Post-Dam effects on Geomorphology of the Green River

Brooke N. Eustis

Following the closure of Flaming Gorge Dam, geomorphic conditions along the Green River changed considerably. The lack of sediments from headwaters, decreased stream power downstream of Flaming Gorge Dam, and establishment of vegetation along river banks and sand bars has driven these changes in channel morphology. Just downstream of Flaming Gorge Dam, the erosion of fine sediments facilitates bed armoring. As sediment from tributaries enters the river system, channel aggradation becomes apparent primarily at the margins of the channel. Reduced peak flows and stability provided by vegetation prevent the erosion of sediments. The effects of Flaming Gorge Dam on channel narrowing can be assessed by studying geomorphically similar reaches above and below the confluence of the Yampa River, a large unregulated tributary. The Yampa River resets the Green River to more closely resemble pre- dam conditions.