| South Coldwater Creek valley was buried to a depth of 10 to 75 meters by volcaniclastic debris during the May 18, 1980, eruption of Mount St. Helens. To avert catastrophic breaching of nearby Spirit Lake blockage, a tunnel was bored from Spirit Lake basin into South Coldwater Creek valley and was opened in April 1985. Formation and development of the South Coldwater Creek channel during 1980-85 and the response of South Coldwater Creek to augmented discharge during April to September 1985 illustrate interactions among changes in channel slope, width, depth of incision, and sediment load. These interactions relate to the characteristics of unstable stream channels, effects of augmented discharge that exceeds previous channel-forming discharge, and effects of large fluctuations in water and sediment discharge on stream channels. -- Meyer, 1994 |
