20021189 Ver 1_COMPLETE FILE_20020729

MEMORANDUM
TO: John Dorney Regional Contact: Michael L Parker
Non-Discharge Branch WQ Supervisor: Rex Gleason
Date:
SUBJECT: WETLAND STAFF REPORT AND RECOMMENDATIONS
Facility Name Avon Creek Bank Stabilization County Gaston
Project Number 02 1189 County2
Recvd From APP Region Mooresville
Received Date 7/29/02 Recvd By Region 8/2/2002
Project Type bank stabilization
Certificates Stream Stream Impacts (ft.)
Permit Wetland Wetland Wetland Stream ClassAcres Feet '
Type Type Impact Score Index Prim. Supp. Basin Req. Req.
-1,615.00 r-?
13 ? P-7 O N F -F-11--13o r C -r30,837 ?
. x
x F_ - PT _0N Mitigation Wetland
MitigationType Type Acres Feet'
Is Wetland Rating Sheet Attached? Q Y (@) N Did you request more info? Q Y 0 N
Have Project Changes/Conditions Been Discussed With Applicant? Q Y0 N
Is Mitigation required? p Y O N Recommendation: QQ Issue O Issue/fond O Deny
Provided by Region: Latitude (ddmmss) 351520 Longitude (ddmmss) 811020
ay N `J 3
cc: Regional Office
Central Office Page Number 1
WA
Michael F. Easley
\0? pG Governor
Co 7 William G. Ross, Jr., Secretary
j Department of Environment and Natural Resources
Alan Klimek, PE
Division of Water Quality
August 22, 2002
City of Gastonia
Attn: Mr. Thorne Martin
PO Box 1748
Gastonia, NC 28053-1748
Subject: Stream Stabilization/Enhancement
Avon Creek
Gaston County, NC
DWQ# 021189
Dear Mr. Martin:
This Office is in receipt of the plans for the stream restoration projects of approximately 1615 feet of
Avon Creek in the Catawba River Basin originally submitted to this Office on July 29, 2002. DWQ Staff
reviewed the plans and determined that stream enhancement or stabilization using soft techniques would be
achieved. As such, the stream impacts associated with the project may proceed without written approval from
the Division. Please be advised that seven copies of a complete, formal application and a $475.00 fee is
required for projects intended for compensatory mitigation credit (see General Certification No. 3353, issued
March 18, 2002). Any request for mitigation credit shall be addressed under separate cover.
If you have any questions regarding this matter, please contact Mr. Todd St. John at [phone].
YL4
R. Dorney
nds Unit Su erv or
cc: Mr. Todd St. John, Wetlands Unit
Mooresville Regional Office
Mr. Andrew Bick, PE, Buck Engineering, 8000 Regency Parkway, Suite 200, Cary, NC 27511,
File
North Carolina Division of Water Quality, 401 Wetlands Certification Unit,
1650 Mail Service Center, Raleigh, NC 27699-1650 (Mailing Address)
2321 Crabtree Blvd., Raleigh, NC 27604-2260 (Location)
Triage Check List
Date: -7 / 6-K .,'Project Name:
y
DWQ#: OX I 1 K9
County: (SaSdiDy_
To: ? ARO Mike Parker ? WaRO. Deborah Sawyer
? FRO Ken Averitte ? WiRO Joanne Steenhuis
02LMRO Mike Parker ? WSRO Jennifer Frye
? RRO Steve Mitchell
From: ` Aku Telephone : (919) 133
The file attached is being forwarded to your for your evaluation.
Please call if you need assistance.
Stream length impacted
? Stream determination
? Wetland determination and distance to blue-line surface waters on USFW topo maps
? Minimization/avoidance issues
? Buffer Rules (Meuse, Tar-Pamlico, Catawba, Randleman)
? Pond fill
? Mitigation Ratios
? Ditching
? Are the stream and or wetland mitigation sites available and viable?
? Check drawings for accuracy.
? Is the application consistent with pre-application meetings?
? Cumulative impact concern
1
Comments: -' Ve/v-e t u 7
BUCK 8000 Regency Parkway
Suite 200
Cary, North Carolina 27511
Phone: [phone]
ENGINEERING Fax: [phone]
www.buckengineering.com
TO: NC Division of Water Quality RE
410 Wetlands Unit
1650 Mail Service Center
ATTENTION:
DATE:
July 26, 2002 JOB NO.
LETTER OF TRANSMITTAL
1021A
Avon Creek Bank Stabilization Project
050
Raleigh, NC 27699-1650
Mr. Todd St.John
We are sending via:
Overnight [ Regular Mail F] Pick-up P?j Hand Delivered
The following items:
Correspondence 0 Plans F-1 Specifications 0 Other as listed below:
COPIES DATE NO.
I ;?TIO , „ ,
D-E
7 Jul 2002 Avon Creek Bank Stabilization Permit Pack ` e

THESE ARE TRANSMITTED as checked below:
e For Approval B As Requested F-1 Approved As Submitted e Returned For Corrections
For Your Use For Review And Comment Approved As Noted Forward To Subcontractor
REMARKS:
This is a Clean Water Management Trust Fund project for the City of Gastonia so the review fee is waived. One copy of
the permit package was submitted to the COE for their review. Please call me at [phone] if you have any
questions. Thanks.
11n
WETLANf1qrRCjip
AUTy SECTION
COPY TO: SIGNED: Andrew Bick, PE

Avon Creek
Bank Stabilization Pla?r,kE copy
City of Gastonia
BUCK.
1 `J ( I N I I R IN( AE?
July 26, 2002
{? F 'jUL 2? 9- 6'002
? D
Avon Creek Bank Stabilization Plan
Gastonia, Gaston County, North Carolina
July 26, 2002
Prepared For:
City of Gastonia
Attention: Mr. Thorne Martin
P.O. Box 1748
Gastonia, North Carolina 28053-1748
[phone]
Prepared By:
Buck Engineering, PC
8000 Regency Parkway, Suite 200
Cary, North Carolina 27511
[phone]
Vy 4 4 "
William A. Harman, PG
Principal In-Charge
04'At' Ad
Andrew Bick, PE
Project Manager
i

Executive Summary
' Lineberger Park and the project reach of Avon Creek are located in the central portion of
Gastonia, North Carolina. The Avon Creek basin is largely urbanized with primarily
' residential land uses upstream of the project reach. The site is located in the eight-digit
hydrologic unit code (HUC) 03050101.
Bank stabilization will take place on Avon Creek and an unnamed tributary (UT) that
flows into Avon Creek from the west. The project site is near the upland limit of the
Avon Creek basin. The drainage area of the study reach is 0.75 square mile. The bank
' stabilization work is a part of a larger project to improve Lineberger Park. The goals of
the project are to establish a floodplain at a lower elevation, reduce bank erosion at high
' flows, and create a focal point for the improved park. The project will also improve the
local aquatic habitat and protect water quality. The project is funded by the North
Carolina Clean Water Management Trust Fund and is not intended for mitigation.
The reach of Avon Creek that flows through the park is 985 feet long and the reach of the
UT through the park is 630 feet long. Both streams are classified as Rosgen "G" stream
t types and are characterized by low sinuosity and moderate to deep channel incision. The
stream beds are dominated by shallow riffles and runs. Pools in most areas are relatively
shallow and are generally the results of scour obstructions such as debris and bedrock
outcrops. The substrate consists mainly of sand sized particles. Bedrock knickpoints are
present near the confluence of the two streams.
' This report describes the recommended bank stabilization approach, including detailed
descriptions of floodplain excavation, structure installations, and riparian vegetation
planting.
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Table of Contents
1 Introduction ................................................................................................................. 1
1.1 Project Description ............................................................................................. . 1
1.2 Project Goals ...................................................................................................... . 1
2 Existing Condition Survey .......................................................................................... 4
2.1 Summary Information for Existing Reaches ....................................................... 4
2.2 Geology and Soils .............................................................................................. . 5
2.3 Land Use ............................................................................................................ . 5
2.4 Avon Creek ......................................................................................................... 5
2.4.1 Channel Morphology ................................................................................. . 5
2.4.2 Vegetation Assessment ............................................................................... 6
2.5 UT to Avon Creek ............................................................................................... 7
2.5.1 Channel Morphology .................................................................................. 7
2.5.2 Vegetation Assessment ............................................................................... 7
3 Reference Reach Analysis .......................................................................................... 8
4 Bankfull Stage Verification ........................................................................................ 9
5 Natural Channel Design ............................................................................................ 10
5.1 Design Summary ............................................................................................... 10
5.2 Avon Creek ....................................................................................................... 10
5.3 UT to Avon Creek ............................................................................................. 11
5.4 Riparian Buffer Restoration .............................................................................. 11
6 Sediment Transport Discussion ................................................................................ 13
7 References ................................................................................................................. 14
Appendices
Appendix 1 Existing Condition Profiles, Cross Sections, Photographs and Bed Material
Analysis
Appendix 2 Design Cross Sections
Appendix 3 Planting Specifications
Appendix 4 Reference Reach Data
List of Figures
Figure 1.1 Avon Creek Project Location
Figure 1.2 Avon Creek and UT Drainage Areas
Figure 4.1 Bankfull Stage Verification for Avon Creek
111

List of Tables
Table 2.1 Selected existing condition parameters
Table 5.1 Natural channel design parameters for Avon Creek
Table 5.2 Natural channel design parameters for UT to Avon Creek
Sheets
Sheet 1
Sheets 1 A and 1 B
Sheets 2 and 2A
Sheets 3 and 4
Sheet 5
Title Sheet
Symbology
Details
Proposed Design
Planting Plan
iv

I Introduction
1.1 Project Description
The City of Gastonia proposes to stabilize the banks along a section of Avon Creek and
an unnamed tributary (UT) of Avon Creek. Avon Creek flows south into Catawba Creek
and is part of the Catawba River Basin. The Avon Creek watershed upstream of the
project site has a total drainage area of 0.75 square miles and is located in the eight-digit
hydrologic unit code (HUC) 03050101. The proposed bank stabilization project is in
Lineberger Park, near the headwaters of Avon Creek. The project location is shown on
Figure 1.1 and the watershed delineation is shown on Figure 1.2.
The project reach of Avon Creek is about 985 feet long and the UT project reach is about
' 630 feet long. Both streams are classified as straightened Rosgen "G" stream types with
moderate to deep channel incision. Bank height ratios range from 1.9 to 2.0 on Avon
Creek and 1.6 to 1.7 on the UT. Bankfull cross-sectional area is about 34 square feet on
' Avon Creek and about 17 square feet on the UT. Localized areas of active streambank
erosion are present along both reaches. Reach sinuosity is 1.03 for Avon Creek and 1.07
for the UT.
1.2 Project Goals
t The goals of this project are to:

F

1. Stabilize Avon Creek and the UT using natural channel design techniques,
2. Improve floodplain functionality,
3. Reduce bank erosion at high flows,
4. Develop the stabilized streams as park focal points,
5. Provide access to the streams,
6. Improve aquatic habitat and the natural aesthetics of the stream corridor.
The project is funded by the North Carolina Clean Water Management Trust Fund and is
not intended for mitigation.
I Avon Creek Bank Stabilization Plan 1 The City of Gastonia

Avon Creek Bank Stabilization Plan 2
The Citv of Gastonia
Figure 1.1 Avon Creek Project Location
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Avon Creek Bank Stabilization Plan 1 3
The City of Gaston
I.
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2 Existing Condition Survey
2.1 Summary Information for Existing Reaches
Summary information for the existing Avon Creek and the UT is presented below in
Table 2.1. Narrative descriptions of the existing conditions are presented in Sections 2.4
and 2.5.
Table 2.1 Selected existing condition parameters

Reach Avon UT
Rosgen Stream Type G5c G5
Drainage Area (square miles) 0.75 0.07
Reach Length (ft) 985 630
Substrate Riffle d50 (mm) 0.4 0.4
Typ. Bankfull Area (sq ft) 34 17
Typ. Bankfull Width (ft) 15 11
Typ. Width/Depth Ratio (ft) 6.5 7.9
Typ. Bankfull Mean Depth (ft) 2.3 1.4
Typ. Bank Height Ratio 1.9 1.7
Typ. Entrenchment Ratio * 1.8 1.9
Typ. Meander Length Ratio 6.7 8.2
Typ. Radius of Curvature Ratio 3.3 2.7
4 Typ. Belt Width Ratio 1.3 1.6
Sinuosity 1.03 1.07
Valley Slope (ft/ft) 0.0048 0.0261
0
Channel Slope (ft/ft)
0.0046
0.0243
*The banks have been mechanically altered from a natural slope, thus increasing the
entrenchment ratio artificially.
Avon Creek Bank Stabilization Plan 4 The City of Gastonia
d
2.2 Geology and Soils
' The geologic setting of the site is the Kings Mountain Belt of the Piedmont physiographic
province. The Kings Mountain Belt is comprised of metamorphic and intrusive rocks,
chiefly gneiss, schist and granite.
' The soil survey of Gaston County indicates that the floodplain is underlain by Chewacla
loam and the Cecil-Urban land complex. The Chewacla soil is frequently flooded and
' consists of a thin surface layer underlain by sandy loam that transitions to sandy clay
loam with increasing depth. The depth to bedrock in the Chewacla unit is greater than 5
feet. The Cecil-Urban complex consists of a thin surface layer underlain by clay and clay
loam to a depth of about 5 feet. The deeper soil is saprolite that transitions to bedrock at
depths of more than 6 feet.
1 2.3 Land Use
' Land use in the upland portion of the Avon Creek basin is mainly single-family
residential. Land immediately adjacent to the project reaches is park and open space.
Tennis and basketball courts and a swimming pool are located on the west side of the
' creek, while the east side of the creek contains playground equipment, picnic tables and
small shelters. Four footbridges cross Avon Creek and one footbridge crosses the UT. A
paved sidewalk passes through the left cell of a double box culvert beneath Garrison
' Boulevard.
Land use adjacent to the UT is similar to Avon Creek, with park land along the right bank
' and residential areas along the left bank. City right-of-way is relatively narrow toward
the upstream end on the left bank, with less than 5 feet between a fence line and the top
of bank in some areas.
' We have not performed a detailed utility search. Based on our field observations, the
primary utility of concern is a sanitary sewer line about 80 feet west of the right bank of
' Avon Creek. This line crosses the UT aboveground near station 5+80 and continues
uphill parallel to the left bank of the UT. A network of concrete swales conveys
stormwater runoff from the upland portions of the park to the creeks. Many of the swales
' are in disrepair, particularly at the discharge points above the creek beds. A concrete
storm sewer outlets to the left bank of the UT near station 0+80.
2.4 Avon Creek
2.4.1 Channel Morphology
' The project reach of Avon Creek is classified as a Rosgen G5c stream with a sinuosity of
1.03. Bankfull width to depth ratios are in the 6 to 7 range. The entrenchment ratio
(flood prone area width divided by bankfull width) is about 1.8, which is higher than the
Avon Creek Bank Stabilization Plan 5 The City of Gastonia
' typical G entrenchment ratio of 1.4 or less and more indicative of a moderately
entrenched stream. However, the high bank height ratios and low sinuosity indicate that
' the stream is functioning as a G stream rather than an E stream. The relatively high
entrenchment ratio is apparently due to past grading efforts that flattened the bank slopes
and increased the top width.
' Bank height ratios (top of bank height divided by bankfull height) are about 1.9. A bank
height ratio of 1.0 is ideal because it indicates that the stream has access to the energy
' dissipating effects of its floodplain at bankfull stage and above. Rosgen (2001) converted
bank height ratios to stability ratings. He found that streams with bank height ratios
between 1.3 and 1.5 have an "unstable" stability rating. Bank height ratios greater than
' 1.6 were rated as "highly unstable." Using this system, the entire project reach is
classified as highly unstable.
' Results from the existing condition survey are shown in Appendix 1 and include cross
sections, a longitudinal profile, and a bed surface material distribution. Bulk sediment
samples were collected from the channel bed and sieved in our laboratory. Grain size
' analysis indicates the median particle size in the riffles is 0.43 mm and the median
particle size in the pools is 0.40 mm, only slightly smaller. These grain sizes are
indicative of a sand bed stream. Small riprap-sized particles measuring 200 mm and
' larger were present in the bed, but it was apparent that these particles had fallen into the
channel from the banks and had not been transported by flows.
' Instability within Avon Creek is mainly due to low sinuosity, lack of a vegetated buffer,
and high bank height ratios. Apparent efforts in the past to straighten the stream have
resulted in an incised channel. Efforts have also been made to armor the banks with
' concrete and stone. Despite these imposed changes, the stream is starting to form a new
floodplain at a lower elevation. Some areas of active bank erosion are visible,
particularly on the right bank near the downstream end of the project reach. In general,
' however, the relatively flat bank slopes and grass cover have prevented large-scale
erosion.
' A box culvert beneath East Fourth Street sets the invert grade at the upstream end of the
reach and a double box culvert beneath Garrison Boulevard sets the invert grade mid-
reach. Bedrock knickpoints near the confluence with the UT provide grade control
t between the culverts. The longitudinal profile (shown in Appendix 1) shows some small-
scale diversity of riffles and pools. The average slope for this reach is 0.0046.
2.4.2 Vegetation Assessment
' The Avon Creek project reach lacks a defined buffer. Several mature trees and shrubs are
present on both banks, but they are widely spaced. The banks and the majority of the
' floodplain are maintained lawn, with red maple (Acer rubrum), sugar maple (Acer
saccharum), and Bartlett flowering pear (Pyrus calleryana) planted within the left bank
floodplain. The area upslope of the right bank is sparsely populated by tulip poplar

Avon Creek Bank Stabilization Plan 6 The City of Gastonia
' (Liriodendron tulipifera), white oak (Quercus alba), water oak (Quercus nigra),
flowering dogwood (Corpus florida), boxelder (Ater negundo) and southern magnolia
' (Magnolia grandiflora). Scattered along the streambanks of the main creek are a few
black willow (Salix nigra), Chinese privet (Ligustrum sinense), and one sycamore
(Platanus occidentalis).
' 2.5 UT to Avon
Creek
' 2.5.1 Channel Morphology
' The UT is classified as a Rosgen G5 stream. Bankfull width to depth ratios are in the 8 to
9 range. Bank height ratios range from 1.9 to 2.0 and the reach sinuosity is 1.07. The
entrenchment ratio at the surveyed riffle is 1.9, which is normally indicative of a
' moderately entrenched stream type. However, as discussed previously, the low sinuosity
and high bank height ratios indicate the stream is functioning as a G channel. Using
Rosgen's stability rating system, the entire reach is classified as highly unstable.
' Results from the existing condition survey are shown in Appendix 1 and include cross
sections, a longitudinal profile, and a bed surface material distribution. Pebble counts
' using the modified Wolman procedure (Wolman, 1954) indicate the median particle size
in the riffles is 0.35 mm and the median particle size in the pools is 0.06 mm. These
particle sizes are representative of a sand bed stream.
' As in the case of Avon Creek, instability within the UT is mainly due to low sinuosity
and high bank height ratios. Apparent efforts in the past to straighten the stream have
' resulted in a relatively steep and incised channel. Bedrock knickpoints are visible near
the confluence with Avon Creek. Two small masonry walls were constructed on these
knickpoints, apparently to direct flow away from one bank. Areas of significant bank
' erosion are visible in the UT at roughly mid-reach.
A 48-inch pipe culvert beneath a yard sets the invert grade at the upstream end of the
' reach. The confluence with Avon Creek sets the invert grade at the downstream end of
the reach. The longitudinal profile (shown in Appendix 1) shows only slight diversity of
riffles and pools with relatively long runs in the upstream half. The channel slope is
0.0243.
' 2.5.2 Vegetation Assessment
Similar to Avon Creek, the UT lacks a defined vegetative buffer. A narrow forested area
' upslope of the right bank consists of white oak, northern red oak (Quercus rubra). and
flowering dogwood. The floodplain along the left bank includes red maple, sugar maple
and southern red oak (Quercus falcata). The streambanks along the downstream half of
' the reach are predominantly maintained lawn.
Avon Creek Bank Stabilization Plan 7 The City of Gastonia

3 Reference Reach Analysis
' To begin our reference reach search, we observed conditions along Avon Creek upstream
and downstream of the project reach. Neither the upstream nor downstream reaches were
suitably stable. We identified a reference reach on McClintock Creek located southeast
' of downtown Charlotte, about 24 miles east of the project site. Buck Engineering
personnel performed the reference reach survey of McClintock Creek for another project
' in November 2000. We also examined DuHart Creek in Gastonia as a reference.
The McClintock reference reach is an E5 stream with a 0.3 square-mile drainage area.
' The median sediment particle size in McClintock Creek is equal to that for Avon Creek
and the two creeks have similar drainage areas and are located in similar hydro-
physiographic provinces. The DuHart reference reach is a B4c stream with an 8 square-
mile drainage area. While the drainage area for DuHart Creek is significantly larger than
those of the project reaches, the DuHart stream type is similar to the B5c design stream
type. Reference reach data are presented in Appendix 4.
' The project will address channel dimension, but not pattern or profile (except for scour
pools created by cross vanes). The McClintock reference reach is useful principally for
' confirmation of the design bankfull dimensions, specifically bankfull depth. The DuHart
reference reach is useful primarily for the pool to pool spacing / bankfull width ratio.
The use of the reference reach data is discussed in more detail in the Natural Channel
' Design Section.

Avon Creek Bank Stabilization Plan 8 The City of Gastonia
I

4 Bankfull Stage Verification
1
During the existing conditions survey, the bankfull stage was identified in the field as an
' upper scour line, typically present about 2 feet above the baseflow water surface
elevation. For verification that this upper scour line is a valid indicator of bankfull flow,
we compared the cross sectional areas for the surveyed cross sections to the regression
' line on the North Carolina Piedmont Regional Curve (Harman et al., 1999 and Doll, et
al., 2002) as shown below in Figure 4.1.

Figure 4.1 Bankfull stage verification for Avon Creek
North Carolina Piedmont Regional Curve
Bankfull Verification for Avon Creek
1000
100
0
u
rn
d
10
U
s
I !-
.. ........ ..... .. ...

X

X
• •. ¦ .

0.1 1 lU lUU IUUU I
Drainage Area (mi z )
I
i
• Urban Data ? Rural Data ¦ McClintock riffle x Avon riffle
X DuHart riffle - Power (Rural Data) - Urban Regression
' The surveyed cross sections all plot below the urban regression line and above the rural
line in Figure 4.1. This indicates the upper end of the Avon Creek watershed may be less
urbanized (lower runoff volume) than the watersheds and streams included in the urban
' piedmont regional curve. The offset from the urban line is roughly the same for the
project reaches and the two reference reaches, indicating the bankfull indicators in the
field were properly identified. This consistent offset also confirms that the hydro-
' physiographic characteristics of the reference reach watersheds are similar to those in the
Avon Creek watershed.

Avon Creek Bank Stabilization Plan 9 The City of Gastonia

5 Natural Channel Design

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5.1 Design Summary
The proposed design will restore channel dimension and improve floodplain functionality.
Summaries of the proposed design parameters for Avon Creek and the UT are provided in
Tables 5.1 and 5.2. Descriptions of the designs are presented below.
5.2 Avon Creek
Stabilization of Avon Creek will consist of excavating bankfull benches and constructing
in-stream structures such as cross vanes and root wad revetments. The primary objective
is to increase the entrenchment ratio by providing a floodplain. As mentioned previously,
stream pattern and reach-wide profile will not be adjusted. In-stream structures will alter
profile on a small scale. Structure locations will be selected to promote bedform
diversity, which should improve over time from its present condition. For example, cross
vanes will tend to form scour pools downstream. The following table summarizes our
proposed design approach.
Table 5.1 Natural channel design parameters for Avon Creek
Existing DuHart
Reference McClintock
Reference Design
Rosgen Stream Type G5c 134c E5 135c
Drainage Area (sq mi) 0.75 8.0 0.3 0.75
Reach Length (ft) 985 828 254 985
Bankfull Width (ft) 15 46 9.1 15
Bankfull Mean Depth (ft) 2.3 2.6 1.6 2.3
Width/Depth Ratio (ft) 6.5 17.0 6.0 6.5
Bankfull Area (sq ft) 34 122 14 34
Entrenchment Ratio 1.8 4.1 2.2 3.4
Pool to Pool Spacing (ft) 50 160 60 70
Pool to Pool Spacing /
Bankfull Width 3.3 3.5 6.6 3.5
Bank Height Ratio 1.9 1.1 1.1 1.0
A plan view of the proposed bank stabilization, including structures, is presented on
Sheet 3. The bankfull benches will vary in width to protect existing mature trees and the
two southern footbridges that will remain in place. The two northern footbridges will be
removed prior to the stabilization project. Several concrete swales discharge to Avon
Creek; the swales will be truncated where they intersect the benches, and rip rap outfall
protection will be provided to prevent bench erosion below the new outfalls. The
Avon Creek Bank Stabilization Plan 10 The City of Gastonia

' benches will also transition to meet the existing wingwalls downstream of the Fourth
Street culvert and upstream of the Garrison Boulevard culvert. The existing walkway on
' the left bank leading to the left cell of the Garrison culvert will be protected in place.
' 5.3 UT to Avon Creek
Stabilization of the UT downstream of the footbridge at station 3+30 will consist of
' excavating bankfull benches and constructing in-stream structures. The benches will
taper to meet the existing top of bank adjacent to the sanitary sewer line crossing.
Upstream of station 3+30, stabilization will consist solely of in-stream structures.
' Excavating benches in this area would be impractical due to very high banks, steep
topography and limited right-of-way. The following table summarizes our proposed
design approach.
' Table 5.2 Natural channel design parameters for the UT

CI

Existing DuHart
Reference McClintock
Reference Design
Rosgen Stream Type G5 B4c E5 B5c
Drainage Area (sq mi) 0.07 8.0 0.3 0.07
Reach Length (ft) 683 828 254 683
Bankfull Width (ft) 11 46 9.1 11
Bankfull Mean Depth (ft) 1.4 2.6 1.6 1.4
Width/Depth Ratio (ft) 7.9 17.0 6.0 7.9
•2 Bankfull Area (sq ft) 17 122 14 17
qL) Entrenchment Ratio 1.9 1.5 3+ 3.8
Pool to Pool Spacing (ft) 50 160 60 40
Pool to Pool Spacing /
Bankfull Width 4.5 3.5 6.6 3.5
Bank Height Ratio 1.7 1.1 1.1 1.0
A plan view of the proposed bank stabilization, including structures, is presented on
Sheets 3 and 4. Several concrete swales discharge to the UT; the swales will be
truncated where they intersect the benches, and rip rap outfall protection will be provided
' to prevent bench erosion below the new outfalls. The bank stabilization work will also
protect an existing storm sewer outfall on the left bank near station 0+65.
5.4 Riparian Buffer Restoration
A combination of native herbaceous and woody vegetation will be planted to establish a
riparian buffer along the project reaches. The buffers will extend approximately 30 feet
laterally from the creek-side edge of the bankfull bench. Species used for seeding and
woody vegetation, as well as plant spacing, will depend upon the City's requirements for
Avon Creek Bank Stabilization Plan 1 1 The City of Gastonia

' the park setting. Species selection will also be subject to availability and cost at the time
of planting. Permanent seeding may include, but not be limited to, switch grass
' (Panicum virgatum), deer-tongue grass (Panicum clandestinum), soft rush (Juncus
effusus), sedge (Carex spp.), ironweed (Vernonia noveboracensis), joe pye weed
(Eupatorium fistulosum), and virginia wildrye (Elymus virginicus).
' Trees and shrubs that may be used include, but are not limited to, persimmon (Diospyros
virginiana), sycamore (Platanus occidentalis),blackgum (Nyssa sylvatica), river birch
' (Betula nigra), sweet birch (Betula lenta), witch-hazel (Hamantelis virginiana),
hornbeam (Carpinus caroliniana), silverbell (Halesia carohniana), spicebush (Lindera
benzoin), and alder (Alms serrulata). Species to be used for live staking include silky
' dogwood (Cornus amomum) and black willow (Salix nigra). Temporary vegetation for
erosion control will consist of annual rye (cool season) or millet (warm season)
depending on the construction schedule. Planting details are provided in Appendix 3.

Avon Creek Bank Stabilization Plan 12 The City of Gastonia

6 Sediment Transport Discussion
' The primary goal of this project is to improve bank stability. Overall, the low-flow
channels in Avon Creek and the UT are stable. Local instability is primarily due to high
' banks and sparse vegetation, and most of the bank erosion appears to be occurring at
stages at or above bankfull. We did not perform sediment transport competency and
capacity analyses because the design does not change pattern or profile. The bankfull
' cross sectional area, width and depth will change only in areas where in-stream structures
and bankfull benches are placed.
' Cross vanes will improve the competency and capacity of the stream at low flow and
encourage deposition along the bank toes rather than at the center of the channel.
However, the overall sediment transport capacity and competency of both streams, which
' we judge to be adequate for their sediment load, will not change.
Qualitatively, improved floodplain functionality can be shown to reduce bank erosion.
' Shear stress is defined as: (unit weight of water) x (hydraulic radius) x (channel slope).
Hydraulic radius is defined as (channel area) / (wetted perimeter). The addition of
benches will increase the wetted perimeter, thereby decreasing the hydraulic radius of the
' cross section, and decreasing shear stress on the banks at bankfull stage and above.

Avon Creek Bank Stabilization Plan 13 The City of Gastonia

I
7

1

D

7 References
Andrews, E.D., 1983. Entrainment of gravel from naturally sorted riverbed material,
Geological Society of America Bulletin, 94, 1225-1231.
Doll, B. A., D.E. Wise-Frederick, C.M. Buckner, S.D. Wilkerson, W.A. Harman, R.E.
Smith, and J. Spooner, 2002. Hydraulic Geometry Relationships for Urban
Streams throughout the Piedmont of North Carolina. In Press.
Harman, W.A., G.D. Jennings, J.M. Patterson, D.R. Clinton, L.O. Slate, A.G. Jessup, J.R.
Everhart, and R.E. Smith, 1999. Bankfull Hydraulic Geometry Relationships for
North Carolina Streams. Wildland Hydrology. AWRA Symposium Proceedings.
Edited by: D.S. Olsen and J.P. Potyondy. American Water Resources Association.
June 30-July 2, 1999. Bozeman, MT.
Rosgen, D.L. 1994. A classification of natural rivers. Catena 22:169-199.
Rosgen, D. L. 2001. A stream channel stability assessment methodology. Proceedings
of the Seventh Federal Interagency Sedimentation Conference, March 25-29, 2001,
Reno, Nevada. pp. II-18 to II-26.
Wohl, E. 2000. Mountain Rivers. Water Resources Monograph 14. American
Geographic Union. Washington, DC.
Wolman, M.G., 1954. A Method of Sampling Coarse River-Bed Material. Transactions
of American Geophysical Union 35: 951-956.
Avon Creek Bank Stabilization Plan 14
The City of Gastonia

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11I G5'c 26.8 14.03 1.91 2.99 /.35 2.3 2.0 725.12 729.13
Cross-section 2+27
740
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w 726
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0 50 100 150 200 250 300 350 400
Station - - o - . Bankfull - - o - - Floodprone
D50 (mm) 0.4 1.03
Slope (fUft 0.0046 Sinuosity
The banks have been mechanically sloped from their natural form, thus artificially increasing the entrenchment ratio.

Feature Stream
Type
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lbe the
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Pool G5c 23.9 11.86 2.01 3.31 5.89 2.3 2.3 722.49 726.89
Cross-section 7+05
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0 50 100 150 200 250
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The banks have been mechanically sloped from their natural form, thus artificially increasing the entrenchment ratio.
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0 20 40 60 80 100 120 140
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The banks have been mechanically sloped from their natural form, thus artificially increasing the entrenchment ratio.
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Featufe Stream
Type
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BKF Width
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Cross-section 4+67
------------------
0 20 40
60 80 100 120 140
Station > - • Bankfull - - o - • Floodprone
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Appendix 3
Planting Specifications
1.0 Permanent Seeding Specifications
Permanent seeding will be used in combination with woody plantings extending to
bankfull elevation along the restored reaches. Permanent seeding will occur in
conjunction with temporary seeding where applicable. This mixture will also be used in
any terrestrial (not inundated) riparian area that has been disturbed by construction. This
mixture shall be planted in combination with woody plant installations. Seeding should
be done evenly over the area using a mechanical or hand seeder. A drag should be used
to cover the seed with no more than '/Z inch of soil. Where a drag cannot safely be
utilized, the seed should be covered by hand raking.
1.1 Seedbed Preparation
On sites where equipment can be operated safely, the seedbed shall be adequately
loosened. Disking may be needed in areas where soil is compacted. Steep banks may
require roughening, either by hand scarifying or by equipment, depending on site
conditions. If seeding is done immediately following construction, seedbed preparation
may not be required except on compacted, polished or freshly cut areas. If permanent
seeding is performed in conjunction with temporary seeding, seedbed preparation only
needs to be executed once.
1.2 Fertilizing/Liming
Areas fertilized for temporary seeding shall be sufficiently fertilized for permanent
seeding; additional fertilizer is not required for permanent seeding.
1.3 Seeding
A riparian seed mix at the rate of '/4 pound per 1,000 square feet or 10 pounds per acre
shall be used for seeding. The following table lists a recommended herbaceous,
permanent seed mixture. Species listed below are subject to availability and cost.

n

r,

f,

Riparian Seed Mix
Common Name Scientific.Name %
Soft Rush Juncus a sus 20
Deerton ue Panicum clandestinum 20
Switch grass Panicum vir atum 10
Ironweed Vernonia noveboracensis 10
Virginia Wildr a El mus vir inicus 10
Ho Sedge Carex lu ilina 10
Fox Sedge Carex vul inoidea 10
Joe P ye Weed Eu atorium astulosum 10
2.0 Live staling
Live stake materials should be dormant and gathered locally or purchased from a
reputable commercial supplier. Stakes should be 1/2 to 2 inches in diameter, 2 to 3 feet in
length, and living (based on the presence of young buds and green bark). Stakes shall be
angled on the bottom and cut flush on the top with buds oriented upwards. All side
branches shall be cleanly trimmed so the cutting is one single stem. Stakes should be kept
cool and moist to improve survival and maintain dormancy.
Live staking plant material shall consist of a random assortment of materials selected
from the following:
Silky Dogwood (Corpus amomum)
Black Willow (Salix nigra)
Silky Willow (Salix sericea)
Elderberry (Sambucus canadensis)
Other species may be substituted upon approval of Engineer/Project Manager.
Planting shall take place in early spring. Stakes should be installed randomly 2 to 3 feet
apart using triangular spacing or at a density of 160 to 360 stakes per 1,000 sq ft along
the stream banks above bankfull elevation. Site variations may require slightly different
spacing. Stakes shall be driven into the ground using a rubber hammer or by creating a
hole and slipping the stake into it. The stakes should be tamped in at a right angle to the
slope with 4/5 of the stake installed below the ground surface. At least two buds (lateral
and/or terminal) shall remain above the ground surface. The soils shall be firmly packed
around the hole after installations. Split stakes shall not be installed. Stakes that split
during installations shall be replaced.

I
J
I

Fi

3.0 Bare root vegetation
Bare root vegetation to be planted along both sides of the new channel stream banks
above bankfull elevation and in the floodplain restoration area shall consist of a random
assortment of shrub and tree species including, but not limited to the following:
Common Name Scientific. Name
Sycamore Platanus occidentalis
River Birch Betula ni ra
Sweet Birch Betula lenta
Silverbell Halesia carolina
Persimmon Dios yros virginiana
Black um N ssa sylvatica
Witch-hazel Hamamelis vir iniana
S icebush Lindera benzoin
Tag alder Alnus serrulata
Hornbeam Car inus caroliniana
Planting shall take place in late winter/early spring. Listed species are subject to
availability and cost. Immediately following delivery to the project site, all plants with
bare roots, if not promptly planted, shall be heeled-in in constantly moist soil or sawdust
in an acceptable manner corresponding to generally accepted horticultural practices.
While plants with bare roots are being transported to and from heeling-in beds, or are
being distributed in planting beds, or are awaiting planting after distribution, the
contractor shall protect the plants from drying out by means of wet canvas, burlap, or
straw, or by other means acceptable to Engineer/Project Manager and appropriate to
weather conditions and the length of time the roots will remain out of the ground.
Soil in the area of shrub and tree plantings shall be loosened to a depth of at least 5
inches. This is necessary only on compacted soil. Bare root vegetation may be planted in
holes made by a mattock, dibble, planting bar, or other means approved by
Engineer/Project Manager. Rootstock shall be planted in a vertical position with the root
collar approximately 1/2 inch below the soil surface. The planting trench or hole shall be
deep and wide enough to permit the roots to spread out and down without J-rooting. The
plant stem shall remain upright. Soil shall be replaced around the transplanted vegetation
and tamped around the shrub or tree firmly to eliminate air pockets.
Spacing guidelines for rooted shrubs and trees are provided in the following table.
Type Spacing # Per 1,000 s ft
Shrubs (<10 ft tall) 3 to 6 ft 25 to 110
Shrubs and trees (10-25 ft) 6 to 8 ft 15 to 25
Trees (>25 ft tall) 8 to 15 ft 4 to 15

4.0 Shrub and Tree Transplants
' Native shrubs and trees less than 3 inches in diameter shall be salvaged on-site in areas
designated for construction, access areas, and other sites that will necessarily be
disturbed. Vegetation to be transplanted will be identified by the Engineer/Project
' Manager. Transplanted vegetation shall carefully be excavated with rootballs and
surrounding soil remaining intact. Care shall be given not to rip limbs or bark from the
shrub and tree transplants. Vegetation should be transplanted immediately, if possible.
Otherwise, transplanted vegetation shall be carefully transported to designated stockpile
areas and heeled-in in constantly moist soil or sawdust in an acceptable manner
' appropriate to weather or seasonal conditions. The solidity of the plants shall be
carefully preserved.
Installation of shrub and tree transplants shall be located in designated areas along the
stream bank above bankfull elevation or in floodplain restoration areas as directed by the
Engineer/Project Manager. Compacted soil in the area of vegetation transplants shall be
loosened to a depth of at least 1 foot. Transplants shall be replanted to the same depth as
they were originally growing. The planting trench or hole shall be deep and wide enough
to permit the roots to spread out and down without J-rooting. The plant stem shall remain
' upright. Soil shall be replaced around the transplanted vegetation and tamped around the
shrub or tree firmly to eliminate air pockets.

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