Upstream-downstream linkages

What are upstream-downstream linkages?

Rivers are networks. What happens upstream – disturbance, restoration, management – should, at least theoretically, have an impact downstream. However, the degree to which a given upstream occurrence has a particular downstream expression is still relatively unknown, as are the variables that control the spatial and temporal scale of that expression. By working to better understand the processes that influence the strength of downstream impact, we can better anticipate the response of downstream ecosystems to upstream alterations and better target management and restoration activities designed to protect downstream waterbodies. 

— Projects —

Patterns of sediment flux in urban watersheds

Take-home point: Variations in annual sediment export from low-order tributaries are not expressed at the watershed outlet, suggesting that storage modulates downstream sediment delivery even in urban watersheds. Activities undertaken to reduce tributary sediment loading thus may not be expressed at the watershed outlet for some time. 

Publications

Kemper, Miller, Welty, 2019, Geomorphology (link)

Linking tributary erosion to distal downstream forest establishment

Take-home point: Erosion in tributary watersheds drove enhanced cottonwood forest establishment in distal downstream areas, suggesting tributary geomorphic processes play a notable role in downstream ecological dynamics 

Publications

Kemper, Rathburn, Friedman, Nelson, Mueller, Vincent, 2022, Catena (link)

Kemper, Thaxton, Rathburn, Friedman, Mueller, Scott, 2022, ESPL (link)

Estimating watershed-scale sediment storage in the Colorado River Basin

Take-home point: First-order approximations of sediment storage are 21-130 billion cubic meters for the Upper Colorado and 314-482 billion cubic meters in the Lower Colorado, with the majority of sediment stored in the lower elevation reaches of each subbasin.

Publications

Kemper, Wohl, Schulz, Raffae, Bailey, Morrison, Knox, River Research & Applications (link)

Downstream impact of erosion mitigation efforts in a mountain catchment

— this work is ongoing —

Combining high-frequency sensor data with geomorphic mapping, we are examining how erosion mitigation projects in tributary watersheds interact with large storms to influence sediment export at the watershed mouth 

Collaborators

W. Dany Davis, NYC Dept. of Env. Protection;

Jason Siemion, US Geological Survey;

Andrew Schroth, University of Vermont;

Kristin Underwood, University of Vermont; 

Scott Hamshaw, US Geological Survey