has installed roughly six miles of barriers in areas between the river and nearby homes. Hesco barriers wire mesh structures filled with sand and gravel have been placed around homes, public buildings and other vulnerable locations.
Officials say the dashboard helps residents understand the level of risk and the purpose of these protective measures, while allowing homeowners to see how high floodwaters could potentially rise near their properties.
Scientists involved in the project say Juneau’s experience demonstrates the importance of making technical hazard information directly accessible to communities.
The same approach could potentially be adapted for other recurring hazards including hurricanes, storm surges and river floods by providing residents with timely forecasts that support individual decisions.
For Juneau residents living near the Mendenhall River the system has become part of their regular flood season routine. Some now check the dashboard several times a day, prepare sandbags and keep emergency equipment ready.
The experience highlights a broader shift in disaster preparedness when a hazard cannot be completely prevented accurate forecasting and clear communication can help communities understand when danger is approaching and make decisions before floodwaters arrive.