Cohutta Wilderness

Index

Introduction

The Cohutta Wilderness Area was established by Congress in 1975 to protect the unique natural features of the area including rugged, densely forested mountains and clear, cool rushing streams. The Wilderness Area total 37,042 acres with 35,247 acres on the Chattahoochee National Forest in Georgia and 1,795 acres on the Cherokee National Forest in Tennessee. Drained by the Jacks and Conasauga River flowing northward from Georgia into Tennessee, the Cohutta was sparsely settled throughout its early history but has been extensively logged over the years. Both River drainages were logged with horses pulling timber to the rivers where narrow gauge railroads transported the logs out to the valleys below. There is little or no floodplain and stream gradients are steep, marked by waterfalls and rapids.

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Air Quality Related Values

Visibility

Several vistas on high ridges in the Wilderness afford views across adjacent ridges to high peaks to the north and west and also down into the deep river gorges. Hikers pass along these views on several trails and often seek solitude at such vistas.

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Natural Background Visibility
Site Specific Rayleigh scattering coefficient: Clearest 20% Natural Clearest 20% 2000-2004 Baseline Haziest 20% Natural Haziest 20% 2000-2004 Baseline Average Annual Natural Annual Average 2000-2004 Baseline
Standard Visual Range (km) 272 102 138 19 196 46
Haze Index (dv) 4.32 13.73 10.78 30.25 7.42 21.6

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Streams

The high-quality, clear, cool streams and rivers flow down steep gradients over waterfalls and rapids in the Wilderness. The headwaters are essentially free of sediment entry and support populations of native brook and brown trout. Both the Jacks and Conasauga Rivers are classified as high quality native trout streams providing habitat for reproducing populations of brown and rainbow. Rough Creek and the unnamed left headwaters fork of the Conasuaga River are the only streams with populations of native brook trout. These trout fisheries represent a major recreation opportunity in the Cohutta. The consistent flow of high quality clear water in the wilderness also permits the presence of the Coosa Bass and the blue shiner. Changes in water quality could have drastic effects on the trout population followed by loss of the recreation use.

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Vegetation

The mixture of plant communities and landforms in the Cohutta Wilderness is one part of the total environment which makes this a special area and enhances the overall wilderness experience. Without this mixture of plants, the experience would be reduced significantly. Most of the Wilderness is second growth hardwood-pine forest with unique plant communities interspersed in the understory. The major hardwood species include northern red oak, white oak, chestnut oak and yellow poplar. Conifers such as white pine, shortleaf pine and Virginia pine are mixed with the hardwoods. Most of the forest is young, due to past logging in the area. A large number of understory species are found according to soil and site conditions. The Georgia Botanical Society has identified over 40 varieties of rare and uncommon plants in the area. Changes in soil productivity could easily affect species growth and plant succession throughout the entire Wilderness.

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Resource Concern Thresholds

AQRV Type: VISIBILITY
Sensitive Receptor Sensitive Receptor Indicator Thresholds
Natural Visibility Light Extinction In specific Class I areas to maintain consistency with Regional Haze implementation plans or BART, the visibility threshold for concern is not exceeded if the 98th percentile change in light extinction is <5% for each year modeled, when compared to the 20% best natural background values.
Natural Visibility Light Extinction For sources generally further than 50 km from a Class I area, the visibility threshold for concern is not exceeded if the 98th percentile change in light extinction is <5% for each year modeled, when compared to the annual average natural condition value for that Class I area.
Plume Blight Absolute Contrast Screening Analysis: For near field sources (within 50 km of a Class I area), no additional analysis will be requested if screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions.
Plume Blight Absolute Contrast Refined Analysis: No further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 modeled against natural conditions.
Plume Blight Color Difference Index Screening Analysis: For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions.
Plume Blight Color Difference Index Refined Analysis: No further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 when modeled against natural conditions.

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AQRV Type: WATER
Sensitive Receptor Sensitive Receptor Indicator Thresholds
Perennial Streams Acid Neutralizing Capacity In perennial streams, no more than 0.1 microequivalent/liter measurable decrease in acid neutralizaing capacity is acceptable
Perennial Streams Chronic Acid Neutralizing Capacity To maintain healthy biological functioning in perennial streams, the chronic acid neutralizing capacity must be >= 25 ueq/l.
Perennial Streams Chronic pH To maintain healthy biological functioning, the chronic pH of perennial streams must be >= 6.0.
Perennial Streams Episodic Acid Neutralizing Capacity To maintain healthy biological functioning in perennial streams, the episodic acid neutralizing capacity must be >= 0 ueq/l.
Perennial Streams Episodic pH To maintain healthy biological functioning, the episodic pH of perennial streams must be >= 5.5.
Perennial Streams pH In perennial streams, no more than 0.1 measurable decrease in pH is acceptable

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Pollutant Exposure Concern Thresholds
Pollutant Exposures Level Name Thresholds
Nitrogen DEPOSITION Nitrogen deposition may be expected to cause cation leaching in soils when N levels are greater than 12 kg/ha/yr. Below 5 kg/ha/yr, negative effects to soil and vegetation are not expected
Nitrogen EXCEEDANCE The Deposition Analysis Threshold for nitrogen deposition below which estimated impacts from a source are considered negligible is 0.010 kg/ha/yr.
Ozone W126 Biomass reduction of ozone sensitive species may occur when the W126 ozone metric (for April-September) is > 14.5 ppm-hours. This should be evaluated in conjunction with the N100 value.
Ozone N100 METRIC Biomass reduction of ozone sensitive species may occur when the number of hours from APRIL-SEPTEMBER with an ozone concentration greater than or equal to 0.100ppm equals or exceeds 4. This should be evaluated in conjunction with the W126 value.
Sulfur DEPOSITION Sulfur deposition may be expected to cause cation leaching and increased aluminum toxicity in soils when levels are greater than 20 kg/ha/yr. At 5 kg/ha/yr or below, sulfur negative effects to soil and vegetation are not expected.
Sulfur EXCEEDANCE The Deposition Analysis Threshold for sulfur deposition below which estimated impacts from a source are considered negligible is 0.010 kg/ha/yr.

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General Information
State(s):Georgia, Tennessee
County(s):Fannin, Gilmer, Murray, Polk
Forest Service Administrative Unit(s):Southern Region (Region 8) -- Chattahoochee - Oconee National Forest, Cherokee National Forest
Size:36977 acres
Elevation Range:800 - 4,200 feet
Image(s):https://www.wilderness.net/images/
Detailed wilderness information:https://www.wilderness.net
GIS Map/Official Boundary:https://www.wilderness.net/NWPS/

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updated: 02/28/13