Stream Ecosystem Responses to Stream Simulation Design of Road-Stream Crossings
Wildlife & Ecosystems
Research Idea Scope
Scope: Research Objectives:
The Clean Water Act, Endangered Species Act, and National Forest Management Act require that stream-road crossings are designed such that viable populations of native aquatic species are maintained, and plant and animal community diversity is similar to that expected in natural forests. The goals of most aquatic organism passage (AOP) restoration projects focus primarily on providing adequate passage of aquatic organisms (e.g. Burford et al 2009, Gardner et al. 2011) and rarely consider whether aquatic habitat and stream ecosystem function is improved at road-stream crossings. Typical culvert replacements consist of replacing undersized, or degrading structures with larger box, conspan, or bridge structures without restoring the stream bottom within the replacement structure in order to minimize costs. Stream bottoms within the structure are allowed to fill on their own with material transported from upstream without consideration of whether the replacement structure bottom is suitable habitat for passing/sustaining stream organisms and communities. Stream simulation design (SSD; Stream Simulation Working Group 2008) replacements are constructed in a way to structurally mimic a natural stream habitat. The channel bed has similar sediment characteristics and channel geomorphology as natural streams resulting in natural current velocities, flows, and resting areas for organisms. The primary drawback to this technique is the considerable extra costs associated with SSD over traditional road-stream crossing restorations. There are no scientific data demonstrating whether this more expensive design improves stream ecosystem function, habitat and aquatic productivity over that provided by typical replacements. Our research goals will be to: 1. determine whether road-stream crossing replacements using a stream simulation design improves food web structure and function when compared with non stream-simulation design replacement, and 2. estimate ecosystem services value added (if any) by using stream simulation designs.
Differences in habitat and stream ecosystem responses (periphyton, organic matter, invertebrates, and fishes) will be examined in upstream, downstream, and within culvert reaches at 3 pairs of previously restored (<4 years) of road-stream crossings in northern Wisconsin. One crossing of each matched pair was constructed using SSD which mimics natural channel structure, while the other restored crossing was not. Habitat characteristics to be measured at each reach include water depths, current velocities, and substrate composition. Periphyton (attached algal), fine and coarse benthic organic matter standing crop, and invertebrate and fish abundance and biomass will be measured and compared among reaches to determine whether the SSD significantly improves stream habitat and function. These results will provide a novel ecosystem analysis of the effectiveness of the SSD. A cost/benefit analysis using data provided by the Chequamegon-Nicolet National Forest will be conducted to provide managers with critical information on whether extra costs associated with the SSD provides significant ecological benefits over traditional culvert replacements.
Urgency and Payoff
A USDA Forest Service Interim Directive for designing road-stream crossings (2008) calls for using the stream simulation design guidelines when possible. The stream simulation design is currently being promoted and taught through regional workshops directed toward transportation managers, engineers, and local officials across the U.S. by the Stream Simulation Working Group. An evaluation of the ecological benefits of the SSD has not yet been conducted in a rigorous, scientific manner. Given that there are >1 million road-stream crossings in the United States (M. Hudy, USFS, cited in Pess et al. 2005 ) and >6 million artificial barriers to fish passage (US Fish and Wildlife Service, National Fish Passage Program) and the additional costs associated with this advanced design, it is imperative that the benefits of the design be tested in a replicated study design that will stand up to peer-review scrutiny and provide evidence that the ecological benefits gained equal or outweigh the additional costs. An additional payoff of this work will be to develop useful effectiveness monitoring techniques that local governments and state and federal agencies can use to monitor stream ecosystem improvements beyond fish passage at road-stream crossing restoration sites. Results from this research will be presented at regional workshops for transportation officials, highway engineers, and resource managers. Research results will also be published in peer-reviewed scientific journals and distributed to the general public via current websites hosted by the Stream Systems Technology Center and the San Dimas Technology and Development Center.
Dr. Sue Eggert, USDA Forest Service, Northern Research Station (218) 343-6625