Evolution of a Drainage Network: Remote Sensing Analysis of the North Fork Toutle River, Mount St. Helens, Washington

摘要

The May 18, 1980 eruption of Mount St. Helens and subsequent volcanic events caused a large debris avalanche and several smaller pyroclastic flows and mudflows in the upper North Fork Toutle River. Major hydrologic disruptions resulted because of the newly created landscape. Aerial surveillance, mapping and evaluation of hydrologic conditions in upper reaches of the North Fork Toutle River valley were conducted from October 1981 until January 1983. The rate and mode of erosional and depositional landscape development was assessed and the potential for additional catastrophic events was evaluated. Major drainage network development was observed and the geomorphic trends of this evolutionary development were studied. A series of high-intensity, long-duration storm events in February 1982 caused significant changes in drainage network evolution which culminated with the inundation of Jackson Lake, resulting in a flood surge downriver and the failure of the spillway on the northern sediment retention dam.