OOS 39-7 - Synthesis of common management concerns associated with dam removal

Thursday, August 10, 2017: 3:40 PM
Portland Blrm 254, Oregon Convention Center
Desiree Tullos, Oregon State University, Mathias Collins, National Marine Fisheries Service, J. Ryan Bellmore, US Geological Survey, Corvallis, OR, Jennifer Bountry, US Bureau of Reclamation, Patrick V. Connolly, Columbia River Research Laboratory, US Geological Survey, Cook, WA, Patrick B. Shafroth, Ft. Collins Science Center, US Geological Survey, Ft. Collins, CO and Andrew Wilcox, Department of Geosciences, University of Montana

Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding
physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless
of whether these concerns are warranted at a particular site. We used a dam-removal science database supplemented
with other information sources to explore seven frequently raised concerns, herein Common Management
Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The
CMCs addressed are the following: degree and rate of reservoir sediment erosion, excessive channel incision
upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on
local water infrastructure, colonization of reservoir sediments by nonnative plants, and expansion of invasive fish.


Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a
given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions
and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon
producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification
of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other
factors such as natural watershed variability and disturbance history.