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| Green River |
Sublette County, Wyoming |
Primary Project Type: Instream Restoration
Secondary Type: |
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During the mid-1800s, most of the large woody debris and large boulders within t... |
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Primary Problem: Loss of Fish Habitat
Secondary Problem: |
| Main Restoration Action(s): Habitat enhancement |
| Native Fish Focus: N/A |
Is this project part of a watershed scale restoration? No
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| Project Dates: 1987 to 1993 |
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Initial Monitoring:
Restoration Implementation:
Follow-up Monitoring: |
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Lead Agency:
Wyoming Game and Fish Department
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| Project Partners: |
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| Project Location:
Located about 30 miles northwest of Pinedale, the habitat improvement project was situated between the forest boundary and Kendall Bridge.
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| Project Description:
Between 1867 and 1940, tie drives were conducted along the Green River to transport logged trees out of the headlands. These activities greatly influenced a river channel that was originally shaped by glacier activity. To facilitate passage of ties down river and reduce occurrences of tie jams, boulders and other debris were often removed from the channel, with dynamite if necessary. Thus, many pre-treatment river reaches in the project area were dominated by long, wide, shallow riffles and glides that offered little shelter for trout. Deep pools and large woody debris were scarce and both summer and over-wintering habitat was poor. Late summer cover was very poor, with less than 1% of the river offering shelter to trout. Cobble and boulders cemented with sand and gravel armored the river bottom. In addition to habitat degradation, the Green River has long been popular with anglers and received increased fishing pressure. Although wild trout have always been present, poor habitat limited fishery productivity. River water flowing down from the granitic Wind River Mountains contained few nutrients. Consequently, trout were stocked for many years to satisfy angler demands. Stocked trout included rainbow, brown, and brook trout, yet large fish were not common prior to restoration activities. In 1986, the US Forest Service (USFS) cabled several experimental trees along the east bank of the Green River near the Guard Station. This large woody debris attracted many trout and created discussion about improving trout habitat on a wider scale. After a habitat assessment identified 71 sites where structures could help, a multi-year habitat improvement project was launched. |
| Project Goals: The project goal was to increase trout carrying capacity of the Green River by increasing the quantity and quality of trout shelter. Structures near the forest boundary also were designed to control lateral erosion and head-cutting created by past channelization activities. |
| Project Methods:
Several habitat improvement structures were constructed within the Green River to provide overhead shelter for trout, deflect river currents away from eroding banks, and trap excess sediment. The improvement plan was designed to narrow and deepen the base flow channel while leaving the flood channel intact. All devices were designed to function at all flows. Between 1987 and 1990, a Wyoming Game and Fish construction crew installed 27 tree jams, six rock funnels, several individual cover trees, and numerous fish rocks between the forest boundary and Kendall Bridge. A steep, eroding bluff near the forest boundary also was stabilized with a 330 ft tree/rock revetment (Figures 1 and 2). Boulders and trees were hauled to the project by contractors; structures were built using loaders and a tracked hoe to move rocks and trees.
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Over 300 feet of tree and rock revetment were used to protect this eroding bank ... |
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This photograph provides a close-up view of how trees and rocks were secured to ... |
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| Monitoring Data and Collection
Methods: Two stations were selected within the Green River project area to evaluate fish populations using electrofishing techniques: the first station was a 1.2 mile section through the upper project area from Kendall Bridge to the Whiskey Grove Campground; the second station was a 2.6 mile section located between the Guard Station and the forest boundary. The first station was sampled in 1989 before any habitat improvement structures were added to the river. The second station also was sampled with a single pass in 1989. A total of 11 tree jams, three rock funnels, and one 330 ft tree/rock revetment were constructed within Station 2. Additionally, the Habitat Quality Index (HQI) protocol was used to evaluate fish habitat within the project area.
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| Was this project effective
and how was this determined? The popular upper Green River fishery was strongly supported by stocked trout prior to restoration activities. Survival of natural recruitment was hindered by a lack of large woody debris and deep pool shelter, especially during winter. By 1996, new shelter offered by the habitat improvement structures prompted a four-fold increase in trout numbers and a doubling of biomass. Many of these fish were wild, naturally reproduced stock. In addition, large trout were more numerous after the installation of improvement structures. A combination of special regulations and better cover for trout produced a strong fishery with a variety of age classes.
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(Before) Figure 1. Its equilibrium disturbed by channelization downstream on pri... |
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(After) Figure 2. The same steep bluff shown in Figure 1 as it appeared ten year... |
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Confounding Effects/Additional
Information: Performance of the habitat improvement structures generally was good, despite several large flood events. Deterioration of some cables, however, allowed several trees to wash away. Trees anchored midstream were vulnerable to damage, as they received the full force of strong currents. They also were more prone to move up and down than trees anchored to the banks, thus causing extra stress on cables. Trees anchored along the banks generally were more stable, especially those where silt deposits accumulated and further anchored the trees. The lesson from this project was clear: tree-jams required annual inspection and prompt maintenance of faulty cables. Lone tree covers did not endure as well as groups of trees, nor did they attract fish as well.
Durability and performance of the rock funnels was good. They acted as grade controls and created pocket pools. As intended, much of the base flow flowed through the slot, where water velocity was often very swift (>3 fps), especially during flood flows. But flow through the slots was not swift enough to break the bottom armor and scour pools below the structures. Consequently, those pools were excavated with a tracked hoe. After excavation, flow through the slot maintained pool depth and configuration and attracted many trout. |
| Project
Specs (all specs are estimates): |
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Overall Estimated Cost:
$166,500 ($27,750/year, $37,000/mile): Wyoming Game and Fish paid 56%, US Forest Service 27%, and Trout Unlimited 16%. Wyoming Game and Fish furnished planning and construction expertise, funds, labor, materials, and equipment; US Forest Service contributed funds, rocks, and trees; and Trout Unlimited provided funds to rent additional heavy equipment.
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| For more information on this project
contact: |
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Allen Binns, Wyoming Game and Fish Department, Email: Allen.Binns@wgf.state.wy.us
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| This information
was collected by: Michelle White |
| Project last updated on: 4/30/2007 |
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