Scientist sizes Dyea dangers
By ANDREW CREMATA
Earthquakes, tsunamis and glacial outburst floods are just a few of the potential dangers that face residents of Skagway and Dyea. It may be an unsettling topic for friendly dinner conversation, but these and other threats were discussed at the National Park Services auditorium on Oct. 1, by Denny Capps in his presentation, Geologic Hazards of the Taiya Watershed.
Capps came to Skagway from Louisiana as a volunteer to map new and potential glacial outburst events, and identify other potential geohazards that could affect us now or in the future. One photo from his slide presentation drew a collective gasp from the audience of about 30. It was the Taiya River bridge with water raging over the bridge itself. Or was it?
This is not the Taiya River bridge, he said, but the similarities really struck me. And this COULD happen in Dyea.
A glacial outburst flood is the release of large amounts of stored water by glacial action, said Capps. The West Creek Glacial Outburst flood cost the city some $250,000, not including the personal losses of Dyea residents who were directly affected by the disaster. Fred and Cathy Hosford suffered $27,000 in losses and damage. They did receive aid from our local Fraternal Order of Eagles but the majority of the expense turned out to be a total wash. Another such event could be looming over the future of Dyea.
The Taiya watershed covers an area of 190 square miles. All water in this region flows out through Dyea. That is a lot of area to explore. Indeed, the rough terrain would have been impossible to examine if not for the assistance of Temsco helicopters.
One specific area of concern is the Nourse Glacier. Historical records provide evidence that a glacial outburst flood occurred here. Satellite reconnaissance photos combined with physical observations point to a major event sometime around 1885. Could it happen again?
The Nourse Glacier holds two individual lakes within its grasp, and its grasp is slipping. The upper Nourse hanging lake poses the largest threat. Capps relates, It is held in by a 400-foot-high moraine that is one third of a mile wide. The lake itself is 100 feet deep. The glacier, like 99 percent of the glaciers in Southeast Alaska is retreating, about one mile in the last 50 years. (See sidebar)
Why is this important? As the glacier melts it exposes the moraine to forces such as erosion that can undermine the very structure of a hanging lake. Slides during the presentation exposed the West Creek moraine as being structurally unsound months before the actual event. Once the glacier had receded enough, the moraine began to erode. Photographs even showed water seeping through the seemingly impenetrable structure.
The threat that this type of event poses for residents of the Dyea area is substantial. Capps recommends further evaluation of the stability of the moraine in response to earthquakes and fluvial incision, annual monitoring of the glacier and even seeking funding for an early warning device. An early warning would provide mere minutes for those who are threatened, but those few minutes could be life-saving.
Earthquakes can trigger glacial outburst floods. They can also do plenty of damage on their own. A photo of major and minor faults that run through and around the Skagway area looked less like a map and more like a completed word search puzzle. The most dangerous fault in our area is the Denali fault. No, it is not a misprint, this fault runs from Denali all the way directly through Haines and continues south from there. The Nov. 3, 2002 earthquake was on this fault in the region of Denali National Park. We all felt this 7.9 behemoth here in Skagway. In fact, the effects of this earthquake were recorded all the way to Arkansas. The chances of an earthquake of that magnitude happening under our feet is slim, but even though earthquakes cannot be predicted Capps pointed out that the largest possible earthquake we face here is a 4.5-6.0.
On average residents of Skagway feel an earthquake once every two to three years. Capps pointed out, I still havent actually felt an earthquake, but I really hope I get to before I leave town. A collective chuckle from the audience seemed to place him in the minority.
Another major fault lies to our west. This is the Fairweather fault where the Pacific and North American tectonic plates collide. However, an earthquake need not be local to affect Skagway, an earthquake as far away as Japan could trigger the dreaded tsunami or tidal wave.
There have been three tsunamis in Skagway since 1958. The largest, in 1994, caused $21 million in damage and took the life of one person. This events most likely cause was an underwater landslide.
It can get a lot worse.
On July 9, 1958 a 7.9 earthquake rattled the Yakutat area. This earth-shaking event caused a landslide of some 40 million cubic yards of rock that rattled and rolled into Gilbert Inlet at the head of Lituya Bay. The wave it created was 1,740 feet high, stripping every living thing from the sides of the surrounding mountains. An early warning device would not be of much use in this type of scenario, but prayer might be.
Capps stresses that his work thus far has only been reconnaissance, and that future work is reliant on funding. When queried by a member of the audience if any potential glacial outburst events pose a direct threat to Skagway, Capps answered that he has not even begun to examine the area. More money would be needed to expand the area he is able to explore. This is a dynamic system with so many factors involved, that much time and effort will be needed to ensure that a repeat of the West Creek disaster doesnt happen, he said.
Kathy Hosford isnt worried. She says that the dike the city built in response to the disaster is a sight to behold. She relates, I feel protected, and I want everyone to know that Dyea is back on the map!
Is global warming responsible?
For those who have been watching the Harding Glacier, visible from downtown Skagway, it is obvious it has been shrinking at a substantial rate. This is the trend with the vast majority of glaciers in Southeast Alaska, some 99 percent of them. This melting trend can cause a host of potential hazards for those who live in their vicinity. Is global warming to blame?
Dr. Maynard M. Miller seems to think so. Dr. Miller is the Director and Professor of the Glaciological and Arctic Sciences Institute at the University of Idaho. Since 1959 Dr. Miller has spent much of his life on the cold surface of the Juneau Ice Field, and his findings are startling.
The Juneau Ice Field is 5,000 square miles of rock and ice, half of which is just ice. The Juneau Ice Field is distinguished as being extremely useful for monitoring because it is a temperate (warm) glacier, he relates, and the flow rate is 100 times faster than cold ones.
Temperate glaciers are directly affected by temperature, much more so than ones at higher elevations like glaciers in the St. Elias range. Because glaciers are sensitive to temperature, Dr. Miller believes they are an indicator of climate changes on a global scale.
On a local level, many longtime Skagway residents remember much colder and harsher winters in their younger days. Resident and local weather guru Richard Dick explains, Back in the 40s the winter weather was always cold, windy and snowing. Today the weather is always changing. It will be warm, then cold. He predicts another mild winter with very little snow.
Dr. Miller has physical evidence backing up these stories of harsh winters past. When his team began taking measurements in the late 40s and 50s from a major research station atop the Taku Glacier, the minimum temperature was 35 to 40 below Fahrenheit. In the past seven years the minimum temperature has been a balmy minus ten degrees.
This is especially disturbing to Dr. Miller. He continues, Starting in 1995, we should be in a cooling phase that lasts until 2005. Global warming has overridden this 90-year cycle. When we go into our warm phase in another 30 to 40 years, it is going to be hot.
Dr. Miller stressed that while these changes may not be greatly felt here in the way of temperature changes, mostly our grandchildren will feel it in warmer parts of the planet.
Dr Miller sums it up, We are in a climatic revolution which will have major economic and political ramifications. The die is cast. There is no way we will stop the juggernaut of global warming now that it is started. AC