Chapter 6 Population-Land Cover

Chapter 6
Population Growth, Land Cover Changes and Water Quality

6.1 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. For more information on nonpoint
source pollution visit http://h2o.enr.state.nc.us/nps/.
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 6 – Population Growth, Land Cover Changes and Water Quality 69

6.2 Managing the Impacts of Growth and Development and Stormwater
Runoff

6.2.1 Introduction to Stormwater Runoff

Stormwater runoff is rainfall or snowmelt that runs off the ground or impervious surface (i.e.,
buildings, roads, parking lots). In some cases, it drains directly into streams, rivers, lakes and
oceans. In others, particularly urbanized areas, stormwater drains into streets and manmade
drainage systems consisting of inlets and underground pipes, commonly referred to as a storm
sewer system. Storm sewer systems are designed simply to capture the stormwater and convey it
to the nearest surface waterbody. These sewers should not be confused with sanitary sewers,
which transport human and industrial wastewaters to a treatment plant before discharging into
surface waters.

Common stormwater pollutants include sediment, nutrients, organic matter, bacteria, oil and
grease, and toxic substances (i.e., metals, pesticides, herbicides, hydrocarbons). Stormwater can
also impact the temperature of a surface waterbody, which can affect the water’s ability to
support certain fish and aquatic communities.

Uncontrolled stormwater runoff has many impacts on both humans and the environment.
Cumulative effects include flooding, undercut and eroding streambanks, widened stream
channels, threats to public health and safety, impaired recreational use, and increased costs for
drinking and wastewater treatment. For more information on stormwater runoff, visit the DWQ
Stormwater Permitting Unit at http://h2o.enr.state.nc.us/su/stormwater.html or the NC Stormwater
information page at http://www.ncstormwater.org/. Additional fact sheets and information can also
be found at http://www.stormwatercenter.net/intro_factsheets.htm and
www.bae.ncsu.edu/stormwater/index.html.

6.2.2 Effects of Growth and Development

Urban growth poses one of the greatest threats to aquatic resources more than any other human
activity. 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 increases, some of the potential water supply is also lost (Orr and Stuart,
2000).

As development in surrounding metropolitan areas consumes neighboring forests and fields, the
impacts on rivers, lakes and streams can be significant and permanent if stormwater runoff is not
controlled (Orr and Stuart, 2000). 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 also increases. These effects are compounded
when small streams are channelized (straightened) or piped, and storm sewer systems are
installed to increase transport of stormwater downstream. Bank scour from these frequent high
flow events tends to enlarge urban streams and increase suspended sediment. Scouring also
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 70

destroys the variety of habitat in streams, leading to degradation of benthic macroinvertebrate
populations and loss of fisheries (EPA, 1999).

Based on the 2000 Census, the overall population of the New River basin is 49,653. This
number is estimated based on the percent of the county land area that is partially or entirely
contained within the New River basin. Although counties in the New River basin are not among
the fastest growing counties in the state, the effects of development are impacting water quality.
Two of the three counties in the basin experienced growth rates in excess of ten percent during
the last decade of the 20th century. The sparsely developed watersheds of the north and western
portions of the basin generally contain streams with high water quality, excellent aquatic
communities and species populations, and are considered Supporting based on current use
support methodologies. Impacts are quickly noted, however, in the southern and central
watersheds where urbanization is focused around city centers and interstate corridors. It is no
surprise then that the greatest concentration of streams with noted impacts lie in the areas of
Boone and Blowing Rock. Between 1990 and 2000, Jefferson and West Jefferson also
experienced increasing populations, and impacted waters are also found in these areas. As the
counties in the New River basin continue to grow, there will likely be a loss of natural areas and
an increase in the amount of impervious surface associated with new homes and businesses.

The New River basin has an abundance of surface water that has supported the current domestic
expansion in the urban areas. Even today, there is sufficient water to serve its diverse domestic,
agricultural, energy and recreational needs except in periods of severe drought. It is those
periods of drought that point to the impending threats of the availability of good quality water.
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. For more information on county
population density, refer to Appendix I. Appendix II lists local governments and Appendix III
provides information related to land cover changes.

6.2.3 Controlling Stormwater Pollution

Many daily activities have the potential to cause stormwater pollution. Any situation where
activities can contribute more pollutants to stormwater runoff is an area that should be
considered for efforts to minimize stormwater impacts. A major component in reducing
stormwater impacts involves planning up front in the design process. New construction designs
should include plans to prevent or minimize the amount of runoff leaving the site. Wide streets,
large cul-de-sacs, 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. In many
instances, the presence of intact riparian buffers and/or wetlands in urban areas can reduce the
impacts of urban development. Establishment and protection of buffers should be considered
where feasible, and the amount of impervious cover should be limited as much as possible.

“Good housekeeping” to reduce the volume of stormwater leaving a site and reducing the amount
of pollutants used in our own backyards can also minimize the impact of stormwater runoff.
DWQ has published a pamphlet entitled Improving Water Quality in Your Own Backyard:
Stormwater Management Starts at Home. The pamphlet provides information on how
homeowners and businesses can reduce the amount of runoff leaving their property and how to
reduce the amount and types of pollutants in that runoff. This document is available on-line at
http://h2o.enr.state.nc.us/nps/documents/BackyardPDF.pdf or by calling [phone].
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 71

Preserving the natural streamside vegetation (riparian buffer) is one of the most economical and
efficient BMPs. In particular, forested buffers 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). For more
information or to obtain a free copy of DWQ’s Buffers for Clean Water brochure, call (919) 733-
5083, ext. 558.

6.2.4 Protecting Headwaters

Many streams in a given river basin are only small trickles of water that emerge from the ground.
A larger stream is formed at the confluence of these trickles (Figure 13). 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., 2003). However, degradation
of headwater streams can (and does) impact the larger stream or river.

Figure 13 Diagram of Headwater Streams within a Watershed Boundary

There are three types of headwater streams: 1) perennial (flow year-round); 2) intermittent (flow
during wet seasons); and 3) ephemeral (flow only after precipitation events). 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., 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.
However, these insects, both in larval and adult stages, are also food for small mammals, such as
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 72

river otter and raccoons, birds and amphibians (Erman, 1996). Benthic macroinvertebrates in
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,
refer to EPA’s Watershed Academy website at
http://www.epa.gov/OWOW/watershed/wacademy/acad2000/watershedmgt/principle1.html.

6.3 The Role of Local Governments

6.3.1 Introduction and Overview

Below is a summary of management actions recommended for local authorities, 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 in 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
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 73

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 (i.e.,
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.

(a) Over the short term, currently feasible retrofit projects should be identified
and implemented.
(b) In the long 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 EPA Section 319 or the North Carolina Clean Water Management
Trust Fund (CWMTF).

(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 best management practice (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 nonstorm inputs of toxics; reducing
pollutants available for runoff during storms; and managing water to reduce
stormwater 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 be
advantageous to implement retrofit BMPs before embarking on stream channel restoration, as
restoration is 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 Section 319 or state sources including North Carolina CWMTF.
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 74

(4) Actions recommended above (i.e., stormwater quantity and quality retrofit BMPs) are likely
to reduce nutrient/organic loading, and to some extent, its impacts. 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 biological oxygen demand (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 also be beneficial.

(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.
(d) Reducing and properly managing pesticide and fertilizer use.

6.3.2 Reducing 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 growth. 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 New River basin. These streams will be important as sources of benthic
macroinvertebrates and fish 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 urbanizing 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.
Chapter 6 – Population Growth, Land Cover Changes and Water Quality 75

(5) Minimize impervious surfaces including roads and parking lots.
(6) Develop public outreach programs to educate citizens about stormwater runoff.

Action needs be taken at the local level to plan for
new development in urban and rural areas. 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.
For more detailed information regarding
recommendations for new development found in the
text box (above), 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 New
River basin in order for citizens to understand the
value of urban planning and stormwater management.
For an example of local community planning efforts
to reduce stormwater runoff, visit
http://www.charmeck.org/Home.htm.

6.3.3 Existing Programs to Control
Stormwater Runoff

In North Carolina, there are a number of programs directly tied to the management and control of
stormwater runoff from new development activities near sensitive waters. These sensitive waters
include:

ƒ Water Supply Watersheds
ƒ High Quality Waters (HQW)
ƒ Outstanding Resource Waters (ORW)
ƒ Nutrient Sensitive Waters

There is also a federal program that requires stormwater permits for point source dischargers of
stormwater from certain industrial activities and from large municipalities. For more
information on stormwater programs across the state, refer to Chapter 7.

Chapter 6 – Population Growth, Land Cover Changes and Water Quality 76