AWRA-WA May 2021 Virtual Lunch Meeting

When
13 May 2021
12:00 PM - 1:00 PM
Location
Virtual Event
Registered
112 registrants

Registration

Everyone

Registration is closed

The American Water Resources Association Washington Section presents:

AWRA-WA Virtual Lunch Meeting--

Long-term Geomorphic Effects of the Glines Canyon Dam Removal on the Elwha River, WA, USA

Speaker: Alyssa DeMott, Central Washington University

Thursday, May 13th, 2021

12:00 PM to 1:00 PM

VIRTUAL MEETING!!! You will receive a link to participate via our webinar service when you register AND the day before the event.

Thank you to Green Economics for sponsoring the technology of this event!

Abstract: The Elwha River once provided vital habitat for a variety of salmonid species, but after two dams were emplaced on the river in the early 1900s, habitat diminished, and salmon populations declined. From 2011-2014, the dams were finally removed to restore the Elwha ecosystem. To understand the long-term geomorphic impacts of the Glines Canyon Dam removal on the Elwha River, I quantified changes in four parameters: in-channel large wood, main channel sinuosity, channel braiding, and sedimentation. High-resolution imagery from 2012-2020 was used to map large wood and digitize main and secondary river channels, and field surveys were completed at study sites to assess sediment-size distribution six years after the completion of the dam removal. Analysis of large wood revealed that the number of individual logs peaked during the dam removal but decreased after the removal and remained low. Logjam area increased steadily throughout the eight-year study period while the number of logjams stayed constant, suggesting that individual logs were recruited into existing logjams over time. Main channel sinuosity increased during and after the removal, peaking in 2017. After 2017, sinuosity decreased for the remainder of the study period, but has yet to return to sinuosity conditions from before the removal. Channel braiding peaked during the dam removal process, dropped, and remained relatively consistent for the remainder of the study period, reaching a possible equilibrium state that is more braided than before the dam removal. A comparison of sediment-size distribution data from before, during and after the dam removal revealed that six years after the completion of the removal, sediment bars are no longer dominated by the armored, coarse sediment observed when the dam was in place, nor are they dominated by the pulse of fine sediment released during the dam removal. In 2020, a more mixed sediment-size distribution was observed. Quantitative geomorphic data from this study allows us to understand the changes that occur on a gravel-bed river following a large dam removal. The results demonstrate the complexity and interconnectedness of various geomorphic parameters and suggest that while some geomorphic parameters may establish a new equilibrium in the years following a dam removal, others will continue to evolve over longer timescales.

Our Speaker: Alyssa DeMott is currently a graduate student at Central Washington University in Ellensburg, WA, and will be completing her master’s degree in geological sciences in June 2021. She received her bachelor’s degree in geological sciences at the State University of New York (SUNY) at Geneseo in 2019. At SUNY Geneseo, she conducted planetary geomorphology research and had the opportunity to work on NASA’s Mars InSight Mission as an undergraduate research assistant. Though she is passionate about both planetary and terrestrial geomorphology, she ultimately decided to pursue graduate research focused on fluvial geomorphology. Her thesis project examines the geomorphic impacts of a large dam removal on the Elwha River in northwest Washington. After she graduates, she will be working as a geomorphologist in Washington, and she looks forward to expanding her knowledge of river restoration and aquatic habitat.

Fees

Free for EVERYONE!!!

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