Fluvial Biogeomorphic Evolution of the Upper South Fork Toutle River, WA After the 1980 Eruption of Mount St. Helens

摘要

The eruption of Mount St. Helens in 1980 severely impacted the woody vegetation within the geomorphic floodplain as well as the morphology of the Upper South Fork Toutle River. Historic aerial imagery and LiDAR data were used in combination to create snapshots of the channel and vegetation in 1980, 1983, 1996, 2003, and 2014. This data was mapped and analyzed using GIS, with the primary focus on 2D channel change, vegetation change, and channel-vegetation interactions from 1980 to 2014. No vegetation was discernable in 1980-83 but the vegetation present in 1996 increased in area and in density from 1996 to 2014. The number of channels locations were dependent on vegetation density and presence while vegetation growth occurred predominately in areas previously occupied by the channel.