Elwha Watershed Information Resource
Riparian
The riparian area is the transition zone between aquatic and terrestrial ecosystems. Riparian areas are important because they provide shoreline stability, reduce downstream flooding, improve water quality, and provide habitat for wildlife (Naiman, De camps and McClain 2005).
Riparian vegetation:- Holds soil around stream banks preventing erosion;
- Absorbs runoff;
- Filters sediment and pollutants from the water; and
- Provides habitat for fish, amphibians, birds, and small mammals.
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| Water flowing over rocks in the Elwha River. Gary Thayer, National Park Service. |
During the initial dam removal, short-term negative impacts from sediments and turbidity will affect the riparian plant and animals communities. However, once the sediment load is reduced, dam removal will be a major benefit to plants and animals of the Elwha because of recovered habitat and increased nutrients.
Studies have found that close to 70 percent of the vertebrate wildlife species use riparian corridors, and more breeding bird species use riparian habitat than any other habitat in North America. Riparian restoration after dam removal will be significantly beneficial to fish and wildlife species that are threatened, rare, or are species of special concern (Washington Department of Fish and Wildlife 2007), such as:
- Bald eagle (Haliaeetus leucocephalus),
- Bull trout (Salvelinus confluentus),
- Marbled murrelet (Brachyramphus marmoratus),
- Northern red-legged frog (Rana aurora),
- Northern spotted owl (Strix occidentalis caurina), and
- Van Dyke’s salamander (Phethdon vandykei).
Before the dams are removed, researchers are collecting information on vegetation, soil, tree succession, and sediments to establish existing characteristics of the Elwha riparian environment. These studies will provide baseline data that researchers can use to compare future riparian changes against after dam removal. Three such studies are discussed in the following sections:
River and floodplain ecosystem responses
Baseline monitoring of floodplain vegetation geomorphology, and soils prior to dam removal, Elwha River, Olympic National Park
Study Overview: This project consists of the measurement of various vegetation and physical characteristics at sites in the Elwha River valley. The study sites are along fifteen permanent, cross-valley transects. Five of these transects are located below Elwha Dam, five are between Elwha Dam and Glines Canyon Dam, and five are upstream of both dams.
Research Activities: Along each transect, researchers surveyed the cross-sectional topography, estimated the surface soil texture, sampled vegetation by line-intercept, point-intercept, and stem density, diameter, and species composition and cover within quadrats.
Woody vegetation plot surveying was conducted in 2003 and 2004, herbaceous plot sampling in 2005 and 2006, and soils were sampled in 2006 and 2007. A total of 138 tree quadrats, 274 shrub quadrats, and 276 herbaceous quadrats were sampled. Additionally, over 150 trees were aged to determine the age structure of the Elwha’s riparian forests.
All data have been entered into electronic format, proofed, and basic summaries and analyses of the woody vegetation data have been conducted. Analyses of herbaceous vegetation and overall patterns of plant diversity are being directed by a project collaborator, Dr. Rebecca Brown of Eastern Washington University. Dr. Brown has undertaken more detailed floristic studies, using the permanent transects as a sampling template.
Work in 2007 will include thorough physical and chemical analysis of floodplain soils from a subset of research quadrats, as well as mycorrhizae. Collaborators on other aspects of soils (such as soil microbial communities and marine-derived nutrients) include Jeff Duda, Bill Eaton, Andy Bach, and Steve Perakis. Collectively, these data provide a solid baseline to which future changes to vegetation can be compared after the two dams are removed.
Collaborators:- Andy Bach, Western Washington University
- Vanessa Beauchamp, United States Geological Survey
- Jeff Braatne (deceased), University of Idaho
- Rebecca Brown, Eastern Washington University
- Jeff Duda, United States Geological Survey
- Bill Eaton, Peninsula College
- Chanoane Hartt, University of Idaho
- Steve Perakis, United States Geological Survey
- Pat Shafroth, United States Geological Survey
River and floodplain ecosystem responses
Study Overview: This study is investigating changes in channel and floodplain dynamics since construction of the first Elwha dam in 1912.
The dams on the Elwha River have:
- Reduced sediment supply to the lower Elwha River, which has reduced river channel movement (a natural river process) and reduced habitat diversity for salmon and other aquatic species.
- Trapped millions of tons of sediment in the reservoirs, much of which will be released when the dams are removed.
Researchers expect released sediments to temporarily decrease the quality of salmon habitat during the first few years after dam removal. However, over the long term (several decades) they expect the natural transport of sediment to restore channel movement and ultimately restore a greater diversity of river and floodplain habitats downstream of the dams. Researchers hypothesize that restored habitat diversity will lead to restored species diversity both in the river and on its floodplain.
Research Activities: Researchers are evaluating how river and floodplain habitats have changed since dam construction using historical aerial photographs. As the dams are removed, these researchers will monitor the effects of released reservoir sediments on river and floodplain ecosystems. This study began in 2000 and is expected to continue for at least 10 years post dam removal.
Collaborators:- Tim Beechie, NOAA Northwest Fisheries Science Center
- Martin Liermann, NOAA Northwest Fisheries Science Center
- Sarah Morely, NOAA Northwest Fisheries Science Center
- George Pess, NOAA Northwest Fisheries Science Center
- Michael Pollock, NOAA Northwest Fisheries Science Center
Patterns of early conifer succession on montane river flood plains in Olympic National Park, Washington
Study Overview: This project is investigating patterns of early conifer succession on river floodplains. River floodplains play many crucial roles in maintaining ecologically healthy rivers and watersheds. These dynamic and spatially heterogeneous areas often:
- Filter sediments and harmful substances from the water;
- Contribute to the replenishment of aquifers used for drinking water and irrigation;
- Help alleviate downstream flooding; and
- Function as hot spots of biological diversity.
In the Pacific Coastal Ecoregion (an area extending from northern California to Alaska), coniferous trees growing on river floodplains can have far-reaching influences on river processes and biocomplexity. With their ability to grow to extraordinarily large sizes and to resist decay, conifers often form the basis of channel-spanning log jams that change the course of rivers. Pacific salmon (Oncorhynchus species) and other animal and plant species have evolved to capitalize on these large- and small-scale disturbances. However, knowledge of the pathways of early conifer succession on river floodplains is incomplete.
The central goals of this project are to:- Discover where the most common riparian conifer trees (Picea sitchensis, Pseudotsuga menziesii, and Abies grandis) establish on floodplains of a variety of rivers on the Olympic Peninsula, Washington; and
- Quantify patterns of environmental conditions associated with their presence at patch and reach scales.
Using aerial photographs and field surveys, sites will be located along a characteristic floodplain reach of each of five rivers (Elwha, Hoh, North Fork Skokomish, Queets, and Quinault) inside Olympic National Park, Washington.
Specific project objectives are to:- Quantify young conifer (0-40 years old) distribution along study reaches on each river;
- Describe the relationship between conifer abundance and a suite of standard biological and environmental variables such as overstory, shrub cover, substrate size class, depth to cobble, elevation above summer low water, soil moisture, soil nutrient status, and conifer growth rates; and
- Compare growth rates and relative vigor of young conifers among species and sites.
This project will make important and immediate contributions in understanding riparian ecology in the Olympic Peninsula. It will provide key data to the Elwha River dam removal and river restoration project, and will have regional ecological applications. The knowledge gained in this research will be key in:
- Understanding how floodplain forests develop over time,
- Predicting future trajectories of natural river systems, and
- Managing, conserving, and restoring the river floodplains in the region.
Research Activities: Data on the Elwha river sites was collected in 2006 and analysis and completion of work is expected in December 2007. Field approaches included surveying and mapping floodplain reaches, belt transects, and nested quadrat sampling. Chemical analyses will include standard soil C:H:N analysis.
Collaborators:- Robert Naiman, University of Washington
- Scott Stolnack, University of Washington
Reference
Naiman, R. J., H. Dé camps, and M. E. McClain. 2005. Riparia - Ecology, Conservation and Management of Streamside Communities. Elsevier Academic Press. Burlington, MA.
Washington Department of Fish and Wildlife. 2007. Species of Concern.
Additional Resources
Balian, E. V., and R. J. Naiman. 2005. "Abundance and production riparian trees in the lowland floodplain of the Queets River, Washington." Ecosystems. Volume 8. Pages 841 to 861.
Beechie, T. J. and others. 2006. "Channel pattern and river-floodplain dynamics in forested mountain river systems." Geomorphology. Voume 78. Pages 124 to 141.
Deferrari, C. M., and R. J. Naiman. 1994. "A multiscale assessment of the occurrence of exotic plants on the Olympic Peninsula, Washington." Journal of Vegetation Science. Volume 5, Number 2. Pages 247 to 258.
Drake, D.C., R. J. Naiman, and J. S. Bechtold. 2006. "Cycling and fate of salmon-derived N in riparian forest soils and trees--a 15N tracer study." Ecology. Volume 87. Pages 1256 to 1266.
Fetherston, K. L., R. J. Naiman, and R. E. Bilby. 1995. "Large woody debris, physical process, and riparian forest development in montane river networks of the Pacific Northwest." Journal of Geomorphology. Volume 13. Pages 133 to 144.
Gregory, S. V. and others. 1991. "An ecosystem perspective of riparian zones." Bioscience. Volume 41, Number 8. Pages 540 to 552.
Helfield, J. M., and R. J. Naiman. 2001. "Effects of salmon-derived nitrogen on riparian forest growth and implications for stream productivity." Ecology. Volume 82, Number 9. Pages 2403 to 2409.
Latterell, J. J. and others. 2006. "Dynamic patch mosaics and channel movement unconfined river valley of the Olympic Mountains." Freshwater Biology. Volume 51. Pages 523 to 544.
Naiman, R. J. and others. 2002. "Pacific salmon, nutrients, and the dynamics of freshwater and riparian ecosystems." Ecosystems. Volume 5. Pages 399 to 417.
Naiman, R. and others. 1993. "The role of riparian corridors in maintaining regional biodiversity." Ecological Applications. Volume 3. Pages 209 to 212.
Pohl, M. 2004. "Channel bed mobility downstream from the Elwha dams, Washington." Professional Geographer. Volume 56, Number 3. Pages 422 to 431.
Shafroth, P.B.and others. 2002. "Potential respones of riparian vegetation to dam removal." BioScience. Volume 52. Pages 703 to 712.