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BRASSTOWN CREEK WATERSHED RESTORATION PROJECTS:

PROJECTS ON LITTLE BRASSTOWN CREEK:

Project Background

The Sheppard reach of Little Brasstown Creek has a drainage area of 6.25 square miles and is located immediately below the Mason/Stalcup project reach.  Land uses are mainly agricultural and forested land.  The Sheppard reach was severely degraded by stream bank erosion and channel instability caused by past channel modifications, cattle access, and inadequate riparian buffers.  Existing vegetation consisted of mainly grasses in open pasture and cattle had full access to the stream along the majority of the 4,000-foot reach.  The goals of the project were to improve water quality and aquatic habitat, stream stability, and riparian and floodplain functionality.

Early in 2003, natural channel design principles were applied to restore the channel’s dimension, pattern and profile to a natural, stable form. The design for the upper 2/3 of the reach was to stabilize the existing unstable E4 channel by changing the dimension, pattern and profile. Root wads, cross vanes, j-hooks, log vanes and constructed riffles were all used to stabilize the new channel and improve aquatic habitat. Transplanted vegetation, live stakes and brush layers were used to provide bank stability.  Due to a good existing riparian buffer on the left bank of the lower reach, no pattern adjustment was made, but areas of existing erosion were stabilized using root wads and brush layers.  Three weeks after construction was complete, the Sheppard project survived a major flood event (10-year reoccurrence interval)!  Only minor repairs were required.

Native trees and shrubs were planted with the 30-foot riparian buffer area along both sides of the stream. A new 4-strand barbed wire fence along the entire project reach protects the buffer area as livestock graze on the farm.

2008 Status

More than half (2539 feet) of the Sheppard stream restoration project was monitored in 2005, 2006 and 2007.  The monitored reach is moderately stable with some areas of concern and a few areas where repair work should be considered. The restored reach contains 21 rock structures that are holding grade and providing stream bank protection. Most structures showed little or no change and are functioning as intended.  A few appear to have contributed to localized stream bank erosion; structures A, B, and K noticeably deteriorated between 2005 and 2007. The restored stream is currently classified as a C4 channel.  The streambed slope is 0.004 feet/foot, with a sinuosity of 1.47.  Between 2005 and 2007, the streambed material has become coarser, with a current median particle size representing coarse gravel.

The restored reach has mostly stable riffles and pools located in the expected planform locations.  The locations of riffles and pools generally did not change between 2005 and 2007.  Cross-sectional dimensions remained similar between 2005 and 2007.  Stream bank erosion is occurring mostly along the outside of meander bends with high near-bank shear stress and failing structures. However, most of the in-stream structures are functioning to reduce near-bank stress and hold grade.  In two locations where structures are not functioning properly, stream bank erosion indicates a relatively urgent need for repair to restore stability and prevent further erosion. 

Planted vegetation in the riparian buffer along the new channel at Sheppard is generally thriving.  Air and water temperatures are both being moderated by the dense buffer.  As shown on Figure 3 (page 15) of Section 3, peak water temperatures downstream of the restored reach were consistently lower than measured upstream temperatures suggesting that riparian vegetation is having the desired cooling effect on the stream.  There are, however, some bare banks inside the planted buffer need attention.

Sheppard also had consistently lower Total Suspended Solids concentrations in downstream water samples.  The average reduction there was 41% and the only one of seven events to show an increase, only went up by 1%.  Like Mason/Stalcup upstream, this project is effectively managing a fairly heavy sediment load and would benefit from reduction of TSS from upstream sources.

The benthic macroinvertebrate assessment yielded a bioclassification of Good during each of the monitoring years.  However, between 2005 and 2007, the number of EPT taxa and EPT abundance slightly decreased.

3-Year Study Recommendations

In addition to continuing to monitor this reach in subsequent years, recommended actions include:

• Install live stakes on bare banks and consider early removal of invasives to prevent later large-scale problems

• Evaluate potential implications of a beaverdam at Structure R

• Consider bank and structure repair in the vicinity of Structure C

Brasstown Project Summary

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