20170998 Ver 1_More Info Received_20170915

Homewood, Sue
From: Justin Church <[e-mail]>
Sent: Friday, September 15, 2017 12:47 PM
To: Homewood, Sue
Subject: Eric Green Project
Attachments: DESIGN_CONSIDERATIONS.pdf
Sue,
Please see attached. I think I have answered the concerns we discussed, but please let me know if I can provide
something more.
Thanks
Jc
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Justin Church, PE, CFM
Principal Engineer
BREC, P.A.
126 Executive Drive, Suite 220
Wilkesboro, NC 28697
(o) 336.844.4088
(c) 828.773.6543
http://brec.biz

ERIC GREEN STREAM RESTORATION
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BREC, P.A.
15 September 2017
Justin Church, PE
Principal Engineer
Eric Green Stream Restoration

General Information
The Eric Green Stream Restoration project is a proposed priority two restoration
of a degraded reach of Stony Fork near Deep Gap in Watauga County, NC. The
primary goal of the project is to mitigate channel instability and stream bank
erosion by modifying the dimension, pattern, and profile of the channel to create
floodplain connectivity with a re-established riparian buffer protected by livestock
exclusion fencing.
2.0 Design Considerations
The restoration plan was guided by natural channel design methodologies.
Reference reach data was taken from a collection developed by the North
Carolina State University Stream Restoration Program. Bankfull indicators in the
field showed a bankfull cross sectional area of 14f t2. This is slightly less than
the regional curve data of 17 f t2 for the area but within an acceptable range. A
design W/D ratio of 13 was selected to match field observations and maintain a
sufficiently narrow channel to transport sediment while maintaining the bankfull
depth at an elevation that can be supported by early onset vegetation.
Pool spacing is a primary design consideration given the channel gradient of
approximately 3.5%. Based on reference reach data and information published
by Wildland Hydrology (see figure below), pool to pool spacing was set in the
3Wbkf ± 0.25Wbk f. This pool frequency matches the valley and keeps the riffles
sufficiently steep to maintain pool scour and sediment transport. In select areas,
the pool spacing is less than 3Wbk fin order to work with the existing alignment as
much as possible without creating excessively long pools or transverse riffles.
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BREC, P.A. Eric Green Stream Restoration 2

Parameter
Design Stream
Reference Stream
Min
Median
Max
Min
Median
Max
Stream name
Stony Fork
Fork Creek Upstream
Stream type
B3
134cDrainage
area, DA (sq mi)
0.9
2.7
Mean riffle depth, dbkf (ft)
1.0
1.4
Riffle width, Wbkf (ft)
13.5
19.2
(ft)
Width-to-depth ratio, [Wbkf/dbkf]
20.2
13.0
22.9
39.1
13.6
Pool length ratio [L�,/Wbkf]
1.3
Riffle cross-section area, Abkf (sq ft)
2.0
14.0
1.4
5.7
27.2
27.0
40.5
Pool width, Wbkf, (ft)
16.2
16.9
20.2
21.6
32.1
44.3
4.0
0.9
POOL width ratio, [Wbkfp/Wbkf]
1.2
1.3
1.5
0.8
1.2
1.6
30.7
67.6
Pool cross-section area, Abp (sq ft)
18.2
21.0
25.2
31.5
44.0
54.0
Pool area ratio, [Abkf,/Abp]
1.3
1.5
1.8
1.2
1.6
2.0
Pool length, LP
Each pool to pool spacing includes a riffle to be established using existing cobble
material. Riffles are identified on the profiles of the plansheets and by the
contours of the grading plan (no widget is shown on the plans for them since they
are to be constructed of native material). All structures will be low profile with a
maximum vane arm height of z Dbkf, and to the maximum extent practical, they
will be constructed of logs rather than boulders to create a more natural
appearance.
BREC, P.A. Eric Green Stream Restoration 3
(ft)
16.9
20.2
27.0
22.9
39.1
155.1
Pool length ratio [L�,/Wbkf]
1.3
1.5
2.0
0.8
1.4
5.7
Pool -to -pool spacing, p -p (ft)
27.0
40.5
54.0
25.2
90.8
175.0
Pool -to -pool spacing ratio, [p-p/Wbkf]
2.0
3.0
4.0
0.9
3.3
6.4
Riffle length, Lr;f (ft)
17.5
20.2
27.0
5.9
30.7
67.6
Riffle length ratio, [L,.;f/Wbkf]
1.3
1.5
2.0
0.2
1.1
2.5