20051748 Ver 1_Erosion Evaluation 3_20070803

Z'Pbve ff 05- ni
EcoScience Corporation
1101 Haynes Street, Suite 101 Raleigh,
North Carolina 919-828-3433
EcoScience
MEMORANDUM

TO: George Howard,
Restoration Systems, LLC (RS)
FROM: Jens Geratz
DATE: January 25, 2007
RE: Erosion Evaluation No. 3 (01-03-2007)
-Lpp1
06-276.03
INTRODUCTION
The North Carolina Division of Water Quality (NCDWQ) Section 401 permit condition #8
associated with the Lowell Mill Dam - Little River Watershed Restoration Site requires that a
"survey [of] the present lake bed and its flooded tributaries [shall occur] at least every two weeks (bi-
weekly) or within three days of a rain more than or equal to one inch at Princeton, NC."
Modifications to the permit condition described above are proposed. The text below describes the
reason behind the modification and proposed methodology to satisfy, in spirit, the permit condition
set forth in the permit.
The permit condition requested by NCDWQ presents several logistical difficulties. First, only a
USGS river gauge is present near Princeton. No publicly available or trustworthy real-time weather
data are available in or around Princeton, NC. The nearest weather station to Princeton is located in
Smithfield, NC. Second, because the Smithfield weather station is outside the Little River
watershed, ESC believes using data from this source is not indicative of accurate river stage
conditions within the former impoundment. Thus, ESC has investigated and developed a new
method for determining when a field evaluation should be performed.
In preparation of the erosion evaluation, EcoScience Corporation (ESC) collected three years of
continuous daily precipitation and river stage data from 1990 through 1993. The data showed that a
one inch rainfall event is a relatively commonplace weather occurrence. If the permit condition #8
remains as stated, then more than 33 field evaluations (>10 per year) would have been required
during the period for which ESC collected the correlated rain/river stage data. It is important to note
that one inch rain events do not appear to have a corresponding rise in river stage. Since the
perceived purpose of the NCDWQ permit condition is to evaluate the former impoundment after
increased river stage to monitor for erosion, then a one inch rainfall event is not the best indicator for
the initiation of a site evaluation. Isolated thunderstorms can produce large amounts of precipitation
in a localized area, without contributing significant rain to the overall watershed. To monitor
multiple weather stations in real-time throughout the watershed to identify a regional precipitation
EcoScience Corporation
' Mr. George Howard, Restoration Systems, LLC
January 25, 2007
Page 2 of 5
event is time consuming and not practicable. Alternatively, ESC proposes to use the correlation
' between large, regional rain events that cause more than a 750 cubic feet per second (cfs) reading at
the Princeton gauging station (USGS 02088500) to be the "initiation threshold" for a field
evaluation. ESC estimates that this initiation threshold will occur after a river stage rise equal to
' approximately 30 percent of bankfull. Once the initiation threshold for evaluation has been
exceeded, ESC proposes that we monitor the river stage until the river falls below 500 cfs, which is
proposed as an "evaluation threshold" river stage. Once the river stage falls below the evaluation
threshold, ESC personnel will perform an erosion evaluation within a 72 hour period. Using the
initiation and evaluation thresholds for the field effort will facilitate ESC personnel in reviewing the
' former impoundment under the safest and most data productive periods after a substantial rise in
river stage.
In order to satisfy the modified permit condition #8, RS has authorized EcoScience Corporation
(ESC) to conduct weather related erosion evaluation within the former Lowell Mill Dam
Impoundment (ESC Proposal P06-004 January 19, 2006). The purpose of the evaluation is to
document any evidence of erosion within the former dam impoundment including but not limited to
bank failure, loss of stream bank trees, severe head-cuts, and the loss or gain of large depositional
features.
A rainfall event ranging from 2.0 to 3.7 inches occurred in the upstream watershed (Figure 1)
between December 22 and December 26, 2006. The resulting peak in river stage of over 1890 cubic
' feet per second (cfs) was recorded at the USGS Princeton river gage on December 26, 2006 (Figure
3). The "initiation threshold" from this storm occurred on December 25 and the "evaluation
threshold" on December 31. An erosion evaluation was conducted within the formerly impounded
reaches of the Little River on January 3, 2007.
LITTLE RIVER EROSION EVALUATION
A two-person team performed a 7-mile canoe transit of the Little River. The point of ingress was the
bridge crossing at Old Beulah Road (SRI 934) and the point of egress was the former Lowell Mill
Dam location (Figure 3). The team stopped at the mouth of the two credited tributaries as well as at
previously established observation points along the river. At each observation point photographs
' were taken if significant changes had occurred since the first transit or to note continued stability of
certain stream features.
' River Observation Point I
River Observation Point 1 is located within Horsehead Bend (Figure 3). At this point on the Little
River, the sediment deposition on vegetation was clearly observed at or above bankfull height
' following the rise in storm flow. Numerous other areas along the canoe transit were observed to
have sediment deposition at a similar stage (Photo 1).
EcoScience Corporation
Mr. George Howard, Restoration Systems, LLC
January 25, 2007
Page 3 of 5
River Observation Point 2
' River Observation Point 2 is located at the Wildlife Resource Commission boat ramp (Figure 3). At
this location sediment was observed to have been deposited approximately 8 feet up the ramp
signifying the high water mark following the rise in storm flow (Photo 2).
' River Observation Point 3
' River Observation Point 3 is located approximately 1000 feet downstream of the Wildlife Resource
Commission boat ramp (Figure 3). At this location a log jam caused by a tree fall was creating an
obstruction across the entire width of the Little River. The logjam has been completely dislodged.
No new observations since last report.
River Observation Point 4
River Observation Point 4 is located approximately 600 feet below the US Highway 301 (US 301)
bridge crossing (Figure 3). Battery Bar, named for the presence of discarded batteries, was formerly
a large depositional area constricting flow at this location. Since dam removal and the return of lotic
conditions on the Little River, the sand bar has eroded significantly due to an increase in sediment
transport capacity. Slight channel adjustments are expected to continue until the Little River
dimensions are in regime with discharge and sediment transport rates (Photo 3-4).
River Observation Point 5
River Observation Point 5 is located approximately 1100 feet below the CSX Seaboard Rail crossing
(Figure 3). At this location well established herbaceous vegetation was observed during the first
transit along both banks of the river below the elevation of the former dam crest pool. The
' vegetation is currently dormant but is still visible and will continue to help stabilize the banks as it
continues to grow next spring. No new observations since last report.
River Observation Point 6
River Observation Point 6 is located approximately half way between the CSX Seaboard Rail
crossing and the Interstate 95 (I-95) overpass (Figure 3). Formerly inundated banks remain stable
with dormant herbaceous vegetation. Conditions remain the same since the last transit.
River Observation Point 7
River Observation Point 7 is located at the I-95 overpass (Figure 3). Most vegetation along the
banks is currently dormant but is still visible and will continue to help stabilize the banks as it
continues to grow next spring. The bridge piers located within the Little River contained no debris
and no evidence of scouring was observed (Photo 5).
River Observation Point 8
River Observation Point 8 is located approximately 300 feet upstream of the former dam site (Figure
3). At this location a change in river dynamics was observed during the first transit as a result of a
logjam break directly upstream of the former dam. In addition to the removal of large woody debris,
EcoScience Corporation
' Mr. George Howard, Restoration Systems, LLC
January 25, 2007
Page 4of5
1
several feet of sediment and organic debris had been scoured from the river bank and transported
' downstream. Some woody debris remains along the banks, however flow is no longer impeded.
Vegetation has covered the banks and no signs of erosion were observed (Photo 6).
River Observation Point 9
River Observation Point 9 is located along the inside bend (left bank) of the Little River at the
former dam site (Figure 3). At this location, fluvial deposition continues to accumulate on the point
bar that was constructed at the time of dam demolition. Volunteer herbaceous vegetation in addition
to the planted vegetation has established along the bar. Swift moving water was observed flowing in
the center of the channel, with slack water present along the north bank, where the channel remains
over-widened (Photo 7-8). Additional sediment is expected to continue to deposit along the point
bar as the Little River narrows to a width and depth consistent with bankfull dimensions. Toe of
slope protection and vegetation along the south embankment of the former dam site was intact
following the rise in storm flow. Newly installed stairs serving as a canoe launch to the Little River
were also intact and stable (Photo 9).
River Observation Point 10
River Observation Point 10 is located at the bridge crossing of Weaver Street (Figure 3). Most
vegetation along the banks is currently dormant but is still visible and will continue to help stabilize
the banks as it continues to grow next spring. The bridge piers located within the Little River
contained no debris and no evidence of scouring was observed (Photo 10).
¦ River Observation Point 11
River Observation Point 11 is located on the along the outside bend (right bank) of the Little River
' approximately 200 feet downstream from the WRC boat ramp (Figure 3). At this location the
outside bank of a bend in the river has experienced scour from increased flow. Alluvial banks with
' underlying bedrock have been exposed at the location of the scour (Photo 11). This feature is
common on banks along the outer bends in the river, where the underlying bedrock maintains
stability.
River Observation Point 12
River Observation Point 12 is located at the confluence with Little Buffalo Creek (Figure 3). The
flow pattern at this location is very dynamic due to the presence of mid-channel islands created by a
meander cut-off. The confluence to Little Buffalo Creek is stable with no signs of erosion (Photo
12). Immediately downstream of the confluence are two mid-channel islands that divert the flow of
water around them (Photo 13-14). Woody debris was present on the upstream side of both islands,
but flow was not impeded between them. Scouring was observed on the perimeter of the islands
were water flow is being diverted, as well as on the surface from overland flow during high river
stage.
EcoScience Corporation
' Mr. George Howard, Restoration Systems, LLC
January 25, 2007
Page 5 of 5
River Observation Point 13
River Observation Point 13 is located at the bridge crossing US 301 (Figure 3). Most vegetation
along the banks is currently dormant but is still visible and will continue to help stabilize the banks
as it continues to grow next spring. The bridge piers located within the Little River contained no
debris and no evidence of scouring was observed (Photo 15).
SUMMARY
Conditions observed during the current transit are similar to conditions observed during the previous
transits. The formerly exposed banks of the Little River below the elevation of the former dam crest
pool are covered with dormant herbaceous vegetation and continue to appear stable. Exposed banks
along the channel were rarely observed, suggesting limited occurrences of bank failure or erosion.
Erosion is restricted to channel bed and bank associated with channel adjustments in locations where
sediments have accumulated due to low water slope, and high sediment input locations near
confluences with larger tributaries. Woody debris was less evident throughout the former
impoundment during this erosion transit. The bridge piers and abutments at the various bridge
crossings over the Little River have accumulated only small amounts of woody debris and continue
to exhibit no visible evidence of scouring.
LITTLE RIVER EROSION EVALUATION FIGURES
>Z M
Z .T co ?+ c? > (0
uoo J?ZO :3 - ?NCp N
OH oo ?+rNN T cn
s c? JQ_
W0NQ ?U NNW a.. r
+? Wc. 0=J ?Z ~? N O O.? o u
V W W co z a
W Q
V o LOU

d
L
d
N
_T
co
C
z N `0i
a
m
O (D
n
U _
U) W
C ?L
Cu co
0
O a0)
E ~ Cfl Co Co Co (0 Co CO Cfl (fl 0 m
co ?T7 7 7 0 0
00) 00 r-- Cp Lo 4 CM N 0
V) co co CD (o co (0(0 co (o (o
7 `- 7 r l- r r r r
00 r-- Cfl Lo 4 co (N
O ?
n
.- ? (

LL. I,,-) -jf?

N
a?
ca
U)
U)
Z)
U a?
ZU c
O
C c +•
O O m
%U
U L
L O W
N ? .O
L
E O
? O W
N
' O
=
a
N A
- O
C) 0o
0
+r J
C
N
W
?LL
1
1
1
1
a)
rn
m
U
? U
Yo
C rn
a) o0
CD o
° °o o ° °
o In C) Lo
(sIO) ebieyosia Apea xeW
tp,1, p/Lp
lp,Z0/Lp
lp,/pal p
901, "lei
9p p1/eL
9p,61>?
9016)a l
N
901,1> L
90,9a/e`
s9,>
901
901ka [
90161a?L
901,?a I
901,eleL
9010.?, l
a)
rn
c ca
o .?
c??a
.Q ?
ao
u Z.
U O c
o
U
U O o
CA z
V U

0
Z
W
CD
W
J
z

a
z O
F-
D w p o >
0 o of Q ?
z o w

0 z 0 m Of ?
o mZ;
U U o 0 o O

fy z z z cn

0 Cr ?7- o?
w z
Q Z X X X ?O
w w w of w

,r
?T v
o
? o co
O
Z Q Z Z 0 N N
N
JQO z oo Z?OV? z v o
win ?Lu UQ GQ? ° a
Z C)
= 0J?O 0 N M
OJ0 O0
LU -1
J y z? WQya O 3
LU = o W m a
cc v 0 m m
O o v w

ti?61 bS - at/Ob

C
zw
w0?
w U cn Q
wOf cnCkf
JQ=?-
3Of Um
38 010
O
w
w
w
z
w
J
Q
O U
O (n
N
m = = r m m m
LITTLE RIVER EROSION EVALUATION PHOTOS
e. ?
{I'" i 1 i yy I I k ?n?, w. 77R?
Photo 2. River Observation Point 2: Sediment deposition and high water
mark (red line) at the Wildlife Resource Commission boat ramp. Little River,
Johnston County.
Photo 1. River Observation Point 1: Sediment on vegetation indicating
discharge at or above bankfull in Horseshoe Bend. Little River, Johnston
County.

O q

" P9

.
44,
a
-
?
3 6$
r??? vY »
y
g?, ?

?
, ?sr
?
? ?
.
'•` fir. ?:'
?? ? ,4, t\. .. .
?
?
Photo 4. River Observation Point 4: Looking upstream towards Battery Bar
at the point at which channel dimension have reestablished. Little River,
Johnston County.
Photo 3. River Observation Point 4: Looking downstream at Battery
Bar. Little River, Johnston County.

Photo 6. River Observation Point 8: Stable, vegetated bank that was
previously a site of erosion. Little River, Johnston County.
Photo 5. River Observation Point 7: The bridge pilings (1-95) located
within the Little River contained no woody debris and no evidence of
scouring was observed. Little River, Johnston County.

Photo 7. River Observation Point 9: Continued sediment deposition
and bar formation along the inside bend of the river at the former dam
site. Little River, Johnston County.

Photo 8. River Observation Point 9: Increasing size of the bar forming
as a result of additional sediment deposition. Note slack water the right of
the dam remnant from over widened channel. Little River, Johnston
County.

4y?

?Y#

Photo 10. River Observation Point 10: The bridge pilings (Weaver
Street) located within the Little River contained no woody debris and no
evidence of scouring was observed. Little River, Johnston County.
Photo 9. River Observation Point 9: Toe of slope protection and canoe
launch staircase along the south embankment. Little River, Johnston
County.

44
-,.?'"°. T p" .. ? ? '.: Sri, z ^?'a_ ? ? - ? t
Photo 12. River Observation Point 12: Stable confluence to Little
Buffalo Creek. Little River, Johnston County.
Photo 11. River Observation Point 11: Undercut alluvial banks
exposing the underlying bedrock. Little River, Johnston County.

Photo 13. River Observation Point 12: Meander cut-off immediately
downstream of the confluence with Little Buffalo Creek. Water flows both
behind and in front of the pictured stand of trees. Little River, Johnston
County.
1
r ?
t
?I

S
Photo 14. River Observation Point 12: Meander cut-off with woody
debris deposition. Little River, Johnston County.

f` t yw
rt
?
J
t?v'
?
?
-
'?
r
j

?•
r

_
?t
f ?
? rrv
?
I .?.
" ?t, ? ? ` .r
Caw
yam •. ? s-.?Y ,?..
LAM

Photo 15. River Observation Point 13: The bridge pilings (US 301)
located within the Little River contained no woody debris and no evidence
of scouring was observed. Little River, Johnston County.