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Monday, April 9 • 10:00am - 10:15am
SYMPOSIA-05: Recent History of South Platte River Riparian Ecosystem and Channel Change

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AUTHORS: Jessica Salo*, University of Northern Colorado; Gabrielle Katz, Metropolitan State University of Denver

ABSTRACT: Water management has substantially altered the hydrology of the South Platte River in Colorado over the past 150 years. Although the river experiences substantial natural inter-annual flow variability, the altered annual flow regime is characterized by enhanced seasonal consistency of surface and ground water levels. Today, the river supports a broad cottonwood-willow riparian forest that established from 1900-1930, in a pulse of channel narrowing that accompanied historic flow alterations. The status of this forest in not well understood and little is known about its historic spatio-temporal pattern. We investigated recent changes to by developing and testing methods to assess riparian land cover change and channel movement on the South Platte River downstream of Greeley, Colorado. We digitized floodplain land cover on orthophotos taken at roughly 10 year intervals for three 30 km river segments in Weld, Morgan and Logan Counties, Colorado. Preliminary results indicate there is variability in land cover between the three reaches and major changes have occurred between 2006 and 2015. In all three segments, the major land cover types for both time periods included agricultural land use, riparian forests, and riparian herbaceous vegetation. Notable changes are present from 2006 to 2015. Specifically, active channel area increased 10-110% between 2006 and 2015, a period that included high flows and major flooding in 2013. In the two upstream segments, this change was accompanied by loss of dense forest and increase in open forest area. In the downstream segment, open forest area decreased while riparian herbaceous cover increased during this interval. This project is the first step to understanding historic rates and patterns of South Platte River riparian land cover dynamics to provide important context for informing management of this critical natural resource.

Monday April 9, 2018 10:00am - 10:15am CDT
Water Tower Parlor