Spencer Shaw ’22
Faculty Collaborator: Sarah Schanz, Geology
The geomorphic impacts of dams on downstream systems has been extensively studied; yet very little work has quantified the impact on channels upstream. Understanding geomorphic effects of dams becomes increasingly pertinent as hydropower solutions are more frequently utilized. It is predicted that dams lead to deposition upstream and reduction of channel slope because of a change in base level. This hypothesis was tested by measuring the slope of the modern channel and the floodplain, which represents a paleo-channel, in the West Elk Creek, near Gunnison, CO. A 1-dimensional model predicted aggradation resulting from slope changes at approximately 8km up the drainage. RTK GPS units and GIS analysis were used to find the surface slopes. An analysis of covariance yielded no significant difference between the slopes. Field work showed that aggradation is localized from downed logs in the channel. Sediment pit observations yielded no evidence of regional aggradation. One theory is that the 58-year-old Blue Mesa dam is not old enough for significant slope changes to occur and localized aggradation was not accounted for. Dam emplacement may have effects long term, but changes are outside the practical life span of modern dams. More research is needed to understand the temporal scale of aggradation from base change.