by Julie Ash and Grant Gurnee, Walsh Environmental
|Fig. 1. Aerial view of the Edwards Reach|
A large-scale, high-profile river corridor restoration project is underway in Edwards, Colorado, thanks to the Eagle River Watershed Council, the Eagle River Water and Sanitation District (ERWSD), the Colorado Department of Public Health and Environment (CDPHE), and landowners along the river. The Watershed Council was awarded funds in January 2007 from the Eagle Mine Natural Resource Damage Recovery Fund (NRDF) through the CDPHE. The Eagle Mine NRDF supports activities that restore damaged or lost natural resources traceable to operations of the Eagle Mine and projects such as the Edwards Eagle River restoration project, which will implement natural resources restoration in a vital portion of the Eagle River Watershed. Final design and planning is in progress and construction of the first phase of the restoration is slated for fall 2008.
The Edwards Eagle River restoration project site is roughly 1.6 miles long and covers an area of 168 acres in the heart of the Edwards community. This broad, flat river reach is highly visible from all areas of Edwards (Fig. 1). The project reach, also called the Edwards Reach, begins about one-half mile downstream of the Edwards Spur Road Bridge and ends at the Hillcrest Drive Bridge.
The Project is ideally suited for restoring lost resource values for three important reasons. First, because of the unique location of the Edwards Reach, which is situated between long stretches of high quality riparian and aquatic habitats on its upstream and downstream ends, investment in this 1.6 mile project reach will yield almost 50 miles of continuous high quality riparian and aquatic habitat. Thus, investment in a small piece therefore benefits a vastly larger area both directly and indirectly, so that the “whole is greater than the sum of its parts”.
|Fig. 2. Unstable bank conditions and lack of riparian vegetation|
Second, the conditions within the Edwards Reach boundaries are some of the most severely degraded in the entire valley. The Eagle River Inventory and Assessment (ERIA), completed in 2005 by Colorado State University’s Engineering Research Center, prioritized possible restoration activities in the Eagle River watershed based on the potential for improvement of river system integrity. The ERIA identified the Edwards Reach as one of three projects that offer wide-ranging benefits, including large-scale reestablishment of wetland and riparian functions. The relative greater severity of aquatic and riparian habitat degradation in this reach makes it an optimal target for restoration of lost resource values. Investment in this reach will yield greater systems benefits per unit effort than that achievable along other reaches that are in better condition.
Third, the Edwards Reach is a highly used and much loved resource and amenity for all of Eagle County. From gated drives to trailer park courts, an extremely diverse population of about 5,000 resides along the project reach. On the upstream end is the 72-acre Eagle River Preserve and on the downstream end is an unimproved public boat launch, serving approximately 800 people per day on an average Saturday during the summer. This statistic indicates heavy use of the reach by local boating communities, including river rafting and kayaking. The high visibility and popularity of this reach make it an ideal location for the investment of resources with the goal of restoring lost resource values.
The Edwards Reach of the Eagle River completely lacks a mature riparian habitat typical for this region and contains sections with poor quality aquatic habitat. This degraded reach effectively disconnects high quality riparian and aquatic habitats found upstream with that found downstream. Channel conditions and aquatic habitat remain degraded from historic agricultural land use practices compounded by increasing development linked to non-point source pollution. The most prevalent impacts are related to excessive fine sediment deposition, agricultural livestock grazing, and sparse riparian vegetation coverage (Fig. 2).
|Fig. 3. Fine sediment accumulations|
In this lowest gradient reach of the Eagle River, where the valley abruptly widens and flattens, the channel has an extremely high width to depth ratio and a reduced capacity to transport fine sediment, especially at lower flows. Therefore, fine sediment accumulations are visible (Fig. 3) throughout the Edwards Reach. Such accumulations have been identified as significant habitat for the tubifex worm (Tubifex tubifex), an organism implicated with whirling disease (Myxobolus cerebralis) in trout. Further, the fine sediment accumulations choke the channel bed substrate, degrading cover and food supply for cold-water fishes such as trout.
High instream temperatures and low dissolved oxygen levels occur in the Edwards Reach during low flow periods and are detrimental to cold-water aquatic habitat. The overly high width to depth ratios in the reach contribute to poor aquatic habitat and the reach lacks both mature overhead canopy and instream cover for shading and cooling.
With its relatively large population and high popularity, the Edwards Reach is heavily used and currently experiencing detrimental effects from “loving the river to death”. Access patterns to the river from adjacent residences are unformalized and consist of an excessive number of social trails. Access for boaters is also unformalized, causing greater impacts than would be expected in a more controlled setting. The Project will provide well-managed educational and recreational components designed to benefit the public, the natural habitats, and the river corridor itself.
The Edwards Eagle River Restoration project will make significant improvements to the Eagle River by reconnecting high quality natural resources that are present upstream and downstream. Restoration, enhancement, and protection activities are proposed on both north and south banks, in the stream channel, as well as within the floodplain. In addition to direct river improvements, the project will reduce current land use impacts throughout the corridor, improving bank conditions and water quality for the river, both within the project reach and further downstream.
The goal of reducing fine sediment accumulations will be achieved through improved channel hydraulics, which enables sediment mobilization even under low flow conditions. Two specific issues are particularly relevant in this reach due to aspects of the channel morphology related to prominent pool-like features called sinkholes. Sediments mobilized in reaches upstream of sinkholes will deposit in sinkholes during low flows. Second, localized increases in fine sediment mobilization during low flows coupled with reductions in fine sediment supply throughout the project reach creates a “sediment neutral” condition in terms of sediment transport balance.
The natural resource benefits resulting from the restoration efforts include:
- improved surface water quality via reduced temperatures, increased dissolved oxygen levels, local fast water and turbulent water zones, reduced fine sediment supply, and reduced land use impacts, including sediment reductions from boat launch and park area, social trails, and from cattle grazing activities
- enhanced sediment control via reduction of fine sediment accumulations through channel modifications coupled with reduced fine sediment supply
- restored stream health and function via appropriate channel geometry, concentrated low flows, increased sinuosity for riffle-pool development, and increased flow diversity
- enhanced aquatic habitat via newly created overhead cover for shading, cooling, and detritus supply; instream habitat cover, including woody debris component, for shading, cooling, protective cover, and invertebrate food source and substrate; reduced tubifex worm habitat; and reconnection of high quality fisheries found upstream and downstream from the Edwards Reach
- restored riparian corridor via new streamside plantings to reconnect riparian corridors, icreased diversity of species and strata, and stabilization of eroding banks
- enhanced wildlife habitat via riparian and floodplain woody plant installations, increased diverity of species and strata, enhancement of existing wetlands, and increased nesting opportunities and habitat utilization
The restoration design and planning requires collaboration from a long list of project partners, including planners, designers, permitting agencies, funding sources, local landowners and many other stakeholders. The Colorado Division of Wildlife, Eagle County, the U.S. Army Corps of Engineers, and others have provided technical and planning input. With all entities leveraging resources in this way, the target of expeditiously and economically restoring natural resources values is assured. This final vision is one that all will no doubt take pride in achieving.