Leaky Ice Dam Prompts Evacuations in Alaska as Record Floods Loom

A water basin in Alaska is overflowing its ice dam, the Mendenhall Glacier, and flooding the state capital, Juneau. Experts expect the likely record-breaking event to peak today, and officials have asked residents in parts of the city and borough to evacuate.

The flood doesn’t come as a surprise. Years ago, a small glacier on the other side of Mendenhall Glacier—which is just 12 miles (19 kilometers) from Juneau—receded and left a basin in its wake, according to the Associated Press. Since then, rainwater and snowmelt fill the basin during the warm months of the year, with water sometimes leaking under or around the Mendenhall Glacier into Mendenhall Lake on the other side, then into the Mendenhall River and downstream.

This mechanism has caused problems since 2011. 2023 and 2024 saw back-to-back record-breaking floods. Last August, the river reached 16 feet (5 meters), which was around one foot (0.3 meters) more than the previous year. This year, experts say the flooding could reach between 16.3 and 16.8 feet (4.96 to 5.12 meters).

“This will be a new record, based on all of the information that we have,” Nicole Ferrin, a weather service meteorologist, said at a news conference Tuesday, as reported by the Associated Press.

Alaska Governor Mike Dunleavy issued a state disaster declaration on Monday, explaining that “hydrologic monitoring by the National Weather Service (NWS) and U.S. 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,” as detailed in a statement by the Division of Homeland Security and Emergency Management.

“A release is expected at any time. Flooding is likely to affect the Mendenhall River and surrounding neighborhoods in the Mendenhall Valley,” the statement continues, adding that authorities installed over two miles of flood control barriers along the Mendenhall River. In fact, the expected water release took place yesterday morning.

“We are prepared for this situation. We’ve been preparing for this situation,” said Sabrina Grubitz, public safety manager for the Central Council of the Tlingit and Haida Indian Tribes of Alaska and the commander of a unified local government task force responding to the flood, according to the Alaska Beacon.

The basin’s overflow comes during a summer that has already seen numerous deadly floods throughout the United States. The tragic events have pulled the U.S. Federal Emergency Management Agency’s (FEMA) outdated flood maps back into the spotlight, along with their significant implications for how communities prepare for such natural disasters.