Changes in Channel Morphology in Response to Tamarisk Removal Along The Virgin River in St. George, Utah

Authors: Dakota Whitman*, University of Oregon
Topics: Geomorphology, Geographic Information Science and Systems, Remote Sensing
Keywords: geomorphology, biogeography, vegetation mapping, remote sensing, fluvial geomorphology, GIS, geographic information systems
Session Type: Virtual Poster
Day: 4/9/2021
Start / End Time: 3:05 PM / 5:50 PM
Room: Virtual 52
Presentation File: Download

Perennial dryland rivers in the southwestern United States are rare sources of consistent water supply and biodiversity in otherwise water-stressed environments. However, Tamarisk, an invasive shrubby tree, has colonized vast portions of floodplains on perennial dryland rivers, leading to reductions in water supply and biodiversity. River channels are also altered as a result of Tamarisk colonization, with channel incision and bank stabilization being observed on some rivers. Much research has been done on the adverse effects on river channels from Tamarisk after it has colonized a floodplain; however, little-to-no research has been done on the geomorphic effects that occur post-removal. A section of the Virgin River in St. George, Utah, provides an opportunistic case study to measure not only how the channel has reacted historically to Tamarisk colonization, but also how sections have reacted to Tamarisk removal. To achieve this, historic aerial imagery of the reach was obtained from 1953 up to the near-present day in 2017 and georectified to contemporary imagery from the National Agricultural Imagery Program (NAIP). Vegetation communities, the active channel, the channel centerline, and channel width measurements were all digitized for each year of imagery obtained. Given that there is little precedence in the literature, this research provides a way to test multiple hypotheses of how the channel may react over time to removal. The data obtained from this research can then be used in future studies done at different sites in the region.

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