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|Title:||Overview of Tanana River monitoring and research studies near Fairbanks, Alaska|
|Authors:||Northwest Hydraulic Consultants.|
United States. Army. Corps of Engineers. Alaska District.
Tanana River Monitoring and Research Program
Neill, C. R. (Charles Robert), 1926-
Buska, James S.
Chacho, Edward F.
Collins, Charles M.
Gatto, Lawrence W.
River groin construction
River levee construction
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Special report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 84-37.|
Abstract: The Tanana River changes character in the vicinity of Fairbanks, from the braided pattern upstream of North Pole to the anastomosing or irregular meander pattern upstream of the Chena River confluence. This transition in planform is accompanied by a marked decrease in gradient and a change in dominant bed material from gravel to sand, Within the past 50 years the river has been affected by a variety of human activities, including flood control works, access causeways and gravel extractions. The river's cross-section shows large variations in width and depth from one location to another, but total cross-sectional area and mean velocity are relatively constant at a discharge of about 60,000 cfs, close to the mean annual flood. Annual flow hydrographs are quite similar from one year to another. Sediment transport in the river averages about 360,000 tons per year of bed load, approximately equally divided between sand and gravel sizes, and about 28,000,000 tons per year of suspended load, of which about 35% is sand and the rest silt and clay. Natural channel processes are dominated by within-bank shifts in channel and bar patterns and cross-sectional shapes, erosion of the main floodplain and island banks being fairly localized and generally proceeding at modest rates. No relationships have been discerned between rates of bank erosion and soil, permafrost or vegetation factors. Response to human intrusions is generally difficult to disstinguish from natural processes beyond the immediate vicinity of the intrusions and more than a short time after cessation of activity. Details are discussed regarding observation of inferred response to groin construction and gravel extraction. Generally structural intrusions and gravel extraction activities that have not constituted a major disturbance to the river system have achieved their desired results with no apparent adverse effects of any significance. Blockage of the north channel at Goose Island by causeways, reoccupation of gravel extraction areas from permanent bars and islands, and secondary channel closures are believed to have considerable effects on flow and erosional patterns for some distance downstream. The Phase III in-river levee and groin construction constituted a strong local disturbance of the river system where local river slope was steepened and large quantities of bed material were put into transport from pilot channel enlargement as the river adjusted to the new alignment. As of the end of 1982, the full and final effects of this disturbance were not clear. Recommendations are given regarding impacts from human activities, alleviation of impacts, levee protection, further interpretive analysis and future monitoring of river behavior.
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|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Special Report|