PERFORMANCE EVALUATION OF RIVER RESTORATION

S.R. Clayton, G.S. Beattie and P. Goodwin

Ecohydraulics Research Group, University of Idaho

College of Engineering, University of Idaho, 800 Park Boulevard, Suite 200,

Boise, Idaho, 83712 U.S.A.

Tel: (208) 364-4085, Fax: (208) 387-1246, E-mail: sclayton@uidaho.edu

Abstract: During the past two decades there has been increasing resources expended on the restoration and enhancement of river and wetland ecosystems in the United States. More recently, increasing concern has been expressed by natural resource agencies and independent scientific reviews about the effectiveness of local restoration projects and the value of the cumulative effect of individual projects on the watershed aquatic ecosystem. Evaluation of these types of projects is complicated by the paucity of threatened and endangered species that these projects are designed to assist in recovery as well as the temporal and spatial variability associated with aquatic habitat requirements. The Red River Wildlife Management Area in Central Idaho has been developed as a research site to evaluate different restoration approaches and to develop performance evaluation methodology. A method is presented to link geomorphic analysis with sediment, water quality and hydrologic output from a river model with fish habitat needs.

Keywords: restoration, river modeling, fluvial geomorphology, fish habitat, floodplains

1    INTRODUCTION

Many wetland and river restoration or enhancement projects have now been completed for over 20 years in the Western United States. These implemented projects provide an opportunity to assess different ecological enhancement philosophies and strategies. The primary problems with these early enhancement projects (for example, Josselyn, 1993; Race, 1985) include:

l         No clear enhancement objectives specified in the original design

l         No prescribed performance criteria for project assessment

l         Lack of monitoring data to detect the site evolution and assess whether the project is performing according to design expectations

l         Inadequate or non existent funding for maintenance or implementation of adaptive management strategies

l         Failure to account for physical processes necessary to establish and sustain target ecological conditions at the site

l         Failure to anticipate physical processes at the watershed scale that influence conditions at the local enhancement site.

Examples of this last point include bio-stabilization projects that become engulfed by debris flows, stabilized banks being undermined by a larger trend of channel degradation, and wetlands being overwhelmed by sedimentation or inundated due to the reduction of natural sedimentation processes. Accounting for both the physical processes in the watershed and the genetic and phenotypic characteristics of the indicator species targeted in the restoration goals makes the prioritization of restoration activities complex. This is of particular importance if the restoration plan is part of an anadromous fish recovery where the fish population is subject to natural variability and external factors such as dams obstructing migration, fish harvesting and climate change.

An example of the scientific peer review process at the basin scale is the Independent Scientific Review Panel (ISRP) that provides scientific guidance to the Bonneville Power Administration Fish and Wildlife Mitigation program in the Columbia River Basin. ISRP called for habitat objectives to be established for each major subbasin and coordinated with overall ecological production goals (www.efw.bpa.gov/Environment/EW). Basin-wide assessment of the entire Interior Columbia Basin (area exceeds 58.4 million ha) is being developed by the Northwest Power Planning Council, and the knowledge encapsulated into the program EDT - Ecosystem Diagnostic and Treatment (Lestelle et al., 1996). The ISRP also raised the following challenging questions:

(1) When a subbasin is identified as critical, how should restoration activities be prioritized?

(2) How can the ecological benefits be demonstrated at the watershed scale?

(3) How can the ecological benefit be quantified in the local region of the restoration?

An approach to address the first two questions has been developed for the Upper Salmon Basin in Idaho, USA (Goodwin et al., 2000). This paper describes an approach being developed to explore the third question for the Red River Wildlife Management Area (RRWMA) in the neighboring Clearwater River Watershed in Idaho.

2    THE RED RIVER WILDLIFE MANAGEMENT AREA (RRWMA)

The Red River is a tributary of the South Fork Clearwater River, an important anadromous fisheries stream in north-central Idaho. Elevations at the project site are about 1300 m, and the meadow receives an average precipitation of 0.75 m per year. Semantically, the term restoration implies returning the river to some historic condition that prevailed prior to land-use practices of European settlers during the past century. True restoration is impossible to achieve due to the large-scale irreversible changes to the watershed such as hydraulic mining, timber harvesting, and road construction. Herein, the term restoration is used to imply the enhancement of the site to improve the ecological function of the site.

2.1    Ecological value

Past management throughout the watershed and at the project site has influenced the ecology of the area. Historically, the Red River supported a large diversity of anadromous and resident salmonid species including chinook salmon (Oncorhynchus tshawytscha), steelhead trout (Oncorhynchus mykiss), Westslope cutthroat trout (Oncorhynchus clarki lewsi), bull trout (Salvelinus confluentus), and mountain whitefish (Prosopium williamsoni). A portion of the decline of both resident and anadromous fish populations in the Red River has been linked to habitat and water quality degradation (Bonneville Power Administration, 1996).

2.2    Trends at the RRWMA

The Red River was channelized through mining and agricultural activities as early as the turn of the century. A geomorphic reconstruction of the changes in the meadow has shown the channelization has increased the channel slope and sediment transport potential of the river, and a comparison of aerial photos from 1936 and 1996 showed dramatic differences. Consequences have included a gradual incision of the channel, a coarsening of the bed substrate, and a loss of the diversity in bed morphology such as pools and riffles. Significant secondary responses to the incision include the drawdown of the local groundwater table during the summer months. This drying of the meadow has resulted in loss of wetlands and transition of the indigenous riparian vegetation to upland grasses. The channel incision has caused vertical banks up to 3.0 m in height that cannot support riparian vegetation and induce bank instability. The loss of bed structure diversity has resulted in a straighter and wider shallow channel at low flows. The loss of shade from riparian vegetation combines with the change in channel form to raise water temperatures in the meadow and influences the viability of some life stages of resident and anadromous fish species. Extensive grazing at the site had also contributed to the degradation of aquatic and riparian habitat and loss of spawning and rearing habitat for salmonids.

2.3    Physical characteristics

An historic flow record has been constructed for the site for the period 1965-97 (http://boise.uidaho.edu/redriver). The maximum and minimum mean daily discharges at the project location are 38 m³/s and 0.27 m³/s. Despite the anthropogenic changes to the project reach over time, the channel has maintained a meandering planform. However, the incision and reduction in sinuosity have resulted in decreased sedimentation on the floodplain, reduced hydroperiod through the meadow and altered cross-sectional characteristics from the historic condition. Table 1 summarizes the channel conditions in the meadow before and after restoration, and Figure 1 shows the change in alignment. The slope of the channel following restoration is very similar to the 1936 slope. The restored length and sinuosity are slightly greater than the 1936 condition because there appeared to be some evidence of channel straightening prior to 1936.

    Table 1    Summary of channel conditions at the RRWMA

Fig. 1    Pre-and post-restoration alignments of river channel

3    MONITORING AND PERFORMANCE CRITERIA

Initial reconnaissance work and baseline data collection occurred at Red River in the mid-1990s (http://boise.uidaho.edu/redriver). In Fall 1997, a comprehensive monitoring program was initiated at the site. This monitoring includes streamflows, channel and wetland evolution, composition of bed sediments, turbidity, groundwater, vegetation transects and photopoints, and fisheries spawning and rearing surveys. Over 50 permanently-monumented cross sections were installed and have been surveyed annually (in the late summer or fall) since 1997. Thalweg and water surface surveys have also been completed to monitor sediment balance through the meadow as well as habitat types such as pools and riffles (Table 2).

Changes in a wide range of parameters such as riparian vegetation establishment; channel pattern, profile, and dimensions; substrate composition; water temperature; ground water table; and fish habitat utilization are evaluated. The monitoring program has four objectives: (1) to assure regulatory permit compliance, (2) to measure progress toward attaining project objectives, and (3) to incorporate results into future design and implementation through an adaptive management process, and (4) research - understand fundamental linkages between physical and ecological processes.

4    MONITORING RESULTS

Detailed monitoring started in 1997 has identified several minor remedial actions and adjusted design criteria through the adaptive management strategy. Only the rate of evolution of the site will be discussed here. (Further details are available at http://boise.uidaho.edu/redriver.) If a river system is in dynamic equilibrium, the instream characteristics of a river channel remain the same, but the position of the channel within the floodplain may not. A necessary condition of this concept assumes that if there should be no net loss or gain of sediment in a channel reach (Table 3). The total runoff and timing of storms in a given year govern the sediment delivery and the magnitude of scour or deposition; however, some significant trends are evident. After a small net loss of sediment during the 1997-98 period (possibly due to construction disturbance), the Phase I and II reach has been subject to net deposition. This is consistent with the design philosophy of over-sizing the channel and allowing the channel to create its equilibrium section through deposition. This trend was also predicted by numerical model. Phase III and Phase IV exhibit a trend of erosion and net loss of sediment and confirms that the channel incision process in the meadow is continuing. Models are being used to assess whether the deposition reach and raised water surface levels in Phase I and II are increasing the downstream incision process.

Tracking the rate of change of channel sections make it possible to estimate the length of time it will take a specific reach to achieve dynamic equilibrium. If the desired cross-sectional area can be estimated from hydraulic geometry relationships, then projections of the time can be made from cross-sectional area. These empirical estimates will be tested against future observations and channel evolution models.

  Table 3    Volumetric channel changes at RRWMA 1997-99

 ¹ Channel surveys were undertaken prior to Phase III construction

² Phase IV construction was completed in summer 2000.

 5    CONCLUSIONS

The restoration and enhancement of river, wetland and estuarine ecosystems have become a major scientific challenge during the past decade. Independent scientific review panels provide peer review on the success of programs and individual projects. A common theme posed by review panels questions how it can be proven that the implemented projects actually achieve the objectives of enhancing the ecosystem for specific indicator species. Due to the threatened and endangered status of many species, it is not possible to just undertake species counts, partly because there are so few individuals left and partly because the observed number of many migratory species are subject to fluctuations created by many factors external to the local watershed. A methodology is outlined that measures project performance through monitoring of physical parameters to achieve the goal of the restoration program.

Acknowledgements

This project is part of the Northwest Power Planning Council’s Columbia Basin Fish and Wildlife Program, funded by the Bonneville Power Administration (Project #9303501). Additional funding provided by the National Science Foundation, Award BES-9874754 entitled “Ecohydraulics: Physical Processes in River Ecosystem Management.” The assistance of Idaho Department of Fish and Game, Interagency Technical Advisory Committee, Wildlife Habitat Instititute, TerraGraphics Environmental Engineering, Inc., Pocket Water, Inc., LRK Communications, and USDA Forest Service is gratefully acknowledged.

References

Bonneville Power Administration (BPA). 1996. Lower Red River Meadow Restoration Project Environmental Assessment. DOE No. 1027. Bonneville Power Administration. Portland, OR.

Goodwin, P., J. Muskatirovic, K. Overton, B. Rieman, 2000. Aquatic Systems Review-An Hydroinformatics Perspective. Procs. of Hydroinformatics 2000, July 25-28, 2000. Iowa City, IA.

Josselyn, M.N., 1993. Evaluation of Coastal Conservancy Enhancement Projects: 1978-1992. California State Coastal Conservancy and San Francisco State University, Romberg Center for Environmental Studies. Oakland, CA.

Lestelle, L.C., L.E. Mobrand, J.A. Lichatowich and T.S. Vogel, 1996. Applied Ecosystem Analysis-A Primer. The Ecosystem Diagnosis and Treatment Method. Bonneville Power Adminstration, Project 9404600. 95 p plus appendices.

Race, M., 1985. Critique of Present Wetlands Mitigation Policies in the United States.  Environmental Management. 9(1):71-82.