Chapter 12

Chapter 12
Population Growth, Land Cover Changes and Water Quality

12.1 General Sources of Pollution

Human activities can negatively impact
surface water quality, even when the
activity is far removed from the
waterbody. With proper management of
wastes and land use activities, these
impacts can be minimized. Pollutants that
enter waters fall into two general
categories: point sources and nonpoint
sources.
Point Sources

Piped discharges from:
• Municipal wastewater treatment plants
• Industrial facilities
• Small package treatment plants
• Large urban and industrial stormwater systems

Point sources are typically piped discharges and are controlled through regulatory programs
administered by the state. All regulated point source discharges in North Carolina must apply for
and obtain a National Pollutant Discharge Elimination System (NPDES) permit from the state.

Nonpoint sources are from a broad range of land use activities. Nonpoint source pollutants are
typically carried to waters by rainfall, runoff or snowmelt. Sediment and nutrients are most often
associated with nonpoint source pollution. Other
pollutants associated with nonpoint source
pollution include fecal coliform bacteria, heavy
metals, oil and grease, and any other substance
that may be washed off the ground or deposited
from the atmosphere into surface waters.

Unlike point source pollution, nonpoint pollution
sources are diffuse in nature and occur
intermittently, depending on rainfall events and
land disturbance. Given these characteristics, it is difficult and resource intensive to quantify
nonpoint contributions to water quality degradation in a given watershed. While nonpoint source
pollution control often relies on voluntary actions, the state has many programs designed to
reduce nonpoint source pollution.
Nonpoint Sources

• Construction activities
• Roads, parking lots and rooftops
• Agriculture
• Failing septic systems and straight pipes
• Timber harvesting
• Hydrologic modifications
Cumulative Effects

While any one activity may not have a
dramatic effect on water quality, the
cumulative effect of land use activities
in a watershed can have a severe and
long-lasting impact.
Every person living in or visiting a watershed
contributes to impacts on water quality. Therefore,
each individual should be aware of these contributions
and take actions to reduce them.
Chapter 12 – Population Growth, Land Cover Changes and Water Quality 117
12.2 Managing the Impacts of Growth, Development, and Stormwater
Runoff

12.2.1 Introduction

Urban growth poses one of the greatest threats to aquatic resources. The impacts on rivers, lakes
and streams as development surrounding metropolitan areas consumes neighboring forests and
fields can be significant and permanent if stormwater runoff is not controlled. Greater numbers
of homes, stores and businesses require greater quantities of water. Growing populations not
only require more water, but they also lead to the discharge and runoff of greater quantities of
waste and pollutants into the state’s streams and groundwater. Thus, just as demand and use
increase, some of the potential water supply is lost (Orr and Stuart, 2000).

In addition, as watershed vegetation is replaced with impervious surfaces in the form of paved
roads, buildings, parking lots, and residential homes and driveways, the ability of the
environment to absorb and diffuse the effects of natural rainfall is diminished. Urbanization
results in increased surface runoff and correspondingly earlier and higher peak streamflows after
rainfall. Flooding frequency is also increased. These effects are compounded when small
streams are channelized (straightened) or piped and storm sewer systems are installed to increase
transport of drainage waters downstream. Bank scour from these frequent high flow events tends
to enlarge urban streams and increase suspended sediment. Scouring also destroys the variety of
habitat in streams, leading to degradation of benthic macroinvertebrate populations and loss of
fisheries (EPA, 1999).

Most of the impacts result in habitat degradation (Chapter 13), but urban runoff also carries a
potentially toxic cocktail including oil and grease from roads and parking lots, street litter and
pollutants from the atmosphere. Cumulative impacts from developing and urban areas can cause
severe impairment to urban streams.

12.2.2 Effects of Growth and Development in the Roanoke River Basin

Although the Roanoke River basin is not one of the fastest developing basins in the state, the
effects of development are impacting water quality. Seven of the fifteen counties in the basin
experienced growth rates in excess of 13 percent in the last decade of the 20th century. The
sparsely developed watersheds the western foothills portion of the basin generally contain
streams with high water quality, excellent aquatic species populations, and Supporting use
support ratings. Water quality declines dramatically in streams in the central piedmont
watersheds, in rural and urbanized areas.

Populations of counties that are wholly or partly contained within the basin increased by over
115,000 people between 1990 and 2000. Appendix I presents projected population growth by
county for the Roanoke River basin from 2000 to 2020. Forsyth, Granville, Orange, Person and
Stokes counties are growing the fastest in the basin. These counties have an estimated growth
rate of over 20 percent by 2020. Wentworth, Rural Hall and Kernersville had high growth rates.
Walkertown increased population substantially in the last ten years. Although the Roanoke
River basin population is growing slower than some other river basins, there will be increased
118 Chapter 12 – Population Growth, Land Cover Changes and Water Quality

drinking water demands and wastewater discharges. There will also be loss of natural areas and
increases in impervious surfaces associated with construction of new homes and businesses.

The overall population of the basin based on 2000 Census data is 344,638, with approximately
98 persons/square mile. Population density estimated by subbasin is presented in Appendix I.

Refer to Appendix II for local governments’ listing and Appendix III for land cover changes
related to urbanization.

The Roanoke River basin has an abundance of surface water that has supported industrial and
domestic expansions of the mid-20th century. Even today, there is sufficient water to serve its
diverse domestic, agricultural, industrial, energy production and recreational needs except in
periods of severe drought. However, as population increases in the basin, the availability and
needs of those water supplies will need to be carefully planned and coordinated between state
and local governments. Clean water can likely be provided in sufficient quantity to supply the
future needs of the basin, but only with inspired foresight, planning and management. See
Chapter 18 on Water Resources for more information.

Also, in times of drought much coordination between state and local agencies needs to be
maintained to assure not only sufficient flows for water supply but also for downstream water
quality.

12.2.3 The Role of Local Governments

A summary of necessary management actions needed by local authorities is provided here,
followed by discussions on large, watershed management issues. These actions are necessary to
address current sources of impairment and to prevent future degradation in all streams. The
intent of these recommendations is to describe the types of actions necessary to improve stream
conditions, not to specify particular administrative or institutional mechanisms for implementing
remedial practices. Those types of decisions must be made at the local level.

Because of uncertainties regarding how individual remedial actions cumulatively impact stream
conditions and how aquatic organisms will respond to improvements, the intensity of
management effort necessary to bring about a particular degree of biological improvement
cannot be established in advance. The types of actions needed to improve biological conditions
can be identified, but the mix of activities that will be necessary – and the extent of improvement
that will be attainable – will only become apparent over time as an adaptive management
approach is implemented. Management actions are suggested below to address individual
problems, but many of these actions are interrelated.

Actions one through five are important to restoring and sustaining aquatic communities in the
watershed, with the first three recommendations being the most important.

1. Feasible and cost-effective stormwater retrofit projects should be implemented
throughout the watershed to mitigate the hydrologic effects of development (increased
stormwater volumes and increased frequency and duration of erosive and scouring flows).
This should be viewed as a long-term process. Although there are many uncertainties, costs
in the range of $1 million per square mile can probably be anticipated.
Chapter 12 – Population Growth, Land Cover Changes and Water Quality 119
a. Over the short-term, currently feasible retrofit projects should be identified
and implemented.
b. In the longer term, additional retrofit opportunities should be implemented in
conjunction with infrastructure improvements and redevelopment of existing
developed areas.
c. Grant funds for these retrofit projects may be available from EPA initiatives,
such as Section 319 funds, or the North Carolina Clean Water Management
Trust Fund.

2. A watershed scale strategy to address toxic inputs should be developed and
implemented, including a variety of source reduction and stormwater treatment
methods. As an initial framework for planning toxicity reduction efforts, the following
general approach is proposed:
a. Implementation of available BMP opportunities for control of stormwater
volume and velocities. As recommended above to improve aquatic habitat
potential, these BMPs will also remove toxics from stormwater.
b. Development of a stormwater and dry weather sampling strategy in order to
facilitate the targeting of pollutant removal and source reduction practices.
c. Implementation of stormwater treatment BMPs, aimed primarily at pollutant
removal, at appropriate locations.
d. Development and implementation of a broad set of source reduction activities
focused on: reducing non-storm inputs of toxics; reducing pollutants available
for runoff during storms; and managing water to reduce storm runoff.

3. Stream channel restoration activities should be implemented in target areas, in
conjunction with stormwater retrofit BMPs, in order to improve aquatic habitat.
Before beginning stream channel restoration, a geomorphologic survey should be conducted
to determine the best areas for stream channel restoration. Additionally, it would probably be
advantageous to implement retrofit BMPs before embarking on stream channel restoration, as
restoration is probably best designed for flows driven by reduced stormwater runoff. Costs
of approximately $200 per foot of channel should be anticipated (Haupt et al., 2002 and
Weinkam et al., October 2001). Grant funds for these retrofit projects may be available from
federal sources, such as EPA’s Section 319 funds, or state sources including North Carolina
Clean Water Management Trust Fund.

4. Actions recommended above (e.g., stormwater quantity and quality retrofit BMPs) are likely
to reduce nutrient/organic loading and associated impacts to some extent. Activities
recommended to address this loading include the identification and elimination of illicit
discharges; education of homeowners, commercial applicators, and others regarding proper
fertilizer use; street sweeping; catch basin clean-out practices; and the installation of
additional BMPs targeting BOD and nutrient removal at appropriate sites.

5. Prevention of further channel erosion and habitat degradation will require effective post-
construction stormwater management for all new development in the study area.

6. Effective enforcement of sediment and erosion control regulations will be essential to the
prevention of additional sediment inputs from construction activities. Development of
improved erosion and sediment control practices may be beneficial.
120 Chapter 12 – Population Growth, Land Cover Changes and Water Quality

7. Watershed education programs should be implemented and continued by local governments
with the goal of reducing current stream damage and preventing future degradation. At a
minimum, the program should include elements to address the following issues:
a. redirecting downspouts to pervious areas rather than routing these flows to
driveways or gutters;
b. protecting existing woody riparian areas on all streams;
c. replanting native riparian vegetation on stream channels where such
vegetation is absent; and
d. reducing and properly managing pesticide and fertilizer use.

12.2.4 Maintain and Develop Riparian Buffers

The presence of intact riparian buffers and/or wetlands can reduce the impacts of stormwater
flow from development in urban and rural areas as well as from various agricultural practices.
Establishment and protection of buffers should be considered where feasible, and the amount of
impervious cover should be limited as much as possible. Wide streets, large cul-de-sacs, and
long driveways and sidewalks lining both sides of the street are all features of urban
development that create excess impervious cover and consume natural areas.

Preserving the natural 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, trapping bacteria, 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. Counties and municipalities
should adopt ordinances that require buffers along streams whether in urban or rural areas. To
obtain a free copy of DWQ’s Buffers for Clean Water brochure, call [phone], ext. 558.

12.2.5 Protecting Headwaters

Many streams in a given river basin are only small trickles or seeps of water that emerge from
the ground. A larger stream is formed at the confluence of these trickles (Figure 17). This
constant merging eventually forms a large stream or river. Most monitoring of fresh surface
waters evaluates these larger streams. The many miles of small trickles, collectively known as
headwaters, are not directly monitored and in many instances are not even indicated on maps.
These streams account for approximately 80 percent of the stream network and provide many
valuable services for quality and quantity of water delivered downstream (Meyer et al.,
September 2003). However, degradation of headwater streams can (and does) impact the larger
stream or river and should be protected.

There are three types of headwater streams: ephemeral (flow only after precipitation events),
intermittent (flow during wet seasons), and perennial (flow year-round). All types of headwater
streams provide benefits to larger streams and rivers. Headwater streams control flooding,
recharge groundwater, maintain water quality, reduce downstream sedimentation, recycle
nutrients, and create habitat for plants and animals (Meyer et al., September 2003).
In smaller headwater streams, fish communities are not well developed and benthic
macroinvertebrates dominate aquatic life. Benthic macroinvertebrates are often thought of as
"fish food" and, in mid-sized streams and rivers, they are critical to a healthy fish community.
Chapter 12 – Population Growth, Land Cover Changes and Water Quality 121
However, these insects, both in larval and adult stages, are also food for small mammals, such as
river otter and raccoons, birds and amphibians (Erman, 1996). Benthic macroinvertebrates in

Figure 17 - Diagram of Headwater Streams within a Watershed Boundary

headwater streams also perform the important function of breaking down coarse organic matter,
such as leaves and twigs, and releasing fine organic matter. In larger rivers, where coarse
organic matter is not as abundant, this fine organic matter is a primary food source for benthic
macroinvertebrates and other organisms in the system (CALFED, 1999). When the benthic
macroinvertebrate community is changed or extinguished in an area, even temporarily, as occurs
during land use changes, it can have repercussions in many parts of both the terrestrial and
aquatic food web.

Headwater streams also provide a source of insects for repopulating downstream waters where
benthic macroinvertebrate communities have been eliminated due to human alterations and
pollution. Adult insects have short life spans and generally live in the riparian areas surrounding
the streams from which they emerge (Erman, 1996). Because there is little upstream or stream-
to-stream migration of benthic macroinvertebrates, once headwater populations are eliminated,
there is little hope for restoring a functioning aquatic community. In addition to
macroinvertebrates, these streams support diverse populations of plants and animals that face
similar problems if streams are disturbed. Headwater streams are able to provide these important
ecosystem services due to their unique locations, distinctive flow patterns, and small drainage
areas.

Because of the small size of headwater streams, they are often overlooked during land use
activities that impact water quality. All landowners can participate in the protection of
headwaters by keeping small tributaries in mind when making land use management decisions
on the areas they control. This includes activities such as retaining vegetated stream buffers,
minimizing stream channel alterations, and excluding cattle from streams. Local rural and urban
planning initiatives should also consider impacts to headwater streams when land is being
developed. For a more detailed description of watershed hydrology and watershed management,
122 Chapter 12 – Population Growth, Land Cover Changes and Water Quality

refer to EPA’s Watershed Academy website at
http://www.epa.gov/OWOW/watershed/wacademy/acad2000/watershedmgt/principle1.html.

12.2.6 Reduce Impacts of Future Development

Proactive planning efforts at the local level are needed to assure that development is done in a
manner that maintains water quality. These planning efforts will need to find a balance between
water quality protection, natural resource management and economic development. Growth
management requires planning for the needs of future population increases, as well as developing
and enforcing environmental protection measures. These actions are critical to water quality
management and the quality of life for the residents of the basin.

Areas adjacent to the high growth areas of the basin are at risk of having Impaired biological
communities. These biological communities are important to maintaining the ecological
integrity in the Roanoke River basin. These streams will be important as sources of benthic
macroinvertebrates and fishes for reestablishment of biological communities in nearby streams
that are recovering from past impacts or are being restored.

To prevent further impairment to aquatic life in streams in developing watersheds local
governments should:

1. identify waters that are threatened by development;
2. protect existing riparian habitat along streams;
3. implement stormwater BMPs during and after development;
4. develop land use plans that minimize disturbance in sensitive areas of watersheds;
5. minimize impervious surfaces including roads and parking lots; and
6. develop public outreach programs to educate citizens about stormwater runoff.

Action should be taken at the local level to plan for new development in urban and rural areas.

For more detailed information regarding
recommendations for new development found in the
text box (right), refer to EPA’s website at
www.epa.gov/owow/watershed/wacademy/acad2000/protection,
the Center for Watershed Protection website at
www.cwp.org, and the Low Impact Development Center
website at www.lowimpactdevelopment.org. Additional
public education is also needed in the Roanoke River
basin in order for citizens to understand the value of
urban planning and stormwater management. DWQ
recently developed a booklet that discusses actions
individuals can take to reduce stormwater runoff and
improve stormwater quality entitled Improving Water
Quality In Your Own Backyard. To obtain a free copy,
call [phone], ext. 558. For an example of local
community planning, visit the website at
Planning Recommendations
for New Development

• Minimize number and width of
residential streets.
• Minimize size of parking areas
(angled parking & narrower slots).
• Place sidewalks on only one side of
residential streets.
• Minimize culvert pipe and
hardened stormwater conveyances.
• Vegetate road right-of-ways,
parking lot islands and highway
dividers to increase infiltration.
• Plant and protect natural buffer
zones along streams and tributaries. http://www.charmeck.org/Home.htm.
Chapter 12 – Population Growth, Land Cover Changes and Water Quality 123
124 Chapter 12 – Population Growth, Land Cover Changes and Water Quality