HomeMy WebLinkAbout20080781 Ver 1_Report_20080506o?
Channel Geomorphic Conditions
and Evaluation Report
Duharts Creek, Gaston Mall Project
Gaston County, North Carolina
Project No. 2007-1860
May 24, 2007
0 7 g 1
Cws
Table of Contents
Introduction ...................................................................................
Methods .........................................................................................
Results ...........................................................................................
Bankfull Verification .................................................................
Geomorphic Assessment ...........................................................
Discussion ......................................................................................
List of Enclosures
.........................................................1
.........................................................1
.........................................................1
.........................................................1
.........................................................2
.........................................................2
Figure 1 - Site Location Map
Figure 2 - Channel Reach and Cross-Section Locations
Figure 3 - North Carolina Piedmont Regional Curves
Table 1 - Stream Reach Data Summary
Channel Cross Sections (CSI - CS4)
Longitudinal Profiles
Pebble Count Data
Representative Photographs
MAY 6 2008
DENR - WATER GUAUTY
WETLANDS AND STORMWATER BRANCH
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Introduction
The Duhart's Creek relocation project is located in Gaston County, North Carolina. The project
site is an approximate 60-acre tract located in Gastonia, North Carolina, south of exit 21 from
Interstate 85 (see location map, enclosed). Stream relocation, for the purpose of reducing and
mitigating the impacts of the expansion of the existing Gaston Mall, is proposed for the reach of
Duhart's Creek located within the property boundary. The reach of Duhart's Creek was
assessed using Rosgen Level H Classification methods. The following assessment was done to
evaluate the existing conditions of the streams and to identify potential strategies for stream
restoration. The following report describes the existing conditions of the streams.
Methods
A geomorphic survey was performed by CWS biologists Thomas Blackwell, Patty Perino and
Paul Bright on May 11, 2007. The survey included a longitudinal profile, a cross-sectional
survey, substrate sampling (reach-wide pebble count), Bank Erodability Hazard Index (BEHI)
analysis, and photographic documentation of the reach of Duhart's Creek for which relocation is
proposed. This data was used to classify each reach using the Rosgen Level 11 system.
Results
Bankfull Verification
Bankfull cross-sectional measurements were verified using the North Carolina Piedmont regional
curve (Figure 4). Indicators of bankfull levels were identified in the field and included scour
lines, floodplain benches, and the backs of depositional bars. The observed bankfull widths and
calculated bankfull cross-sectional areas were verified using the drainage area for each stream
channel. The observed widths for Cross Sections 1 to 4 fall on or slightly below the regression
lines for urban North Carolina piedmont streams. This verifies that the bankfull widths and
bankfull cross-sectional areas observed by CWS for these areas are consistent with those of
similar streams in an urbanizing watershed. Locations of cross sections were chosen at areas that
represent the overall character of the channel. Cross-Sectional measurements were not taken
within two bankfull widths of a culvert or other in-stream structure based on current
methodology. In-Stream structures alter the flow and velocity of the channel causing the
presence of non-representative bankfull indicators.
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Geomorphic Assessment
Duhart's Creek flows south-east though the central portion of the property for approximately
1,575 linear feet. A 400 linear foot reach of Duharts Creek was analyzed in this study. The
Level H classification for the study reach of Duhart's Creek was identified as F4. This reach
exhibited substrate consisting of very fine gravel (D50= 2 - 4 mm). The drainage area for this
reach is approximately 1.61 square miles, channel slope is 0.0023 ft/ft, and sinuosity is 1.07.
Mean bankfull width and depth for this reach were 22.6 feet and 1.94 feet, respectively. The
average flood-prone width for the riffle portions of the reach was approximately 31.2 feet.
A Bank Erodibility Hazard Index (BEHI) assessment was performed at two locations within the
reach. These yielded adjusted BEHI scores of 27 and 39 which indicate moderate and high
susceptibility to erosion respectively.
Discussion
CWS believes that Duhart's Creek has opportunities to combine Restoration Priority levels 1 and
2. This section will summarize the opportunities and present our recommendation for the level
of enhancement within the reach.
Priority 1 Restoration - Category that involves building a new morphologically stable channel
at a higher elevation thereby connecting to the original floodplain. The newly constructed
channels will typically be Rosgen type C or E channels.
Priority 2 Restoration - Category that involves restoring morphological stability and
reestablishing a floodplain to an existing channel at the current elevation or higher to create a
Rosgen type C or E channel. This priority of restoration is typically used when relocation of an
incised stream is not feasible.
Based on this evaluation, CWS believes the best option is to relocate portions of these reaches to
re-establish a natural meandering pattern. The relocated areas will be graded to match closely
the existing cross sections. Relocating the channel will allow the sinuosity to be increased, thus
reducing the shear stress along these reaches. The relocated area can be graded to include
floodplain benches, floodplain wetlands, and native riparian vegetation which will help to
improve the water quality and capacity within this channel.
2
?IJ
Legend
2,000 1,000 0 2,000 Feet
Project Outer Boundary
REFERENCE- USGS 7.5' IUPOGRAPHIC MAP SERIES, GASTON!A NORTH QUADRANGLE, DATED 7093
a;
CWS, INC. Figure 1. Site Location Map
550 E. Westinghouse Blvd. Gaston Mall Geomorphic Conditions Report
Charlotte, NC 28273 Gaston County, North Carolina
roiect No. 2007-1860
I Applicant No: Date: _ - - _-- J
CS-3
CS-2
CS-1
Legend
Streams
Wetlands
Project Outer Boundary !? 150 75 0 150 Feet
i
Figure 2. Channel Reach and
. CWS, INC. Cross-Section Locations
550 E. Westinghouse Blvd. Gaston Mall Geomorphic Conditions Report
CAWS Charlotte, NC 28273 Gaston County, North Carolina
[V...••- Project No. 2007-1860
[Applicant No: Date: Sheet of
North Ctirolina Piedmont Regional Curve
1000
-
- l
I 1
I
--
100
; {
-- -
Urban
o
: _
I v
?
0.95
R2
a
:. 10 ? G .
; _ a
44 O 67 :
TIt
j i
I
,
1
0.1
1.0 10.0 ,
100.0 10
00.0
Drainage Areal (AM' 2 j
• ITAiail Data A Ritral Data -"-° Power (I,1ltl'al I)ata) -- TTrball Rem e ? X1+311
North Carolina Piedmont Regional C='urge
10000
--
- - - -
--- -- -
--- - - - - i a ;-7
? 1000 ?.
I
_ : __ ? ;, ? ? ; ;
?.
Urban
y
E
.? i
i
.
a_1i
306.,s4 x
•
Aj 1
r
t
H 100 •
?
_ -- _ _ =' _
S.?il"ill
a
71
6 J_1 ry
1
1a
0.1
1.0 10.0 100.0 1000.0
Drairkage ALrea (sq ird)
+ I it-.ail Data . Pan al Data -°- Power (Rxifal Data) -- Urban Re?TMressi+311
Summary of Existing Conditions
Parameter Existing Condition
Reach Reach 1
Length of Reach Studied ft. 400
Channel Dimen sion
Average Bankful Width ft. 22.6
Mean Bankful Depth ft. 1.94
Average Width/De th Ratio 12.17
Average Bankful Areas . ft. 44.6
Average Bankful Maximum Depth ft. 2.54
Average Width Flood-prone Area ft. 31.2
Average Entrenchment Ratio 1.38
Max Pool Depth ft. 4.12
Ratio Max Pool Depth to Bankful
Depth 1.62
Pool Width ft. 8.0-10.0
Ratio Pool Width/Bankfull Width 0.39
Pool to Pool Spacing ft. 42-127
Ratio Pool to Pool Spacing
to Bankful Width 1.0-4.92
Bank Height Ratio 1.6-2.7
Channel Patt ern
Meander Length ft. N/A
Meander Length Ratio N/A
Radius of Curvature ft. N/A
Radius of Curvature Ratio N/A
Meander Belt Width ft. N/A
Meander Width Ratio N/A
Sinuosity 1.07
Channel Pro file
Valle Slope ft./ft. 0.006
Channel Sloe 0.002
WS Sloe ft./ft. 0.0019
Pool Sloe ft./ft. 0.0016
Channel Mate rials
Bed Material Distribution Material Size mm
d16 0.125 - 0.250
d35 0.5-1.0
d50 2-4 (Very Fine Gravel
d84 8 - 11.3
d95 11.3-16
Rosgen Stream Tye F4
Longitudinal Profile - Duharts Creek
710.0
709.0
708.0
707.0
706.0
705.0
704.0
4.
MOM
0
702.0
W 701.0
700.0
699.0
698.0
697.0
696.0
695.0
- ?3--Water Surface
-? Thalweg
RTOB
-- LTOB
- a- Lbkf
o r ?n o 0 0 0 0 0 o v? o .'
O ?G O ?O N 7 O? M N 00 [? d' ?--? N M O 00 ?O
Station (feet)
Duharts Creek - Cross Section 2 - Riffle
709
707
,705
0 703
701
w
699
697
695
0 10 20
Distance (ft.)
-T
30 40
Bankfull Width
L
Flood-Prone Width
Duharts Creek - Cross Section 3 - Riffle
709
707
705
703
c w
701
699
I 697
695 -? ?-
0 10 20
Distance (ft.)
30 __ 40
Bankfull Width
Flood Prone Elevation
DUHARTS CREEK - Cross Section 4 - Riffle
709
707
Now 705
o 703
> 701
a?
w 699
697
695
0 10 20
Distance (ft.)
30 40
Bankfull Width
Flood-Prone Width]
North (I'arolina Piedmont Rec-Tional C='.ur?-?
10000
4 " 1000
U
w
bb
v
v
i-1 100
10
0.1
1.0 10.0 100.0 1000.0
I ivaillume Area (sq rni}
T_Trl?ati I):it:y AL Riu-al I):ita --? 114- ,-V er iRiwal Data) - TT-ban R.2% el"SlOix
PnhhlP f n»nt _ 11„hnrtc Creek
Metric (mm) Particle Count Tot # % Tot % Cum
062
<0 Silt/Clay s 2 100.0 2.0 2.00
.
125
062 - 0
0 Very Fine Sand 3 100.0 3.0 5.00
.
.
250
125 - 0
0 Fine Sand A 4 100.0 4.0 9.00
.
.
25-0
5
0 Sand
Med N 5 100.0 5.0 14.00
.
.
0
5-1
0 .
Coarse Sand D 18 100.0 18.0 32.00
.
.
1.0-2.0 Ve Coarse Sand 12 100.0 12.0 44.00
2-4 Very Fine Gravel 2 100.0 2.0 46.00
7
4 - 5 Fine Gravel 10 100.0 10.0 56.00
.
5
7 - 8 Fine Gravel G 6 100.0 6.0 62.00
.
3
8 - 11 Medium R 6 100.0 6.0 68.00
.
3-16
11 Medium A 11 100.0 11.0 79.00
.
16 - 22
6 Coarse v 8 100.0 8.0 87.00
.
22
6 - 32 Coarse E 8 100.0 8.0 95.00
.
32 - 45 Ve Coarse L 3 100.0 3.0 98.00
45 - 64 Very Coarse 1 100.0 1.0 99.00
64 - 90 Small c 1 100.0 1.0 100.00
90 - 128 Small b 0 100.0 0.0 100.00
128 - 180 Large b 0 100.0 0.0 100.00
180 - 256
Large I
e
0
100.0
0.0
100.00
256 - 362 Small B 0 100.0 0.0 100.00
362 - 512 Small u 0 100.0 0.0 100.00
512 - 1024 Medium 1 0 100.0 0.0 100.00
1024 - 2048 Large - Ve Large e 0 100.0 0.0 100.00
Bedrock Bedrock r 100.0 0.0 100.00
Percent (%)
p .n o
0 0 0 0 0 0 0 0
<0.062
0.062 - 0.125
0.125 - 0.250
0.25-0.5
0.5-1.0
1.0-2.0
2-4
4 - 5.7
5.7-8
8 - 11.3
11.3-16
b
A
rA
f?
16-22.f
22.6 - 32
32-4°
45-6,
64-91
90-12
128 - 18
180 - 25
256 - 36
362-51
512 - 102
1024 - 204
Bedroc
n
r•
CD
b
CD
O
rr
d
O w.+ N W A ? ? J GO ? ?
O O O O O O O O O C
O O O C C O O O O O
O
Cumulative Percent (%)
Reach-wide Pebble Count Particle Size Distributions - Duharts
0
x,
W
v
x,
964
100.00
90.00
80.00
70.00
60.00
50.00
I !
40.00
30.00 -
20.00
I
10.00 LLL L4
0.00
o r,,
Particle Size (mm)
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Resort Project No. 2007-1860
' ,
r" ,,
r a68 f
#
r sg ?
?
}
f
c
4it7
r?
? t a .-
...
'C ! .yly .a
''.?!(?'y^?
?
? ?
t +r?ti ? P 3 YSY '?},?e wt' t t
?PW? ?
? ?
??'? dM ?' / y,
d ? ?] &
6
rYd +?
...M
r
t • Al
'"°.__'
qq O' ,,fi?nn
.
d
" '
'
iX '41+t 1.
WL ?Y
,r
1
<
S
1
?
.
F
Y
t
N ? ?.
F
,?y""li
A
r
>
'
7
Y
?
{R "3 e
S
Y'
pt - i
I X
(
ib
l[.(c
LA
f
,`f T
. L,V Sf"?4
'?}
1.Y'
d
-rte 46Z
f .?` /?
a
4
j`?i.
w
p
`5
i
,
!?
WwI
Mt' ?(
r
?y
??4??
,L
?Y.,
'
i 1?ll ,?JR,i?•d. ` ?x
l`-?i'N 9'^
J ?M?-EF
.M?j•
L
•^F
' Y yf
"'? 1,?
T
I
.: b.
y?
? .
(
x_
`
W
/?
?
f
l'
/a?
..?
y
I•a
x ?
?
?
?"•? *
`r
,
y?7 ?? 'A ??
?
?.
i
. Y
"
.
.
PS
i $, i
??
?
t.'{i :'{.- ,. ??
? ?
1
Photograph A: Cross-Section 1, across
xy ?F -?-
M ?I \? y3T, i`
} .J' * rt yV Y
Y t,
t
_ ?r
s k ? •'14y
1 R f
-A V
3
Yµ d? I 1! i
? ? ? ? r
i!9
?
1 ,,
{
• yMt ? ? fin' wrl
.
?
,
?
Photograph 13: Cross-Section 1, upstream
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Photograph E: Cross-Section 2, downstream
F: Cross-Section z,
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Photograph G: Cross-Section 3, across
Photograph H: Cross-Section 3, downstream
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
Photograph I: Cross-Section 3, upstream
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Project No. 2007-1860
{{ 41 ?'?? ?? v
?
° t
F ))
.+'
-{pii, A'' + y
1ry
tl )
, i
a
j
n ?
?
f, k 5??
?•
??
ie
"??rl
4 '?;I
? ,e
j (h
'?? ? rr
V?
\p `?•,: ?
? T _.K,
H ?
,
.
p*
?.
"
j e ?Gr { . .• 2
wS w v?
t KU A r ? Yf i
"y
p i r1 i V l
y? a
w r
iil4r+
Photograph L: Cross-Section 4, downstream
? F dt+.,A?'"yy'?L y'?y??. '"s'p? ?- ?:F le?,? f a i n I .r• 4
c
E1Fr• :(+?3.
v rA .:?Y'{-AAG?ti+?}
`< A-Ph,'. `,,,'5"? ii?. ,.y
, ?. .(. s µµ`??r
V
?
r
a & b 4?
a.?•?: .. mom.
Photograph M: Cross-Section 4, upstrcanl
Duhart's Creek - Gaston Mall Redevelopment Project
Channel Geomorphic Conditions and Evaluation Report Protect No. 2007-1860
Photograph N: Unstable Bank on uuriart, s Lreex