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W. G. Sikonia

Publications and source records attributed to W. G. Sikonia.

6 recordsLinked to original sources
USGS1986

Velocity and surface altitude of the lower part of Hubbard Glacier, Alaska, August 1978

The terminus position and locations of numerous points on the lower part of Hubbard Glacier were determined from 1:58,000 scale vertical aerial photographs taken July 30, 1978 and August 23, 1978. The same surface features were located on each set of photography, allowing displacement during the time interval to be measured. Velocity of the lower glacier for the 24-day interval was about 7 m/day. The terminus receded 45 m between the two dates. (Author 's abstract)

Open-File Report↗
USGS1985

Impact on the Columbia River of an outburst of Spirit Lake

A one-dimensional sediment-transport computer model was used to study the effects of an outburst of Spirit Lake on the Columbia River. According to the model, flood sediment discharge to the Columbia from the Cowlitz would form a blockage to a height of 44 feet above the current streambed of the Columbia River, corresponding to a new streambed elevation of -3 feet, that would impound the waters of the Columbia River. For an average flow of 233,000 cubic feet in that river, water surface elevations would continue to increase for 16 days after the blockage had been formed. The river elevation at the Trojan nuclear power plant, 5 miles upstream of the Cowlitz River, would rise to 32 feet, compared to a critical elevation of 45 feet, above which the plant would be flooded. For comparison, the Columbia River at average flow without the blockage has an elevation at this location of 6 feet. Correspondingly high water surface elevations would occur along the river to Bonneville Dam , with that at Portland, Oregon, for example, rising also to 32 feet, compared to 10 feet without the blockage. (USGS)

Water-Resources Investigations Report↗
USGS1980

Columbia Glacier, Alaska: Recent ice loss and its relationship to seasonal terminal embayments, thinning, and glacial flow

In 1974 the U.S. Geological Survey began an intensive investigation of the stability of Columbia Glacier, a calving tidewater glacier terminating in Columbia Bay, near Valdez, Alaska. Aerial photographs taken in 1957 and a sequence of photographs taken at about 2-month intervals since 1976, when analyzed photogrammetrically, provided detailed data on changes in Columbia Glacier's thickness, flow rate, and terminal position. Annual embayments in the glacier 's terminus form during the summer-autumn season in most years; the size of embayments appears to be related to (1) the thickness of the glacier, and (2) the position and nature of subglacial freshwater discharge. Embayments have apparently increased in size in recent years; the largest embayments yet observed formed in 1975, 1976, 1977, and 1978. From April 1, 1977, to April 1, 1978, the total volume of ice calved was about 1.0 cubic kilometer. By January 1979 the glacier front had retreated from Heather Island. Glacier flow varies seasonally and synchronously in the lower 17 kilometers of the glacier; large accelerations occur near the terminus in response to embayment formation. Daily speed within 5 kilometers of the terminus increased from about 1.9 meters per day between 1963 and 1968 to about 2.7 meters per day between 1977 and 1978. In the lowest 15 kilometers, the glacier surface was lowered about 9 meters between 1957 and 1974, and about 13 meters between 1974 and 1978. Columbia Glacier is being reduced in mass due, in part, to recent losses caused by large embayments forming annually. If such reduction continues it will result in a drastic retreat.

Alaska↗