Juneau Brings in 41 Industrial Pumps to Prepare for Annual Glacial Lake Outburst Flood

For most communities, preparing for a flood might mean filling sandbags, clearing storm drains and watching the weather.

In Juneau, preparing for one of the largest glacial flooding threats in the country this summer meant bringing 41 industrial pumps into town.

The U.S. Army Corps of Engineers shipped the pumps to Juneau ahead of the 2026 Glacial Lake Outburst Flood, or GLOF, from Suicide Basin beside the Mendenhall Glacier.

The equipment became part of a much larger flood-defense system designed to protect homes, schools, roads and businesses throughout the Mendenhall Valley.

For Juneau residents, the annual event has become increasingly familiar. But the scale of this year’s preparation shows just how unusual the situation has become.

What Is a GLOF — or Jökulhlaup?

A Glacial Lake Outburst Flood, commonly shortened to GLOF, occurs when water trapped by a glacier suddenly escapes.

The phenomenon is also known by the Icelandic term jökulhlaup.

In Juneau, the problem originates at Suicide Basin, a basin alongside the Mendenhall Glacier that fills with rainwater, snowmelt and glacial melt during the warmer months.

The glacier essentially acts as a dam.

As the lake grows, pressure builds until water eventually finds a path beneath the ice. Once that happens, an enormous volume of water can drain from the basin, travel into Mendenhall Lake and surge down the Mendenhall River toward one of Juneau’s most populated residential areas.

Suicide Basin has produced recurring outburst floods since 2011. In recent years, however, the floods have become significantly more destructive.

The Mendenhall River reached record levels in 2023, again in 2024 and once more in 2025. The 2024 event alone damaged nearly 300 homes, bringing the threat directly into Mendenhall Valley neighborhoods.

Why Did Juneau Need So Many Industrial Pumps?

Flood barriers can hold back the Mendenhall River, but they can also create another problem.

Water can still seep beneath or through sections of the barriers. It can also enter neighborhoods through soils, joints and the existing stormwater system.

Once that water ends up on the protected side of a flood barrier, it needs somewhere to go.

That’s where the pumps come in.

Ahead of the 2026 flood season, Juneau worked with the U.S. Army Corps of Engineers to dramatically increase its pumping capacity.

The Corps ultimately shipped 41 industrial pumps to Juneau, with city planning documents calling for dozens of units to be positioned throughout vulnerable areas of the Mendenhall Valley.

These aren’t backyard water pumps.

The equipment is trailer-mounted and designed for extended operation. Some units can operate remotely and use “run-dry” technology, allowing crews to activate them before floodwater arrives.

That allows pumps to continue working even while residents and emergency crews move to safer areas.

Their job is simple but critical: collect water accumulating behind the flood barriers and pump it back into the Mendenhall River.

Lessons From the 2025 Flood

Juneau learned just how important that capability could be during the August 2025 GLOF.

The Mendenhall River reached a record crest of approximately 16.65 feet.

Temporary barriers helped prevent widespread destruction, but water still seeped into several areas behind them. Dozens of homes were affected, and the smaller pumps available at the time struggled to keep up with accumulating water.

That experience helped shape the city’s preparations for 2026.

In addition to the industrial pumps, federal and local crews prepared miles of temporary flood barriers, large sand-filled bags and more than 100,000 traditional sandbags.

Crews also removed downed trees from sections of the Mendenhall River to reduce the risk of debris striking or damaging flood-control barriers.

For a community of Juneau’s size, it amounted to an extraordinary flood-prevention operation.

Juneau’s 2026 GLOF Arrives

In August, monitoring equipment showed that Suicide Basin had filled and begun releasing water.

Officials activated evacuation preparations, staged emergency transportation and shelters, deployed pumps and closely monitored the Mendenhall River as water levels climbed.

Early forecasts suggested the river could once again approach the record levels seen in 2025.

Instead, Juneau received some welcome news.

The Mendenhall Lake gauge crested well below the highest initial forecasts, and the amount of reported property damage was substantially lower than many residents feared.

It was still a major flood event.

But compared with what Juneau had experienced in previous years — and what officials had prepared for — the outcome was considerably better.

The Other Side of the Mendenhall Glacier

To visitors, the Mendenhall Glacier remains one of Juneau’s most recognizable natural attractions.

Thousands of travelers visit the area each year to see the glacier, walk to Nugget Falls and explore the surrounding Tongass National Forest.

Many visitors also combine time at the glacier with a Mendenhall Glacier and whale watching tour, experiencing two of the natural features that define Southeast Alaska in a single day.

For the people who live beneath the glacier, however, Mendenhall has taken on another meaning.

Each summer now brings monitoring of Suicide Basin, flood forecasts, evacuation planning and preparations throughout the Mendenhall Valley.

It’s a reminder that Juneau’s relationship with its glaciers isn’t limited to sightseeing.

The landscape surrounding the city is actively changing, and residents are learning how to adapt alongside it.

An Increasingly Familiar Part of Summer in Juneau

Juneau’s 2026 preparations included an industrial pumping operation on a scale few communities would ever expect to need.

Forty-one industrial pumps. Miles of flood barriers. More than 100,000 sandbags. Multiple local, state and federal agencies preparing before Suicide Basin even began to drain.

The flood ultimately came in lower than initially feared, but the response illustrates how much has changed in only a few years.

A jökulhlaup may be an unfamiliar word almost everywhere else in the United States.

In Juneau, it’s becoming part of the local vocabulary.

For travelers interested in experiencing the glacier and the surrounding area firsthand, the Mendenhall Glacier remains one of the most popular things to do in Juneau.

Visitors can also explore our Juneau whale watching tours to experience another side of the wild landscape that makes Southeast Alaska unlike anywhere else.