Chapter 5 Stressors

Chapter 5
Water Quality Stressors

5.1 Stressor and Source Identification

5.1.1 Introduction – Stressors

Water quality stressors are identified when impacts have been noted to biological (fish and
benthic) communities or water quality standards have been violated. Stressors apply to one or
more use support categories and may be identified for Impaired as well as Supporting waters
with noted impacts. Identifying stressors is challenging because direct measurements of the
stressor may be difficult or prohibitively expensive. DWQ staff use field observations from
sample sites, special studies, and data from ambient monitoring stations as well as information
from other agencies and the public to identify potential water quality stressors. It is important to
identify stressors and potential sources of stressors so that the limited resources of water quality
programs can be targeted to address the water quality problems. Specific aquatic life stressors
are defined in Section 5.2.

Most stressors to the biological community are complex groupings of many different stressors
that individually may not degrade water quality or aquatic habitat, but together can severely
impact aquatic life. Sources of stressors are most often associated with land use in a watershed,
as well as the quality and quantity of any treated wastewater that may be entering a stream.
During naturally severe conditions such as droughts or floods, any individual stressor or group of
stressors may have more severe impacts to aquatic life than during normal climatic conditions.
The most common source of stressors is from altered watershed hydrology.

Stressors to recreational uses include pathogenic indicators such as fecal coliform bacteria,
escheria coli and enterrococci. Stressors to fish consumption are mercury and any other
substance that causes the issuance of a fish consumption advisory by the NC Department of
Health and Human Services (NCDHHS).

5.1.2 Introduction – Sources of Stressors

Sources of stressors most often come from a watershed where the hydrology is altered enough to
allow the stressor to be easily delivered to a stream during a rain event along with unusually
large amounts of water. DWQ identifies the source of a stressor as specifically as possible
depending on the amount of information available in a watershed. Most often the source is based
on the predominant land use in a watershed. Sources of stressors identified in the New River
basin during the most recent assessment period include urban or impervious surface runoff,
construction sites, road building, agriculture and forestry. Point source discharges are also
considered a water quality stressor source.
Chapter 5 – Water Quality Stressors 59

5.1.3 Overview of Stressors Identified in the New River Basin

The stressors noted below are summarized for all waters and for all use support categories.
Figure 10 identifies stressors noted for Impaired streams in the New River basin during the most
recent assessment period. The stressors noted in the figure may not be the sole reason for the
impairment. Figure 11 presents the stressors identified for those waters with noted impacts. For
specific discussion of stressors to the Impaired or waters with noted impacts, refer to the
subbasin chapters (Chapters 1 – 3). Stressor definitions and potential impacts are discussed in
the remainder of this chapter (Chapter 5).
0.0
2.0
4.0
6.0
8.0
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12.0
Habitat Degradation Toxic Impacts
Fr
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Figure 10 Stressors Identified for Impaired Streams in the New River Basin

0.0
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Fecal Coliform Bacteria Habitat Degradation Low pH
Fres
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Figure 11 Stressors Identified for Streams with Noted Impacts in the New River Basin
Chapter 5 – Water Quality Stressors 60

5.1.4 Overview of Stressor Sources Identified in the New River Basin

The sources noted below are summarized for all waters and for all use support categories. Figure
12 identifies sources of stressors noted for waters in the New River Basin during the most recent
assessment period. Refer to the subbasin chapters (Chapters 1 – 3) for a complete listing and
discussion of sources by stream.
0
10
20
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WWTP NPDES Agriculture Pasture Impervious
Surface
Road
Construction
Unknown
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Figure 12 Sources of Stressors Identified in the New River Basin

Wastewater treatment plants (WWTPs) were noted as a potential source to 12.3 stream miles in
the New River basin. WWTPs are just one of many sources that can contribute excess nutrients
that may increase the potential for algal blooms and cause exceedances of the chlorophyll a
standard. Better treatment technology and upgrades to the Jefferson and West Jefferson WWTPs
in the New River basin are likely to decrease the number of stream miles impacted by WWTPs.

Field observations and information from the local Soil and Water Conservation Districts
(SWCD) indicate that agricultural activities may be impacting water quality in several
watersheds of the New River basin. In several areas where pasture was noted as the
predominant land use, cattle had direct, easy access to the stream. Agriculture was noted as a
potential stressor source for 13.8 stream miles. Pasture was noted as a potential stressor source
for 69.5 stream miles. For more information related to agricultural water quality initiatives, refer
to Chapter 8.

Impervious surface accounted for noted impacts to 22.0 stream miles and road construction
activities accounted for noted impacts to 8.9 stream miles. Impervious surface cover and road
construction activities are often associated with increased development. Refer to Chapter 6 for
Chapter 5 – Water Quality Stressors 61

more information related to population growth and land cover changes and its potential impacts
on water quality.

Stressor sources could not be identified for 79.6 stream miles in the New River basin. These
stream segments may be in areas where sources could not be identified during field observations,
but the streams had noted impacts (i.e., habitat degradation). DWQ and the local agencies will
work to identify potential sources for these stream segments during the next basinwide cycle.

5.2 Aquatic Life Stressors – Habitat Degradation

5.2.1 Introduction and Overview

Instream habitat degradation is identified as a notable reduction in habitat diversity or a negative
change in habitat. This term includes sedimentation, streambank erosion, channelization, lack of
riparian vegetation, loss of pools and/or riffles, loss of organic (woody and leaf) habitat, and
streambed scour. These stressors to aquatic insect and fish communities can be caused by many
different land use activities and less often by discharges of treated wastewater. In the New River
basin, 11.0 stream miles are Impaired where at least one form of habitat degradation has been
identified as the stressor. There are an additional 131.2 stream miles where habitat degradation
is a noted impact to water quality. Many of the stressors discussed below are either directly
caused by or are a symptom of altered watershed hydrology. Altered hydrology increases both
sources of stressors and delivery of the stressors to the receiving waters. Refer to the subbasin
chapters (Chapters 1 – 3) for more information on the types of habitat degradation noted in a
particular stream segment.

Good instream habitat is necessary for aquatic life
to survive and reproduce. Streams that typically
show signs of habitat degradation are in watersheds
that have a large amount of land-disturbing
activities (i.e., construction, mining, timber harvest,
agricultural activities) or a large percentage of
impervious surfaces. A watershed in which most of
the riparian vegetation has been removed from
streams or channelization has occurred also exhibits
instream habitat degradation. Streams that receive a
discharge quantity that is much greater than the
natural flow in the stream often have degraded
habitat as well.

Quantifying the amount of habitat degradation is
very difficult in most cases. To assess instream
habitat degradation in most streams would require
extensive technical and monetary resources and
perhaps even more resources to restore the stream. Although DWQ and other agencies (i.e.,
SWCD, NRCS, town and county governments) are starting to address this issue, local efforts are
needed to prevent further instream habitat degradation and to restore streams that have been
Impaired by activities that cause habitat degradation. As point sources become less of a source
Some Best Management Practices

Agriculture
• No till or conservation tillage practices
• Strip cropping and contour farming
• Leaving natural buffer areas around
small streams and rivers

Construction
• Using phased grading/seeding plans
• Limiting time of exposure
• Planting temporary ground cover
• Using sediment basins and traps

Forestry
• Controlling runoff from logging roads
• Replanting vegetation on disturbed areas
• Leaving natural buffer areas around
small streams and rivers
Chapter 5 – Water Quality Stressors 62

of water quality impairment, nonpoint sources that pollute water and cause habitat degradation
need to be addressed to further improve water quality in North Carolina’s streams and rivers.

5.2.2 Sedimentation

Sedimentation is a natural process that is important to the maintenance of diverse aquatic
habitats. Overloading of sediment in the form of sand, silt and clay particles fills pools and
covers or embeds riffles that are vital aquatic insect and fish habitats. Suspended sediment can
decrease primary productivity (i.e., photosynthesis) by shading sunlight from aquatic plants,
therefore, affecting the overall productivity of a stream system. Suspended sediment also has
several effects on various fish species including avoidance and redistribution, reduced feeding
efficiency which leads to reduced growth by some species, respiratory impairment, reduced
tolerance to diseases and toxicants, and increased physiological stress (Roell, June 1999).
Sediment filling rivers and streams decreases their storage volume and increases the frequency of
floods (NCDENR-DLR, 1998). Suspended sediment also increases the cost of treating
municipal drinking water.

Streambank erosion and land-disturbing activities are sources of sedimentation. Streambank
erosion is often caused by high stormwater flows immediately following rainfall events or
snowmelts. Watersheds with large amounts of impervious surface transport water to streams
more rapidly and at higher volumes than in watersheds with more vegetative cover. In many
urban areas, stormwater is delivered directly to the stream by a stormwater sewer system. This
high volume and concentrated flow of water after rain events undercuts streambanks often
causing streambanks to collapse. This leads to large amounts of sediment being deposited into
the stream. Many urban streams are adversely impacted by sediment overloading from the
watershed as well as from the streambanks. Minimizing impervious surface area and reducing
the amount of stormwater outlets releasing stormwater directly to the stream can often prevent
substantial amounts of erosion.

Land-disturbing activities such as the construction of roads and buildings, crop production,
livestock grazing and timber harvesting can accelerate erosion rates by causing more soil than
usual to be detached and moved by water. In most land-disturbing activities, sedimentation can
be controlled through the use of appropriate best management practices (BMPs). BMPs that
minimize the amount of acreage and length of time that the soil is exposed during land-
disturbing activities can greatly reduce the amount of soil erosion. For more information on
sedimentation as it relates to changes in land use, refer to Chapter 6.

Livestock grazing with unlimited access to the stream channel and banks can also cause severe
streambank erosion resulting in sedimentation and degraded water quality. Although they often
make up a small percentage of grazing areas by surface area, riparian zones (vegetated stream
corridors) are particularly attractive to cattle that prefer the cooler environment and lush
vegetation found beside rivers and streams. This concentration of livestock can result in
increased sedimentation of streams due to "hoof shear", trampling of bank vegetation, and
entrenchment by the destabilized stream. Despite livestock’s preference for frequent water
access, farm veterinarians have reported that cows are healthier when stream access is limited
(EPA, 1999). For more information on the livestock exclusion, refer to Chapter 3.

Chapter 5 – Water Quality Stressors 63

5.2.3 Loss of Riparian Vegetation

During the 2002 basinwide sampling, DWQ biologists reported degradation of aquatic
communities at several sites throughout the New River basin in association with narrow or
nonexistent zones of native riparian vegetation. Riparian vegetation loss was common in rural
and residential areas as well as in urban areas (NCDENR-DWQ, August 2004b). The loss of
riparian vegetation and subsequent reduction of organic aquatic habitats (Section 5.2.4) is most
commonly associated with land clearing for development, agriculture, pastureland and forestry.
Instream organic habitat loss has also been caused by stream channelization or debris removal
activities.

Removing trees, shrubs and other vegetation to plant grass or place rock (also known as riprap)
along the bank of a river or stream degrades water quality. Removing riparian vegetation
eliminates habitat for aquatic macroinvertebrates that are food for trout and other fish. Rocks
lining a streambank absorb the sun’s heat and warm the water. Some fish require cooler water
temperatures as well as the higher levels of dissolved oxygen cooler water provides. Trees,
shrubs and other native vegetation cool the water by shading it. Straightening a stream, clearing
streambank vegetation, and lining the streambanks with grass or rock severely impact the habitat
that aquatic insects and fish need to survive.

Establishing, conserving and managing streamside vegetation (riparian buffer) is one of the most
economical and efficient BMPs. Forested buffers in particular provide a variety of benefits
including filtering runoff and taking up nutrients, moderating water temperature, preventing
erosion and loss of land, providing flood control and helping to moderate streamflow, and
providing food and habitat for both aquatic and terrestrial wildlife (NCDENR-DWQ, February
2004). To obtain a free copy of DWQ’s Buffers for Clean Water brochure, call [phone],
ext. 558.

5.2.4 Loss of Instream Organic Microhabitats

Organic microhabitat (i.e., leafpacks, sticks and large wood) and edge habitat (i.e., root banks
and undercut banks) play very important roles in a stream ecosystem. Organic matter in the form
of leaves, sticks and other materials serve as the base of the food web for small streams.
Additionally, these microhabitats serve as special niches for different species of aquatic insects,
providing food and/or habitat. For example, many stoneflies are found almost exclusively in
leafpacks and on small sticks. Some beetle species prefer edge habitat, such as undercut banks.
If these microhabitat types are not present, there is no place for these specialized
macroinvertebrates to live and feed. The absence of these microhabitats in some streams in the
New River basin is directly related to the absence of riparian vegetation. Organic microhabitats
are critical to headwater streams, the health of which is linked to the health of the entire
downstream watershed. For more information related to headwater streams, refer to Chapter 6.

5.2.5 Channelization

Channelization refers to the physical alteration of naturally occurring stream and riverbeds.
Typical modifications are described in the text box. Although increased flooding, streambank
erosion and channel instability often occur in downstream areas after channelization has
occurred, flood control, reduced erosion, increased usable land area, greater navigability and
Chapter 5 – Water Quality Stressors 64

more efficient drainage are frequently cited as the
objectives of channelization projects (McGarvey,
1996). Direct or immediate biological effects of
channelization include injury and mortality of aquatic
insects, fish, shellfish/mussels and other wildlife
populations, as well as habitat loss. Indirect biological
effects include changes in the aquatic insect, fish and
wildlife community structures, favoring species that are
more tolerant of or better adapted to the altered habitat
(McGarvey, 1996).

Restoration or recovery of channelized streams may
occur through processes, both naturally and artificially
induced. In general, streams that have not been excessively stressed by the channelization
process can be expected to return to their original forms. However, streams that have been
extensively altered may establish a new, artificial equilibrium (especially when the channelized
streambed has been hardened). In such cases, the stream may enter a vicious cycle of erosion
and continuous entrenchment. Once the benefits of a channelization project become outweighed
by the costs, both in money and environmental integrity, channel restoration efforts are likely to
be taken (McGarvey, 1996).

Typical Channel Modifications

• Removal of any obstructions,
natural or artificial, that inhibit a
stream’s capacity to convey
water (clearing and snagging).
• Widening, deepening or
straightening of the channel to
maximize conveyance of water.
• Lining the bed or banks with
rock or other resistant materials.

Channelization of streams within the continental United States is extensive and promises to
become even more so as urban development continues. Overall estimates of lost or altered
riparian habitats within US streams are as high as 70 percent. Unfortunately, the dynamic nature
of stream ecosystems makes it difficult (if not impossible) to quantitatively predict the effects of
channelization (McGarvey, 1996). Channelization has occurred historically in parts of the New
River basin and continues to occur in some watersheds, especially in small headwater streams.

5.2.6 Recommendations for Reducing Habitat Degradation

In March 2002, the Environmental Management Commission (EMC) sent a letter to the
Sedimentation Control Commission (SCC) expressing seven recommendations for improving
erosion and sedimentation control, based on a comprehensive performance review of the
turbidity standard conducted in 2001 by DWQ staff. Specifically, the recommendations are that
the EMC and SCC:

(1) Evaluate, in consultation with the Attorney General’s Office, whether statutory authority
is adequate to mandate temporary ground cover over a percentage of the uncovered area
at a construction site within a specific time after the initial disturbance of the area. If it is
found that statutory authority does not exist, then the EMC and SCC should prepare
resolutions for the General Assembly supporting new legislation to this effect.

(2) Prepare resolutions supporting new legislation to increase the maximum penalty allowed
in the Sedimentation Pollution Control Act from $5,000 to $25,000 for the initial
response to a noncompliant site.

(3) Jointly support a review of the existing Erosion and Sediment Control Planning and
Design Manual by the NC Division of Land Resources (DLR). This review should
Chapter 5 – Water Quality Stressors 65

include, but not be limited to, a redesign of the minimum specifications for sedimentation
basins.

(4) Evaluate, in consultation with the Attorney General’s Office, whether the statutory
authority is adequate for effective use of the "Stop Work Order" tool and, if found not to
be adequate, to prepare resolutions for the General Assembly supporting new legislation
that will enable staff to more effectively use the "Stop Work Order" tool.

(5) Support increased research into and experimentation with the use of polyacrylamides
(PAMs) and other innovative soil stabilization and turbidity reduction techniques.

(6) Jointly support and encourage the awarding of significant monetary penalties for all
activities found to be in violation of their Stormwater Construction General Permit, their
Erosion and Sediment Control Plan, or the turbidity standard.

(7) Hold those individuals who cause serious degradation of the environment through
excessive turbidity and sedimentation ultimately responsible for restoration of the area.

DWQ will continue to work cooperatively with DLR and local programs that administer
sediment control in order to maximize the effectiveness of the programs and to take appropriate
enforcement action when necessary to protect or restore water quality. However, more voluntary
implementation of BMPs is needed for activities that are not subject to these rules in order to
substantially reduce the amount of widespread sedimentation present in the New River basin.
Additionally, more public education is needed basinwide to educate landowners about the value
of riparian vegetation along small tributaries and the impacts of sedimentation to aquatic life.

Funding is available through numerous federal and state programs for landowners to restore
and/or protect riparian buffer zones along fields or pastures, develop alternative watering sources
for livestock, and fence animals out of streams (refer to Chapters 8 and 12). EPA’s Catalog of
Federal Funding Sources for Watershed Protection (Document 841-B-99-003) outlines some of
these and other programs aimed at protecting water quality. A copy may be obtained by calling
the National Center for Environmental Publications and Information at [phone] or by
visiting the website at http://www.epa.gov/OWOW/watershed/wacademy/fund.html. Local contacts for
various state and local agencies are listed in Appendix VIII.

5.3 Aquatic Life Stressors – Water Quality Standards

5.3.1 Introduction and Overview

In addition to the habitat stressors discussed in the previous section, the stressors discussed
below are identified by water quality standards. These are usually direct measures of water
quality parameters from ambient water quality monitoring stations. The water quality standards
are designed to protect aquatic life. As with habitat degradation, altered watershed hydrology
greatly increases the sources of these stressors as well as delivery of the stressors to the receiving
waters. The following are water quality standards that were identified for waters with noted
impacts. Refer to the subbasin chapters (Chapter 1 – 3) for more information on the affected
waters.

Chapter 5 – Water Quality Stressors 66

5.3.2 pH

The pH water quality standard for Class C waters is between 6.0 and 9.0. In the New River basin
during the most recent assessment period, pH was identified as a potential stressor for 7.2 stream
miles for waters with noted impacts. Refer to Section 1.4.4 for more information.

5.3.3 Toxic Impacts

Toxic impacts are noted as a stressor during biological monitoring. Waters are not impaired due
to toxic impacts, but toxic impacts can be noted as a potential stressor on the system. During the
most recent assessment period, toxic impacts were noted on 6.5 stream miles. The effected
streams are located in the Peak Creek watershed and receive runoff from an abandoned lead and
copper mining facility. Refer to Section 1.3.2 for more information.

5.4 Recreation Stressor – Fecal Coliform Bacteria

Water quality standards for fecal coliform bacteria are intended to ensure safe use of waters for
recreation and shellfish harvesting (Administrative Code 15A NCAC 2B .0200). The North
Carolina fecal coliform standard for freshwater is 200 colonies/100ml based on the geometric
mean of at least five consecutive samples taken during a 30-day period and not to exceed 400
colonies/100ml in more than 20 percent of the samples during the same period.

No waters in the New River basin are Impaired for fecal coliform bacteria; however, there were
21.4 stream miles that were Not Rated due to fecal coliform bacteria levels that exceed the
annual screening criteria. Current methodology requires additional bacteriological sampling for
streams with a geometric mean greater than 200 colonies/100ml or when concentrations exceed
400 colonies/100ml in more than 20 percent of the samples. These additional assessments are
prioritized such that, as monitoring resources become available, the highest priority is given to
those streams where the likelihood of full-body contact recreation is the greatest. None of the
stream segments with elevated bacteria levels are classified for primary recreation (Class B).
Therefore, they were not prioritized for additional sampling during the most recent assessment
period.

Fecal coliform bacteria live in the digestive tract of warm-blooded animals (humans as well as
other mammals) and are excreted in their waste. Fecal coliform bacteria do not actually pose a
danger to people or animals. However, where fecal coliform are present, disease-causing
bacteria may also be present and water that is polluted by human or animal waste can harbor
other pathogens that may threaten human health. Pathogens associated with fecal coliform
bacteria can cause diarrhea, dysentery, cholera and typhoid fever in humans. Some pathogens
can also cause infection in open wounds.

The presence of disease-causing bacteria tends to affect humans more than aquatic creatures.
High levels of fecal coliform bacteria can indicate high levels of sewage or animal wastes that
could make water unsafe for human contact (swimming). Fecal coliform bacteria and other
potential pathogens associated with waste from warm-blooded animals are not harmful to fish or
aquatic insects. However, high levels of fecal coliform bacteria may indicate contamination that
increases the risk of contact with harmful pathogens in surface waters.
Chapter 5 – Water Quality Stressors 67

Under favorable conditions, fecal coliform bacteria can
survive in bottom sediments for an extended period of
time (Howell et al., 1996; Sherer et al., 1992;
Schillinger and Gannon, 1985). Therefore,
concentrations of bacteria measured in the water column
can reflect both recent inputs as well as the resuspension
of older inputs.
Sources of Fecal Coliform
in Surface Waters

• Urban stormwater
• Wild animals and domestic pets
• Improperly designed or managed
animal waste facilities
• Livestock with direct access to
streams
• Improperly treated discharges of
domestic wastewater, including
leaking or failing septic systems
and straight pipes

Reducing fecal coliform bacteria in wastewater requires
a disinfection process, which typically involves the use
of chlorine and other disinfectants. Although these
materials may kill the fecal coliform bacteria and other
pathogenic disease-causing bacteria, they also kill
bacteria essential to the proper balance of the aquatic
environment, and therefore, endanger the survival of
species dependent on those bacteria.

There are a number of factors beyond the control of any state regulatory agency that contribute to
elevated levels of disease-causing bacteria. Therefore, the state does not encourage swimming in
surface waters. To assure that waters are safe for swimming indicates a need to test waters for
pathogenic bacteria. Although fecal coliform standards have been used to indicate the
microbiological quality of surface waters for swimming and shellfish harvesting for more than
50 years, the value of this indicator is often questioned. Evidence collected during the past
several decades suggests that the coliform group may not adequately indicate the presence of
pathogenic viruses or parasites in water.

The detection and identification of specific pathogenic bacteria, viruses and parasites such as
Giardia, Cryptosporidium and Shigella are expensive, and results are generally difficult to
reproduce quantitatively. Also, to ensure the water is safe for swimming would require a whole
suite of tests for many organisms, as the presence/absence of one organism would not document
the presence/absence of another. This type of testing program is not possible due to resource
constraints.

Chapter 5 – Water Quality Stressors 68