Over a five-day period in the fall of 2006, Glacier National Park was hit with the flood of a decade, if not decades.

(Editor’s note: This is part of a Daily Inter Lake series tracing major stories from the past decade.)

Over a five-day period in the fall of 2006, Glacier National Park was hit with the flood of a decade, if not decades.

“It seems pretty clear this was an historic event,” said one park ranger soon after the deluge that caused severe damage to Going-to-the-Sun Road and other parts of the park.

From Nov. 2 through Nov. 7, 11 inches of rain was recorded at an automated weather station on Flattop Mountain, and on Nov. 7 alone, 8.5 inches of rain fell. All of the moisture came down on a foot of snow that had an additional two inches of water content.

What followed were cascades of water descending through many of the park’s central and northern drainages, overwhelming creek channels and causing lakes to rise by several feet.

In the Many Glacier Valley, Swiftcurrent Lake rose to a level where its outlet was overwhelmed and water was crossing over the only road to Many Glacier Hotel. The lower floor of the hotel was flooded with about six inches of water at one point.

But the heaviest and most expensive damage was on Sun Road.

The worst of it was just east of Logan Pass, below the East Tunnel, where there were three washouts. Two of them left much of the road intact, but the largest wiped out both lanes, creating a chasm spanning more than 100 feet.

“It’s a big, big hole,” Ranger Matt Graves said at the time. “It’s significant because there’s no material. Everything’s gone.”

On the west side of the Continental Divide, Sun Road was closed at Lake McDonald Lodge because of flood damage about a mile beyond Avalanche Campground, where the asphalt was scoured off the road.

For days after the flooding, park officials continued to discover damage as they were able to get up the road. At Logan Creek, the stream had rerouted itself a new channel that went across the road surface.

Further up the road, beyond the Loop, there was a massive debris slide, with trees, rocks and earth blocking both lanes of the road.

Flood waters caused damage elsewhere in the park, wiping out a horse bridge on Upper McDonald Creek and nearly taking out a viewing platform on the same creek.

The damage could have been worse if the heavy rain had fallen on the Divide Creek drainage, where there is a long history of flooding. Such a flood likely would have caused havoc in the downstream village of St. Mary.

Within a couple of weeks of the flooding, heavy snow fell, blocking Sun Road for the rest of the winter after only the most urgent repairs had been carried on lower elevations of the road.

More damage was discovered the following spring, including erosion damage to some trails.

By that time Glacier officials had secured emergency funding from the Federal Highways Administration. Repairs started on Sun Road in the tracks of plows clearing snow from the road.

At the 100-foot gap below the East Tunnel, a portable bridge was installed. Repairs on all three washouts in that area involved the installation of super-sized culverts and reinforced retaining walls.

Despite the extensive damage, hurried initial repairs allowed for Sun Road to be opened to traffic over Logan Pass by July 1, 2007.

About a year after the flooding, more than $5 million had been spent and most repairs on Sun Road were complete. But it took until the spring of 2009 to finish off all flood-related repairs in the park.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com