The largest dam removal project in U.S. history was conducted from September, 2011 to August, 2014 on the Elwha River in northwest Washington State. (Check out the Elwha River Restoration Blog by the National Park Service for more information about this exciting restoration project.) Our group is studying the fate of mud released from the former reservoirs to the coastal ocean. This system is providing excellent opportunities to study tidally dominated dispersal of fine-grained sediments, which has implications for signatures of natural and anthropogenic events like landslides, river floods, and dam removal in energetic coastal environments. Between 2011 and 2015, we deployed large bottom-boundary layer sensor platforms and collected grab samples, CTD/OBS casts, and water samples to study the dispersal and short-term deposition patterns of mud delivered by the river.
From 2015-2018, we are transitioning into a study focused on evolution of nearshore muddy deposits and the impact of fine-grained sediment on benthic communities. During dam removal ~10 Mt of sediment washed downriver, and previously abundant kelp virtually disappeared from the adjacent nearshore ecosystem. These kelp provide important habitat for ecologically important species such as salmon. The link between current benthic light availability and sediment delivery and transport was investigated in order to understand conditions during dam removal. Seven instrument platforms were been deployed for two-week periods to monitor were deployed on the 10-m isobath along a 16 km transect centered on the river mouth for seven fortnightly periods in 2016 and 2017 to monitor near-bed photosynthetically available radiation (PAR), suspended sediment, wave climate, current velocity, temperature, and salinity. Read more about the project on the Washington Sea Grant website.
Funding source: National Science Foundation, Washington Sea Grant
People: Andrea Ogston, Chuck Nittrouer, Ian Miller (WA Sea Grant), Emily Eidam, Kristen Lee Webster, Hannah Glover
Collaborators: Jon Warrick (USGS), Steve Rubin (USGS), Helen Berry (DNR)
Glover, H.E., Ogston, A.S., Miller, I.M., Eidam, E.F., Rubin, S.P., Berry, H.D. 2019. Impacts of Suspended Sediment on Nearshore Benthic Light Availability Following Dam Removal in a Small Mountainous River: In Situ Observations and Statistical Modeling. Estuaries and Coasts. https://doi.org/10.1007/s12237-019-00602-5.
Ritchie, A.C., Warrick, J.A., East, A.E., Magirl, C.S., Stevens, A.W., Bountry, J.A., Randle, T.J., Curran, C.A., Hilldale, R.C., Duda, J.J., Gelfenbaum, G.R., Miller, I.M., Pess, G.R., Foley, M.M., McCoy, R., Ogston, A.S., 2018. Morphodynamic evolution following sediment release from the world’s largest dam removal. Sci. Rep. 8, 13279. https://doi.org/10.1038/s41598-018-30817-8
Rubin S.P., Miller I.M., Foley M.M., Berry H.D., Duda J.J., Hudson B., et al. (2017) Increased sediment load during a large-scale dam removal changes nearshore subtidal communities. PLoS ONE 12(12): e0187742.
Eidam, E.F., Ogston, A.S., Nittrouer, C.A., Warrick, J.A. 2016. Tidally dominated sediment dispersal offshore of a small mountainous river. Continental Shelf Research, 116, 136-148.
Miller, I.M., Ogston, A., Dolan, J., 2015. Sedimentology of intertidal sediment deposits after dam removal on a coastal river. Coastal Sediments 2015, San Diego.
Gelfenbaum, G. Stevens, A.W., Miller, I., Warrick, J.A., Ogston, A.S., Eidam, E., 2015. Large-scale dam removal on the Elwha River, Washington, USA: Coastal Geomorphic Change. Geomorphology, 246, 649–668.
Data collected: 2011 – 2015
Time-series data were collected using a variety of acoustic, optical, and peripheral sensors mounted on two bottom-boundary-layer tripods. Each tripod measured ~2 m tall to allow for investigations of sediment transport processes within the boundary layer. Details of each tripod deployment including major sensors deployed are given below; data are available upon request to PI Andrea Ogston (ogston [at] ocean.washington.edu). Measurements were collected at hourly intervals for up to 6 minutes at frequencies ranging from 1-16 Hz.
Primary instrumented tripod
Secondary instrumented tripod
Data collected: 2016 – 2017
Time series data were collected following the methodology from the NSF program, with the same tripod. The tripod was deployed in two locations (see map). Light monitoring platforms were deployed at 7 locations along the 10-meter isobath. Bed sediment samples were collected across the delta using a shipek and a box corer. Water column profiles and water samples were collected during tripod and instrument platform deployments and recoveries.
Light monitoring platforms
NOTE: Full time-series records are not available for all instruments for all deployments due to memory, battery, and/or biofouling issues.
Data is available upon request.
News & public presentations
Sediment flow at Elwha River’s mouth an outdoor classroom for University of Washington students (Peninsula Daily News, Apr 2015)
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