Post-glacial valley evolution and post-disturbance channel response as a context for restoration, upper Colorado River, Rocky Mountain National Park
Date
2010
Authors
Rubin, Zan K., author
Wohl, Ellen E., 1962-, advisor
Rathburn, Sara L., 1962-, advisor
Bledsoe, Brian P., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
In 2003 a human-caused debris flow initiated by a breach in Grand Ditch in Rocky Mountain National Park delivered ~36,000 m3 of sediment into the Colorado River. The debris flow deposited up to ~1 m of sediment in the Lulu City wetland and major reworking of the Colorado River channel also occurred. The objectives of this study are to determine 1) how the 2003 deposit in Lulu City wetland relates to the historic range of variability in rates and processes of aggradation during the Holocene; and 2) if recovery of channel forms and processes has occurred in the Colorado River during the six years following 2003. Ground penetrating radar surveys, soil descriptions, and radiocarbon dating were used to quantify rates and processes of fill in Lulu City wetland. Channel recovery was assessed by comparing sediment transport rating curves to reference sites, monitoring changes in channel geometry, and quantifying bed material gradation. Results indicate that aggradation rates in Lulu City wetland varied through the late Holocene at periods correlated with distinct climates, and have increased approximately sixfold during the past 1-2 centuries of anthropogenic influence. Results from the Colorado River indicate channel forms and processes recovered between 2003 and 2009. Bed armoring and removal of fine sediments occurred, and channel stability persisted from 2003-2009. Results from the Lulu City wetland and impacted Colorado River can be used to guide effective restoration following the 2003 debris flow.
Description
Department Head: Sally J. Sutton.