The Yukon Flats are centered on the confluence of the Yukon River, Chandalar and Porcupine Rivers in central Alaska. Alaska Highway through mountains with permafrost requiring patching. Gradually, a network of roads was constructed that today links many of the communities. Commercial river traffic ended a few years later. The construction of the Alaska Highway in 1942 ( Figure 18), to provide a road link from the Lower 48 to Alaska through Canada as a defense measure during World War II, signaled an end to a way of life in the Yukon. Although only a few struck it rich, the 1897 gold rush to the Klondike in the Yukon Territory led to commercial mining in the Yukon River Basin. At its peak in 1900, Dawson City ( Figure 17) was home to as many as 25,000 people from every corner of the world. However, these first economically beneficial strikes in the Yukon River Basin were only a trickle compared to the tidal wave of miners that would come with the Klondike discoveries at Dawson City, Yukon Territory, Canada in 1897. Additional discoveries were made in the Circle and Rampart areas in 1893. In 1885, miners found placer gold on the Stewart River and in 1886, gold was discovered on the Fortymile River. Beginning in the 1870s, early explorers established a number of trading posts up and down the Yukon River. One of the earliest explorations of the Yukon Basin by Europeans was undertaken by Robert Campbell of the Hudson Bay Company. Interest in furs, not gold, lured the first outsiders to the Yukon. Those who did not trade with the coastal Tlingits of southeastern Alaska remained free of effects from other cultures until the 19 th century. After crossing, by both boat and walking, Beringia or the land bridge that once linked Asia and America, these early people occupied Alaska and the western part of the Yukon Territory. The aboriginal people of the Yukon River Basin may be among the oldest known residents of North America. River sand bar habitat and wet herbaceous plants west of Circle, Alaska.ĭry herbaceous, ice/snow and rivers, streams and lakes.Ģ.2. The Cordilleran Ice Sheet was a major ice sheet that periodically covered muchįigure 16. The causes of soil erosion and sedimentation were permafrost, alpine glacial melting, gold mining, gas and oil drilling, pipeline construction ( Figure 12), cold war military sites, forest fires and steep slopes. The primary objective was to document the sedimentation in the Yukon watershed with little accelerated soil erosion as a result of agriculture or urban development. With hotter and dryer conditions there has been an increase in forest fires and melting of the permafrost ( Figure 9) which leads to increased water flows, sediment transport ( Figure 10) and organic carbon transfer to Yukon River bottomlands, Yukon Flats, Yukon Delta ( Figure 11) and the Bering Sea. The cumulative effects of man’s activities on the Yukon River Basin cannot be made due to limited availability of water quality data. Anthropogenic effects on the water quality of the Yukon River include pre-regulation mining ( Figure 8), old Cold War military sites and atmospheric processes. Most of the water flow is between May and September. The causes of the soil erosion and sedimentation were permafrost, alpine glacial melting, drilling for gas and oil, road construction, gold mining, cold war military sites, pipeline construction, forest fires and steep slopes. The primary objective was to document the sedimentation in the Yukon watershed with little soil erosion as a result of agriculture or urban development. Annual temperatures have been rising since the 1840s which could contribute to higher runoff water flows and greater sedimentation. The ecological functioning, with food and nutrient delivery, migratory cues, breeding, habitats, and riparian and floodplain ecological cycles are all dependent on the transported sediment at specific times of the year. The glacier, snow and permafrost melting, runoff, erosion, transport, deposition and storage of gravelly, sandy, silty and clayey sediments determine the habitat distribution and water quality within the river channels and floodplains. The physical, chemical and biological attributes of the Yukon River and tributary basins impact soil erosion, sediment transport and sediment delivery.
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