Chena River Lakes Project, Fairbanks, Alaska. Overview of Tanana River Monitoring Research Studies Near Fairbanks, Alaska

摘要

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. 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 being fairly localized and generally proceeding at modest rates. Details are discussed regarding observation of inferred response to groin construction and gravel extraction. Recommendations are given regarding impacts from human activities, alleviation of impacts, levee protection, further interpretive analysis and future monitoring of river behavior.