This presentation is part of the Cape Perpetua Speaker Series, hosted by the Cape Perpetua Collaborative.
Valley bottom streams, rivers and wetlands have been altered across North America since European settlement. Looking back at how these systems functioned in the past, prior to impacts, allows understanding of a systems natural processes and the intrinsic resilience of an intact system. Splash damming, log drives and mill pond creation in combination with beaver removal have resulted in a reduction in the amount of water stored across the landscape during both times of flooding and times of drought.
Prior to 1950 there were millions of beavers across the United States, but trapping counts confirm that millions of beavers were removed during European settlement. Based on reports from early explorers, complex wetlands were prevalent across and spanning valley bottoms prior to European settlement. These wetland complexes represented intact natural systems with beaver present, building and maintaining dams. Removing beavers resulted in the unraveling of these wetlands. This alteration would have occurred with relative speed. Without the prevalence of beavers, dams fail. This causes the large wetland complexes to drain, and water levels to drop, carrying away large amounts of water and sediments that would have otherwise been captured and accumulated behind beaver dams year after year. Failed dams also cause stream velocities to increase, resulting in more erosion. This vicious cycle of stream channel incision, more scouring, and deepening of the stream itself, disconnects the stream from its floodplain and lowers the water table. This results in a self-perpetuating flood and drought cycle exacerbating each condition year after year.
ABOUT THE SPEAKER
Kami Ellingson is a hydrologist with over 20 years of field experience, ranging from landslide studies following the 1996 storm event in western Oregon, to road, stream and estuary restoration. Kami has led the restoration of the Salmon River estuary since 2007 and has been recognized nationally and internationally for the success of physical restoration and collaborative partnerships. Kami received both her Bachelor’s degree in Natural Resources Management and her Master’s in Forest Engineering and Hydrology from Oregon State University.