dam history forecasts catastrophe on the alsek

‘Then one time, you know, when my father’s mother was a little girl up at Tmx kayani on the Tatshenshini, there was a flood all over It…

‘Then one time, you know, when my father’s mother was a little girl up at Tmx kayani on the Tatshenshini, there was a flood all over It was because my father’s people made fun of a seagull. They threw it in the fire. It was a young one and couldn’t fly. They threw it in again. All its feathers burned off. They laughed at it.

“And then a great flood came. And there was no place to be safe. That glacier broke that used to go across the Alsek” (Frederica De Laguna, interviewing Emma Ellis, August 5, 1972)

That’s how a resident of the Yakutat region of southeast Alaska described the cause and effect of the damming of the Alsek back in the 1800s.

The Lowell Glacier surged across the Alsek River Valley, blocking the Alsek River and created a huge lake that filled the valley for miles. Then the dam burst and a huge wall of water swept down the Alsek River to Dry Bay, causing carnage and death as it went.

Jeff Bond, surficial geologist with the Yukon Geological Survey, gave an interesting account, from a scientist’s vantage point, of the same events at a slide show he presented at the MacBride Museum on Thursday October 16 title: Neoglacial Lake Alsek: The Little Ice Age Flooding of Haines Junction.

It’s part of the family lecture series sponsored by the MacBride Museum on the “ologies”. You know … geology, archeology, paleontology, and so forth. Check with the MacBride Museum — there are more interesting lectures to come.

The Alsek River has been dammed numerous times over the past few thousand years.

The most recent events occurred around 1852, and 1909, and they turned Haines Junction into lakefront, if not lake bottom, property.

Bond relates it to the Little Ice Age, a period that spans several centuries from the 1400s till the 1800s.

During that time, the temperature dropped a couple of degrees below what we now experience, but that was enough to cause a dramatic shift in climate all over the world.

Prior to that period, the weather was warmer. The Norse settled Greenland, and the British grew grapes, and produced wine, which they exported to France

By the 15th century, things had turned colder. The Thames River froze over for the first time in 1408, and the Norse were gone from Greenland. In the French Alps, glaciers began to advance. Bond showed pictures of the Mer de Glace glacier at Chamonix, France at a stage of advance in which an entire valley was filled with ice. That same valley today is ice-free.

When the glacier made its maximum advance, it ground away farms and entire villages. He showed one slide taken during a visit to Chamonix some years ago, where a monstrous boulder, perched at the end of a glacial moraine, rested on the stone foundation of what was once a farmhouse. This was stark evidence of the havoc that can result when one of these unstoppable rivers of ice surges down a valley.

Imagine watching, year by year, as a massive wall of ice advances until it crushes your home into splinters!

Bond explored some explanations for this glacial activity. Sunspots were suggested as one cause. Sunspots actually increase the warmth of the sun. Bond presented evidence that suggested that glacial surges could be related to periods when there was no sunspot activity. (He also suggested that the absence of sunspots this summer explains in part why we had such crummy weather).

Another possibility to consider, he suggested, was volcanic activity. Cooling would be enhanced by increased atmospheric dust. The period between 1812 and 1815 was a time of enhanced volcanic activity that culminated in1816 AD, the “year without summer”, that afflicted Europe and North America resulting in summer frosts.

This is where Haines Junction comes into the picture. He placed the village in the geographical context of the Alsek River and the Lowell Glacier. The residual moraines along the hillsides where the Lowell Glacier enters the Alsek Valley are now high above the current-day ice and indicate how thick the glacier was at its maxeimum during the Little Ice Age.

Just downstream from the Lowell Glacier is another glacier, the Tweedsmuir, which was surging this summer and which has advanced a few hundred metres in the last year. The US Geological Survey has a webcam monitoring the situation because of the potential damage to the Alaskan community in Dry Bay that will result from this activity.

Currently, there is a narrow channel between the glacial front through which the Alsek River flows. An advance of another hundred metres or so could dam the river and create a reservoir behind the ice. Fortunately, the lake formed by this surge does not pose any threat to the community of Haines Junction.

Research funded by Foothills Pipeline in the 1980s facilitated a study of the lakes formed by different surges of the Lowell Glacier. Wave-cut shorelines are visible for hundreds of metres up the hillsides of the Alsek valley, and tree-ring dating of the driftwood along these old beaches has enabled some dating of the different events.

From this work, Bond showed graphic depictions of old shorelines along the Alsek and Dezadeash valleys in the area of Haines Junction. The deepest lake in recent times was formed in the late 1400s at an elevation of 640 metres. A later event, in the early 1700s created a reservoir almost as deep; a third event, around 185, created a body of water at around 595 metres elevation. Other lesser damming episodes probably occurred during the Little Ice Age, but evidence of these would have been washed away by subsequent events.

Bond showed a series of modified Google images of the Haines Junction and Alsek River area that illustrated what these elevated water levels would do to the landscape. In the highest of the recent damming events, present-day Haines Junction was underwater, and a lake extended as far up the Dezadeash valley as Marshal Creek.

During lesser damming episodes, Haines Junction would have been at least lakefront property.

While this paints a gloomy picture of the prospects for property owners in Haines Junction, It suggests even worse things are in store for the people living downstream. Oral Traditions of the First Nations tell of terrible floods with great loss of life that occurred down the Alsek Valley and into Dry Bay.

Scientific evidence supports this. Bond showed pictures of giant ripples or flood dunes up to four metres high that give mute testimony to the violence of the catastrophic flooding that must have occurred when the ice gave way.

The force of a wall of water many metres high, surging down the Alsek valley would have been something to behold, and to fear.

Traditional and scientific knowledge are hard to ignore. If you plan to buy real estate at the Junction, think about a lot up high with a good view.

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