GEI has been working to support WaterVation on multiple stream restoration projects over the past few years; the two projects highlighted here have recently been completed.
The site on Sunlight Creek in Park County, Wyoming was completed for Wyoming Department of Game & Fish and consisted of approximately 4,000 linear feet plagued by extreme lateral channel migration over the past 40 years. This was caused by changes in land use practices and exacerbated by subsurface irrigation return flows. Brook trout habitat had been significantly reduced because of ongoing aggradation which eliminated bedform diversity and clogged spawning gravels. GEI supported a multi-disciplinary design team to provide fisheries specialists and wetland scientists to develop a stream restoration design that was founded on natural channel design principles. The main project goals were mitigation of extreme bank erosion and improvement of in-stream trout habitat for this red-ribbon fishery. Detailed stream assessments were performed to collect geomorphic, ecologic, and biologic data for both the project reach and a reference reach just upstream of the project area. The proposed geomorphic channel design consisted of a major stream realignment and incorporated a low-flow channel, bankfull channel, and geomorphic floodplain that worked in unison to effectively convey sediment through the system. This stable channel now contains foraging habitat, spawning habitat, high-quality overwintering habitat, and refuges from the unstable ice conditions that typically form in medium-sized, high-elevation streams. The proposed channel morphology was further refined using sediment transport models to evaluate sediment competence and capacity. Both one-dimensional and two-dimensional hydraulic models were used to evaluate shear stress and stream power for a range of flood events to ensure the proposed design provided adequate stability for the system during extreme hydraulic conditions, as well as help to design structural elements that would not impede fish migration.
The site on Fountain Creek was completed for El Paso County Public Works in Colorado and consisted of restoration of 3,000 linear feet of stream that had been degraded as a result of upstream urban development and managed/modified instream flows. The project objectives included mitigation of severe erosion of the streambank, enhancement of the degraded instream habitat for native plains fishes, and ultimately reconnection of the stream channel to adjacent floodplain and cottonwood galleries. Given permitting constraints, the design incorporated engineered boulder and log jam structures that causes deposition of the stream’s natural sediment load in desired locations. This facilitates the development of a more natural bedform conducive to increased sediment transport and floodplain reconnection and improved fish habitat; this approach is a viable alternative when the direct construction of bedform features is not practical or permittable. The stability and sediment continuity of the design and the areal increase in foraging and high-flow refuge habitats for resident fishes were verified during the design process using 2D hydrodynamic models.
Our multi-disciplinary team consisted of aquatic ecologists, biologists, wetland scientists, and restoration engineers.