20070812 Ver 1_09 Dec 2004 Sediment Fate & Transport Draft Report (2)_20080502

Sediment Fate and Transport DRAFT Report
Alcoa Power Generating Inc.
Yadkin Division
Yadkin Project Relicensing (FERC No. 2197)
SEDIMENT FATE AND TRANSPORT
REPORT
Draft Report
December 2004
Prepared by
Normandeau Associates, Inc.
and
PB Power
Sediment Fate and Transport DRAFT Report
Table of Contents
EXECUTIVE SUMMARY ...................................................................................................................
1 INTRODUCTION .................................................................................................................... ....1
2 LITERATURE REVIEW APPROACH ................................................................................... .... 2
2.1 Purpose ............................................................................................................................ ....2
2.2 Sources of Information .................................................................................................... ....2
3 SEDIMENT TRANSPORT LITERATURE REVIEW ............................................................ .... 3
3.1 Erosion and Sediment Inventory Special Report ............................................................ .... 3
3.2 Sediment Characteristics of North Carolina Streams 1970-1979 ................................... ....6
3.3 Sources, Sinks, and Storage of River Sediment in the Atlantic Drainage of the
United States ................................................................................................................... ..10
3.4 Water Quality of the Yadkin-Pee Dee River System, North Carolina-Variability,
Pollution Loads and Long-Term Trends ......................................................................... ..12
3.5 A Suspended Sediment Budget for Six River Impoundments on the Yadkin-Pee Dee
River ................................................................................................................................ ..13
3.6 Decreases in Yadkin River Basin Sedimentation: Statistical and Geographic Time-
Trend Analyses, 1951 to 1990 ........................................................................................ ..15
3.7 Water Quality and Quantity Trends in Three Sub-basins of the Yadkin River Basin,
North Carolina ................................................................................................................. ..20
3.8 Dynamic Modeling of Long-Term Sedimentation in the Yadkin River Basin ............... .. 22
3.9 Changes in Land Use and Water Quality in the Yadkin River Basin ............................. ..23
3.10 A River in Jeopardy: the Yadkin and Pee Dee Rivers of North Carolina ...................... .. 25
3.11 Yadkin-Pee Dee River Basinwide Water Quality Plan ................................................... .. 27
4 QUANTITATIVE SEDIMENT TRANSPORT AND SEDIMENTATION DATA ................ .. 32
4.1 Sediment Transport ......................................................................................................... ..32
4.2 Sedimentation Volume .................................................................................................... ..32
4.3 Sedimentation Patterns .................................................................................................... ..34
4.4 Effects of Sediment on Habitat ....................................................................................... .. 35
4.5 Effects of Sediment on Municipal Water Supply Intakes ............................................... .. 35
5 SYNTHESIS OF PREVIOUS INVESTIGATIONS ................................................................ ..36
5.1 Erosion ............................................................................................................................ .. 36
5.2 Sediment Transport ......................................................................................................... ..38
5.3 Sedimentation .................................................................................................................. ..39
6 REFERENCES ......................................................................................................................... ..41
7 LIST OF FIGURES .................................................................................................................. ..43
Figure 1 Location Map of Upper Yadkin River and the Yadkin Project .............................. .. 44
Figure 4-1 High Rock Reservoir Bathymetry in 1997 - Sheet 1 of 3 ...................................... ..45
Figure 4-2 High Rock Reservoir Bathymetry in 1997 - Sheet 2 of 3 ...................................... ..46
Figure 4-3 High Rock Reservoir Bathymetry in 1997 - Sheet 3 of 3 ...................................... ..47
Figure 4-4 High Rock Reservoir Bathymetry in 1917 - Sheet 1 of 3 ...................................... ..48
Figure 4-5 High Rock Reservoir Bathymetry in 1917 - Sheet 2 of 3 ...................................... ..49
Figure 4-6 High Rock Reservoir Bathymetry in 1917 - Sheet 3 of 3 ...................................... .. 50
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APPENDIX A - Figures and Tables from "Erosion and Sediment Inventory Special Report."
APPENDIX B - Figures and Tables from "Sediment Characteristics of North Carolina Streams 1970-
1979."
APPENDIX C - Figures and Tables from "Sources, Sinks, and Storage of River Sediment in the
Atlantic Drainage of the United States."
APPENDIX D - Figures and Tables from "Water Quality of the Yadkin-Pee Dee River System, North
Carolina-Variability, Pollution Loads, and Long Term Trends."
APPENDIX E - Figures and Tables from "Decreases in Yadkin River Basin Sedimentation: Statistical
and Geographic Time-Trend Analyses, 1951 to 1990."
APPENDIX F - Figures from "Dynamic Modeling of Long-Term Sedimentation in the Yadkin River
Basin."
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EXECUTIVE SUMMARY
The Draft Sediment Fate and Transport Report presents the information that is publicly available on
sediment fate and transport in the Yadkin-Pee Dee River basin. The area considered in this study is the
river basin that drains to Winyah Bay, South Carolina and includes the Yadkin, Pee-Dee, Uwharrie, and
Rocky rivers. The study was conducted in accordance with the Final Study Plan that was developed by
Alcoa Power Generating Inc. (APGI) in consultation with the Water Quality Issue Advisory Group
(IAG), supporting relicensing of the Yadkin Project. Specific objectives identified in the Final Study
Plan included:
• identify the sources, estimate the current sediment load, and determine the physical
characteristics of the sediments transported to and through the Yadkin Project reservoirs;
• estimate the volume of sediment trapped in the reservoirs and the deposition patterns; and
• evaluate the fate and transport of sediment qualitatively under existing and potential future
operating scenarios
The study involved two separate components; 1) a literature search performed by Normandeau
Associates to identify the body of research completed in this area, and 2) a review of historic survey
data which is used to evaluate the patterns of sediment deposition within High Rock Reservoir based on
changes in topography and bathymetry that have occurred since High Rock Dam was constructed.
In total, the study reviewed over a dozen articles and technical papers that have examined the issue of
sediment and sedimentation in parts of the Yadkin-Pee Dee River Basin. As discussed in the reports and
articles reviewed, the input of sediment, its transport, and its storage are dependent upon both natural
conditions such as regional geology, hydrology and soils along with man's alteration of the landscape by
development. The input, output and storage of sediment within parts of the Yadkin-Pee Dee River basin
has been shown to vary both spatially and temporally in response to changes in both naturally occurring
and imposed conditions. An understanding of the relationship between the naturally occurring
conditions along with the potential impacts associated with any imposed changes (naturally or by man's
actions) within the basin is essential in order to place the sediment issue into context.
The literature reviewed identifies that the major inputs of sediment to the Yadkin-Pee Dee River include
soil erosion, streambank and channel erosion, and urban runoff The reviewed literature indicates that
the main source of sediment in the Yadkin-Pee Dee River is soil erosion. The rates of soil erosion
within the Yadkin-Pee Dee River basin vary in response to the type of soil material and land use. In
general, the soils found in the Piedmont physiographic province are typically fine grained (silt) and can
be readily eroded when exposed to wind and water. Other natural factors contributing to the erosion of
these soils include the humid climate and topographic relief found within the Piedmont physiographic
province. Although many other rivers in North Carolina also have serious sedimentation problems, the
Yadkin's combination of these factors together with land use patterns within the watershed, results in
some of the highest erosion rates and sediment yields in North Carolina. The majority of the authors of
the publications reviewed as part of the study concluded that the decline in agricultural land use for crop
production since the 18th and early 19th centuries has resulted in a substantial decline in soil erosion and
sediment input to the Yadkin-Pee Dee River. They also note that for those lands remaining in
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agricultural use soil erosion can be further reduced by implementing agricultural best management
practices (BMPs).
Several of the authors also note that increasing development and urbanization may be causing a recent
increase in sediment input to the Yadkin-Pee Dee River and may in the long run exceed the reductions
associated with decreased cropland. Research has shown that development can result in increased
runoff, higher soil erosion and sediment transport. Utilization of urban BMPs may reduce some of these
impacts, but the benefits associated with implementation of urban BMPs may not be measurable for
some time due to the time lag between land use changes and the basin's response. Recognizing this
trend in its Basinwide Water Quality Plan (NCDNR 2003) for the Yadkin-Pee Dee River, the NCDNR
has emphasized the need for the continued implementation of appropriate urban BMPs to reduce this
growing source of sediment.
Overall, the findings of the reviewed research indicate that sediment transport in the Yadkin-Pee Dee
River has decreased over the last several decades. This principal reason for this decreasing trend is the
decline in the land area used for crop production and possibly the implementation of BMP to reduce soil
erosion and stormwater runoff. Although this trend appears to be continuing, several of the streams and
rivers within the Yadkin-Pee Dee River basin have been impaired by high sediment and turbidity levels
(NCDNR 2003). Furthermore, several of the authors warn that the production of sediment associated
with land development may ultimately cause sediment transport in the Yadkin-Pee Dee River to
increase. If this occurs, any gains made in reducing sediment transport in the last decade basin could be
reduced along with the continued impairment of the basins waters.
The study also concludes that storage of sediment in the basin naturally occurs within its streams and
rivers and on their associated floodplains. The construction of dams and the operation of their
associated reservoirs on the Yadkin-Pee Dee River has had an impact on the transport of sediment
through the lower portion of the basin. The impoundment of water by High Rock, Tuckertown,
Narrows, Falls, Tillery and Blewett Falls dams and the resulting reduction in water velocity at each
reservoir have reduced the capacity of the Yadkin- Pee Dee River to transport its sediment, thereby
leading to its deposition in each of the six impoundments.
The amount of sediment deposited in the reservoirs depends upon the amount of sediment supplied and
the storage or residence time of the water in the impoundment. Several of the studies reviewed
estimated the amount of sediment accumulated in the impoundments. The USDA (1979) estimated
annual sediment accumulation in the Yadkin Project reservoirs ranged from 1,354,500 tons/year (903 ac.
ft./yr) for High Rock Reservoir to 21,000 tons/year (14 ac. ft./yr) at Falls Reservoir, while the estimated
annual loss in total storage capacity ranged from 0.36 percent in High Rock Reservoir to 0.05 percent in
Narrows Reservoir. The lower capacity loss for Narrows and Falls reservoirs is due to the reduction in
sediment transport by its accumulation in High Rock Reservoir. The analysis of the survey data
available for High Rock Reservoir reveals that sedimentation has occurred since the construction of the
dam in 1927. The bathymetry of the reservoir shows that sediment has accumulated in the upstream
areas of the reservoir from Crane Creek upstream to the confluence of the Yadkin and South Yadkin
rivers. The effect of 80 years of sediment accumulation has been quantified as a reduction of
approximately 6 percent of total usable storage capacity in the upper 12 feet of the reservoir (typical
drawdown of the reservoir).
Overall, changes in land use within the basin have had an effect on the input of sediment to the Yadkin-
Pee Dee River and on the amount of sediment deposited in the Yadkin Project reservoirs. Although the
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decrease in cropland in the basin has resulted in a decline in sediment transport in the river, continued
land development may represent a growing source of sediment. Only with the continued basinwide
implementation and enforcement of appropriate BMPs and stormwater regulations will the input,
transport and deposition of sediment in the Yadkin Basin continue to decline. Ultimately, the benefits of
these actions will include the improvement of water quality and aquatic habitat in the basins waters.
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INTRODUCTION
Through its Yadkin Division, Alcoa Power Generating Inc. (APGI), a wholly owned subsidiary of Alcoa
Inc., has begun the process of preparing for the relicensing of the Yadkin Hydroelectric Project (FERC
Project Number 2197), located on the Yadkin River in North Carolina. The watershed area above the
lowest dam in the Project encompasses 4,190 square miles. This river is a part of the larger Yadkin -
Pee Dee River Basin that extends from the eastern slopes of the Blue Ridge Mountains to the Atlantic
coast. As part of this effort, APGI is collecting baseline information on resources at the Yadkin Project.
The Yadkin Project consists of a series of four reservoirs, dams, and powerhouses. From upstream to
downstream the Project includes, High Rock Reservoir, Tuckertown Reservoir, Narrows Reservoir and
Falls Reservoir (Figure 1 in Section 7). The High Rock Reservoir covers approximately 15,180 acres,
has a shoreline length of 360 miles and is the largest of the four reservoirs. Tuckertown Reservoir
covers 2,560 acres and has a shoreline length of 75 miles. Narrows Reservoir covers 5,355 acres and
has a shoreline length of 115 miles. Falls Reservoir, the smallest of the four reservoirs covers 204 acres
and has a shoreline length of 6 miles. Both High Rock and Narrows reservoirs and to a lesser extent
Tuckertown are highly dissected with numerous side channels and bays. Forest and residential land uses
dominate the shorelines of High Rock and Narrows reservoirs while the shoreline zone of Tuckertown
and Falls reservoirs is mostly undeveloped and forested.
The Yadkin-Pee Dee River basin upstream of the Project is a significant source of sediment to the
Project waters which can result in significant issues to water users throughout the river basin.
This report presents the information that is currently available on sediment fate and transport in the
Yadkin-Pee Dee River basin. The information presented herein originates from two sources. First, a
literature search was performed to identify the body of research completed in this area, and the studies
are summarized in Section 3 of this report. In addition, survey data collected throughout the history of
the Yadkin Project is presented in Section 4 to illustrate the changes in topography and bathymetry that
have occurred since the Project was constructed. Finally, in Section 5 the collected body of information
is used to meet, to the extent possible, the following objectives identified in the Final Study Plan:
• identify the sources, estimate the current sediment load, and determine the physical
characteristics of the sediments transported to and through the Yadkin Project reservoirs;
• estimate the volume of sediment trapped in the reservoirs and the deposition patterns; and
• evaluate the fate and transport qualitatively under existing and potential future operating
scenarios.
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2 LITERATURE REVIEW APPROACH
2.1 PURPOSE
The purpose of this review is to provide a summary of existing literature on erosion, sediment transport
and sedimentation in parts of the Yadkin - Pee Dee River basin. The results of this literature review
will form the basis for an assessment of the impacts of Project operations on sediment transport into and
through the Yadkin Project system.
2.2 SOURCES OF INFORMATION
Using publicly available information, a literature search on erosion, sediment transport and
sedimentation in the Yadkin-Pee Dee River system was performed using GeoRef. GeoRef is a
searchable electronic database that is maintained by the American Geological Institute (AGI).
According to the AGI, GeoRef is the most comprehensive database of bibliographic information in the
geosciences. This list of publications was supplemented by other publicly-available information and
documents. Of particular interest to this study are reports of investigations performed by the U. S.
Geological Survey (USGS), the North Carolina Department of Environment and Natural Resources
(NCDENR) and research performed by Duke University. Additional information was provided by Dr.
Daniel Richter of Duke University and copies of some of the publications were provided by Long View
Associates.
The discussion of the literature reviewed is presented in chronological order so that the reader can
follow the historical development of the erosion, sediment transport and sedimentation issues in parts of
the Yadkin - Pee Dee River Basin and Yadkin Project over time. This approach allows for a critical
review of the work performed and a means for following any trends in the research results. All of the
publications cited in this review report are listed by author in the references (Section 6.0).
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3 SEDIMENT TRANSPORT LITERATURE REVIEW
Comprehensive research on soil erosion and sediment transport on the Yadkin-Pee River began in 1970s
and is continuing today. The initial research on sediment in the Yadkin-Pee Dee River was performed
by the U.S. Department of Agriculture (USDA) in the late 1970s and was followed by several studies
performed by the USGS in the 1980s. In the 1990s and early 2000s several investigations of erosion
and sediment transport were performed by faculty and graduate students at Duke University. The results
of these studies are summarized in the following sections. Any figures and tables referenced in this
section are found at the end of this report in the appendices.
3.1 EROSION AND SEDIMENT INVENTORY SPECIAL REPORT
In 1979 the USDA published a "Special Report: Erosion and Sediment Inventory for the Yadkin-Pee
Dee River Basin in North Carolina and South Carolina" (USDA 1979). This study represents the first
comprehensive assessment of soil erosion, sediment transport and sedimentation in the Yadkin-Pee Dee
River basin.
This study had multiple objectives, including the determination of the annual rates of soil erosion by
source and land use, the transport of sediment through the drainage, its impact on water quality and on
the major reservoirs located within the drainage basin. The overall approach used in this study was
based on an agricultural and non-point pollution source study performed for the State of South Carolina.
As noted in the report, seven hydrologic units of approximately 250,000 acres were selected to represent
specific land resource areas in South Carolina. Two hydrologic units were selected in North Carolina.
One of these (Unit 03-07-02) includes several counties found in the headwaters of the Yadkin Project.
The total annual erosion for each source and land use was determined for each county or part of the
county lying within the drainage basin. Annual erosion for each major sub basin was then extrapolated
from the data and erosion rates were determined for each land resource area using similar methods.
The types of erosion evaluated were sheet and rill erosion, rural road associated erosion, urban and built-
up erosion, gully and pit erosion and stream channel erosion. Wind erosion was not evaluated. The
erosion rate for each of these was then estimated for each county in the drainage basin (refer to Table III
in Appendix A) and compiled for each of the four Land Resource Areas (LRAs): Southern Piedmont,
Georgia-Carolina Sand Hills, Southern Coastal Plain and Atlantic Coastal Flatwoods (refer to Table IV
in Appendix A). The Yadkin Project is located within the Southern Piedmont LRA.
Sheet and rill erosion was estimated using the Universal Soil Loss Equation (USLE). A statistical
sampling approach was used to estimate erosion within each of the hydrologic units. This sampling
approach consisted of a random selected series of plots each containing 160 acres. Three points in each
plot were sampled for land use and all factors in the soil loss equation. USDA technicians recorded data
at approximately 600 points in each hydrologic unit. Land use was based on adjusted data of 1967 to
make it current to April 1978. The data collected from all of the points were compiled for each
hydrologic unit and the erosion rates were estimated for each land use, by county, in tons per acre per
year.
The erosion associated with rural roads was also estimated based on a statistical sampling system. Each
sampling point was considered as a 50 foot reach of road. The total mileage of each road type within
the hydrologic unit was divided by the number of points sampled. The soil loss in tons per year was
computed for each incremental length of road. At each sampling point the sum of the bank heights
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eroding, annual bank slope recession and volume weight of soil eroded was recorded. Since erosion
would be greatest on dirt roads the width of the eroding roadbed was also recorded. The total annual
erosion for each unit was then summarized for each road type
Data were gathered for the hydrologic units by sampling points and observations to estimate erosion
from urban and developed land. The average annual erosion rate from all sources by major land use
type was estimated as: Piedmont - four tons per acre, Sand Hills and Coastal Plain - three tons per acre
and Coastal Flatwoods one ton per acre. In this analysis it was assumed that approximately 50 percent
of the urban and built-up area is covered by roof tops and concrete so the rate of erosion per acre was
reduced by one half.
During the sheet and rill erosion survey USDA technicians collected erosion rate data on all significant
gullies and pits encountered in each 160 acre sample plot. The erosion estimate was based on a
measurement of the height of the bank and width of the eroding bed, length of the bank and eroding bed,
annual recession of the bank and bed and of volume weight of the eroding soil in pounds per cubic foot.
The total soil loss was then tabulated for all gullies and pits recorded in the hydrologic unit.
Stream channel erosion was estimated using information compiled for the Erosion and Sediment
Inventory, Public Law 92-500, Section 208 reports for North and South Carolina. In North Carolina,
two percent of the stream bank mileage was sampled for each county. In South Carolina, 1,000 foot
sections of channel were sampled using a random pattern for each hydrologic unit. Technicians from
both states determined if stream channel erosion was negligible, slight, moderate and/or severe based on
the degree of bank recession. The average annual volume of soil eroded from stream channels was used
to calculate an erosion rate in tons per mile and this was extrapolated along the drainage basin.
Estimates of sedimentation were made for the sub basins and the drainage areas of the major reservoirs
found in the Yadkin-Pee Dee River basin. The gross annual erosion was calculated using the results of
the erosion study. Average annual sediment yields were calculated using SCS engineering methods,
which were not discussed. The average annual sediment concentrations were determined for points of
interest using the calculated sediment available for transport above the point and the annual runoff flow
for the drainage area.
Estimates of Soil Erosion
The erosion study results are summarized in Tables III through IV and in Figure II (in Appendix A). The
estimated sheet and rill erosion for each of the major land use types varied in the Southern Piedmont,
but was the highest when compared with the results for the Georgia-Carolina Sand Hills, Southern
Coastal Plain and Atlantic Coastal Flatwood LRAs. Within the land use types, the estimated sheet and
rill erosion was highest for cropland (10.7 tons per acre per year) while it was the lowest for forest land.
The high sheet and rill erosion values for cropland reflect the erosiveness of the soils in this region, the
land use management and the large amount of land used as cropland in this hydrologic unit.
The estimated erosion associated with rural roads was highest for the Southern Piedmont LRA. This
value was 221 tons per mile per year. The estimated erosion associated with urban and built up land
was also highest for the Southern Piedmont LRA. This value was 2.0 tons per acre per year.
The estimated gully and pit erosion for the Southern Piedmont LRA was 897.4 tons per mile per year.
When compared with the three other LRAs this value was the less than Georgia-Carolina Sand Hills and
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the Southern Coastal Plain, but higher than the Atlantic Coastal Flatwoods. No explanation is provided
in the report as to why the Georgia-Carolina Sand Hills have the highest gully and pit erosion rate.
For the four LRAs, the Southern Piedmont had the highest estimated stream channel erosion, 22.5 tons
per year (Table IV in Appendix A). The estimated stream channel erosion decreased downstream and
probably reflects a transition from higher gradient channels and drainages with moderate relief to an
area having low gradient channels and drainages with low relief.
Overall, the SCS (1979) estimated that approximately 25,500,000 tons of soil is lost annually from all
sources within the Yadkin-Pee Dee River Basin by erosion. Seventy four percent of this material
originates in North Carolina, while 26 percent originates in South Carolina. Individual sources of
erosion, ranked from highest to lowest were: 69 % cropland, 19 % rural road, 4 % urban and built up
land, 4 % forest land, 2 % other land, 1 % pasture and hay land, 1 % stream channel and minor amounts
from gully and pits.
When ranked by LRA, the areas having the highest to lowest estimated erosion were: Southern
Piedmont, Georgia-Carolina Sand Hills, Southern Coastal Plain and the Atlantic Coastal Flatwoods.
Since the Yadkin Project is located in the Southern Piedmont LRA, its drainages are experiencing the
highest amounts of erosion in the Yadkin-Pee Dee drainage basin. Annual erosion rates in the Southern
Piedmont LRA are roughly 85 % higher than the Georgia-Carolina Sand Hills, 180 % higher than the
Southern Coastal Plain and 360 % higher than the Atlantic Coastal Plain (Table IV in Appendix A).
The average annual erosion rates for all sources is presented in Figure 11 in Appendix A. This figure
clearly shows that the counties within the upper Yadkin River have the highest average annual erosion
rates. In reviewing the data presented in Table III (Appendix A), which presents the gross erosion by
land use, it is evident that the highest erosion rates are associated with croplands and rural roads. Due to
the large amount of cropland and rural roads found within the counties in the upper Yadkin River, the
estimated erosion rates are also high in these areas.
The report does note that "streams in the Piedmont Major Land Resource Area (MLRA) have the
highest suspended sediment concentrations in the basin. This is due to its higher rates of erosion,
swifter streams and higher content of silt and clay particles in the soil." As noted in the report, the
factors affecting sediment concentrations are the amount and the grain size of the material to be
transported, the transport capacity of the stream and obstructions located in the stream. Reservoirs trap
all of the material too large to be transported in suspension, which approximately equates to the bedload.
Varying amounts of the suspended sediment are also trapped depending on the material size, reservoir
capacity and stream inflow.
Estimates of Sedimentation
In the report, the gross erosion (tons/year) was estimated for each of the sub basins along the Yadkin-
Pee Dee River (Table V in Appendix A). These included estimates for High Rock Reservoir,
Tuckertown Reservoir, Narrows Reservoir and Falls Reservoir. These estimates were then used to
calculate the annual sediment accumulation and annual capacity loss for the major impoundments in the
drainage basin (Table VI in Appendix A). Lastly, the total sediment, bedload, suspended sediment and
average suspended sediment concentration for selected points along the Yadkin-Pee Dee River were
estimated (Table VII in Appendix A).
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For the study area, the estimated annual sediment accumulation and annual capacity loss was:
Annual Sediment
Reservoir Accumulation Annual Capacity Loss
High Rock 903 ac. ft. 0.36%
Tuckertown 86 0.20
Narrows 131 0.05
Falls 14 0.23
As shown in this table, High Rock has the highest annual sediment accumulation volume, which would
be expected since it is the first reservoir on the Yadkin-Pee Dee River. Lower values are observed for
the three downstream reservoirs. Due to the deposition of sediment in the Yadkin Project reservoirs, the
estimated amount of sedimentation and average suspended sediment concentration decreases as you go
downstream.
3.2 SEDIMENT CHARACTERISTICS OF NORTH CAROLINA STREAMS 1970-1979
Although published in 1993, this report by Clyde Simmons of the USGS provides a detailed analysis of
erosion, sediment transport and sedimentation for North Carolina streams (including the Yadkin-Pee
Dee River) for the period of 1970-1979. This report expands on the results of an earlier examination of
the water-quality characteristics of streams in forested and rural areas of North Carolina by Simmons
and Heath (1979 and 1982).
This report is based upon the analysis of sediment concentration data collected from a statewide
monitoring network for the period of 1970 to 1979. A total of 152 stations were included in the
analysis. The stations were grouped by physiographic province which included the Blue Ridge,
Piedmont and the Coastal Plain (Figure 1 in Appendix B). The objectives of this study included; 1) an
analysis of the effect of land use on characteristics of suspended-sediment transport, 2) a comparison of
suspended sediment transport with selected basin characteristics and 3) the development of
mathematical relations for estimating suspended-sediment yield for unmeasured basins.
In his assessment of the effects of land use on the characteristics of sediment transport, Simmons (1993)
subdivided the sampling network into five classes:
¦ Forested basins representing background (pristine) conditions
¦ Forested basins having minor developments
¦ Rural basins affected by agriculture
¦ Rural basins heavily affected by nonagricultural activities
¦ Urban basins
For each of the classes Simmons (1993) calculated the estimated mean annual suspended-sediment
discharge, the estimated mean annual suspended-sediment yield, maximum and minimum suspended-
sediment concentration. He then evaluated the results within the classes, between classes and the
physiographic provinces.
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He then evaluated the relationship between several basin characteristics and suspended sediment. The
basin characteristics examined included stream discharge, particle size, land use and gross erosion. This
analysis was not based on a statistical comparison and is more of a qualitative assessment.
Lastly, Simmons (1993) developed equations for estimating suspended-sediment yield from rural and
urban drainage basins. These equations were developed from a statistical analysis of selected drainage
basin characteristics with suspended-sediment yield and suspended-sediment discharge. The basin
characteristics examined included:
¦ Drainage area
¦ Channel slope
¦ Soil-infiltration ratio
¦ Average water discharge
¦ Percentage in forests
¦ Percentage in urban development
¦ Average percentage surface slope in basin
¦ Maximum observed stream velocity
¦ Rainfall factor
¦ Percentage of basin's land area in row crops
¦ Water discharge for 2-year, 10-year and 25-year floods
The data were analyzed by multiple linear regressions using the Statistical Analysis System (SAS). To
improve the reliability of the relationships Simmons (1993) developed the following guidelines:
¦ Drainage area should not exceed 400 sq. miles
¦ Individual analyses should be grouped by pre-dominant land-use category and soil class
¦ Basins containing major reservoirs and large-scale channelization should be omitted from
analysis
¦ The independent variables that provide the highest correlation and smallest standard error of
estimate were drainage area, average water discharge, 2-year flood and 10-year flood.
¦ Reliable predictive equations were possible for determining values of suspended-sediment
discharge for specific land-use categories.
¦ Data in logarithmic format provided the best statistical results.
Additional statistical analyses were performed to compute correlation coefficients by soil class for rural-
agricultural basins, by discriminant analysis and by least squares to fit general linear models.
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Effects of Land Use on Characteristics of Sediment Transport
State wide the amount of sediment produced by a drainage basin is influenced by its extent of
development and its physiographic setting. The highest estimated mean annual sediment yield was
associated with urban land use (464 tons/ sq. mi) followed by rural with agricultural and nonagricultural
land use (209 tons/sq. mi), rural with agricultural land use (174 tons/sq. mi), forested with minor
development (132 tons/sq. mi) and forested (33 tons/sq. mi).
The forested drainage basins (seven total, none in the Yadkin Project basin) were selected as being
representative of pristine or background conditions. Due to the high forest cover and limited ground
disturbance, the principal source of sediment in these basins is thought to be the erosion of the stream
channels and banks. Within this land use group the highest estimated sediment yields (44 tons/sq. mi)
were in the Piedmont and Blue Ridge provinces, while the lowest (5.5 tons/sq. mi) were in the Coastal
Plain. This difference is most likely due to the higher stream gradients in the Piedmont and Blue Ridge
compared to the Coastal Plain. None of the forested drainage basins studied are located in the drainage
of the Yadkin Project.
For those forested drainage basins (seven total, none in the Yadkin Project basin) with minor land
development, unpaved roads and limited agricultural production the estimated sediment yield increases
over the undisturbed forested condition. In these basins, the estimated sediment yield varied with
physiographic province, with the Piedmont having the highest (178 tons/sq. mi) and the Coastal Plain
having the lowest (60 tons/sq. mi). The difference in sediment yields by physiographic province and by
land use (with or without minor development) is shown in Figure 11 (Appendix B).
Simmons (1993) also examined the sediment production from rural basins affected by agriculture and by
a combination of agriculture and non-agricultural uses. He defined the rural basins as "those in which
agricultural activities are the primary sources of fluvial sediments above background levels." This is
based on observations from field inspections that noted agricultural-type activities were the primary
source of increased sediment loading to streams and rivers in these basins. A total of 83 basins were
included in this group, 13 of which are located in the Yadkin Project drainage. By physiographic
province the Piedmont drainages had the highest estimated sediment yield (239 tons/sq. mi) and the
Coastal Plain drainages (29 tons/sq. mi) had the lowest. Simmons (1993) notes that the higher values for
the Piedmont Province are most likely due to the location of the farmlands on floodplains. Due to the
hilly nature of the Piedmont, most agricultural development has occurred on the floodplain in the valley
bottoms. This concentration of farmland along streams and rivers has significantly decreased the
transport distance between the source area and receiving area for sediment produced by farming.
For the rural basins affected by agriculture, Simmons (1993) shows the average annual suspended-
sediment yield and average-sediment concentration for the major drainages in North Carolina in Figure
16 (Appendix B). Relative to the Yadkin Project this figure shows that the average suspended- sediment
yield, for drainages 400 sq. miles or less, in the Upper Pee Dee River (Yadkin River) are the highest in
the state. These high values reflect the erosivity of the soils, the relief in this physiographic province
(Piedmont), the gradient of the streams and the impact of agricultural land use practices.
An additional 38 rural basins (two in the Yadkin Project basin) were evaluated where they had been
affected by nonagricultural activities. These activities included highway construction, large-scale site
development, urbanization and the presence of reservoirs. An increase in suspended sediment would be
expected at development and highway construction sites in response to the removal of protected
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vegetations and the disturbance of erodable soils. For reservoirs, their impact would be the reduction of
suspended sediment since they act as sediment traps.
Statewide the mean annual suspended sediment yield for the rural basins affected by nonagricultural
activities was 209 tons/ sq. mi. By physiographic province it ranged from 302 tons/sq. mi. (Piedmont)
to 64 tons/sq. mi. (Coastal Plain). A major influence on suspended sediment concentrations in these
drainages is the presence of dams. As noted by Simmons (1993) sediment transport in 10 of the basins
is affected by the trapping effects of upstream reservoirs. The inflow and storage characteristics for the
reservoirs and their estimated trap efficiencies are summarized in Table 9 (Appendix B). Three of the
basins are located in the Piedmont Province with the Yadkin-Pee Dee River being one of them. At these
three basins the estimated mean annual suspended-sediment yield ranges from 12 tons/sq. mi. (Roanoke
River at Roanoke Rapids) to 99 tons/sq. mi. (Reedy Fork near Gibsonville), which are well below the
average of 302 tons/sq. mi. for the Piedmont. These low values reflect the storage of sediment in
reservoirs upstream of these gaging stations.
A total of 17 basins (three in the Yadkin Project basin) were categorized as being urban. Two of the
basins were located in the Coastal Province, 15 basins were located in the Piedmont Province and one
basin was located in the Blue Ridge Province. In the urban basins land-use activities directly related to
urban and municipal development are probably the primary sources of fluvial sediment (Simmons
1993). Increased sediment yield in these basins can result from the disturbance of erodable soils and the
increased runoff from impervious surfaces, which increases flood flows and channel erosion.
The estimated mean annual suspended-sediment yield for the urban basins was highest in the Piedmont
Province (515 tons/sq. mi) and lowest in the Coastal Plain Province (76.5 tons/sq. mi). The highest
estimated value (1,500 tons/sq. mi) was for Irwin Creek, which flows through Charlotte (Figure 20 in
Appendix B). For the Yadkin Project basin, estimates were made for Salem Creek, Muddy Creek and
the South Fork of Muddy Creek, all of which originate in the Winston-Salem metropolitan area. These
values ranged from 470 tons/sq. mi. for South Fork Muddy Creek to 410 tons/sq. mi. for Salem Creek,
which are lower that the average for the Piedmont, but still an order of magnitude higher than those
estimated for the Coastal Plain (Figure 20 in Appendix B).
Comparisons of Suspended-Sediment Transport Characteristics with Selected Basin
Characteristics
Simmons (1993) discusses the relationship between suspended-sediment transport with selected basin
characteristics such as stream discharge, suspended-sediment particle size, land use, the effects of
stream-slope change across the Fall Line and gross erosion. Since the project area is above the Fall Line
- the boundary between the Piedmont and the Coastal Plain physiographic provinces - his findings on
this subject are not discussed in this review.
The relationship between stream discharge and suspended-sediment transport is illustrated by a graph of
streamflow and suspended-sediment for the Yadkin River at Yadkin College (Figure 21 in Appendix B).
This figure clearly shows that the concentration of suspended sediment increases with increasing
streamflow. Simmons (1993) notes that in 80 percent of the basins studied the highest concentration of
suspended sediment occurs immediately prior to maximum flow.
Simmons (1993) also evaluated the percentage of time required for suspended sediment transport. As
summarized in Table 12 (Appendix B), for the three stations (numbers 78, 81 and 93) located in the
Yadkin Project drainage basin, 50 percent of the sediment is transported during flows that occurred
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between 0.4 and 2.6 percent of the time during 1970 and 1979. For example, for the Yadkin River in
Elkin, 50 percent of the suspended sediment was transported by flows that represented 2.4 percent of the
total flow from 1970-1979. These data support the view that the greatest amount of suspended sediment
is transported during high flow events.
The suspended-sediment data were also examined to determine the grain-size distribution of this
material. Simmons (1993) reports that the median grain size varied with physiographic province. The
coarsest material (silt/sand) was found in the Blue Ridge, followed by clay/silt in the Piedmont and clay
in the Coastal Plain. This distribution reflects both the source area and the average stream
gradient/velocity. For the Piedmont, this province is transitional between the Blue Ridge (high relief
and gradient) and the Coastal Plain (low relief and gradient). The Piedmont is also underlain by bedrock
that weathers into silty/clay soil, so the median grain-size would be expected to be small. This soil
texture is also highly erosive and can be readily transported by flowing water.
Using the suspended-sediment data, Simmons (1993) estimated the suspended-sediment discharge and
sediment delivery ratio (SDR) for selected rural drainages (Table 16 in Appendix B). The SDR was
calculated by dividing the annual suspended-sediment by gross erosion. The gross erosion data were
obtained from the USDA Soil Conservation Service (now NRCS). The sediment-delivery ratio provides
an estimate of the amount of sediment that is actually transported as sediment from the basin. Three of
the selected drainages are located in the Yadkin Project basin including the Yadkin River at Patterson
and at Elkin and Leonard Creek near Bethesda. The estimated SDR for these basins ranged from 0.15 to
0.37 which is in the range for the Piedmont basins.
Estimated Sediment Transport from Basins
Simmons (1993) developed regression equations for the estimation of annual suspended-sediment
discharge for rural and urban basins. He found that the strongest statistical relationships were obtained
when the data were grouped by soil class. Since the type of soil present in a drainage basin is one of the
principal controls of soil erosion this approach was logical. For the rural basins he found that the best
single variable for estimating annual suspended-sediment discharge was drainage basin area (refer to
table 18 in Appendix B). He also developed regression equations using the best three variables, which
included drainage basin area, average water discharge and the percentage of basin's land in row crops.
The use of these three variables increased the coefficient of determination (W) for each of the soil
classes evaluated. For the urban basins he presents only one equation, based on drainage basin area, and
that was for the soils found in the Piedmont Province. Several of these equations could be used to
estimate the annual suspended-sediment discharge for rural and urban drainages located in the Yadkin
Project basin. For the rural basins, however, these relationships have been recently revised (Calvo-
Alvarado and Gregory 1997).
3.3 SOURCES, SINKS, AND STORAGE OF RIVER SEDIMENT IN THE ATLANTIC
DRAINAGE OF THE UNITED STATES
In 1982, Robert Meade of the USGS published a comprehensive review article on the difficulty of
predicting sediment movement on a river-basin scale (Meade 1982). In this article the author states that
"the modeling of sediment movement on a river-basin scale is in a primitive state." The prediction of
sediment transport is difficult because of the numerous sources and sinks that are found within the
drainages and the time scale that is used in any assessment. The factor of time complicates the ability to
predict sediment transport because there can be a considerable lag from when the sediment is initially
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produced and when it reaches a stream to when it is transported through the system. He notes that "on a
millennial or longer time scale, eroded upland soil may be the original source of sediment and the
coastal zone may be the ultimate sink. At shorter time scales, the most important sources and sinks are
the storage sites along the way between the uplands and the estuaries. The sediment moves in and out of
storage in ways that we are not yet able to predict."
Meade reviewed existing information on erosion, sediment transport and sedimentation for the drainages
located along the Atlantic coastline. His analysis was based on a review of academic and government
research reports.
Meade outlined the difficulty of trying to predict the movement within a drainage basin. The major
challenges to this undertaking is the lag between when erosion occurs and when it becomes transported
by streams and rivers and the numerous in stream sources and sinks (storage) for sediment. In his paper
he discussed the major sources of sediment and how they have changed over time, the major in stream
sources and sinks of sediment, including the effects of reservoirs on sediment transport and lastly on
how the coastal zone is the ultimate sediment sink.
In his discussion of the relationship between streamflow and sediment transport, Meade compares the
discharge and sediment concentrations of the Yadkin-Pee Dee River with the Juniata River in PA, the
Merrimack River in MA, and the Edisto River in SC. What differentiates the Yadkin-Pee Dee River
from the others is the magnitude of sediment transported. The suspended sediment concentrations on
the Yadkin-Pee Dee River were an order of magnitude higher than the three other drainages when
measured at the same discharge (Figure 2 in Appendix Q. He notes that "because of these consistently
high concentrations, the sediment yields from the Piedmont are consistently the highest per unit area of
any physiographic province on the Atlantic slope."
The original source of the sediment transported in the Atlantic drainages is soil erosion. He notes that
land use within the drainages has contributed to soil erosion and that land use changes over time. The
results of research by Trimble (1974) showed that intense crop farming in the Piedmont region
contributed to excessive erosion. Other contributing factors to this erosion were the steep hillsides and
the deep soils found in this region.
Meade also notes that that soil erosion in the southern Piedmont was recognized as a serious problem as
by 1860, but that it most likely reached its peak by 1920 and has been declining in the last 50 years. He
credits the implementation of soil-conservation practices in the 1930s as a contributing factor in the
reduction of sediment yields. More importantly he notes that the decrease in farming, by about a third
since the end of World War II, in North Carolina may be a more significant factor.
A significant sink for sediment in a drainage system are reservoirs. Even moderately sized reservoirs can
trap large amounts of sediment. Based on a relationship between the storage capacity of reservoir and
its drainage area (the capacity watershed ratio) developed by Brune (1953), Meade states that "a
reservoir that is only large enough to hold one hundredth of the water that flows into to it can trap half
the sediment that flows into its upper end. A reservoir that can retain a tenth of the annual water inflow
can trap 80 to 90% of the inflowing sediment." Although Meade did not look at the Yadkin-Pee Dee
River, he did present two examples. These included the Roanoke River at Scotland Neck, North
Carolina (Kerr Reservoir) and the Santee River in South Carolina (Lake Marion and Lake Moultrie). At
both of these locations the existing reservoirs effectively trap about 90% of the sediment flowing down
the rivers. Thus, these facilities represent a significant sink for sediment being transported through their
respective drainage basins.
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3.4 WATER QUALITY OF THE YADKIN-PEE DEE RIVER SYSTEM, NORTH
CAROLINA-VARIABILITY, POLLUTION LOADS AND LONG-TERM TRENDS
Douglas Harried and Dann Meyer of the USGS reported the results of their review of the water quality
of the Yadkin-Pee Dee River in 1983 (Harned and Meyer 1983). The objectives of this study was to
define the variation in water quality in the Yadkin-Pee Dee River basin, determine the pollutant load and
determine any trends water quality. The report provides a comprehensive assessment of water quality
conditions of the Yadkin-Pee Dee River up to the early 1980s. Relative to the Yadkin Project only the
suspended sediment and turbidity sections of the report were reviewed.
Relative to sediment, Harried and Meyer (1983) looked at suspended sediment and turbidity in the
Yadkin-Pee Dee River drainage. Their evaluation examined streamflow and suspended sediment data
available from four monitoring stations: Yadkin River at Yadkin College, South Yadkin River near
Mocksville, Rocky River near Norwood and the Pee Dee River near Rockingham. The Yadkin College
station is located upstream of the Yadkin Project and data from this gage is representative of inflow
sediment load. The South Yadkin River discharges into the Yadkin River upstream of High Rock
Reservoir and represents a major tributary. The Rocky River is a tributary to the Yadkin Pee Dee River
downstream of Tillery and thus, is located downstream of the Yadkin Project. The USGS gage in
Rockingham, North Carolina is located downstream of the Yadkin Project and would represent the
outflow from the dams. This gage would also include the effects of the Tillery Dam and the Blewett
Falls dams, which are below the Yadkin Project (High Rock, Tuckertown, Narrows and Falls dams). A
summary of the suspended sediment and turbidity data is presented in Table 2 (Appendix D).
As noted by Harried and Meyer (1983), little turbidity data are available for the Yadkin College and
Norwood gaging stations, but the data are more complete for the Rockingham gage. Because these are
the same gages that the suspended sediment data are taken from the same area is covered.
In their analysis of the suspended sediment data Harried and Meyer (1983) plotted the suspended
sediment concentration and discharge data on log-log paper for three of the stations: Yadkin College,
Rocky River, and Rockingham. A linear regression analysis was then performed to determine the
statistical relationship between these variables. The suspended sediment data were then used to estimate
the annual sediment transport at the four gaging stations for the period of 1974-1978. The suspended
sediment load data were then used to calculate sediment volumes transported by the Yadkin-Pee Dee
River.
The number of turbidity samples available for analysis ranged from two at the Rocky River gage in
Norwood to 49 at the gage in Rockingham. Due to the limited amount of data no quantitative analysis
was performed other than the basic statistics of mean and range.
As mentioned, Harried and Meyer (1983) developed linear regression equations for suspended sediment
and discharge for the Yadkin River, the Rocky River and the Pee Dee River. The r values for these
equations ranged from 0.56 for the Pee Dee River to 0.89 for the Rocky River. Results for the South
Yadkin River at Mocksville were not discussed.
On the Yadkin River at Yadkin College and on the Pee Dee River at Rockingham the relationship
between suspended sediment and discharge showed some interesting characteristics. For the Yadkin
River, the concentration of suspended sediment plateaus at discharges above 7,500 cfs (Figure 9 in
Appendix D). The authors believe that this suggests that the sediment supply potential has been almost
reached. For the Pee Dee River, two clusters of data are observed, one at low discharge (300-1,000 cfs)
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and one at high discharge (7,000-30,000 cfs) (Figure 10 in Appendix D). The authors suggest that this
clustering may be the result of flow regulation.
For the period of 1974 to 1978, the authors estimated the total annual load of suspended sediment in the
Yadkin River (Yadkin College), South Yadkin River (Mocksville), Rocky River (Norwood) and Pee
Dee River (Rockingham). They note that with the exception of the Pee Dee River the total sediment
transport is roughly proportional to drainage area, with sediment yield greatest at Yadkin College and
least at Rockingham (Table 3 in Appendix D). They also note that their estimates should be interpreted
as minimum values because the sediment transported into the reservoirs hasn't been taken into account
and bedload has not been estimated.
These data show that the suspended sediment input at Yadkin College is not matched by the suspended
sediment output at Rockingham. This difference represents the amount of sediment deposited in the
reservoirs. The authors estimate that approximately 1 million tons of sediment per year is deposited into
the reservoirs by the three streams (Table 3 in Appendix D). This represents about 800 ac-ft/year or
roughly 0.10 percent of the total volume of the reservoirs. Between 68 and 92 percent of this sediment
is derived from the upper Yadkin River and the South Yadkin River, both of which drain into High
Rock Reservoir. Thus, this reservoir is the most heavily loaded in the series of impoundments. Lastly,
they note that about 27 percent of the sediment that enters the reservoir system is transported past the
Rockingham station, so it can be concluded that the Yadkin-Pee Dee reservoirs capture at least 73
percent of the sediment that enters them.
The authors also compare their results with those presented by the SCS in 1979. The estimates by
Harried and Meyer (1983) are lower than those reported by the SCS. They explain that this difference is
due to the methods employed. The SCS performed an analysis of soil, erosion and land-use information
to estimate erosion rates and amounts, while Harried and Meyer's (1983) study was based on the results
of water quality samples, which would give a more reliable estimate of actual erosion, sediment
transport and sedimentation on the Yadkin-Pee Dee River.
3.5 A SUSPENDED SEDIMENT BUDGET FOR SIX RIVER IMPOUNDMENTS ON THE
YADKIN-PEE DEE RIVER
In 1993, Van Fischer, in partial fulfillment of the requirements for the Master of Environmental
Management degree in the School of the Environmental at Duke University presented his Master's
Project titled "A Suspended Sediment Budget for Six River Impoundments on the Yadkin-Pee Dee
River" (Fischer 1993). The objective of his study was to extend the data analysis presented in Harried
and Meyer's report (USGS 1983) on the water quality of the Yadkin-Pee Dee River and to estimate
sediment transported during the fifteen year period of 1974 to 1988. In addition, the study presented a
means to estimate the rate of sediment deposition and the rate at which the Yadkin-Pee Dee River
reservoirs are filling with sediment.
Fischer (1993) based his study on streamflow and sediment concentration data taken from four gaging
stations on the Yadkin-Pee Dee River. These gages included the Yadkin River at Yadkin College, South
Yadkin River near Mocksville, Rocky River near Norwood and the Pee Dee River near Rockingham.
The data collected at the Yadkin College station represents the inflow from the upper portion of the
drainage basin. The South Yadkin River discharges into the Yadkin River upstream of High Rock
Reservoir and represents its major tributary. The Rocky River is a tributary to the Yadkin-Pee Dee
River downstream of Tillery and as a result is located downstream of the Yadkin Project. The USGS
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gage in Rockingham, North Carolina is located downstream of the Yadkin Project and represents the
outflow of the Yadkin Project dams and the two dams (Tillery and Blewett Falls) located downstream.
The length of record and frequency of measurement of stream flow and sediment concentration varied at
the sites:
Station Record Frequen
Yadkin College 1951 to 1988 Daily
Mocksville 1958 to 1968 Daily
Norwood 1976 to 1991 64 total
Rockingham 1976 to 1991 108 total
Fischer used a least squares regression analysis to estimate the daily suspended sediment yield at three
of the four stations. This analysis was based on the relationship between suspended sediment
concentrations and streamflow. For the Yadkin College gage, the daily streamflow and suspended
sediment concentration measurements were used directly. To improve the regression for the Mocksville
data set, Fischer divided the data into two seasonal periods: October to April (winter) and May to
September (fall). The Norwood and Rockingham gages had relatively small data sets and they were not
subdivided into seasons. For these three stations the suspended sediment and discharge values were log
transformed and a linear regression analysis performed.
The Yadkin College data provided the best estimate of annual suspended sediment load for the years
1974 to 1988. He credits this to the availability of daily measurements, which minimized the error
inherent in the regression analysis. Using these data he calculated that the mean suspended sediment
yield for the Yadkin River at the Yadkin College station was 805,370 metric tons (887,754 tons) a year
or 12,080,570 metric tons (13,316,325 tons) for the 15 year period. The drainage basin area above the
Yadkin College gage is 5,905 sq. km. (2,280 sq. mi.), so on a unit area basis the sediment yield for the
Yadkin River upstream of the impoundments is 136.4 metric tons/sq. km/year (389.4 tons/sq. mi./yr).
For the Mocksville, Norwood and Rockingham gages, Fischer's estimated suspended sediment yields
were based on linear regressions on log transformed suspended sediment and discharge values. Based
on this analysis he presented the following results:
Station Sediment Load Total Sediment Load (15 Years)
Mocksville 96,770 mt/yr 1,451,600 mt
Norwood 198,020 mt/yr 2,970,330 mt
Rockingham 419,760 mt/yr 6,296,360 mt
mt = metric tons
The cumulative flow measured at Yadkin College, Mocksville and Norwood only represents
approximately 58 percent of the flow measured at the Rockingham gage. Mean discharge at these
combined gages is 137 cu. m/sec (4,837 cu. ft./sec.) and the mean discharge at Rockingham over the 15
year period was 237 cu. m/sec. (8,369 cu. ft./sec), which leaves a deficit of 100 cu. m/sec (3,531 cu.
ft./sec). This deficit represents the flow contributed by the Uwharrie and Little Rivers and numerous
tributaries that aren't gaged. To estimate the sediment contributed by these tributaries he used an
estimate of 105 mt/yr (115.7 tons) made by Simmons (1988) and he also summed the yield of Yadkin
College, Mocksville and Norwood basins and divided by the drainage basin area for an estimated yield
of 107 mt/yr (117.9 tons). So the missing sediment falls in the range of 790,020 (1,856,269 tons/sq.
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mi./yr) to 805,070 mt/sq. km/yr (1,891,631 tons/sq.mi./yr) with an average of 797,550 mt/sq. km/year
(1,873,962 tons/sq. mi./yr).
In reviewing the 15 year period of record Fischer (1993) notes that the annual suspended sediment
yields varies from year to year. He concluded that this variation was due to "annual variations in the
hydrologic cycle (precipitation)." No trend analysis or comparison with land use change was
performed.
Fischer (1993) notes that in comparing the results for the Yadkin College and Rockingham gages that a
large amount of the sediment is captured by the six impoundments. He estimates that the total of all
suspended sediment inputs is approximately 1,897,710 mt/yr (2,091,832 tons) from 1974 to 1988 and
that sediment discharge from the reservoirs at Rockingham was about 419,760 mt/yr (462,698 tons).
Thus, net throughflow, approximately 1,480,210 mt (1,631,624 tons) of sediment, or 78% of input is
deposited in the reservoirs on an annual basis.
He also estimated the amount of deposition in the reservoirs and the amount of time that it will take to
fill the live portions of the reservoirs. Based on an estimated density of 1.165 mt/cu. in. (72.7 lbs/cu. ft)
he estimated the volume of sediment deposited into the six reservoirs (total) for a year. Using this
assumed density, the 1,480,210 mt/yr (1,631,625 tons) converts to 1,270,570 cu. m./yr (44,864,760 cu.
ft/yr) of deposition. He then divided this value into the total volume of the reservoirs, 675 million cu.
m.(23,834,745,763 cu. ft), to estimate the number of years that it would take to fill them. As a result,
Fischer estimated that it would take 530 years to fill the reservoirs located on the Yadkin-Pee Dee River.
Fischer (1993) notes that his estimates should be considered conservative (low end of the range) since
there are no data for bedload. He explains that bedload can account for 20 to 40 percent of the total
sediment load in most drainages. Using an average value of 30 percent, he estimates that an additional
570,000 mt/year (628,307 tons) of sediment would discharge into the reservoirs. So the total sediment
being retained by the reservoirs would be about 2,500,000 mt/yr (2,755,731 tons) or 85 percent of the
total load.
3.6 DECREASES IN YADKIN RIVER BASIN SEDIMENTATION: STATISTICAL AND
GEOGRAPHIC TIME-TREND ANALYSES, 1951 TO 1990
In 1995, Daniel Richter and Karl Korfmacher along with Robert Nan of Duke University published the
findings of a comprehensive assessment of sedimentation in the Yadkin River basin for the period of
1951 to 1990 (Richter and others 1995)
The objective of this study was to evaluate 40-year time trends in sediment transport by the Yadkin
River in North Carolina during a period in which this river basin was rapidly shifting from being
dominated by agricultural uses to one with a mixture of land uses, including additional areas of low
erosivity forest and pasture, and high erosivity urban and suburban development. The research tested
the hypothesis that the transport of river sediment has decreased over the past 40 years.
This study had several tasks including; an analysis of 19th and 20th century land use changes, the
development of a GIS Database, the estimation of gross soil erosion and the statistical and time trend
analysis of the Yadkin River suspended sediment data collected at the USGS gaging station in Yadkin
College, North Carolina.
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Land Use Analysis
The analysis of land use change was performed on two different data sets. The first data sets examined
were the USDA Forest Service Inventories for 1937-1990. Six different data inventories during this
time period were reviewed to determine the change in four different land cover types: row crops,
pasture, forest and urban-suburban. The second data sets examined were 20 US Department of
Commerce Agricultural Censuses from 1870 to 1987 for the four major counties (Forsyth, Surry, Wilkes
and Yadkin) in the basin. The emphasis in this review was documenting the change in the four major
crops (corn, tobacco, wheat and soybeans) grown in these counties over time.
GIS Database
A GIS database was developed to perform the land-use trend analysis and to estimate gross erosion
within the study area. The database was developed using information available at scales of 1:24,000
(1955 and 1988), 1:100,000 (1975) and 1:250,000 (1975). Base coverages created for the GIS analysis
included:
Coverage 1;24,000 1;100,000 1:250,000
DEM ¦ ¦
Slope ¦ ¦
Aspect ¦ ¦
Hydrology ¦
Watershed Boundary ¦ ¦
General Soils ¦
Roads ¦ ¦
Detailed Soils ¦
Land use-land cover ¦ ¦
Datasets for each of the coverages were compiled using the best available information, typically from
the 1:24,000 and 1:250,000 scale sources.
Using the 1:250,000 scale database a stratified image based on elevation, slope and proximity to rivers
and streams was created. From this stratified image, 185 sampling points were randomly selected.
Around each point a one sq. km. area was created and used as the sample area.
Gross Erosion Analysis of Rural Basin Areas
An analysis of gross erosion was performed to provide estimates of spatial changes in sediment sources
and volume over time. Estimates of gross erosion were made at two scales. For 1975, the gross erosion
estimates were made at a scale of 1:250,000 for the complete basin, while for the 1950s and late 1980s
the estimates were made using the 185 sq. kilometer sample areas within the basin.
To estimate gross erosion the Universal Soil Loss Equation (USLE) was used. USLE can be
mathematically expressed as:
A=R*K*LS*C*P
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Where:
A = gross erosion from sheet and rill erosion
R = a measure of rainfall intensity
K = a soil erodibility factor
LS= combined length and steepness of slope
C = vegetative cover factor
P = conservation practice adjustment
The rainfall intensity was estimated using either long-term county R factors obtained from the USDA
NRCS or a seasonally variable R factor derived from daily precipitation records. The K factors for the
general soil coverage were calculated based on the distribution of the soils making up a given soil
association in the STATSGO (State Soil Geographic) database. Individual K factors were taken from
the USDA NRCS USLE Handbook and used to estimate area-weighted average K factors for soil
associations. The LS factors were estimated from basin slope coverage data or calculated for each of the
185 sample areas. The C factors for various land use-land cover classes were assigned based on
information provided from several NRCS district conservationists based in the study area. The P value
was assumed to be equal to a value of one due to the lack of data for the 1955 database and the inability
to detect any changes in conservation practices from aerial photography. The C-factors estimates were
provided by county NRCS conservationists.
Statistical and Time Trend Analysis of Suspended Sediment Data
Daily suspended sediment data was obtained from the USGS for the gaging station located at Yadkin
College for the period of 1951 to 1970. Statistical analyses performed on this data included: arithmetic
means, discharge-weighted means, medians and frequency analyses. Analyses on transformed and
untransformed data using daily, monthly and annual compilations of discharge, sediment concentration
and sediment transport.
Several different approaches were used to evaluate the time trends of sediment transport over the 40-
year record. These statistical methods included: the non-parametric Mann-Kendall tests of no trend
used to test residuals that had low serial correlation; non-parametric seasonal Kendall tests were used for
data with skewed distributions, seasonality and serial dependence; and confidence intervals of
monotonic trends.
Changing Land Use in the Yadkin River Basin
The change in land use in the Yadkin River Basin was evaluated using USDA Forest Service Inventories
(1937-1987) and USDC Agricultural Census (1870-1987). The results of the analysis of the Forest
Service data are shown in Figure 5 (Appendix E). The most notable changes are the decreases in
rowcrop land since the 1930s, from around 45 percent to 18 percent of the land area and the increase in
the urban and residential uses from about 5 percent to 18 percent in the North Carolina Piedmont over
five decades. Also, smaller increases in forest and pasture land were evident in the basin since the late
1930s.
The USDC Agricultural Census provides more specific information on the change in agricultural land
use. The authors (Richter and others 1995) that the most significant trend is the reduction in the amount
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of land under cultivation. As shown in Figure 6 (Appendix E) the amount of cultivated land began to
steady decline in the 1920s, with a short lived increase in the 1970s and 1980s. Since the 1920s the
amount of cropland used for wheat, tobacco and corn production have significantly declined, while the
amount of land used for soybean production increased and then remained stable. For additional
information on the change in agricultural land use since the 1920s refer to Table 5 (Appendix E).
The authors (Richter and others 1995) note that the decline in the amount of land used for agricultural
production has also led to a decrease in gross soil erosion. They also remark that "the sources of
sediment in the Yadkin River are not simply decreasing but are rather shifting from being largely a
result of agricultural activities to being a result of a variety of human activities, increasingly associated
with urban and suburban development.'
GISAnalysis of Land Use-Land Cover
The second approach to estimating the change in land use was a GIS analysis. The land use-land cover
data for 1955, 1975 and 1988 were classified into four groups; urban, agriculture, forest, water and
other. The agriculture class was the sum of harvested cropland, other cropland and cropland pastured
and other pastureland. The results of the GIS analysis and the USDC Agricultural Census are
summarized in Table 7 (Appendix E). The GIS results show that agricultural use declined by 4 percent
(27.28 percent to 23.27 percent) from 1955 to 1988. Comparatively the USDC Agricultural Census
indicates that the decline in agricultural land use was even greater roughly nine percent (27.50 percent to
18.12 percent). The GIS analysis also showed that the greatest change in agricultural land use was in
cultivated cropland, with combined rowcrop and covercrop areas decreasing by 39 percent between
1955 and 1988.
Gross Soil Erosion Rates from Rural Basin Areas
Estimates of gross soil erosion rates were made based on information derived from 1:250,000 scale and
the 1:24,000 map coverage. For the 1;250,000 scale map coverage erosion rates were estimated holding
the basin R factor constant and by varying the R factor by county. Of the 18 strata classes analyzed only
four had annual erosion rates at or above the 11.2 Mg per hectare per year (4.1 tons/ac/yr) NRCS upper
limit of tolerable erosion loss.
The 1:24,000 map coverage data and rainfall based R factors were used to estimate gross erosion rates
for the 1950s (1953 to 19570 and the 1980s (1986-1990). The results of this analysis showed that
between the 1950s and 1980s that simulated gross erosion rates from rural lands decreased by 17 percent
or from 14.4 to 11.9 Mg per hectare per year (5.3 to 4.4 tons/ac/yr). The primary factor in reducing the
aggregate erosion rate across the basin was the decline in land under cultivation for row crops.
The authors (Richter and others 1995) also modeled the impact of the implementation of Best
Management Practices (BMPs) on erosion. They note that since the late 1980s BMPs have been
implemented on nearly all farms in the Yadkin River basin and that gross erosion rates have been
dramatically reduced. To assess the potential reduction in gross erosion by implementing these BMPs
the estimates were recalculated using lower C values derived from discussions with NRCS personnel.
With the R factor held constant and using the new C values the estimated gross erosion rate decreased
by nearly 42 percent from 14.4 to 8.4 Mg per hectare per year (or 5.3 to 3.1 tons/ac/year).
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Statistical Analysis of Yadkin River Suspended Sediment
The results of the statistical analysis of the 40 year suspended sediment concentration data record show
that the Yadkin River transports a tremendous amount of sediment, annually about 819,000 Mg
(742,997 tons). Per unit drainage basin area the mean annual suspended sediment yield is 1.39 Mg per
hectare (0.5 tons/acre). During the period of 1951 to 1990 the daily median suspended sediment
concentration was 70.0 mg/L, while the daily arithmetic mean was 150.6 mg/L (Table 19 in Appendix
E). The statistics for daily suspended sediment concentration and sediment yield for each decade are
presented in Tables 21 and 22 (Appendix E).
As noted by the authors (Richter and others 1995) the daily suspended sediment concentration and
sediment yield data are highly skewed. Skewness is a measure of the symmetry of a distribution, with a
normal distribution having a skewness of zero, whereas the results for the Yadkin River are positively
skewed. This is explained by the fact that the bulk of the suspended sediment (71 percent) is transported
by flows that occur about 10 percent of the time (36 to 37 high-flow days per year) and that about 26
percent of the annual transport occurred in three to four days per year (or one percent of the time).
As shown in Figure 12 (Appendix E) sediment transport by the Yadkin River varies highly from year to
year. The variable nature of sediment transport is directly associated with discharge. As shown in
Figure 13 (Appendix E), sediment transport increases with increasing discharge. This relationship
between discharge and sediment transport was examined using linear regression techniques. As shown
in Figure 14 (Appendix E) annual sediment transport and annual discharge are positively related and
that 79 percent of the variation in sediment transport is associated with the variation in discharge.
Time Trend Analyses of Yadkin River Suspended Sediment
Since no obvious monotonic time trend was obvious in the suspended sediment data (Figure 13 in
Appendix E) several statistical analyses were performed to remove the influence of the hydrologic
variability and to identify any underlying trends. This analysis included the fitting of regression
equations to sediment-hydrologic data and their time-ordered residuals and the testing of trends in the
time-ordered residuals using the Mann-Kendall test.
Based on the results of this analysis sediment transport in the Yadkin River at Yadkin College is
decreasing at a rate of about 6900 Mg per year (Figure 17 in Appendix E). The Sen-slope estimate
indicated that sediment transport was decreasing significantly by about 7,789 Mg per year (2,860
tons/year) between 1951 to 1990 and is equivalent to 0.013 Mg per hectare per year (0.0047 tons/ac/yr)
Monthly suspended sediment data were also analyzed by regression methods and tested with the non-
parametric seasonal Kendall test. The seasonal Kendall and Sen slope estimators of monthly sediment
transport indicated that sediment transport was decreasing at about 0.0115 Mg per hectare (0.0042
tons/acre) of the 477 month record. This decrease in sediment transport is equal to about 0.46 Mg per
hectare (0.17 tons/acre) over 40 years.
Daily log transformed suspended sediment concentration data were also evaluated using the statistical
methods used in analyzing the annual and monthly data. The results of these analyses also indicated a
decreasing slope of sediment concentration over time.
The authors (Richter and others 1995) also note that the production of sediment over the year changes in
response to rainfall and runoff The highest sediment transport (total sediment weight per month) is
observed from February through June, coinciding with the months of highest runoff The highest
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sediment concentrations (weight per unit discharge) typically occur from May through August. The
seasonal differences in sediment concentration are believed to be due to the higher amounts of erosion
that occur during the summer as a result of the intensity of convective summer storms.
Lastly, to determine whether sediment transport was decreasing in all months of the year the authors
(Richter and others 1995) performed a Chi-square test. The results of this analysis indicated that
negative trends in sediment transport during the period of 1951 to 1990 was present in all 12 months of
the year and was most pronounced during June through August.
Changes in Land Use-Land Cover and Gross Soil Erosion and the Implications to Water
Quality Management
The authors (Richter and others 1995) conclude that sediment transport is declining in the Yadkin
River, although at a relatively slow rate. The estimated reduction in sediment transport over the 40 year
period (1951 to 1990) is roughly 0.0115 Mg per hectare per year (0.004 tons/yr) which is equivalent to a
reduction of 0.83 percent of the mean annual transport of 1.39 Mg per hectare (0.5 tons/yr). The data
also indicated that the Yadkin River is transporting about 30 percent less suspended sediment on an
annual basis than in 1951, when the study period began. Although these reductions are an improvement
the amount of sediment being transported by the Yadkin River could be 10 times greater than what they
were prior to forest clearing and agricultural development.
The authors (Richter and others 1995) also note that watershed management can play an important role
in improving water quality conditions. The decline in agricultural land use coupled with the
implementation of BMPs have greatly reduced the contribution of sediment from agricultural lands.
The transition of land use from agricultural to urban is of particular concern. As urban development
increases appropriate watershed management measures will need to be implemented to reduce this
growing source of sediment. The control of this source is important considering the relatively slow
recovery of the Yadkin River from the impact of historical land use change.
3.7 WATER QUALITY AND QUANTITY TRENDS IN THREE SUB-BASINS OF THE
YADKIN RIVER BASIN, NORTH CAROLINA
In 2000, Jamie Henkels, in partial fulfillment of the requirements for the Master of Environmental
Management degree in the School of the Environmental at Duke University presented the findings of his
Master's Project titled "Water Quality and Quantity Trends in Three Sub basins of the Yadkin River
Basin, North Carolina" (Henkels 2000). Although not published, this presentation can be viewed at the
The Forest, Soil and Water Lab web site at Duke University. (http://discus.env.duke.edu).
The purpose of Henkels (2000) research was to evaluate whether different sub basins of the Yadkin
River are contributing different amounts of nonpoint pollution (sediment) and how is this related to land
use. This investigation included an analysis of the relationship between hydrology and precipitation and
the relationship between turbidity and streamflow.
Henkels (2000) study focused on three sub basins located in the Upper Yadkin River: the Mitchell
River, Ararat River and Muddy Creek. Land use within the Mitchell River is primarily forested, the
Ararat River basin is rural with agricultural land use, while Muddy Creek is largely developed and
includes the western portion of Winston-Salem.
In this study, Henkels (2000) performed an analysis of the change in land use overtime, the relationship
between hydrology (runoff) and precipitation and the relationship between turbidity and streamflow.
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For land use he examined the changes in land use in the three drainage basins over the years 1982, 1987
and 1992. The results of this analysis are presented as the percent change of county area for each of the
following land use types: cropland, forestland, pastureland, rural and urban land.
In the hydrologic analysis, Henkels focused on the relationship between rainfall events and flow
responses, the lag time of flow response after rainfall events and performs a comparison of lag time
between the drainage basins. For this analysis he selected the study period of 1970 to 1998 and his
sources of information included the USGS, the Surry County Soil and Water Conservation District
(SWCD), North Carolina Dept. of Environment and Natural Resources, and the City of Winston-Salem.
The first step in his analysis was to normalize the data for the purpose of comparing the data sets. He
then determined the lag time between precipitation and runoff events for the Ararat River, Mitchell
River and Muddy Creek. These data were analyzed by plotting the correlation coefficients of the time
lags versus the time lag in days.
Lastly, he looked at the relationship between turbidity and streamflow. The study period for his analysis
were from 1980-1998 for the Ararat River and from 1988-1991 for Muddy Creek. For his analysis he
log transformed both the streamflow and turbidity data and then plotted the turbidity and flow values
versus one another and performed a regression analysis. He did this for both the entire data set and then
individually for Muddy Creek and the Ararat River.
The results of Henkels (2000) study were presented by topic. In his analysis of land use he lumped the
drainages of the Mitchell and Ararat Rivers together since they are not urbanized. In these drainages the
predominant land uses are cropland, forestland and pastureland (88 percent) with urban land use
representing less than six percent of the county area. During the period of 1982 to 1992 the following
trends in these drainage were noted; cropland decreased by 12 percent, forestland increased by three
percent, pastureland increased by eight percent, rural land was unchanged and urban land increased by
two percent.
For the Muddy Creek drainage the predominant land uses are forestland (40 percent) and urban land (25
percent). Over the period 1982 to 1992 the following trends were noted; cropland decreased by five
percent, forestland decreased by three percent, pastureland and rural lands were unchanged and urban
land increased by eight percent.
In his analysis of the drainages hydrology he examined the time lag between precipitation and
streamflow. To analyze their relationship he plotted their correlation coefficients versus the lag time in
days and found that; runoff reaches each stream in one day, the Ararat River has the highest correlation
coefficient between these values and that the Mitchell River has the lowest one day correlation. The
difference in the response between the Ararat and the Mitchell Rivers may be explained by the
difference in their land use. The Ararat River is primarily agricultural while the Mitchell River is
principally forested. When looked at on a decade basis, there was no significant difference for the
Mitchell River and he credits this to little land use change over time. For the Ararat River only one
significant difference was noted between 1970 and 1990. He provides no discussion of the results for
Muddy Creek.
Lastly, he reported that in his analysis of turbidity and streamflow that when the log transformed
turbidity and flow data are plotted, a relationship between the two variables is evident. In general, as
flow increases turbidity is found to increase. When the two data sets are separated and replotted, the
turbidity values for Muddy Creek are found to be significantly higher than that for the Ararat River.
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This would suggest that the urbanization of the Muddy Creek watershed (Winston-Salem) is causing an
increase in turbidity concentrations.
Henkels (2000) concludes that there haven't been any significant changes in flow regime in the three
drainages studied during the last three decades, but that turbidity is now a greater problem in the urban
watershed (Muddy Creek) than the agricultural watershed (Ararat). He also states that non-point source
pollution continues to be a problem and that management strategies for the Yadkin River basin must
shift in response to land use change from agricultural and forested to urban.
3.8 DYNAMIC MODELING OF LONG-TERM SEDIMENTATION IN THE YADKIN
RIVER BASIN
In an article published in Advances in Water Resources, Jagdish Krishnaswamy, Michael Lavine, and
Daniel Richter of Duke University and Karl Korfmacher of Denison University discuss the development
of a statistical model to evaluate long-term sedimentation in the Yadkin River basin. The specific
objectives of this study were to model the sediment response of the Yadkin basin using Bayesian
dynamic linear regression models (DLMs) and to determine its ability to detect long term trends in basin
sedimentation in response to land use changes. This paper expanded upon the approach taken by
Richter and others (2000) in their report on the trends in land use and sediment transport in the Yadkin
River basin.
The study focused on the upper Yadkin River Basin, upstream of the USGS gaging station in Yadkin
College, North Carolina. As noted previously, this basin drains portions of the western piedmont and the
Blue Ridge escarpment of North Carolina and Virginia. Since this gage is located upstream of the High
Rock Reservoir the data do not reflect the effect of any of the Yadkin Project reservoirs, but documents
sediment transport inflow into the project.
In the study, the authors (Krishnaswamy and others 2000) used Bayesian DLMs to evaluate the
relationships between erosivity and streamflow with sediment concentrations and the relationship
between rainfall and streamflow. The data used for the analysis included rainfall, streamflow and
sediment concentration values for the period of January 1951 to September 1990. The streamflow and
sediment concentration data were obtained from the USGS Yadkin College gage, while the rainfall data
were taken from eight recording stations in the drainage basin. All data were aggregated to a monthly
time step.
The following DLMs were developed as part of the study; 1) log sediment concentration and log
erosivity, 2) log streamflow and log rainfall and 3) log concentration and log streamflow. The authors
note that the advantage of using a DLM over a static linear regression is that the parameters evolve with
time by incorporating new data and by discounting older data. Also, since the hydrologic system is non-
stationary, the use of a static linear regression model is limited.
In this analysis the change in the slope coefficient (B) reflected physical changes underlying the
relationship. For instance, an increase in the slope of the coefficient for erosivity over time may show a
change in land use such as forest conversion, reforestation and/or urbanization. The study focused on
the change in the slope parameter (B) for each of the relationships over time and then explained the
reason for any observed changes.
Plots (Figures 4-6 in Appendix F) of the change in the coefficients for erodibility-sediment, flow-rainfall
and flow-sediment relationships were presented. All three plots show a change occurring sometime in
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the late 1960s or early 1970s. For erosivity, a period of decreasing values between 1951 and 1973 is
followed by a period of increasing values. Thus, there was an increase in sediment per unit basin
hydrologic energy. This suggests an increase in basin erodibility. The relationship between flow and
rainfall shows an increased flow per unit rainfall in the latter period, while for flow and sediment the
slope increases to the early 1980s and then begins to decline.
The authors (Krishnaswamy and others 2000) explain that these changes are consistent with and are
possibly explained by changes in land use throughout the basin starting in the late 1960s, which reversed
the declining trends in basin erodibility and run-off. During the past three decades land use has changed
from primarily rural/agricultural to a mixture of uses. For example, the area under row crops decreased
by 5.9%, while urban development increased by 13%.
The decrease in the ability of rainfall to erode soils between 1951 and 1970 is most likely due to the
regrowth of forests and pastures on abandoned agricultural lands. The more recent rising trend in
erodibility and changes in the rainfall-flow processes may be related to the increase in urban areas and
road construction. These types of land use generate impervious surfaces close to the main stem of the
river leading to quick run-off and consequently erosion accelerated in the late 1960s to early 1980s. The
increase in the availability of sediment between mid-1960s and early 1980s as reflected in the rising
trend in the sediment coefficient is also attributed to the recent urban development.
The authors (Krishnaswamy and others 2000) then state that "the agricultural changes have substantially
decreased gross soil erosion on extensive rural areas of agricultural land throughout the Piedmont
region." They also repeat the findings of Richter and others (1995) in that "it is postulated that the
sources of sediment in the Yadkin River are not simply decreasing but are rather shifting from being
largely a result of a variety of human activities, increasingly associated with urban and suburban
development". They also conclude that "the continued effects of urbanization in stabilizing the decline
in overall basin surface erodibility and perhaps increasing sedimentation will perhaps be revealed by
DLMs estimated in the near future" (Krishnaswamy and others 2000).
The authors (Krishnaswamy and others 2000) of this report use a more robust statistical method to
analyze relationship between erosivity, streamflow and sediment concentrations in the Yadkin River
than those used in the past (USDA 1979, Harried and Meyer 1983, Simmons 1993 and Richter and
others 1995). Using this non-stationary approach they are able to show the variability and trends of
these parameters over time. The changes in these parameters appear to be correlated to past changes in
land use in the drainage basin, although they suggest that the positive effects of declining agricultural
land may become offset by continuing development. The effect of this transition from agricultural to
increasing urban land use as the sediment source is also cited in the following study.
3.9 CHANGES IN LAND USE AND WATER QUALITY IN THE YADKIN RIVER BASIN
In 2001, Carla Norwood, in partial fulfillment of the requirements for the Master of Environmental
Management degree in the School of the Environmental at Duke University presented the findings of
her Master's Project titled "Changes in Land Use and Water Quality in the Yadkin River" (Norwood
2001). Although not published, this presentation can be viewed at the The Forest, Soil and Water Lab
web site at Duke University (http:Hdiscus.env.duke.edu). Norwood's study represents the most recent
research of the sediment issue on the Yadkin River.
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The objective of Norwood's study was to evaluate land use and sediment change in the Yadkin River
Basin, over the period of 1951-2000, looking at what trends were evident and what relationships might
be apparent. The study area included the Yadkin River Basin from its headwaters to the USGS gaging
station in Yadkin College. Thus, the study area stops upstream of the High Rock reservoir and does not
include any of the Yadkin Project reservoirs.
The study approach included a review of the changes in land use and sediment concentrations in the
Yadkin River basin over time. Changes in land use were evaluated by reviewing the US Agricultural
Census (1945-1997), US Census (1950-2000) and digital land use data (1975 and 2001) sets for four of
the counties in the drainage basin (Forsyth, Surry, Wilkes and Yadkin).
In the second part of the study, Norwood (2001) evaluated the trend in suspended sediment
concentrations recorded at the USGS Yadkin College gage. She looked at flow, sediment concentration
and sediment transport for the period of 1951 to 2000. Daily sediment values were available for the
period 1951-1995; no records were available for 1995 to 1996, while weekly values were available for
1996-2000. To fill the gap in 1995-1996, Norwood performed a log transformation on the flow and
sediment data recorded for 1951-2000 and 1990-2000 and plotted log flow (X) vs. log sediment
concentration (Y). She found that the 1990-2000 data had a stronger relationship and using this she was
able to estimate the sediment concentrations in 1995-1996 based on the recorded flow data for this
period.
Norwood (2001) then summarized the sediment concentration data computing a monthly mean and
plotting it versus time. She noted that identifying a time trend in the data was difficult due to
seasonality and its being skewed. To evaluate the trend she performed a seasonal trend decomposition
with LOESS. This allowed for a nonparametric statistical test for trend and graphical analysis. By
correcting for flow, she looked at the long term trend and seasonality components in sediment
concentrations.
In the discussion of her results on land use change, Norwood presents several graphs that illustrate the
change in land use over time and its potential contribution to sediment concentrations in the Yadkin
River drainage. In one plot she shows that relative sediment contribution has changed over time:
Time
Pre-1700s
Late-1700s
1880s
1920s
1950s-Present
Land Use
Native American Cultivation
Early Settlers
Cash Crops
Land Abandonment
Urbanization?
Sediment Contribution
Low
Medium
Highest
High
High and Increasing
The decline of agriculture from the 1940s to late 1990s for the four counties studied is illustrated in a
chart. Overall, the acreage in production decreases by roughly 100,000 acres or by over 40% during this
time period. In addition, the greatest change occurs in the production of corn and wheat with both
declining over this period.
Alternatively, the population in the four counties studied steadily increased from 1900 to 2000, with
population going from around 100,000 to approximately 475,000. This represents an increase of
roughly 3.8% per year. The greatest amount of growth was recorded in Forsyth County, which includes
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Winston-Salem. This area experienced the greatest amount of urban development in the region from
1975 to 2001. Other major towns or cities are located within the upper Yadkin basin.
In her analysis of sediment transport Norwood found that when corrected for variation in flow the long
term (1950-2000) concentration of sediment in the Yadkin River was found to decrease by 38% (63 to
39 mg/1). As shown by Norwood there is a strong seasonality to sediment concentrations for the Yadkin
River. The highest concentrations occur in the summer (June, July and August), while the lowest
concentrations occur in the late fall and early winter (November, December and January). For the
period of record, the flow corrected concentration of sediment was also found to decrease.
Norwood (2001) presents a plot showing the proportional change in sediment concentration and percent
land use for cash crops over the period of 1945 to 2000. During this period both the percent area under
cultivation for crops and sediment concentration in the Yadkin River are found to decrease. In a second
plot she includes the change in population density over time. While the density of population increased
over time, the concentration of sediment in the Yadkin River fell.
Based on these findings Norwood suggests that the decline in sediment concentrations reflects the
decline in agricultural use of land in the drainage basin and that sediment concentrations in the 1980s
could be as ten times greater than those experienced pre-1800 settlement. This indicates that it may take
a long time for the river to recover from past impacts. Norwood (2001) also notes that the impact from
urbanization might be masked by the decline of agricultural land use. This is because the urbanized
areas represent a relatively small area of the drainage basin. Lastly, she notes that there is a lag time
between the change in land use type from agricultural to urbanized, so the impact of this change might
not be observed until well into the future.
3.10 A RIVER IN JEOPARDY: THE YADKIN AND PEE DEE RIVERS OF NORTH
CAROLINA
This report was prepared by members of Clean Water of North Carolina (CWFNC), which included
Brad Carpenter, Scott Jackson and Hope Taylor-Guevara. The report was issued in October 2002.. As
stated by the authors (Carpenter and others 2002) the purpose of this report was to "explore the impact
human activity has on the Yadkin-Pee Dee watershed". For this report the Yadkin-Pee Dee River was
divided into three units: the Upper Yadkin, the South Yadkin and the Lower Yadkin.
The authors state that "the Yadkin River faces threats from several directions. Population growth and
sprawl are the underlying causes of water quality problems. Sediment in muddy runoff comes from
road and home construction, from the increased velocity of flow in urban areas and also from
agricultural and timbering operations. Nutrients come mainly from wastewater treatment plants,
fertilizer and animal wastes. Harmful bacteria are frequently associated with the nutrients. Toxic
substances come from industrial sources, as do waste materials that add color to the water." For these
reasons a review of the existing conditions and actions that could be taken to improve the quality of the
Yadkin-Pee Dee River was performed by CWFNC.
The review of this report was limited to the discussion of the issue of sediment and to the discussions of
the Upper, Lower and South Yadkin drainages which are either upstream or include the Yadkin Project.
The report is a compilation of existing material, relying particularly on the results of the Basinwide
Water Quality Plan prepared for the Yadkin-Pee Dee River by the NCDNR Water Quality Section in
1998. This plan was recently revised and updated by the NCDNR in 2003. The report also is based on
two earlier publications "A Citizens Report on the Mid-Yadkin River Basin" prepared in 1991 by the
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Clean Water Fund of North Carolina (now Clean Water for North Carolina) and "A River Runs Through
Us" which is a compilation of articles that appeared in the Salisbury Post in 1997.
The report "A River in Jeopardy" identifies sediment as the greatest threat to water quality in the
Yadkin-Pee Dee River. The environmental impacts associated with high sediment loads is the
deposition of sediment on streambeds, thus suffocating fish eggs, clogging fish gills, and reducing
visibility for predators. Sediment can also carry bacteria, nutrients and toxins. Lastly, high
concentrations of sediment may also increase the cost of water treatment for those communities using
the Yadkin-Pee Dee River as a water supply.
The major sources of sediment in the Yadkin-Pee Dee River cited in the report include those that
remove vegetation and expose bare ground such as: construction, urban runoff, golf courses, agriculture
and livestock operations. The report notes that sources of sediment in the Yadkin-Pee Dee River have
changed over the past century. Erosion from agriculture was at its highest in the 19th and early 20th
centuries. In the late 20th century decreasing amounts of land were in agricultural production. As a
result, sediment levels in Southeastern rivers had declined to one third of their 1910 levels (Carpenter
and others 2002). While sediment loads from agricultural lands have decreased increasing loads from
construction and urban development may cause increased sediment loading to the river in the future.
To reduce the impact of erosion and sedimentation the authors (Carpenter and others 2002) recommend
that riparian buffers and construction BMPs be employed. They also note that sediment is "not a long-
lasting contaminant. If we can reduce the amount of new sediment entering the Yadkin-Pee Dee system,
this river will improve as storms wash the existing sediments downstream."
Upper Yadkin Sub Basin
The report then examines the state of each of the three sub basins. The Upper Yadkin Sub Basin
includes the uppermost portion of the Yadkin River above its confluence with the South Yadkin River.
In the Upper Yadkin, the report notes that the estimated soil loss in this watershed has declined from 4.2
tons/acre/year in the 1970s to 3.7 tons/acre/year in the early 1990s. Of the sediment input to the Upper
Yadkin River roughly 70 percent of it is captured and retained by the reservoirs located downstream in
the Lower Yadkin Sub Basin.
Due to the high rates of soil erosion in the Upper Yadkin Basin several subdrainages have been
impacted to the point of being considered impaired and are included on the states 303(d) list. These
streams include Faulkner Creek (sediment) and Salem Creek (turbidity).
South Yadkin Sub Basin
The South Yadkin Sub Basin includes the watersheds of the South Yadkin River and Back Creek. The
authors note that the study performed by the USDA in 1979 estimated that the South Yadkin Sub Basin
lost 5.1 tons of sediment per acre per year in 1978, making this the most impaired sub basin at that time.
They do not provide any information on any more recent estimates so any change in soil losses and
sediment yield is not presented. Since there are no reservoirs on the South Yadkin Sub Basin near its
outlet the sediment produced from this watershed is partially retained in the reservoirs located
downstream in the Lower Yadkin Sub Basin.
The report notes that due to the high sediment production in this watershed that Fourth Creek has been
impacted and is considered impaired due to high turbidity.
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Lower Yadkin Sub Basin
The Lower Yadkin Sub Basin begins at High Rock Reservoir and ends at the South Carolina state line,
so it includes the Yadkin Project. The report notes that the 1970s sediment analysis estimated that the
Lower Yadkin Sub Basin lost 2.7 tons of sediment per acre per year, which is much less than the Upper
Yadkin or the South Yadkin. The lower soil loss estimates are explained as being the result of the lower
population of the Lower Yadkin and the higher proportion of forested land (Uwharrie National Forest).
Although the estimated rate of soil loss is less in this sub basin, several streams have been impacted and
are considered impaired by the NCDNR. These include: Grants Creek (turbidity), McKee Creek
(sediment) and the Rocky River (turbidity).
Based on their review of the exiting information on sediment in the Yadkin River the report authors
make the following recommendation:
"Substantial improvement in non-point source pollution control, particularly sediment. While
sedimentation impacts due to farming have gradually diminished due to better practices and
decreased farming in the basin, the Yadkin still runs brick red after any significant rainfall, and
dowmiver habitats, water quality and reservoirs have been highly impacted. It will require
economic incentives for farmers and developers, strict enforcement of sedimentation and
erosion regulations for all sectors, and serious regional transportation and development planning
to prevent further rapid degradation of the Yadkin's waters and quality of life in the basin."
3.11 YADKIN-PEE DEE RIVER BASINWIDE WATER QUALITY PLAN
In 2003, the North Carolina Department of Environment and Natural Resources, Division of Water
Quality, Water Quality Section released the Yadkin-Pee Dee River Basinwide Water Quality Plan. This
document is the first five year update of the plan originally issued in 1998. The Basinwide Water
Quality Plan (BWQP) for the Yadkin-Pee Dee River provides a comprehensive overview of water
quality issues in this basin. The BWQP was presented in the three sections: Section A General
Basinwide Information, Section B Water Quality Data and Information by Sub basin and Section C
Current and Future Water Quality Initiatives. Relative to the Yadkin Project, the BWQP was reviewed
focusing on the sediment and turbidity issues.
In Section A the hydrology, land cover, population and growth trends in the basin along with its natural
resources, water quality issues and the physical impacts to wetlands and streams are discussed. In the
summary of water quality information for the Yadkin-Pee Dee River (Chapter 3) sediment loading was
identified as a problem based on the results of the Lakes Assessment Program (LAP). The report states
that "excess sediment reduces the storage of lakes overtime, introduces nutri ents, and reduces aesthetic
appeal by giving the water a muddy appearance. Soils of the Yadkin-Pee Dee River basin are highly
erodable. The most notable example of this problem can be seen in the upper end of High Rock
Lake."(NCDNR 2003).
The Ambient Monitoring System (AMS) has reported turbidity as an issue in several watersheds. More
than 10 percent of the samples collected at 11 stations in the Yadkin-Pee Dee River basin exceeded
turbidity water quality standards within the most recent assessment period (1996 to 2001). The
drainages where exceedances were reported in the Yadkin Project basin included: the Yadkin River
(three different locations), Ararat River, South Yadkin River, Town Creek Arm of High Rock Reservoir
and the Abbotts Creek Arm of High Rock Reservoir (two locations).
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Turbidity was also identified as a water quality issue in the results of the Yadkin-Pee Dee River Basin
Association Monitoring Program (YPDRBAM). More than 10 percent of samples exceeded turbidity
water quality standards at 13 monitoring stations. The report notes that "turbidity at four mainstream
Yadkin River monitoring locations exceeded the water quality standard in 13-21 percent of the samples
collected. Water from both the South Yadkin River (mostly agricultural use) and the upper end of North
Fork Crooked Creek (mostly developed/urban land use) exceeded turbidity standards in approximately
24 percent of the samples"(NCDNR 2003). Other streams located within the Yadkin Project basin
reporting turbidity values greater than the water quality standard included: Dutchman Creek and Fourth
Creek.
In Chapter 4 (Water Quality Issues), sedimentation is identified as one of the major contributors to
habitat degradation in the Yadkin-Pee Dee River basin. The potential sources of sediment include those
land-disturbing activities such as the construction of roads and buildings, crop production, livestock
grazing and timber harvesting. The Plan notes that sediment produced from these activities may be
deposited in streams smothering aquatic insects that fish feed on and may also bury fish spawning areas.
Physically, sediment deposition may also fill river and streams decreasing their volume and increasing
the frequency of floods (NCDNR 2003).
Suspended sediment can also impact the aquatic ecosystem by decreasing primary productivity
(photosynthesis) by shading sunlight from aquatic plants. Suspended sediment can also affect various
fish species including avoidance and redistribution, reduced feeding efficiency, respiratory impairment,
reduced tolerance to diseases and toxicants and increased physiological stress. The removal of
suspended sediment from water for its use as a drinking water supply is also costly (NCDNR 2003).
During basinwide monitoring performed by DWQ biologists in 1999, streambank erosion and
sedimentation were reported throughout the Yadkin-Pee Dee River basin as being moderate to severe.
Lower bioclassification ratings were assigned due to sedimentation covering substrate and or partially
filling pools. In addition, unstable and/or eroding streambanks were also noted in the lower ratings
(NCDNR 2003).
The BWQP outlines the actions that can be taken to reduce sediment production and transport in the
watershed. These actions include:
¦ Implementation of Best Management Practices (BMPs)
¦ Development of stronger rules for sediment control
¦ Application of recent research results on sediment control
¦ Regulation of instream mining operations
In Section B of the BWQP, the water quality of each sub basin is discussed. A total of eight sub basins
delineated in the BWQP fall within the Yadkin Project basin including:
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Sub Basin Code Basin Name
03-07-01 Upper Yadkin River and Kerr Scott Reservoir
03-07-02 Mitchell River, Fisher River and Deep Creek Watersheds
03-07-03 Ararat River Watershed
03-07-04 Muddy Creek, Grants Creek and High Rock Reservoir
03-07-05 Dutchman Creek Watershed
03-07-06 South Yadkin River Watershed
03-07-07 Abbotts Creek Watershed
03-07-08 Yadkin River below High Rock Dam (Narrows Reservoir)
For this review, only sediment and turbidity issues are discussed for each of these basins.
Upper Yadkin River
The Upper Yadkin River and Kerr Scott Reservoir drainage encompasses the head waters of the Yadkin
River in the Blue Ridge and Piedmont physiographic provinces. This basin has a total area of 830 sq.
mi., has a population density of 76 persons per sq. mi. and the majority of its land cover is forest or
wetland (81 percent). Urban land cover is only 0.6 percent of the watershed.
The results of the AMP indicate that elevated turbidity values have been recorded at two locations on
the Yadkin River (NC 268 and SR2327). Only one stream in this basin, an unnamed tributary to
Mulberry Creek, is included in the State's 303(d) list of impaired waters and that was unrelated to
sediment and turbidity.
Mitchell River, Fisher River and Deep Creek Watersheds
The Mitchell River, Fisher River and Deep Creek watersheds drainage an 822 sq. mi. area that has a
population density of 111 persons per sq. mi. with the majority of its land cover as forest/wetland (59.4
percent) and pasture (32.2 percent). Urban land cover is only 1.2 percent of the watershed.
Elevated turbidity values have been reported for the Little Yadkin River and at three locations along the
Yadkin River (SR 1605, SR 1003 and US 158) as part of the AMP. No waters in this sub basin are
included on the State's draft 2002 303(d) list.
Ararat River Watershed
The Ararat River watershed drains part of southern Virginia and North Carolina. It includes 198 sq. mi.
of land having a population density of 183 persons per sq. mi.. The majority of the land cover in this
sub basin is either forest/wetland (59.1 percent) and pasture (32.7 percent). Urban land cover is 3.0
percent of the watershed.
Results of the AMP and the YPDRBAM indicate that elevated turbidity levels have been documented at
two locations on the Ararat River (SR 2080 and SR 2044). Currently, portions of two streams in this sub
basin, the Ararat River and Faulkner Creek, are included on the State's draft 303(d) list as impaired
waters due to sediment problems.
Muddy Creek, Grants Creek and High Rock Reservoir
This sub basin is located entirely within the Piedmont physiographic province in North Carolina. It
drains a total area of 730 sq. mi. having a population density of 461 persons per sq. mi.. Land cover is
predominantly forest/wetland (55.9 percent) and pasture (31.7 percent). Located within this sub basin is
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Winston-Salem and as a result the amount of urban land cover (6.0 percent) is higher than in the
preceding sub basins.
The majority of the waters within this sub basin exhibit some level of impacts to water quality.
Turbidity has been identified during the AMP and YPDRBAM as an issue on the Yadkin River at two
locations (NC 150 and US 64), Grants Creek (near its mouth), Muddy Creek (SR1485) and in the
Abbotts Creek Arm of High Rock Reservoir (NC 47 and SR 2295). Portions of two streams, Salem
Creek and Grants Creek, are included on the State's draft 303(d) impaired waters list for turbidity.
Dutchman Creek Watershed
With a drainage area of 130 sq. mi. this sub basin is the smallest of the seven located within the Yadkin
Project basin. The population density in this sub basin is 91 persons per sq. mi. while the principal land
covers are forest/wetland (56.8 percent) and pasture (35.1 percent) along with cultivated cropland (5.5
percent).
Water quality is generally good to fair throughout this sub basin, although many streams are small and
have not been monitored. Elevated turbidity values have been recorded on Dutchman Creek as part of
the YPDRBAM and sedimentation has been noted as a problem in this drainage. As noted in the BWQP
(NCDNR 2003) no waters in this sub basin are included in the State's draft 2002 303(d) list.
South Yadkin River Watershed
The South Yadkin River watershed includes a 907 sq. mi. area. The population density of this area is
104 persons per sq. mi. and the principal land use cover is forest/wetland (54 percent) and pasture (38
percent) with some cultivated cropland (6.2 percent).
The BWQP (NCDNR 2003) states that the water quality in this watershed cannot be generalized
because of the wide variation in conditions between sub basins and within sub basins. Elevated
turbidity values have been recorded on several streams within this watershed. The AMP has noted
elevated turbidity values on the South Yadkin River (SR 1159) and Fourth Creek (SR 2308), while the
YPDRBAM has recorded elevated turbidities on the South Yadkin River (US 601), Fourth Creek (SR
2308) and Second Creek (US 601). Due to the turbidity problems, Fourth Creek is included on the
State's draft 2002 303(d) impairment list.
Abbotts Creek Watershed
The Abbotts Creek Watershed encompasses 237 sq. mi. and discharges into High Rock Reservoir, the
uppermost reservoir of the Yadkin Project. This watershed includes the population centers Lexington,
Thomasville and High Point which is reflecting in its high population density of 428 persons per sq. mi.
The majority of the land cover is forest/wetland (56.5 percent) and pasture (31.8 percent) with a
considerable amount of urban development (7.8 percent).
The water quality in the majority of the waters within this sub basin exhibit some level of impact. The
results of the various water monitoring programs in the sub basin have identified turbidity as a problem
in the Rich Fork (SR 2123). The BWQP (NCDNR 2003) notes that two streams, Brushy Creek and
Hamby Creek, are included on the State's draft 2002 303(d) list due to impairment due to sedimentation.
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Yadkin Pee Dee River below High Rock Dam
This sub basin includes the Yadkin-Pee Dee River below High Rock Dam, Lick Creek, Narrows
Reservoir, Mountain Creek and Tillery. Relative to the Yadkin Project this sub basin includes
Tuckertown Reservoir, Narrows Reservoir and Falls Reservoir. The total area within this watershed is
294 sq. mi.. This area is relatively undeveloped with a population density of 68 persons per sq. mi..
The majority of land cover is forest/wetland (67.9 percent) and pasture (20.9 percent) and little urban
development (0.8 percent).
Overall the water quality in this sub basin is considered generally good. Although three of these sub
basins streams are included on the State's draft 2002 303(d) list, none have been included due to
sediment or turbidity issues.
In Section C, the BWQP (NCDNR 2003) reviews the current water quality initiatives underway in the
Yadkin-Pee Dee River basin. It is noted that sedimentation and streambank erosion are two of the
important water quality issues identified basinwide. To address these problems participants in five
workshops held on the basin planning initiative recommended: better management of stormwater from
developed areas, more enforcement of sediment/erosion control laws and ordinances and the widespread
implementation of voluntary best management practices.
The BWQP then discusses the existing federal, state, regional and local initiatives in place to address
water quality issues and also provides an overview of future water quality initiatives. One of the most
important existing programs is the Agricultural Sediment Initiative (ASI). Beginning in 2000, the NC
Association of Soil and Water Conservation Districts and the NC Soil and Water Conservation
Commission started an effort to assess stream channels and watersheds of streams on the State's 2000
303(d) list due to sediment where agriculture was included as a potential source. The primary objective
of the ASI was to assess the severity of sedimentation in the Yadkin-Pee Dee River watershed so that
local strategies could be developed to address sedimentation problems (NCDNR 2003). A number of
drainages within the Yadkin Project basin were identified for significant restoration and protection work
including: Fourth Creek, Brushy Fork, the Ararat River and Faulkner Creek.
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4 QUANTITATIVE SEDIMENT TRANSPORT AND SEDIMENTATION DATA
In this section the quantitative sediment transport and sedimentation data that is presented in the
numerous papers discussed in the literature review are summarized for comparison and discussion. In
addition to the data extracted from the literature review, data developed throughout the history of the
Yadkin Project can also illustrate sediment deposition within the Yadkin Project. This section also
presents this additional data, the methods used to calculate deposition, and where possible, compares the
sediment deposition based upon the various sources.
4.1 SEDIMENT TRANSPORT
All of the quantitative data on sediment transport for the Yadkin-Pee Dee River from Kerr-Scott
Reservoir to the USGS gage station a Rockingham, NC has been extracted from the literature reviewed
in Section 3 of this report and is summarized in Table 4-1. The bedload and suspended sediment data
for all reservoirs were taken from tables in "Erosion and Sediment Inventory for the Yadkin-Pee Dee
River Basin in North and South Carolina" [USDA, 1979]. The suspended sediment load for each of the
four USGS gage stations and the estimated sediment density used to convert the sediment data presented
in Table 4-1 to ac-ft per year are from "A Suspended Sediment Budget for Six River Impoundments on
the Yadkin-Pee Dee River" [Fischer 1993]. Table 4-1 also depicts the relative locations of major
reservoirs and gage stations along the Yadkin-Pee Dee River and their drainage basin areas.
While the sediment transport data from the two sources is not directly comparable because the two
studies do not provide estimates at any common locations, the data from the two sources appears to be
relatively consistent. Average annual sediment load increases from upstream to downstream except at
the reservoirs where a significant portion of the sediment is trapped. At High Rock Reservoir, the
sediment transport entering the reservoir is estimated at 1,049 ac-ft per year (bedload plus suspended
sediment) and downstream of Blewett Falls Dam the sediment transport leaving the reservoir is 141 ac-
s per year.
4.2 SEDIMENTATION VOLUME
With regard to sedimentation, the USDA study provides an estimate of the amount of sediment trapped
in each reservoir in the Yadkin-Pee Dee River. This data is also summarized in Table 4-1 and reflects
that the reservoirs trap 100 percent of the river's bedload and from 40 to 90 percent of the suspended
sediment load. As seen in Table 4-1, the reservoir with the highest annual sediment accumulation is
High Rock Reservoir. The reservoirs with the highest percent of sediment remaining in the reservoir are
Kerr Scott, Narrows, and High Rock reservoirs.
Additional detail regarding sediment deposition in High Rock Reservoir is provided by several
topographic and bathymetric surveys performed by the Yadkin Project at various times since 1917. The
first survey was performed in 1917 prior to the construction of High Rock Dam and is documented on a
set of 79 Tallassee Power Co. maps entitled "Topography and Property Survey - High Rock Basin."
These maps depict the pre-impoundment topography of Yadkin River Basin from the confluence of the
Yadkin/South Yadkin rivers downstream to the proposed location of High Rock Dam. A second
topographic survey was performed in 1997, documenting the topography around High Rock Reservoir
from 12 feet below normal full pool outwards to approximately one quarter mile beyond
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Table 4-1. Comparison of USDA Sediment Analysis and USGS Sediment Measurements
UDSA Analysis' USGS z
Measurements
Location of

Reservoir or USGS
Gage Station
Drainage Area

sq mi Entering/

Exiting
Reservoir

Bedload
t/ r
y
ac-ft/yr
Suspended

Sediment , ac-ft/yr
and % Suspended
Sediment Retained
Sediment Remaining in

Reservoir
(Bedload plus a portion of
Suspended Sediment)
ac-ft/ r

Suspended Sediment

ac-ft/yr
Kerr Scott Reservoir 350 entering 19 78 (87%) 88
exiting 0 10
Yadkin College Gage 2280 561
S. Yadkin Gage 306 (tributary) 67
High Rock Reservoir 3,973 entering 218 870 (79%) 903
exiting 0 185
Tuckertown Reservoir 4,080 entering 16 248 (54%) 151
exiting 0 113
Narrows Reservoir 4,180 entering 9 149 (82%) 131
exiting 0 27
Falls Reservoir 4,190 entering 1 32 (41%) 14
exiting 0 19
Tillery Reservoir 4,600 entering 28 129 (67%) 115
exiting 0 42
Rocky River Gage 1372 (tributary) 138
Blewett Falls Reservoir 6,839 entering 33 171 (67%) 141
exiting 0 57
Rockingham Gage 6,863 292
Notes:
i Reservoir sedimentation data from Tables V to VII of the "Erosion and Sediment Inventory for the Yadkin-Pee Dee River Basin in North and South Carolina" (USDA
1979), Appendix A. The data was converted from tons/yr to ac-ft/yr using a density of 70.05 lbs/cu ft.
z Gage Station suspended sediment values and the estimate of sediment density at 72.7 lbs/cu ft from "A Suspended Sediment Budget for Six River Impoundments on the
Yadkin-Pee Dee River" (Fischer 1993). Values for suspended sediment at High Rock and Blewett have been estimated for this report by factoring the measured data as a function of
contributing drainage basin area.
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full pond contours. Continental Aerial Survey, Inc. (CAS) performed the aerial survey and prepared
topographic maps with contours at 2 ft intervals.
Sedimentation Estimates Based on Surveys
A storage versus elevation curve for High Rock Reservoir was prepared at the construction of High
Rock Dam based on the 1917 topographic survey. This curve shows the original 1917 storage-
elevation relationship for elevations between 588.9 ft and 633.9 ft USGS. Following the 1997 aerial
survey of High Rock Reservoir, the elevation-storage curve was revised to reflect the observed
sediment deposition in the upper 12 feet. The digital topographic data was used to calculate surface
areas at each 2-ft contour interval and a new storage volume was determined. The difference in
storage volume between the original curve and the revised 1997 curve is 14,919 ac-ft, reflecting the
deposition of sediment in that amount in the upper 12 ft of High Rock Reservoir between 1918 and
1997. This 14,919 ac-ft represents a loss of reservoir storage capacity of approximately 6 percent
over 80 years, an average of 186 ac-ft/yr. While this is not directly comparable to the 903 ac-ft per
year (1,049 ac-ft per year incoming minus 178 ac-ft per year released) total annual sedimentation
estimated by the USDA, it is not inconsistent with that estimate.
4.3 SEDIMENTATION PATTERNS
Detail regarding High Rock Reservoir sedimentation patterns is provided by the 1917 and 1997
surveys. To illustrate sediment deposition patterns in High Rock Reservoir, the 1917 topographic
maps showing the initial bathymetry of High Rock Reservoir and the 1997 bathymetry have been
shaded to reflect reservoir water depths greater than and less than 10 ft. These maps, presented in
Figures 4-1 through 4-6 in Section 7, show the area from Abbots Creek upstream to the confluence of
the Yadkin and South Yadkin rivers. A comparison of the 1917 and 1997 figures reveals the pattern
of sediment deposition during that period. In 1917, the area of the reservoir with water depths greater
than 10 ft, denoted by red shading, includes the majority of the reservoir from High Rock Dam
upstream to the confluence of the Yadkin and South Yadkin rivers. In 1997, while water depths of
greater than 10 ft still extend upstream to the confluence of the Yadkin and South Yadkin rivers, these
depths occur in a narrow channel, reflecting sediment deposition from Swearing Creek to the I-85
bridge. A comparison of the 1997 bathymetry (Figures 4-1 through 4-3 in Section 7) and the original
1917 bathymetry (Figures 4-4 through 4-6 in Section 7) shows the following trends in reservoir
depths:
A comparison of Figure 4-1 with Figure 4-4 (Section 7) reveals that from Abbots
Creek to Crane Creek, the area of the reservoir with water depths greater than 10 feet,
as depicted in red, is similar in 1917 and 1997.
• A comparison of Figure 4-2 with Figure 4-5 (Section 7) reveals that:
¦ From Swearing Creek to just downstream of I-85, the reservoir area that was
greater than 10 ft deep (depicted in red) in 1917 was less than 10 ft deep
(depicted in pink) in 1997, indicating that reservoir water depths have
decreased.
¦ Sedimentation in the bend upstream of Swearing Creek has shifted the
deepest portion of the reservoir (in red) to the west shoreline.
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From the Yadkin/South Yadkin river confluence to just downstream of the I-85 bridge,
reservoir depths have remained greater than 10 feet in the center of the stream channel
and less than 10 feet in the remaining stream channel. The deepest portion of the river
has narrowed.
• A comparison of the outline of High Rock Reservoir at full pond reveals no substantial
change in the shoreline between the 1917 survey and the 1997 survey. That is, if the
current reservoir outline is laid over the 1917 outline, very little difference in the
reservoir shape is evident.
4.4 EFFECTS OF SEDIMENT ON HABITAT
The preceding review of the literature turned up very little information, data or studies on the effects
of sedimentation on aquatic habitats in the Yadkin Project reservoirs. However, as part of the
relicensing effort, APGI has been conducting a number of studies of the Project reservoirs, including
studies of aquatic habitats and wetlands. Specifically, the Wetland and Riparian Habitat Study is
examining the distribution of wetlands and other important habitats throughout the Project reservoirs.
Based on earlier mapping of wetlands done at the Project (Yadkin Inc., 1999), it is clear that some of
the largest and most abundant wetlands on High Rock Reservoir are in the upper end of the reservoir
and appear to have developed over time on sand bars and other sediment deposits. A more detailed
analysis of these wetlands and the ongoing contribution that sediment may be having on their
development will be discussed in the Wetland and Riparian Habitat Study Report.
Another study being conducted as part of the ongoing relicensing process, the Reservoir Fish and
Aquatic Habitat Assessment will also provide some insight into the potential effects of sediments on
fish habitats. As part of this study, NAI has mapped aquatic habitats throughout much of High Rock
and Narrows reservoirs littoral zones. A key feature of the aquatic habitat maps will be the
breakdown of habitats by general substrate types. This information will lend additional
understanding to the patterns of sediment deposition within the reservoirs and how sediment may be
impacting aquatic habitats.
4.5 EFFECTS OF SEDIMENT ON MUNICIPAL WATER SUPPLY INTAKES
There are four municipal water supply intakes located within the Yadkin Project. Salisbury-Rowan
Utilities (SRU) operates a water supply intake located in the upper, riverine portion of High Rock,
just upstream of the confluence of the Yadkin and South Yadkin rivers. The City of Albemarle
operates intakes located on Tuckertown and Narrows reservoirs, and the City of Denton operates an
intake located on Tuckertown Reservoir.
The literature review discussed previously in this report indicates that a majority of the sediment
passes down the river during periods of high inflow associated with both spring runoff and summer
thunderstorms. In terms of total volume, the highest amount of sediment occurs during the spring and
in terms of concentration, the highest concentration occurs during summer storm events.
In a report entitled "Review of January 1998 Flood of Yadkin River" that was prepared by Stone and
Webster Engineering, it was determined that the High Rock Reservoir elevation has little impact on
water surface elevations at the Salisbury intake during periods of high flow. For river flows between
10,000 and 40,000 cfs at the confluence of the Yadkin and South Yadkin rivers, the range of increase
in elevation at the intake, based on High Rock Reservoir elevation, varies from 0.50 ft to 0.07 ft,
decreasing with increased flows. The report indicates this section of the Yadkin River behaves in a
riverme manner during these periods with associated high flow velocities which carry most of the
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suspended sediment into the reservoir downstream of the I-85 bridges. Thus, the majority of the
sediment load in the vicinity of the SRU intake passes by as suspended sediment in the water, and is
unaffected by the operation of High Rock Reservoir.
According to SRU, suspended sediment in the river water can adversely affect the operation of the
pumping system, increase system maintenance, and generally increase the cost of water processing.
SRU indicates some sediment can also become deposited in the vicinity of the river intake structures
and can affect these facilities. Recent discussions with SRU indicate the pump station has a sediment
pumping system to control accumulation of sediment in the wet well of the pump station. SRU also
indicates periodic dredging of sediment around the intakes has been effective in reducing clogging
due to sediment deposition. A dredging operation exists in the area and has been beneficial to removal
of sediment in the area of the intakes.
The municipal water supply intakes located on Tuckertown and Narrows reservoirs benefit from the
High Rock Reservoir which traps much of the suspended sediment in the upper end of the Reservoir.
The preceding literature review indicates that as much as 70 to 80% of the incoming sediment to High
Rock is retained within the Reservoir. As a result, these facilities are generally much less affected by
sedimentation during periods of normal flow conditions.
5 SYNTHESIS OF PREVIOUS INVESTIGATIONS
The preceding review of the literature on sediment in parts of the Yadkin-Pee Dee River basin shows
that a significant amount of research has been performed on this important subject. As discussed in
the reports and articles reviewed, the input of sediment, its transport or output and its storage are
dependent upon both natural conditions such as regional geology, hydrology and soils along with
man's alteration of the landscape by development. The input, output and storage of sediment within
the Yadkin-Pee Dee River basin has been shown to vary both spatially and temporally in response to
changes in both naturally occurring and imposed conditions. An understanding of the relationship
between the naturally occurring conditions along with the potential impacts associated with any
imposed changes (naturally or by man's actions) within the basin is essential in order to place the
sediment issue into context.
5.1 EROSION
The inputs of sediment to the Yadkin-Pee Dee River include soil erosion, streambank and channel
erosion and urban runoff. As discussed in the reviewed literature, the main source of sediment in the
Yadkin-Pee Dee River is soil erosion. The rates of soil erosion within the Yadkin-Pee Dee River
basin vary in response to the type of soil material and land use. In general, the soils found in the
Piedmont physiographic province are typically fine grained (silt) and can be readily eroded when
exposed to wind and water. Other natural factors contributing to the erosion of these soils include the
humid climate and topographic relief found within the Piedmont physiographic province. The
combination of these factors together with land use results in some of the highest erosion rates and
sediment yields in North Carolina (Simmons 1993), the Atlantic Coast drainages (Meade 1982) and
the United States (Renwick 1996).
In its inventory of soil erosion in the Yadkin-Pee Dee River Basin, the USDA (1979), estimated that
the average annual soil erosion is 3.9 tons/acre or roughly 2,500 tons/sq. mi./year. In this analysis
those counties having the greatest concentration of croplands also had the highest estimated erosion
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rates. Though estimates of the relative contribution to total erosion by croplands varies among the
studies, they generally agree that croplands are significant producers of sediment due to the
disturbance of the ground surface by tilling and because of the sheet and rill erosion produced by
runoff.
Simmons (1993) found in his analysis of suspended sediment data for North Carolina that the basins
located in the Piedmont physiographic province produced the highest sediment yields. He notes that
that "the effects of intense rains combined with the province's steep gradients and highly erodable
clayey soils produced some of the State's highest concentrations of fluvial sediment observed during
this study." In his analysis of sediment yield and land use he found that the highest sediment yields
were from those basins having a significant amount of land in urban use, 464 tons/sq. mi., followed
by those rural basins with agricultural and non-agricultural land use, 209 tons/sq. mi. In the Piedmont
physiographic province these values were slightly higher, 527 tons/sq. mi. for urban basins and 302
tons for rural basins with agricultural and non-agricultural land use. The high sediment production
from urban basins is thought to be related to runoff generated from impervious cover and stream
channel erosion. Simmons (1993) estimates are significantly lower than the USDA's (1979) because
his are based on suspended sediment concentration data, which represents the portion of eroded
material that is actually being transported by streams and rivers.
The studies performed by Richter and others (1995), Henkels (2000) and Norwood (2001) further
examined the impact of land use on sediment production and how land use has changed over time.
Overall, these studies have shown that since the early 1900s the amount of land used for agricultural
purposes has declined. The decline in agricultural land use has also resulted in a decline in soil
erosion and sediment production. Richter and others (1995) documented that cropland in the Yadkin
River Basin (above Yadkin College) has decreased from 45 percent to 18 percent of the land area
since the 1930s. In response to this decline, the estimated gross erosion in the basin, between the
1950s and 1980s, has decreased by 17 percent (Richter and others 1995). Norwood (2001) extended
this analysis to the period 1951 to 2000, and found these land use trends are continuing. With the
decline in cropland as a percentage of the basin area there was an associated decline in sediment in
the Yadkin River.
Henkels (2000) analyzed change in water quality and quantity in the drainages of the Ararat, and
Mitchell Rivers and Muddy Creek, tributaries to the Yadkin River. As part of this analysis Henkels
(2000) looked at the changes in land use over a ten year period (1982 to 1992). He found that in the
combined Ararat and Mitchell River basin the percentage of cropland had decreased by 12 percent,
while in the Muddy Creek drainage it had decreased by five percent. In these drainages urban land
use increased by two percent and eight percent, respectively. Although Henkels (2000) did not find
any significant time trends in water quality or quantity he did note that turbidity values for Muddy
Creek were significantly greater than for the Ararat River. He explained this difference as being
reflective of the greater amount of urbanization in the Muddy Creek basin.
The majority of the authors of the publications reviewed concluded that the decline in agricultural
land use for crop production has resulted in a substantial decline in soil erosion and sediment input to
the Yadkin River. They also note that for those lands remaining in agricultural use soil erosion can be
further reduced by implementing best management practices. This conclusion is supported by the
results of a study performed by the USGS in northeastern Guilford County, North Carolina (Hill
1991). For the two test areas monitored, the area in which BMPs were employed had sediment yields
about one seventh of the area where standard management practices were employed.
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Overall the findings of the reviewed research appear to reach the same conclusion that the decline in
land use for cropland has led to a decrease in gross erosion and sediment yield. Several of the authors
also note that increasing development and urbanization may be causing a recent increase in sediment
input to the Yadkin-Pee Dee River and may in the long run exceed the reductions associated with
decreased cropland. The benefits associated with implementation of BMPs may not be measurable for
some time due to the time lag between land use changes and the basin's response. As shown in the
research performed by the USGS in Charlotte, North Carolina (Bales and others 1999) development
can result in increased runoff, higher soil erosion and sediment transport. Recognizing this trend in
its Basinwide Water Quality Plan (NCDNR 2003) for the Yadkin-Pee Dee River, the NCDNR
emphasized the need for the continued implementation of appropriate BMPs to reduce this growing
source of sediment.
5.2 SEDIMENT TRANSPORT
Several of the articles and reports reviewed evaluated sediment transport in parts of the Yadkin-Pee
Dee River basin. These studies included an analysis of the relationship of sediment transport with
land use, how these variables have changed overtime and what other basin characteristics might
affect sediment transport. The principal studies of sediment transport included those by Harried and
Meyer (1983), Simmons (1993), Richter and others (1995) and Norwood (2001).
Harried and Meyer's (1983) study of the water quality of the Yadkin-Pee Dee River provided an
overview of the transport of suspended sediment through the basin. The highest concentrations of
suspended sediment were found in the Yadkin River at Yadkin College (158 mg/L) with slightly
lower concentrations in the Rocky River at Norwood (149 mg/L) and much lower concentrations
were observed in the Pee Dee River near Rockingham (33 mg/L). The significant decline in the
concentration of suspended sediment between Yadkin College and Rockingham is due to the
deposition of sediment in the six reservoirs between these stations. As part of their study, Harried and
Meyers (1983) also evaluated the relationship between discharge and suspended sediment. They
found that suspended sediment concentrations increase with increasing discharge. At the Yadkin
College gaging station suspended sediment concentrations appear to plateau at discharges greater than
7,500 cfs, which suggests that at these flows sediment transport becomes supply limited - that is, the
ability of the river to transport sediment is greater than the sediment available to it. At the
Rockingham gaging station the suspended sediment data cluster into two groups at low flow and high
flow. This distribution is most likely the result of the operations of the hydroelectric facilities
upstream.
Simmons (1993) examined several factors that influence sediment production and transport. In
addition to his detailed analysis of the relationship between land use and sediment yield (see previous
section) he also examined the influence of stream discharge and particle size on sediment transport
and developed mathematical relationships to estimate suspended-sediment transport from drainage
basins. The relationship between stream discharge and suspended-sediment transport is direct,
meaning that the more discharge the greater the suspended-sediment concentration and load. Also, the
maximum suspended-sediment concentrations were typically found to occur just prior to the
maximum flow during a runoff event for approximately 80 percent of the gaging stations.
Simmons (1979) also examined the frequency of flows required to transport suspended-sediment
through selected drainages in North Carolina. For the Yadkin River and the South Yadkin River, he
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estimated that 50 percent of the total suspended-sediment transported in these drainages occurred over
just 2.5 percent of the total time (92 days) during the 10 year period (1970-1979). This result is
supported by Richter and others (1995) who determined that in the Yadkin-Pee Dee River 26 percent
of total suspended sediment is transported at flows of less than 1 percent exceedance and 71 percent
of total suspended sediment is transported at flows of less than 10 percent exceedance. This means
that the bulk of the suspended sediment is transported during fairly infrequent storm events. During
these events Simmons also found that in the Piedmont physiographic province the size of the
suspended-sediment particles were typically silt and clay, which reflects the texture of the soils in this
region.
The change in sediment transport over time was examined by several of the authors. The most
comprehensive assessment of this was performed by Richter and others (1995). Through a linear
regression analysis of the 40 year (1951-1990) discharge and suspended sediment records for the
Yadkin College gage these researchers found that the transport of suspended sediment in the Yadkin
River basin had decreased approximately 30 percent. The suspected reason for the decline in
suspended sediment transport is believed to be associated with a significant decline in the amount of
cropland in the basin. Norwood's (2001) update of this work confirmed the decline in suspended
sediment concentrations and showed that this trend had continued through to 2000. She also noted
that the amount of cropland within the basin had also continued to decline, but that there was an
increase in urban land use which may represent a new source of sediment to the Yadkin River, though
this may not be observed for some time due to the time lag between land use changes and the basin's
response.
While the source of sediment entering the reservoirs is clearly from upstream sources, the
determination that the majority of the total suspended-sediment transported occurs during the very
high flow events suggests that the mode of reservoir operation may have an impact on sediment
transport through the river basin. Reservoirs that operate as run-of-river would tend to pass the higher
flow events and the suspended sediment load that is transported with them. In contrast, reservoirs
such as High Rock that operate as store-and-release reservoirs store the majority of the inflows during
high flow events, slowing transport of the sediment suspended within. The entrapment of a
significant portion of the sediment load entering the reservoir system provides benefits to the lower
river, which experiences far less sedimentation and turbidity. Moreover, the volume of sediment
being trapped in High Rock Reservoir is estimated at less than one-half of one percent of the total
reservoir volume annually.
5.3 SEDIMENTATION
The storage of sediment in the basin naturally occurs within its streams and rivers and on their
associated floodplains. The construction of the dams and the operation of their associated reservoirs
on the Yadkin-Pee Dee River has had an impact on the transport of sediment through the lower
portion of the basin. The impoundment of water by High Rock, Tuckertown, Narrows, Falls, Tillery
and Blewett Falls dams and the resulting reduction in water velocity at each reservoir have reduced
the capacity of the Yadkin - Pee Dee River to transport its sediment, thereby leading to its deposition
in each of the six impoundments.
The amount of sediment deposited in the reservoirs depends upon the amount of sediment supplied
and the storage or residence time of the water in the impoundment. In the studies performed by the
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USDA (1979), Harried and Meyer (1983), Simmons (1993) and Fischer (1993) they estimated the
amount of sediment accumulated in the impoundments. In the USDA (1979) report (Table VI in
Appendix A) the annual sediment accumulation in the Yadkin Project reservoirs ranged from
1,354,500 tons/year (903 ac.ft./yr) for High Rock Reservoir to 21,000 tons/year (14 ac. ft./yr) at Falls
Reservoir, while the estimated annual loss in total storage capacity ranged from 0.36 percent in High
Rock Reservoir to 0.05 percent in Narrows Reservoir. The lower capacity loss for Narrows Reservoir
is due to the reduction in sediment transport by its accumulation in High Rock Reservoir.
Harried and Meyer (1983) noted that the suspended sediment load at the Yadkin College USGS gage
is significantly higher than that reported for the USGS gage in Rockingham. The difference in
suspended sediment concentrations between these two stations was assumed to be the result of the
deposition of sediment in the six impoundments on the Yadkin-Pee Dee River. Based on these data
they estimated that about 73 percent of the suspended sediment transported by the Yadkin-Pee Dee
River is retained by the six reservoirs. This equates to approximately one million tons of sediment
being deposited into the reservoirs each year. Volumetrically, this represents about 800 ac.ft./year or
0.10 percent of the total volume of the Reservoirs. Simmons (1993) did not provide an estimate for
sediment accumulation in any of the Yadkin Project reservoirs.
Fischer (1993) estimated the total amount of sediment accumulating in six of the reservoirs (High
Rock, Tuckertown, Narrows, Falls, Tillery and Blewett Falls) by taking the difference between the
amount of sediment flowing into and out of the reservoirs. The difference between sediment input
and output was 1,342,847 tons or about 78 percent of the total suspended load. If the bedload is
considered, the total amount of sediment deposited in the reservoirs would increase to 2,268,000
tons/year or 85 percent of the total sediment load.
The authors note that estimating the sedimentation rates in the reservoirs is partly hindered by the
lack of measured bedload. Fischer's (1993) estimate of sedimentation in the reservoirs is based on
published values in the literature as opposed to the results of direct measurements in the Yadkin-Pee
Dee River. Thus, sedimentation is probably underestimated in the majority of these analyses. The
greatest impact would be in the estimation of the rate of sedimentation in High Rock Reservoir, where
most of the bedload would be expected to be deposited.
The analysis of the survey data available for High Rock Reservoir reveals that sedimentation has
occurred since the construction of the dam in 1917. The bathymetry of the reservoir shows that
sediment has accumulated in the upstream areas of the reservoir between the I-85 bridge and Crane
Creek. The effect of 80 years of sediment accumulation has been quantified as a reduction of
approximately 6 percent of total usable storage capacity in the upper 12 feet of the reservoir.
As mentioned in the previous sections, changes in land use within the watershed have had an effect
on the input of sediment to the Yadkin-Pee Dee River and on the amount of sediment deposited in the
Yadkin Project reservoirs. Although the decrease in cropland in the basin has resulted in a decline in
sediment transport in the river, continued land development may represent a growing source of
sediment. Only with the continued basinwide implementation and enforcement of appropriate BMPs
and stormwater regulations will reduce the input, transport and deposition of sediment in the Yadkin
Basin continue to decline. Ultimately, the benefits of these actions will include the improvement of
water quality and aquatic habitat in the basins waters.
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6 REFERENCES
Alcoa Power Generating, Inc. (Alcoa) 2002. Yadkin Hydroelectric Project FERC No. 2197 NC
Project Relicensing Initial Consultation Document. Yadkin Division, Badin, North Carolina.
Bales, J., Weaver, J.C. and J.B. Robinson 1999. Relation of Land Use to Streamflow and Water
Quality at Selected Site in the City of Charlotte and Mecklenburg County, North Carolina,
1993-98. U.S. Geological Survey Water Resources Investigations Report 99-4180. Prepared
in Cooperation with the City of Charlotte and Mecklenburg County. p. 95.
Brune, G.M. 1953. Trap Efficiency of Reservoirs. Transactions of the American Geophysical Union.
Vo. 34, No. 3.
Calvo-Alvarado, J.C. and J.D. Gregory 1997. Predicting Mean Annual Runoff and Suspended
Sediment Yield in Rural Watersheds in North Carolina. Water Resources Research Institute
of the University of North Carolina Report No. 307. p. 134.
Carpenter, B., Jackson, S. and H. Taylor-Guevara 2002. A River in Jeopardy: The Yadkin and Pee
Dee Rivers of North Carolina. Clean Water for North Carolina. p. 25.
Fischer, V.D. 1993. A Suspended Sediment Budget for Six River Impoundments on the Yadkin-Pee
Dee River. Master's Project. School of the Environment, Duke University. p. 21.
Harried, D. and D. Meyer 1983. Water Quality of the Yadkin-Pee Dee River System, North Carolina-
Variability, Pollution Loads, and Long Term Trends. Chapter E in Water Quality of North
Carolina Streams. United States Geological Survey Water-Supply Paper 2185-E. Prepared
in Cooperation with the North Carolina Department of Natural and Economic Resources. p.
71.
Henkels, J. 2000. Water Quality and Quantity Trends in Three Sub basins of the Yadkin River Basin,
North Carolina. Unpublished Master's Project. School of the Environment, Duke
University.
Hill, C.L. 1991. Effects of Land-Management Practices on Sediment Yields in Northeastern Guilford
County, North Carolina. U.S. Geological Survey Water-Resources Investigations Report 90-
4127. Prepared in Cooperation with the Guilford Soil and Water Conservation District. p. 40.
Krishnaswamy, J., Lavine, M., Richter, D. and K. Korfinacher, 2000. Dynamic Modeling of Long-
Term Sedimentation in the Yadkin River Basin. Advances in Water Resources, Volume 23,
p. 881-892.
Meade, R.H. 1982. Sources, Sinks, and Storage of River Sediment in the Atlantic Drainage of the
United States. The Journal of Geology. Volume 90, Number 3, p. 235-252.
North Carolina Department of Environmental and Natural Resources (NCDNR) 2003. Yadkin-Pee
Dee River Basinwide Water Quality Plan. Division of Water Quality, Water Quality Section.
p. 311.
Norwood, C. 2001. Changes in Land Use and Water Quality in the Yadkin River Basin.
Unpublished Master's Project. School of the Environment, Duke University.
Renwick, W.H. 1996. Continent-scale Reservoir Sedimentation Patterns in the United States.
Erosion and Sediment Yield: Global and Regional Perspectives. IAHS Publication No. 236.
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Richter, D.D., K. Korfmacher and R. Nau. 1995. Decreases in Yadkin River Basin Sedimentation:
Statistical and Geographic Time-Trend Analyses, 1951 to 1990. Water Resources Research
Institute of the University of North Carolina. Report No. 297.
Simmons, C.E. 1993. Sediment Characteristics of North Carolina Streams, 1970-1979. United States
Geological Survey Water-Supply Paper 2364. p. 84.
1988. Sediment Characteristics of North Carolina Streams, 1970-1979. United States
Geological Survey Open-File Report 87-701. Raleigh, NC.
Simmons, C.E. and R.C. Heath 1979. Water-Quality Characteristics of Streams in Forested and Rural
Areas of North Carolina. United States Geological Survey Water Resources Investigations
79-108. Prepared in Cooperation with the North Carolina Department of Natural Resources
and Community Development. p. 49.
1982. Water-Quality Characteristics of Streams in Forested and
Rural Areas of North Carolina. Chapter B in Water Quality of North Carolina Streams.
United States Geological Survey Water-Supply Paper 2185. p. B 1-1333.
Stone and Webster Engineering Corporation. 1998. Review of January 1998 Flood of Yadkin River.
Trimble, S.W. 1974. Man-Induced Soil Erosion on the Southern Piedmont: 1700-1970. Soil
Conservation Society of America. p. 180.
U.S. Department of Agriculture (USDA) 1979. Special Report: Erosion and Sediment Inventory,
Yadkin - Pee Dee River Basin, North Carolina and South Carolina. USDA Economics,
Statistics and Cooperative Services, Forest Service and Soil Conservation Service
cooperating with the North Carolina Department of Natural Resources and Community
Development and the South Carolina Water Resources Commission.
Yadkin, Inc. 1999. Yadkin Project Shoreline Management Plan.
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7 LIST OF FIGURES
Figure 1 Location Map of Upper Yadkin River and the Yadkin Project ....................... ...................... 44
Figure 4-1 High Rock Reservoir Bathymetry in 1997 - Sheet 1 of 3 ................................ ......................45
Figure 4-2 High Rock Reservoir Bathymetry in 1997 - Sheet 2 of 3 ................................ ...................... 46
Figure 4-3 High Rock Reservoir Bathymetry in 1997 - Sheet 3 of 3 ................................ ...................... 47
Figure 4-4 High Rock Reservoir Bathymetry in 1917 - Sheet 1 of 3 ................................ ...................... 48
Figure 4-5 High Rock Reservoir Bathymetry in 1917 - Sheet 2 of 3 ................................ ...................... 49
Figure 4-6 High Rock Reservoir Bathymetry in 1917 - Sheet 3 of 3 ................................ ...................... 50
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Figure 1 Location Map of Upper Yadkin River and the Yadkin Project
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Water Depth at Full Pond
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APPENDIX A
Figures and Tables
Erosion and Sediment
Inventory for the Yadkin-
Pee Dee River Basin in
North and South Carolina
USDA 1979
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THOLE V: GROSS EROSION BY SUBBASIN
YADKIN-PEE DEE RIVER BASIN
SubbasIn Area Gross. Erosion
Unit Number _......Evaluation Point (ScL ) _ (Tons/Yr.)
t
li
NORTH CAROLINA
03-07-01
Lake ,err-Scott
350.0
539,885
basin outlet 818.5 1.341,515
03-07-02 Deep Creek Watershed 27.9* 100,580*
Little River Watershed 7.1* 19,617*`
basin outlet 1,572.6 3,663,414
03-07-03 Stewarts Creek Watershed 15.5* 45,719*
4?In cut':: 208.2 597,637
03-07-04 Sala.z-: Lake 25.0 80,960
High Rock Lake 701.7 2,171,794
basin outlet 701.7 2,171,794
03-07-05 Dutchman Creek Watershed 29.9* 99,596*
basin outlet 154.4 510,284
03-07-06 Third Creek Watershed 26.6* 85,110*
basin outlet 963.1 3048.511
03-07-07 Lexington-Thomasville Reservoir 70.3 209,663
basin outlet 254.4 699,893
03-07-08 Tucker Town Lake 158.0 336,244
Badin Lake 82.6 182,742
Falls Lake 10.0 21,929
Lake Tillery 108.5 190.051
basin outlet 359.1 730,966
03-07-09 Asheboro City Lake 16.3 20,342
basin outlet 369.4 522.383
63-07-10 Blewett Falls Lake 387.6 495,077
basin outlet 387.6 49"'-+077
03-07-11 Cannon Lake 18.0 57,024
Lake Fisher 16.0 50,680
Concord Lake 4.7 9.956
basin outlet 272.7 573,042
03-07-12 Lake Stewart 34.8 84,673
basin outlet 439.0 1,005,794
03-107-13 basin outlet 319.4 698,070
03-07-14 Lake Monroe' 40.0 88,320
Lake Lee 50.3 11,062
basin outlet 433.1 955,235
03-07-15 basin outlet 346.7 349.032
.03-07-16 Ledbetter Lake 83.0
0 90,304
432
42
Everetts Mill Pond 39. .
basin outlet 310.9 348,646
03-07-17 basin outlet 123.5 159,270
03-07-50 basin outlet 264.3 278,618
03-07-51 basin outlet 529.8 438,142
03-07-52 basin outlet 157.7 180,006
03-07-53 basin outlet 426.9 304,743
03-07-54 basin outlet 217.4 172,307
03-07-55 basin outlets 3 476,788
03-07-56 Lake Waecamaw 61.6
basin outlet 187.4 96.375
03-07=57 basin outlet 579.7 239.317
03-07-58 basin outlet 279.5 141,064
03-07-59 basin outlets 280.7 55.425
SOUTH CAROLINA
?03707-02 - basin outlet 375.5 76,465
03-07-04 basin outlets 101.6 32.784
03-07-06 basin outlet 124.5 21.515
03-07-08 basin outlet 269.8 133,979
03-07-10 basin outlet 533.4 382,093
03-07-12 basin outlet 718.4 834,350
03-07-14 basin outlet 413.0 412,964
03-07-15 basin outlet 125.8 61,967
03-07-16 basin outlet 465.5 229.384
03-07-18 basin outlet 573.2 316,768
03-07-20 basin outlet 361.1 324,861
03-07-22 basin outlet 129.8 94,324
03-07-24 basin outlet 818.0 684,683
03-07-25 Lska Robinso:. 141.0 129,043
basin outlet 478.0 560,410
03-07-26 basin outlet 971.1 1,070,373
03-07-28 basin outlet 366.4 369.558
03-07-30 basin outlet 416.8 532,985
03-07-32 basin outlet 193.0 265,422
03-07-34 Site No. i. Hiiis Creek . 8.4 7,688
basin outlet 356.2 380,208
* Total above all reservo:'rs
SOURCE: SCS River Basin Planning !itaff.
oecember 1979
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= L lU = .Y •- : IV 0 3 0 0 0 43 O 43 L-0 N
01 X U -0 -)G C d; C _lz c .X ,C ?C O 10 = -Y
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O 0
Z y
TABLE VII: SEDIMENT YIELDS, 8EDLOAD AND SUSPENDED, FOR SELECTED POINTS
YADKIN-PEE BEE RIVER BASIN
Average

Location Total Suspended Suspended
Total Sediment
of Sediment Bedload Sediment
. Subbasln Evaluation Tons/Year Tons/Year T
/Y Stream Flow Concentration
ons
ear Tons/Year . Parts Per Million
NORTH CAROLINA
0 -07-0 Kerr-Scott Lake 148,468 29,694 ll0.774 508,374,720 234
Lake outlet
Subbasin outlet 14,847
203,776 -
40,755 14,847
163
021 508,374,720
1
188
870
5
5 29

03-07-02
Deep Creek Watershed , ,
,
,
9 137
(13 sites)*
Deep Creek Watershed 4,023 805 3,219 2,522,304 1,276
(site outlets)*
Little River Watershed 402 - 402 2,522,304 159
(2 sites)*
Little River Watershed 4,512 902 3,610 3,026,765 1,193
(site outlets)*
Subbasin outlet 451
769,057 -
153,811 451
615
246 3,026,765
1
796
687
585 149
4

03-07-03
Stewarts Creek Watershed , ,
,
, 3
2
(1 site)*
Stewarts Creek Watershed 17,373 3,475 13,898 20,261,331 686
(site outlet)*
Subbasln outlet 1,737
156,783 -
31,357 1,737
125
426 20,261,331
271
626
048 86
462
03-07-04 Salem Lake
Lake outl
t 29,146 5,829 ,
23,317 ,
,
28,919,520 806
e
High Rock Lake 11,658
1,659,924 -
331,985 11,658
1,327,939 28,919,520
5,212,454,284 403
255

03-07-05 Lake outlet b subba51n outlet
Dutchman Creek Watershed 282,187 - 282,187 5,212,454,284 54
(7 Sites)*
Dutchman Creek Watershed 6,118 1,224 4,894 4,375,980 1,118
(site outlets)*
Subbasln outlet 612
124,514 -
24,903 612
99,611 4,375,980
120
157
404 140
634
03-07-06 Third Creek Watershed ,
,
(if sites)*
Third Creek Watershed 3,559 712 2,847 2,776,437 1,110
(site outlets)*
Subbasin outlet 356
740,347 -
148,069 356
592,278 2,776,437
1
114
095
588 200
600
03-07-07 Lexington-Thomasville Reservoir 67,092 13,418 53,674 ,
,
,
71
538
630 800
Reservoir outlet
Subbasin outlet 8,051
151.365 -
30,273 8,051
121
092 ,
,
71,538,630
258
882
324 200

03-07-08
Lake Town Lake
403,235
24,210 ,
379,025 ,
,
5,375,116,800 500
70

8"In.Lake 172.844
240.459 -
13.523 172,844
226,936 5,375,116,800
5,453
200
395
432
2
Lake outlet
Falis'Lake 40,878 - 40,878 ,
,
5,453,395,200 7

"take outlet 50.307
28,675 1.886
- 48,421
28
675 5,466.441.600
5:466
44
1
600

Lake Tillery
Lake outlet a subbasin outlet
239.414
64
642
42.148
- .
197,266
64
642 ,
.
,
6.001,344,000
6 5
33

03-07-09
Asheboro City Lake ,
7,730
1,546 ,
6,184 ,001.344,000
16
586
595 11
373
Lake outlet
Subbasin outlet 387
140,420 -
28,084 387
112
336 ,
,
16,586,595
375
908
532 23

03-07-10
elewatt Falls Lake
310,868
49,892 ,
260,976 ,
,
7,960,489
272 299
33

03-07-11 Lake outlet 6 subbasin outlet
Concord Lak 87,043 - 87,043 ,
7.960,489,272 11
e
Lake outlet 4,331
217 866 3,465 4,741,932 731

Lake Fisher
19,512
3,902 217
15,610 4,741,933
16
142
746 .46
967
Lake outlet
Cannon Lake 1,096
21
669
4
334 1,096
1 ,
,
16,142,746 68

Lake outlet ,
1,083 , 7,335
1,083 18,160.589
18
160
589 955
60

03-07-12 Subbasin outlet
Lake Stewart 140,175 28,035 112,140 ,
,
275,132,920 408

Lake outlet 29,636
6
520 5,927 23.709 35,110,472 675

Subbasin outlet ,
379,241
75,848 6,520
303,393 35,110,472
717,948.611 186
423

.? m cn+ROU ? \..? J
2.7
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- I -, J- 15-=-- -r°
=ti= . k -
neuarrw r
CL 112
RYO
FIGURE If AVERAGE ANNUAL %
EROSION RATES
TONS PER ACRE, ALL SOURCES
Yadkin-Pee Dee River Basin
NORTH CAROLINA, 3" CAROM AND VUWWA
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RM.\ WIMM. RMRRNR W v,{
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APPENDIX B
Figures and Tables
Sediment Characteristics
of North Carolina Streams,
1970-1979
Simmons 1993
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Figure 11. Comparisons of mean annual suspended-sediment yields for forested basins with and without minor development.
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Table 9. Estimated trap efficiencies and related information for major reservoirs affecting suspended-sediment sam-
pling sites, 1970-79

ite
number
(fig. 1)

ame Reservoir inflow and storage characteristics
Reservoir Distance Normal Estimated
name upstream capacity' average
from (cubic feet) annual
sampling water
site inflow
(miles) (cubic feet)
Estimated
trap
efficiency'
(percent)
10 Roanoke River at Roanoke Rapids Roanoke Rapids Lake 3 3x109 210x109 52
10 Roanoke River at Roanoke Rapids Lake Gaston 12 22x109 210x109 86
11 Roanoke River near Scotland Neck Lake Gaston 34 22x109 210x109 86
38 Contentnea Creek near Lucama Buckhorn Reservoir 1 69x106 5x109 53
50 Reedy Fork near Gibsonville Lake Brandt 14 290x106 2x109 90
103 Pee Dee River near Rockingham Blewett Falls Reservoir 3 4x109 255x109 60
137 West Fork Pigeon River below
Lake Logan near Waynesville Lake Logan 3 90x106 5x109 58
139 Pigeon River at Canton Lake Logan 11 90x106 5x109 58
147 Nantahala River at Nantahala Nantahala Lake 12 6x109 16x109 95
148 Tuckasegee River at Dillsboro Dillsboro Powerplant 1 Unknown 25x109 Unknown
151 1 iwassee River above Murphy Chatuge Lake 22 10x109 14x109 97
'Capacity at usable storage.
=Es timated from Brune (1953. fig. 6).
10
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WATER
SUSPENDED
SEDIMENT
0
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1978 1979
Figure 21. Streamflow and suspended-sediment concentration for Yadkin River at Yadkin College, October 1978-April 1979.
Table 12. Estimated percentage of time required for higher flows at selected stations to transport
25 and 50 percent of sediment and water during 1970-79
Percentage of time required for higher
flows to transport 2 5 and 50 percent
of suspe nded sedi ment and water
discharge duri ng 1970-79
Drainage
Site area 25 percent 50 percent
number Name (square of total transport of total tra nsport
(fig. 1) miles) Sediment Water Sediment Water
Blue Ridge Province
127 French Broad River at Rosman 67.9 0.2 9 0.7 30
130 Mills River near Mills River 66.7 .2 9 2.0 24
131 French Broad River at Bent Creek 676 .5 7 3.9 22
138 East Fork Pigeon River near Canton 51.5 .2 7 .6 20
143 Watauga River near Sugar Grove 92.1 .4 3 3.0 17
149 Oconaluftee River at Birdtown 184 .2 6 1.5 22
Piedmont Province
4 Dan River near Wentworth 1,053 0.3 4 0.9 17
7 Hyco Creek near Leasburg 45.9 .2 1 .8 6
12 Tar River near Tar River 167 .4 1 1.6 4
25 Eno River near Durham 141 .2 1 .8 6
32 Middle Creek near Clayton 83.5 .8 2 4.5 10
49 Reedy Fork near Oak Ridge 20.6 .1 2 .4 13
55 Cane Creek near Teer 33.7 .4 1 1.5 5
56 Haw River near Bynum 1,277 .3 2 .9 9
61 Deep River at Ramseur 349 .2 1 .7 6
65 Cape Fear River at Lillington 3,464 .7 3 2.2 10
78 Elk River at Elkville 48.1 .1 3 .4 19
81 Yadkin River at Elkin 869 .5 6 2.4 24
93 South Yadkin River near Mocksville 306 .7 3 2.6 17
97 Big Bear Creek near Richfield 55.6 .1 1 .6 4
111 Henry Fork near Henry River 83.2 .1 4 .4 17
122 Second Broad River at C7iffside 220 .1 5 .4 22
Coastal Plain Province
17 Fishing Creek near Enfield 526 0.8 3 3.0 11
18 Tar River at Tarboro 2,183 2.3 4 7.2 13
23 Durham Creek at Edward 26.0 1.5 2 8.1 9
43 Little Contentnea Creek near Farmville 93.3 1.1 3 4.6 8
45 Creeping Swamp [tear Vanceboro 27.0 .4 2 2.4 4
71 Black River near Tomahawk 676 3.9 6 13 18
72 South River near Parkersburg 379 3.4 5 13 16
76 Waccamaw River at Freeland 680 4.2 4 14 15
105 Lumber River at Boardman 1,228 5.5 6 17 20
Table 16. Gross erosion and sediment-delivery ratio values for selected basins
[mi', square mile; tons/yr, tons per year. Predominant land-use symbols: R, rural-agricultural; N, rural
forested with minor development; U, urban; F, forested (pristine))
affected by nonagricultural development; D,
Suspended-
Site
number
Name
Physiographic Drainage
area sediment
discharge Gross
erosion' Sediment.
delivery Predominant
land
(68. 1) province (mil) (tons/yr) (tons/yr) ratio' use
8 Double Creek near Roseville Piedmont 7.47 3,100 22,400 0.14 R
13 Tar River at Louisburg Piedmont 427 30,000 774,000 .03 R
18 Tar River at Tarboro Coastal Plain 2,183 93,000 4,520,000 .02 R
26 Little River near Orange Factory Piedmont 80.4 11,000 144,000 .08 R
27 Flat River at Bahama Piedmont 149 28,000 262,000 .11 R
29 Neuse River near Falls Piedmont 772 140,000 990,000 .14 N
43 Little Contentnea Creek near Farmville Coastal Plain 93.3 3,300 130,000 .03 R
49 Reedy Fork near Oak Ridge Piedmont 20.6 5,200 66,300 .08 R
58 Haw River near Haywood Piedmont 1,689 280,000 1,060
000 .26 N
61 Deep River at Ramseur Piedmont 349 62,000 ,
603,000 .10 R
62 Tick Creek near Mount Vernon Springs Piedmont 15.5 4,200 47
200 09 R
63 Deep River at Moncure Piedmont 1,434 190,000 ,
2,080,000 .
.09 R
64 Buckhorn Creek near Corinth Piedmont 76.3 5,800 41,000 .14 D
65 Cape Fear River near Lillington Piedmont 3,464 420,000 5,710
000 07 R
66 Flat Creek near Inverness Coastal Plain 7.63 460 ,
1,600 .
.29 D
69 Cape Fear River near Kelly Coastal Plain 5,255 290,000 7,040
000 04 R
77 Yadkin River at Patterson Piedmont 28.8 11,000 ,
30,000 .
.37 R
81 Yadkin River at Elkin Piedmont 869 300,000 1,440
000 21 R
95 Leonard Creek near Bethesda Piedmont 5.16 2,000 ,
13
500 .
15 R
99 Lanes Creek near Trinity Piedmont 4.92 1,100 ,
22,400 .
.05 R
101 Rocky River near Norwood Piedmont 1,372 270,000 4,030
000 07 R
108 Lower Creek at Lenoir Piedmont 28.1 18,000 ,
28,400 .
.63 U
110 Long Creek near Paw Creek Piedmont 16.4 7,200 13,900 52 U
113 Long Creek near Bessemer City Piedmont 31.8 11,000 76
600 .
14 R
123 Broad River near Boiling Springs Piedmont 875 340,000 ,
1,070,000 .
32 N
124 First Broad River near Casar Piedmont 60.5 15,000 167
000 09 R
129 French Broad River at Blantyre Blue Ridge 296 78,000 ,
254,000 .
.31 R
135 French Broad River at Marshall Blue Ridge 1,332 670,000 1,860
000 36 N
145 Little Tennessee River at Needmore Blue Ridge 436 110,000 ,
1,120
000 10 N
146 Nantahala River near Rainbow Springs Blue Ridge 51.9 3,000 ,
46,300 .
.06 F
'Waller, E.R., Jr., U.S. Department of Agriculture, Soil Conservation Service, Raleigh, N.C., written commun., 1984.
"Ratio of suspended-sediment discharge to gross erosion.
Table 18. Relations for estimating suspended-sediment discharge from rural-
agricultural and urban basins by soil class (unchannelized basins ranging in size
from 1 to 400 square miles)
[SEDQ, annual suspended-sediment discharge; DA, drainage area; AVGQ, average water discharge;
ROW, percentage of basin's land area in row crops]
Standard
Soil error of
Condition class Regression equation R' estimate
(fig. 4) (percent)
Rural basins
Best 1, 3, 4 SEDQ = 52.9 DA0`01 0.776 74
single 10, 13 SEDQ = 204 DA'M .951 35
variable 11 SEDQ = 279 DA 0.893 .957 25
14 SEDQ = 258 DAO.911 560 66
Best 1, 3, 4 SEDQ = 88.4 DA2-84 AVGQ-2-20 ROW0151 0.823 72
three 10,13 SEDQ = 203 DA"" AVGQO-335 ROWO.0035 ,952 35
variables 11 SEDQ = 31.0 DA23 AVGQ'•1s ROW0.439 966 25
14 SEDQ = 1,980 DA243 AVGQ-137 ROW-U43 .661 65
Urban basins
Best
single 10,13 SEDQ = 671 DAO•909 0.885 46
variable
APPENDIX C
Figure
Sources, Sinks, and Storage
of River Sediment in the
Atlantic Drainage of the
United States
Meade 1982
A

1000
100
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0 00 •
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10 100 1000 10 100 1000
WATER DISCHARGE (m3/s)
FIG. 2.-Relations between daily concentration of suspended sediment and daily mean discharge of water
in rivers draining different physiographic provinces of the Atlantic slope during the 1970 water year. Data
from U.S. Geological Survey (1974, p. 94-95, 143-144; 1975, p. 50-51, 503-504). Seasonal differences are
indicated by open circles (warm season) and dark circles (cool season). A. Juniata River at Newport,
Plennsylvania, in the Valley and Ridge Province; cool season was February through mid-May. B. Merrimack
River at Lowell, Massachusetts, in central New England; cool season was November through mid-June. C.
Yadkin River at Yadkin College, North Carolina, in the southern Piedmont Province; cool season was
Mid-December to mid-May; warm-season data from mid-May through early August only. D. Edisto River
• Gear Givhans, South Carolina, in the southern Coastal Plain; cool season was mid-December to mid-April.
APPENDIX D
Water Quality of North
Carolina Streams, Chapter E:
the Yadkin-Pee Dee River
Harned and Meyer 1983

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APPENDIX E
Decreases in Yadkin River
Basin Sedimentation:
Statistical and Geographic
Time-Trend Analyses, 1951 to 1990
Richter, Korfmacher and Nau 1995
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1 937 1 956 1964 1975 1984 1990
Year of Survey
Rowcrop
Pasture
Forest
Urban/
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Figure 5. General land uses (1937-1990) of the North Carolina Piedmont, based-on six forest
inventories of the U.S. Department of Agriculture Forest Service (Brown, 1991).
1000
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1870
1910
Year
1950
1990
Figure 6. Time trends of land use in the U.S.A's southern Piedmont for major crops of the
Yadkin River basin (1870-1987), based on 20 U.S. Department of Commerce Census
of Agriculture inventories (Bureau of the Census, 1987).
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Figure 13. The association of annual suspended sediment transport and discharge in the Yadkin
River. Sediment transport is illustrated by filled diamonds and discharge by open
squares. ,
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Figure 14. Linear r9gression of annual discharge and sediment transport in the Yadkin River.

bA
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------- ---- ---- -- -----
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Figure 17. Time-ordered residuals of linear regression illustrated in Figure 14 illustrating
significant improvement of 6901 Mg/yr less sediment being transported by the
Yadkin River since 1951.
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Table 7. Distribution of general land use for the 185 sample areas in 1955, 1975, and 1988, and
a comparison with the total basin coverage estimates of land use in 1975. 1955 and
1988 estimates based on aerial photography. 1975 data are from 1:250,000 U.S.G.S.
Land Use/Land Cover (LULC) data. Combined cropland and pasture areas from the
1987 U.S.D.C. Agriculture Census and the 1987 N.R.C.S. Natural Resource Inventory
(NRI) data for Forsyth, Surry, Wilkes, and Yadkin counties are provided for
comparison.
GIS Stratified Sample Total Basin
Land Use 1955 1975 _. 1988 1975
Class km2 % km2 % km2 % km2 %
Urban 12.3 6.63 15.7 8.68 22.1 11.94 461.4 7.82
Agriculture 50.5 27.28 51.8 28.63 43.5 23.27 1798.0 30.50
Forest 110.3 59.60 112.6 62.24 - 4-09.5 59.20 3596.0 60.99
Water 0.6 0.30 0.5 0.28 1.0 0:56 21.2 0.36
Other 11.5 6.22 0.3 0.16 9.3 5.04 19.4 0.33
Total 185.0 181.0 185.0 5896.0
U.S.D.C. U.S.D.C. Agriculture Census N.R.C.S. NRI
Ag Census/ 1954 1974 1987 1987
N.R.C.S. NRI km2 % km2 % km2 % km2
Agriculture 1469 27.50 905 17.05 958... 18.12 1692 31.85
Table 19. Statistical summary of 40-yr daily data of suspended sediment at the Yadkin College,
North Carolina'sampling station in the Yadkin River (1951-1990).
Attribute Log Trans-
formation Daily
Discharge
(m3/s) Suspended Sediment
Concentration Yield
(mg/L) (Mg/d)
Sample size - 14516 14516 14516
Arithmetic mean No 84.68 150.6 2244.5
Mean Nat. Log Yes 4.200 4.340 6.090
Standard deviation No .. 87.210 223.23 7373.1
Standard error No 0.7200 1.850 61.20
Coeff. of variation, % No. 103.0 148.2 328.5
Coeff. of variation, % Yes 15.04 26.2 27.2
14mimum - 9.34 .. 1 .2.72
Lower quartile - 44.46 35 136.1
Median = 62.86 70 367.4
Upper quaitile - 92.60 160 1188A
Upper 10% - 145.00 379 4599.0
Upper 1% - 470.10 1100 37830
Maximum - 1868.92 2970 165,110
Skewness No 5.99 3.64 7.87
Skewness Yes 0.70 0.24. 0.50
Kurtosis No 58.86 19.07 84.30
Kurtosis Yes 1.57 -0.21 0.10
Table 21. Statistical summary of daily suspended sediment concentration at Yadkin College,
North Carolina in the Yadkin River arranged by decade.

Attributes
Log Trans-
formation

1950s Sediment Concentration (mg/L)

1966s 1970s 1980s
Sample size - 3559 3652 3653. 3652
Arithmetic mean No 181.11 133.52 174.43 114.14
Mean of Nat. Log Yes 4.41 4.31 4.60 4.04
Standard deviation No 268.70 193.42 222.78 193.91
Coeff. of variation, % No 148.4 144.9 127.7 169.9
Coeff. of variation, % Yes 29.1 24.0 226 27.4
Minimum - 1 4 7 2
Lower quartile - 35 38 46 26
Median - 80 68 91 48
Upper quartile - 203 135 203 112
Upper 10% - 486 - 312 433 277
Upper 1 % - 1260 1000 1100 955
Maximum - 2970 2100 2210 2480
-Skewness No 3.30 3.78 288 4.89
Skewness 'yes 0.020 0.35 0.27 0S2
Kurtosis No 15.75 19.21 10.62 35.01
Kurtosis Yes -0.35 0.07 -0.44 -0.03
Table 22. Statistical summary of daily sediment transport or yield at Yadkin College, North
Carolina in the Yadkin River arranged by decade.
Sediment Yield (Mg/d)
Log Trans- 1950s 1960s 1970s 1980s
Attributes formation
Sample size - 3559 3652 3653 3652
Arithmetic mean No 2459.9 1699.1 3036.2 1788.0
Mean Nat. Log Yes 6.043 6.011 6.594 5.729
Standard deviation No 7333.9 5859.9 9017.8 6844.7
Coeff. of variation, % No 298.1 -344.9 297.0 382.8
Coeff. of variation, % Yes 30.8 24.3 23.2 28.7
Minimum - 2.72 14.51 31.75 8.26
Lower quartile - 116.1 147.9 233.1 925
Median - 385.56 337.5 594.2 215.9
Upper quartile - 1388.0 850.5 1905.1 841.0
Upper 10% - 5361.5 3048.1 6232.4 3302.2
Upper 1% - 39009 28214 46811 31025.7
Maximum - 97,976 114,305 165,108 125,192
Skewness No 6.22 9.03 7.23 9.13
Skewness Yes 0.23 0.73 0.78 0.78
Kurtosis No 48.36 110.81 72.49 105.71
Kurtosis Yes -0.25 0.64 007 0.27
APPENDIX F
Figures
Dynamic Modeling of Long-Term
Sedimentation in the Yadkin
River Basin
Krishnaswamy, Lavine, Richter
and Korfmacher 2000
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