STUDY PLAN – PEE DEE RIVER HABITAT MAPPING
AND GROUND TRUTHING
1.0 Introduction
1.1
Background Information on Habitat Mapping Processes
Habitat mapping of reaches 2 and 3 is an essential component in preparing and implementing a
scientifically viable instream flow study. The study area was videotaped from helicopter on
November 2-3, 2003, under base flow conditions (i.e., no power plant releases). The video was
taken in an upstream direction at a height of about 250 to 350 feet above the channel at an
average ground speed of 35 to 45 miles per hour. While this aerial video serves as an extremely
useful supplemental tool when mapping habitat, ground-truthing by boat will aid dramatically in
the mapping process and ultimately finalize the location of study sites. Data collected will be
used in conjunction with aerial video data to quantify habitat presence in the various reaches and
their frequencies. Habitat types will be defined by using a set of variables and then grouped
relative to their similarity. Each reach will be analyzed independently so to give the proper
amount of attention to existing habitat types in each respective reach.
The range of meso-habitat types (shoal, pool, glide, etc.) present in the study area was identified
from the aerial videography and from discussions with Progress Energy and DTA biologists
familiar with the Pee Dee River. Habitat was further typed by four additional classification
levels based on hydraulics, key substrate, cover, and channel morphology. Table 1-1 presents
the draft classification and coding system used in preliminary habitat mapping. This classification
system will be used to further delineate habitat types when mapping on the ground.
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TABLE 1-1
DRAFT HABITAT CLASSIFICATION AND CODING SYSTEM FOR THE PEE DEE
RIVER INSTREAM FLOW STUDY
First Order Second Order Third Order
Fouth Order
Fifth Order
Habitat
Type
Hydraulics
Key Substrate
Cover
Channel
Morphology
1 Pool
0 No entry
0 No entry
0 Absent
0 No entry
2 Glide
1 Shallow/Slow
1 Sandbar
1 LWD - Light
1 Complex
3 Run
2 Moderate/Slow
2 Sand/Gravel Bar
2 LWD - Heavy
2 Backwater
4 Shoal
3 Deep/Slow
3 Gravel Bar
3 Riparian Cover
5 Lateral Step
4 Shallow/Fast
4 Gravel/Cobble
4 Aquatic Cover
5 Moderate/Fast
5 Cobble/Boulder
6 Deep/Fast
6 Boulder/Bedrock
Example
1.3.1.1.0
Deep slow pool with sand bar, light LWD, and no unique channel characteristics
2.2.2.1.2
Moderate depth slow glide with sand/gravel bar, light LWD, and backwater
2.0 Methods
2.1
Reach Descriptions
Reach 2 begins at the Highway 1 bridge in South Carolina at River Mile (RM) 164.8 and ends at
Blewett Falls Dam at RM 188.2. The lower boundary of reach 3 is located at the upstream end
of the grassy islands at RM 197.5 and ends at Tillery Dam at RM 218.0. The two reaches are
further broken down into two subreaches respectively and then sites of interest (Table 2-1).
These sites of interest are areas that we have identified using the aerial video as sites potentially
possessing all of the various habitat types necessary to place transects here for the flow study.
Meso-habitats in the steeper reaches of the study area roughly follow a longitudinal sequence
that is largely determined by shoals that strongly influence upstream hydraulics. The “strength”
of each hydraulic control often determines the magnitude and extent of influence the shoal has
on upstream hydraulics and, perhaps, substrate composition and distribution. The sequence in
the steeper subreaches appears to generally follow this pattern (in a downstream direction):
shoal transitioning into a run
run transitioning into a glide
Appendix C - Page 2 of 10
glide transitioning into a pool
pool transitioning into a shoal
In the Pee Dee River, as flow approaches a shoal, the shoal creates a backwater effect creating a
relatively smooth and even horizontal and vertical velocity profile (Figure 2-1). Depending on
whether the longitudinal bed profile upstream of the shoal is concave or relatively flat, this
smooth profile may be a pool or a glide. Depending on how strong the hydraulic control is and
the bed slope, the pool or glide may extend for several thousand feet upstream.
On the
downstream side of a shoal, as flow leaves the shoal and moves into a glide or pool there is no
backwater effect, resulting in relatively fast, shallow, and potentially more turbulent flow. Note
that between each habitat type is a gradual transition and not a clear demarcation. Also, the
transition area between two specific habitat units will expand, contract, or migrate upstream or
downstream, depending on discharge. This “moving target” effect makes habitat typing based
solely on visually reading the water somewhat problematic.
What is important in habitat
mapping, transect selection, and transect weighting is that not only is the flow character
considered, but also the diverse underlying bed structure and form that creates the habitats is
mapped and represented in the model. Figure 2-1 illustrates a generalized sequence of habitat
types. There are exceptions to this pattern and variations occur between the higher and lower
slope subreaches.
2.2
Methodology
Two Biologists will spend approximately three days mapping habitat in reaches 2 and 3 in midMarch. A Progress Energy employee with extensive knowledge of the river will assist with boat
driving and habitat identification when needed. Mapping will be conducted and in a cataraft and
proceed in a downstream direction.
The cataraft will be equipped with a depth sounder
connected to a Trimble GPS unit. This integrated system will be collecting data down the entire
length of the river at 3 to 5 second intervals. This data will translate into a continuous line that
can be overlaid onto aerial photos of the river. This line will be color coded to represent the
various habitat types and accurately display unit boundaries. Visual observations will determine
boundaries between habitat units and these locations will be marked on the aerial photos.
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TABLE 2-1
STUDY SITES OF INTEREST FOR THE PEE DEE RIVER INSTREAM FLOW STUDY
Reach/
Subreach
R2/SR1
Figure C-4
R2/SR2
Figure C5
Study
Site No.
1
1
Figure C6
2
R3/SR1
Figure C7
1
R3/SR2
Figure C8
1
Location
5.4 mile reach between Hwy 1 and
approximately 2 miles downstream
of the state line.
Aerial video timer: (DVD #2)
0:02:23 – 0:16:10
2.8 mile reach between Mill Creek
at RM 176.5 and Solomons Creek at
RM 179.3.
Aerial video timer: 23:53:00 –
30:53:05
1.4 mile reach between Seaburn
Branch at RM 186 and RM 187.4,
just above Big Island.
Aerial video timer: 51:57:06 to
57:02:00
6.6 mile reach between 1.0 mile
downstream of Hwy 109 Bridge and
about ½ mile above Leak Island.
Aerial video timer: 01:22:00 –
1:33:15
2.6 mile reach between RM 212.6
and RM 215.2.
Aerial video timer: 1:38:25:18 –
1:39:23:00
Study Site Justification/Comments
This reach is approximately 5.4 miles long and is dominated by the Great Island complex. A rare
highfin carpsucker was collected within this area during 1979 (Progress Energy 2003). The study
site may be the entire subreach length. There is one potential navigation impediment identified in
this study site.
Note that Figure C4 shows the site only extending part way down Great Island. The site
actually extends down to just above Hwy 1 to video time 0:02:23.
This subreach includes several split channel areas and major shoals including Buchanan Shoals,
Jones Creek split channels and shoals, U.S. Highway 74 split channels and shoals, and the Big
Island split channel.
This study site section encompasses a multiple island split channel at Jones Creek in addition to
single channel habitat types of glides and runs typical of this Subreach. Boat access areas are
located at U.S. Highway 74 Bridge (Richmond Co.), Progress Energy lands just upstream of
Jones Creek Shoal (Richmond Co.), and private lands near the Mill Creek confluence (Anson
Co.).
This study site section encompasses a single island split channel at Big Island in addition to
single channel habitat types of glides and runs typical of this Subreach. Carolina redhorse and a
highfin carpsucker have been collected in this subreach during environmental studies conducted
by Progress Energy from 1998 to 2002. The upstream boat landing is located near the base of
Blewett Falls Dam, while the downstream boat landing is located at U.S. Highway 74 Bridge.
The lower end of SR1 is relatively homogenous with no unique channel features. The upper end
includes both simple channel types of glides and pools and complex channel types around Leak
and Buzzard Islands. The study site of interest includes slow shallow and moderate depth glides
and moderate to deep pools and glides; typical of the lower end of the subreach. It also includes
simple and complex channel types around Buzzard and Leak Islands. Boat access is located
within 1.5 miles at N.C. Highway 109 Bridge.
SR2 is a relatively homogenous reach of runs and glides with primarily boulder and bedrock
substrate with substantial gravel bars along the river margins. This study section captures the
range of primary channel, substrate, and habitat types present in the reach. Boat access is via an
upstream landing located at the Tillery Plant tailrace and downstream at a private owner landing
near the mouth of Pressley Creek.
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FIGURE 2-1
TYPICAL LONGITUDINAL SEQUENCE OF MESO-HABITAT TYPES IN THE PEE DEE RIVER INSTREAM FLOW STUDY AREA
Appendix C - Page 5 of 10
Along with these continuous measurements, point data will be collected at extremely deep or out
of water areas that are large enough to have a defining affect on the habitat type. For example, if
a stretch of river has a constant depth of 6 to 7 feet and may be defined as either a glide or a pool
but there are point measurements taken in pockets with depths of 15 feet, this will assist us in
correctly defining the unit as a pool.
As more pertinent variables are assessed, the level of certainty and consistency in the evaluation
greatly increases. Habitat units will be further defined by using a suite of visual and measured
variables. Appendix A displays the data sheet that will be used for mapping the Pee Dee.
2.2.1
Hydraulics
A hydraulic definition will be applied to each habitat unit relative to the reach it is in. Depth and
speed will be the two criteria used to delineate units into one of six criteria from shallow/slow to
deep/fast.
2.2.2
Dominant and Subdominant Substrate
When water conditions allow, visual observations of the two most dominant substrate types will
be made. It is anticipated that water clarity will be an issue in all of Reach 2 and Reach 3
downstream of the confluence with Rocky River. When visual observations cannot be made, a
telescoping rod will be used to assess size and quantity of the various substrate classes on the
bottom. Appendix A displays the classification system we will use for grouping substrate types.
2.2.3
Instream Cover
General quantity of instream cover for each subreach has been analyzed by using the aerial
video. Given that as a background, the biologists will classify each bank of each habitat unit as
having one of five types of primary instream cover (light LWD, heavy LWD, riparian cover,
aquatic cover or absence of cover. The right and left banks will be observed exclusively of one
another from the beginning to the end of the unit and an average will be taken.
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2.2.4
Channel Morphology
Channel morphology has been broken down into three categories depending on its complexity.
A majority of the habitat units will be simple, single channels defined as no entry. Habitat units
with multiple or side channels and/or large quantities in channel, out of water substrate, will be
characterized as complex. Units the possess point bars or other downstream obstructions that
create areas of backwater will be defined as backwater.
2.2.5 Distance of Habitat Unit
The distance of each habitat unit will be calculated in the office by using the GPS information.
These distances (accurate to <1m) will allow us to calculate frequencies for the respective habitat
types as well as more accurately confirm the overall length of each reach and subreach.
2.2.6
Width
In general, areas on a river with the greatest width tend to be the shallower units. A midpoint of
each habitat unit will be selected and a laser range finder will be used to measure the width of the
unit to the nearest foot. With this width information collected for each habitat unit, we will be
able analyze our field definitions of the habitat types and make some correlations between widths
on the Pee Dee and the habitat types they represent.
2.2.7
Bank Angle
Steep banks may represent deeper channels and areas of slower moving water. While banks with
a shallower level of entry into the water tend to be more characteristic of a shallow, faster
moving channel. The right and left bank will be observed from the beginning to end of each
habitat unit and will then be independently classified as either having a 0 to 30, 30 to 60 or 60 to
90 degree angle. These bank angles along with depth data will assist in proper classification of
the habitat units.
It is important to note that some of the variables mentioned above may not be consistent enough
to assist us in defining habitat types. Every river is different and variables that assist in one
Appendix C - Page 7 of 10
system may be useless in another. However, given the small amount of time it takes to collect
these supplemental variables versus the potential amount of support they may provide our habitat
analysis, they need to be collected. By using the depth and location data along with the variables
mentioned above, we will be able to define habitat units with a high level of consistency.
2.3
Habitat Definitions
As mentioned above, the four primary habitat types on the Pee Dee River are: Shoal, Run Glide
and Pool. Lateral steps were also documented on the aerial video and will be included in our
classification when observed. Definitions of all the habitat types will follow. The biologists will
be required to classify habitat units at the flows provided by Progress Energy on the days they
are in the field. Some habitat units may be on the borderline between two classifications at the
given flow. Given the typical fluctuation in stage that occurs in both reach 2 and 3, the biologists
will use their knowledge to define the habitat in a manner that most adequately describes it the
highest percentage of the time.
2.3.1
Shoal
For the purposes of the Pee Dee River, shoals will be defined as relatively shallow submerged
ridges that occur with a consistent frequency down the longitudinal profile of the river. Shoals
act as downstream controls to pools and glides and create the hydraulic conditions necessary to
form runs immediately downstream. Substrate composition in shoals will typically be made of
bedrock and coarse substrates. As mentioned earlier the “strength” of each hydraulic control
dictates the magnitude to which it influences the upstream habitat types. Each shoal will create a
unique situation upstream in which pools, glides or both may be identified. Figure 2-1 presents a
visual representation of the variation that can be created by varying “strengths” of shoals.
2.3.2 Run
Immediately downstream of the shoal, there is typically a transition area prior to the water
entering the next pool or glide. This unit consists of relatively fast moving, turbulent water and a
gradually descending bed profile. When habitat mapping, these areas can be visually represented
by an upwelling of water just on the downstream edge of the shoal. This “roiling” affect is
Appendix C - Page 8 of 10
created by the sudden drop in water off of the shoal due to the lack of any backwater effect.
Substrate composition can vary here as many times a run can act as a depositional location for a
shoal resulting in anything from fine sediments at lower flows to cobble and boulders at high
flows. As the water begins to collect and back up further downstream, velocities slow, depths
increase and the transition into a glide or pool occurs.
2.3.3
Glide
Depending on the strength of the shoal and the bed profile directly upstream of the control, a
glide or a pool will be created. A glide is generally defined by slow velocities and a relatively
smooth, nondescript bed profile. Glides will either progress into a more concave bed profile just
upstream of the shoal (creating a pool), or maintain their uniform hydraulic and bed features until
direct contact with the shoal. Substrates here tend to be on the finer side. Due to the slower
velocities and increased depths, finer substrates will typically begin to settle in glides.
2.3.4
Pool
If the bed profile upstream of the shoal is more concave or possesses significant undulations, a
pool will be formed. Pools are visually represented by the slowest velocities of the four main
habitat types and the most extreme depths. Steep banks and narrow channels relative to the rest
of the reach can often be associated with pools. The stronger or more defined the downstream
control (shoal), the more defined the pool. Substrate composition in pools will generally be
made up of fine substrates that have settled here or sheer bedrock.
2.3.5
Lateral Steps
Lateral steps in the Pee Dee are created by a rapid rise and fall in the bed profile. Typically, they
will not act as a strong downstream control and will look more like a small outcrop extending
laterally across a lengthy singular habitat unit. At lower flows, these steps may be represented
by a small cascade as the water falls over the downstream edge of the step. At higher flows,
these steps will most likely be submerged and the hydrology at these locations may be somewhat
disturbed and expressed by some boiling and strange movement. In the Pee Dee, the substrate
composition will typically be made up of sheer bedrock.
Appendix C - Page 9 of 10
2.4
Habitat Classification and Coding System
The two biologists will define each habitat unit in five orders (Table 1-1) beginning with a macro
view and working toward and increased specification with each added order. Once all data is
collected for the two reaches, it will be organized in a spreadsheet. Each habitat type will then
be sorted by the numbers assigned. Once this sort is completed, the data will be in a format that
will allow us to determine the frequency of the various habitat types related to the location data
that the GPS unit has collected. This relationship will be an extremely valuable tool when
determining the most appropriate locations for our study sites.
The data collected here will work with the slope and sinuosity data already acquired from the
aerial video and maptech work, to give us an extremely comprehensive view of the river at a
subreach level and permit us to evaluate candidate sites and select the most relevant and diverse
areas for our study sites.
J:\Projects\Progress Energy\007.0002.0300\Instream Flow-040721\Orig Graphics\Appendix C - Habitat Mapping Plan\Hab Map Study Plan.doc
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