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  • Bridge Creek Restoration and Monitoring Project


Northwest Fisheries Science Center (NWFSC) Fish Ecology FE - Watershed


Bridge Creek
Bridge Creek Restoration and Monitoring Project
The incised and degraded habitat of Bridge Creek is thought to be limiting a population of ESA-listed steelhead (Oncorhynchus mykiss). A logical restoration approach is to improve their habitat through reconnecting the channel with portions of its former floodplain (now terraces) to increase both stream and riparian habitat complexity. Using conventional restoration techniques to achieve such objectives can be quite costly, because it involves moving and grading large volumes of fill with heavy equipment that exposes bare ground, and is usually followed by extensive revegetation efforts. Here, we seek a cost-effective, process-based approach to restore geomorphic, hydrologic and ecological functions of this degraded system helping a small, extant beaver population build longer-lived dams.

Currently, the beaver population is limited because their dams are short-lived. Most beaver dams are constructed within the incision trench and during high discharge events; the full force of flood waters are concentrated on these dams rather than dissipating across floodplains. Consequently most dams breach and fail within their first season. The primary hypothesis we are testing is that by assisting beaver to create stable colonies and aggrade incised reaches of Bridge Creek, there will be measurable improvements in riparian and stream habitat conditions and abundance of native steelhead. The main restoration design challenge is to help beaver build dams that will last long enough to lead to the establishment of stable colonies. If this can be accomplished, the beaver dams should promote enough aggradation to reverse channel incision and reap a number of well documented positive ecosystem benefits associated with dynamic beaver dam complexes that will benefit steelhead and other species.

We are assisting the beaver using an extremely simple and cost-effective restoration treatment. The treatment involves installing round wooden fence posts across potential floodplain surfaces (now terraces) and the channel, approximately 0.5 to 1 m apart and at a height intended to act as the crest elevation of an active beaver dam. This report provides details of the design rationale and design hypotheses employed and summarizes the placement of the 84 BDS structures installed in four reaches in 2009. Additionally, the ongoing monitoring campaign devised to test these design hypotheses is discussed and some preliminary observations from the first year of the campaign are presented. Five variants of the restoration treatment were used; post lines only, post lines with wicker weaves, construction of starter dams, reinforcement of existing active beaver dams, and reinforcement of abandon beaver dams. The biodegradable posts are intended to buy enough time for (1) beaver to occupy the structures and build on or maintain the structures as their own dams, and (2) for aggradation in the slackwaters of the pond from the dam to take place and promote reconnection with a floodplain (terrace).

Just as with natural beaver dams, individual dams are expected to be transient features on the landscape, expanding and contracting, coming and going as they lose functionality for beaver (e.g. when a pond fills with sediment). The treatment design is geared to saturate four distinct reaches of Bridge Creek with beaver dam support (BDS) structures so that enough potential dams are available to the current beaver population that they can pick and choose the best sites to establish stable multi-dam complexes to support healthy and persistent colonies.

Research Themes

Habitats to support sustainable fisheries and recovered populations
Healthy oceans, coastal waters, and riverine habitats provide the foundation for aquatic resources used by a diversity of species and society. Protecting marine, estuarine and freshwater ecosystems that support these species relies on science to link habitat condition/processes and the biological effects of restoration actions. The NWFSC provides the habitat science behind many management actions taken by NOAA Fisheries and other natural resource agencies to protect and recover aquatic ecosystems and living marine resources. The NWFSC also maintains a longstanding focus on toxic chemical contaminants, as a foundation for regional and national research on pollution threats to fisheries and protected resources.

Research Foci

Develop effective and efficient habitat restoration and conservation techniques
Maintaining and re-establishing viability and sustainability of living marine resources requires conservation and rehabilitation or restoration of habitats upon which species depend. Common habitat restoration approaches and tech-niques often presume that habitats are static features of the environment, and that creation of stable habitats is a desirable restoration strategy. However, riverine, nearshore, and marine habitats are created and sustained by dynamic landscape, climatic, and oceanographic processes and biota are adapted to changing habitats that are within the range of natural variability. Hence, current restoration strategies often have limited success, in part because they fail to recognize larger scale processes that drive habitat change, and in part because they fail to recognize intrinsic habitat potential of individual restoration sites. The main goals of this research focus are to: improve understanding of how large-scale processes create diverse and dynamic habitats that support marine and anadromous species, better understand how human activities alter habitat-forming processes and habitats, develop new restoration techniques that are compatible with sustainable habitat-forming processes, and understand the variety of actions needed to adequately conserve intact critical habitats. In addition, NWFSC’s research will improve understanding of how new and existing habitat restoration and protection techniques affect fish and habitat at multiple scales (i.e., reach, watershed, Evolutionarily Significant Unit).


Oncorhynchus mykiss
habitat restoration
flowing body of water contained within a bed that is less than 18 meters wide


Stream temperature data


Genus Oncorhynchus
Species Oncorhynchus mykiss
rainbow trout, steelhead trout, syeelhead trout
Species Oncorhynchus tshawytscha
Chinook salmon, king salmon, spring salmon


Michael Pollock
Principal Investigator