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Research about Elwha River

Source-linked reports with geographic coverage including Elwha River.

45 records · Page 3Linked to original sources
USGS2011

Baseline hydrologic studies in the lower Elwha River prior to dam removal

After the removal of two large, long‑standing dams on the Elwha River, Washington, the additional load of sediment and wood is expected to affect the hydrology of the lower river, its estuary, and the alluvial aquifer underlying the surrounding flood plain. To better understand the surface-water and groundwater characteristics of the river and estuary before dam removal, several hydrologic data sets were collected and analyzed. An experiment using a dye tracer characterized transient storage, and it was determined that the low‑flow channel of the lower Elwha River was relatively simple; 1–6 percent of the median travel time of dye was attributed to transient‑storage processes. Water data from monitoring wells adjacent to the main‑stem river indicated a strong hydraulic connectivity between stage in the river and groundwater levels in the flood plain. Analysis of temperature data from the monitoring wells showed that changes in the groundwater temperature responded weeks or months after water temperature changed in the river. A seepage investigation indicated that water from the river was moving into the aquifer (losing reach) between 1.7 and 2.8 kilometers from the river mouth. Surface‑water measurements and temperature and salinity data collected throughout the estuary helped to characterize the magnitude and nature of water movement in and out of the estuary. Salinity and stage sensors positioned in the estuarine network showed a strong surface‑water connection between the river and estuary waters east of the river. In contrast, there was a weaker connection between the river and estuarine water bodies west of the river.

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USGS2011

Coastal processes of the Elwha River delta: Chapter 5 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

To understand the effects of increased sediment supply from dam removal on marine habitats around the Elwha River delta, a basic understanding of the region’s coastal processes is necessary. This chapter provides a summary of the physical setting of the coast near the Elwha River delta, for the purpose of synthesizing the processes that move and disperse sediment discharged by the river. One fundamental property of this coastal setting is the difference between currents in the surfzone with those in the coastal waters offshore of the surfzone. Surfzone currents are largely dictated by the direction and size of waves, and the waves that attack the Elwha River delta predominantly come from Pacific Ocean swell from the west. This establishes surfzone currents and littoral sediment transport that are eastward along much of the delta. Offshore of the surfzone the currents are largely influenced by tidal circulation and the physical constraint to flow provided by the delta’s headland. During both ebbing and flooding tides, the flow separates from the coast at the tip of the delta’s headland, and this produces eddies on the downstream side of the headland. Immediately offshore of the Elwha River mouth, this creates a situation in which the coastal currents are directed toward the east much more frequently than toward the west. This suggests that Elwha River sediment will be more likely to move toward the east in the coastal system.

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USGS2011

Nearshore biological communities prior to the removal of the Elwha River dams: Chapter 6 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Increases in sediment delivery to coastal waters are expected following removal of dams on the Elwha River, Washington, potentially increasing sediment deposition on the seafloor and suspended sediment in the water column. Biological communities inhabiting shallow, subtidal depths (3–18 m) near the mouth of the Elwha River, between the west end of Freshwater Bay and the base of Ediz Hook, were surveyed in August and September 2008, to establish baselines prior to dam removal. Density was estimated for 9 kelp taxa, 65 taxa of invertebrates larger than 2.5 cm any dimension and 24 fish taxa. Density averaged over all sites was 3.1 per square meter (/m 2 ) for kelp, 2.7/m 2 for invertebrates, and 0.1/m 2 for fish. Community structure was partly controlled by substrate type, seafloor relief, and depth. On average, 12 more taxa occurred where boulders were present compared to areas lacking boulders but with similar base substrate. Four habitat types were identified: (1) Bedrock/boulder reefs had the highest kelp density and taxa richness, and were characterized by a canopy of Nereocystis leutkeana (bull kelp) at the water surface and a secondary canopy of perennial kelp 1–2 m above the seafloor; (2) Mixed sand and gravel-cobble habitats with moderate relief provided by boulders had the highest density of invertebrates and a taxa richness nearly equivalent to that for bedrock/boulder reefs; (3) Mixed sand and gravel-cobble habitats lacking boulders supported a moderate density of kelp, primarily annual species with low growth forms (blades close to the seafloor), and the lowest invertebrate density among habitats; and (4) Sand habitats had the lowest kelp density and taxa richness among habitats and a moderate density of invertebrates. Uncertainties about nearshore community responses to increases in deposited and suspended sediments highlight the opportunity to advance scientific understanding by measuring responses following dam removal.

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USGS2011

Aquatic ecology of the Elwha River estuary prior to dam removal: Chapter 7 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

The removal of two long-standing dams on the Elwha River in Washington State will initiate a suite of biological and physical changes to the estuary at the river mouth. Estuaries represent a transition between freshwater and saltwater, have unique assemblages of plants and animals, and are a critical habitat for some salmon species as they migrate to the ocean. This chapter summarizes a number of studies in the Elwha River estuary, and focuses on physical and biological aspects of the ecosystem that are expected to change following dam removal. Included are data sets that summarize (1) water chemistry samples collected over a 16 month period; (2) beach seining activities targeted toward describing the fish assemblage of the estuary and migratory patterns of juvenile salmon; (3) descriptions of the aquatic and terrestrial invertebrate communities in the estuary, which represent an important food source for juvenile fish and are important water quality indicators; and (4) the diet and growth patterns of juvenile Chinook salmon in the lower Elwha River and estuary. These data represent baseline conditions of the ecosystem after nearly a century of changes due to the dams and will be useful in monitoring the changes to the river and estuary following dam removal.

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USGS2011

Summary and anticipated responses to Elwha River dam removal: Chapter 9 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Starting in September 2011, the removal of two large dams on the Elwha River will begin an unprecedented river restoration project because of the size of the dams, the volume of sediment released, the pristine watershed upstream of the dam sites, and the potential for renewing salmon populations. Ecosystem studies of the Elwha watershed indicate that the effects of almost 100 years of damming are measurable and of consequence. These effects include smaller spawning salmon populations, massive sediment retention behind the dams, coarsening of the riverbed downstream of the dams, low nutrient concentrations in the river waters, and coastal erosion that has accelerated markedly with time. During and after the removal of these dams, the Elwha River and its ecosystems will be altered by a renewal of sediment discharge downstream of the dams and a reintroduction of salmon spawning upstream of the dams. This chapter summarizes the pre-dam and current state of the river and its coastal ecosystems, and describes the likely outcomes of river restoration on the Elwha River ecosystems.

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USGS2011

Proceedings of the 2011 Elwha River Science Symposium

After years of anticipation, volumes of Environmental Impact Statements, multiple mitigation projects, and the multidisciplinary collection of predam removal data, the deconstruction phase of the Elwha River restoration officially began on September 17th, 2011. With their simultaneous decommissioning, the removal of the 64 m tall Glines Canyon Dam and the 33 m tall Elwha Dam represents one of the largest such projects of its kind in North America. It’s also an excellent opportunity to study large-scale ecosystem restoration, as the majority of the reconnected habitat that will become available to recolonizing salmon occurs in the protected wilderness areas of Olympic National Park. As part of a week-long series of ‘Celebrate Elwha’ events, which culminated with a moving ceremony commemorating the official launch of dam removal, I was proud to work with a number of dedicated people, listed below, to organize the two day 2011 Elwha River Science Symposium. Many of the scientists working on the Elwha project have regularly met, since around 2004, for annual meetings. Loosely organized under the auspices of the Elwha Research and Elwha Nearshore consortia, the annual meetings have been informative for many reasons, including the sharing of study plans, field schedules, and preliminary results. It has been a great way for groups of physical scientists and groups of biologists to learn about the questions of interest to each group and to explore areas of overlap. In some cases, these meetings have spawned new collaborations, synergies, and research directions. In planning for the 2011 Elwha River Science Symposium, we sought to retain this espirit de corps, but realized that the start of dam removal heralded an important new phase of the project and called for an event that celebrated this special occasion.

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USGS2010

Seasonal and decadal-scale channel evolution on the dammed Elwha River, Washington

More than 75,000 dams exist in the continental United States to provide water storage, flood control, and hydropower generation (Graf, 1999). Many of these were built during the early twentieth century and are due for relicensing consideration now and in the near future. The cost of repairing aging dams, together with growing understanding of the ecologic effects of river regulation (Williams and Wolman, 1984; Dynesius and Nilsson, 1994; Graf, 1999, 2003; Yang et al., 2007), in some places have prompted dam removal, facilitating restoration of riparian habitat to a more natural state. In the Pacific Northwest region of the U.S., river-restoration efforts are commonly targeted to improve habitat quality for native salmonid fish species, many runs of which have declined precipitiously from their historical conditions (owing, in part, to overfishing and habitat loss and degradation) and are now endangered (e.g., Nehlsen, 1997; Larsen et al., 2004; Pess et al., 2008). Removal of dams that block the upstream migration of anadromous fish is considered an important step toward any potential recovery of Pacific Northwest salmon and steelhead populations.

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USGS2007

Beach morphology monitoring in the Elwha River Littoral Cell, 2004-2009

This report describes the methods used, data collected, and results of the Beach Morphology Monitoring Program in the Elwha River Littoral Cell, starting in 2004. The U.S. Geological Survey and the Washington State Department of Ecology collaborated in the data collection with the support of the local Lower Elwha Klallam Tribe. Beach monitoring efforts consisted of collecting topographic and bathymetric horizontal and vertical position data by using a Real Time Kinematic Differential Global Positioning System (RTK-DGPS). The monitoring program was designed to characterize the littoral system of the Elwha River before the scheduled removal of two large dams in 2012. A primary objective of this work is to quantitatively describe the topography and bathymetry of the Elwha River littoral system so that the effects of dam removal may be quantified. Sediment inputs following dam removal are hypothesized to result in (A) larger amounts of fine sediment grain-sizes entering the littoral system and, (B) a reduction or reversal of coastal erosion.

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