Carrying Capacity Methodology-1983

N
lqoo 3
lease do not remove!!!!!
ivision of Coastal Management
CARRYING CAPACITY METHODOLOGY
Planner in Charge
William E. Collins
Director, Planning and Development
Town of Nags Head, North Carolina
August 24, 1983
9

T
The preparation of this report was funded in part through a grant
provided by the North Carolina Coastal ManagementProgram, through
funds provided .by the Coastal Zone Management Act of 1972, as amended,
which is administered by the United States.Office of Coastal Management,
National Oceanic and Atmospheric Administration.
W

Preface
Carrying capacity analysis is a long-term planning approach
that can help communities assess their capability for growth. The
concept of capacity analysis is not new but has existed for twenty
years. There have been, however, relatively few attempts across the
country to implement the concept as a planning tool. One reason for
lack of implementation of the concept may be the broad gap between
theorists who advocate carrying capacity and practicing planners.
Planners still see carrying capacity analysis as a lofty goal beyond
the reach of most planning departments. Infrequent use of the approach
has slowed the development of carrying capacity techniques which
would be useful to practitioners.; An overview of carrying capacity
is contained in the report below and is intended to present the con-
cept in a form useful to practicing planners.
Despite good intentions, this report is not a cookbook that can
guide a planner through a carrying capacity analysis. This report
is designed as a primer for the practitioner and intended to help
local officials decide whether carrying capacity is for them. The
information below, in addition, will provide the starting point for
developing a carrying capacity study by helping planners through the
initial stage of confusion. Once local planners acquire a grasp of
the concept of carrying capacity,, they must develop an approach
tailored to their particular needs.
Procedures and methodologies for carrying capacity are described
below in fairly simple terms to convey basic concepts and approaches
rather than technical detail pertinent to individual techniques.
Methodologies discussed in Chapter Four are examples and should be
employed only if judged suitable to the user's needs and expectations.
Some adjustments, *furthermore, may be required.

The hurricane evacuation methodology has been quoted from
Hurricane Emergency Planning: Estimating Evacuation Times for
Non -Metropolitan Coastal Communities. Its author is John R. Stone,
Department of Civil Engineering, North Carolina State University.
Stone's article contains footnotes that have not been transferred to
this report. Please refer to the original article for information
about these sources.
The Outdoor.Recreation Facility Standards are quoted from the
State Comprehensive Recreation Plan. It was prepared by Byard Alcorn,
Division of Parks and Recreation, North Carolina Department of Natural
Resources and Community Development.
David Brower provided assistance in the preparation of this
report by compiling a comprehensive collection of publications on
carrying capacity. He also served as a sounding board for ideas
throughout the project.

TABLE OF CONTENTS
CHAPTER Page
I Carrying Capacity: An Overview 1
II The Carrying Capacity Process 7
III Issue Selection Process 13
IV Selected Methodologies 17
V Policy Implications 54
Appendix 60

l
CHAPTER I.
Carrying Capacity: An Overview
Introduction.
The rapid growth in environmental awareness that began in the
1960s has resulted in greater pressure at all levels of government
to assure their citizens a certain minimum level of environmental
quality. This pressure has been particularly keen in environmentally
sensitive and fragile areas such as the coastal zone. Public offi-
cials have, in turn, sought to develop various regulatory controls,
incentives, planning techniques and other means for achieving this
goal. One planning tool that has emerged from this effort is the
use of the carrying capacity. This concept relates characteristics
of development (type, location, density, quantity, quality, etc.)
to the quality of the natural and social environments.
As a concept, carrying capacity has its origins in biological
ecology. Early theories of the dynamics of natural populations,
formalized in the 1920s, suggest the notion of a carrying capacity
or upper limit of population density for a particular species in its
respective environment. In this context, carrying capacity is de-
fined as the maximum population density which can be supported by a
habitat without irreparable habitat degradation or that which can
be supported by the habitat in perpetuity. Different habitat elements
necessary for survival (food supply, nesting space, etc.) can be
expressed as limiting factors which restrict population density.
Population growth will cease when the lowest or most restrictive of
these limits is reached.
The first practical applications of carrying capacity have been
in the management of productive natural resource systems such as
forests and rangeland. The carrying capacity of a range, for in
stance, is the density of livestock that can be supported by the
y
range in perpetuity, i.e., without overgrazing. In this sense,
carrying capacity is closely allied with the notion of sustained

yield. This particular concept is found in fisheries management
and other resource systems. One way of defining sustained yeild is
by the capacity of an environment under particular conditions to
provide a constant yield or harvest.
` The notion of carrying capacity had initially applied to the
management of human populations in the field of recreation planning
` in the early 1960s. Faced with increasing numbers of visitors, park
administrators and planners adopted carrying capacity as a means to
relate the numbers of park users to maintenance of the quality of
the recreational resource and to the recreational experience. Today,
the carrying capacity approach is regularly used in such ways as
setting limits or quotas on backcountry use in national parks and
in the sizing of parking lots.
Carrying Capacity in Urban Planning.
The conceptual development of this planning tool essentially
begins with the work of Ian McHarg. It is his basic premise that
each location has an intrinsic suitability for certain land uses
that do not interfere with the natural biological and physical pro-
cesses of the site. This precept has led to a major shift in the way
land use planning is pursued in this country. A number of studies in
the 1970s have further defined the concept. They have refined and
tested the approach in pilot studies. Governments have incorporated
elements of carrying capacity into their planning methods, i.e.,
land use control regulations. Reviews of these developments have
been found in several works. Publications by Bishop et al. '(1974).
Godschalk and Axler (1977), and Pizor (1982) present summary 'accounts
of the works.
Bishop et al. (1974) has defined carrying capacity as the level
of human activity which a region can sustain at acceptable "quality -
of -life" levels in perpetuity. Godschalk and Parker (1975) have re-
cognized three different but related types of capacity:
1. Environmental: The limit'at which human activity will lead
to undesirable changes in the environment.
2. Perceptual: The amount of activity or degree of change that
can occur before one perceives the environment to be different
than before.
2

3. Institutional: The ability of organizations in the area
to guide development toward public goals.
Since carrying capacity is a young field, there is far from univer-
sal agreement as to how the term should be defined and how it should
be applied. Planners will confront this confusion when using the
available literature. Carrying capacity analysis has been referred
• to as a particular planning tool which is used to generate specific
population sizes or densities that represent the limits of different
systems. Also, it has been used as a plan and development guide for
these systems. Additionally, the term has been described in a more
generalized way to refer to any type of analysis that recognizes
limits on one's ability to use certain resources.
The carrying capacity approach has been applied in a wide vari-
ety of situations across the country by agencies in local, regional
and state governments as well as university researchers. The subjects
of study have ranged from the capacities of small municipal parks to
the environmental and economic capacities of multi -state regions.
` Godschalk and Axler (1977) have reviewed 29 studies which have
been prepared by governments and universities that apply the carry-
ing capacity concept to questions of development planning. Their
findings have been instructive. All of the examined applications
have addressed environmental capacity. Specific systems covered in-
clude soils/slope, vegetation, wildlife, wetlands and other fragile
resources, scenic resources, natural hazards, water quality, water
supply, air quality, and energy availibility. Other systems which
have been examined include public services (transportation, sewage
treatment, sewer service, schools, recreation), economic systems
(employment, housing, agriculture, fisheries, forestry) and percep-
tual/behavioral systems.
Godschalk and Axler (1977) group the methods which are used,to
determine capacities into four categories. The outputs of the
studies have been diverse, ranging from population limits to devel-
opment regulations, as well as suitability maps and public service
thresholds.
(1) Calculations. Simple formulae, computations, and graphs
produce some of the most useful outputs. While the formulae
have been applied to several of the major types of capacities,
3

calculations are most frequently used for determining the
capacities of public services and facilities.
(2) Inventory/interpretation. This category has been the
traditional method for incorporating ecological concerns into
the planning process and the most common method used in the
studies for determining capacities.
r
(3) Comprehensive Models. Several applications developed
comprehensive models to describe entire groups of systems and
their interactions. The general experience has been that this
type of model has been a useful learning tool but suffers from
enormous time and data requirements as well as limited trans-
ferability.
(4) Sector Models. Several other applications have used
sector models to describe the behavior of one or a few support
systems. Such a model consists of a mathematical formula for
modeling a particular system, i.e., water consumption.
Certain problems have been common to a number of applications.
Inadequate data and the need for intergovernmental cooperation have
hampered many planning studies. Carrying capacity studies have been
no exception. A major problem of several studies has been the diffi-
culty of combining different types of data to produce information on
capacities (such as the use of data on soils, air quality and schools
to generate housing suitabilities) in a manner that is not highly
subjective.
Godschalk and Axler (1977) have concluded that there are four
major components of carrying capacity analysis that need substantial
improvement if the technique is to gain widespread acceptance and
success:
1. Standards and criteria,which have been used to determine
thresholds and capacities, need to be rigorously reviewed.
,Also, improved procedures need to be developed for their formu-
lation.
2. Existing data sources need to be made more readily available
and/or updated and interpreted, and new data sources need to be
developed.
3. Carrying capacity methods are in dire need of further devel-
opment and review, particularly in terms of reliability and
effectiveness.
4. The institutional climate for implementing carrying capacity
findings needs to be strengthened.
4

Operational Considerations.
While the basic idea of carrying capacity may be relatively
straightforward, developing it into an operational planning tool
has proven far more difficult. There are a number of outstanding
issues that confront every attempted application, particularly in
defining the concept and approach with sufficient specificity, and
• in finding or developing adequate methodologies for determining
capacity.
Several basic assumptions underlie the use of carrying capacity
analysis in urban development planning and should be understood by
practitioners. As presented by Schneider et al. (1978):
1. There are limits to the amount of growth and development
that the natural environment can absorbe without threatening
public health, safety and welfare through environmental deg-
radation.
2. Critical population thresholds can be identified beyond
which continuation of growth or development at greater densities
will initiate the deterioration of important natural resources
such as water or air.
3. The natural capacity of a resource to absorb. growth is not
fixed, but can be altered by human intervention.
4. The determination of the limit'of capacity of a given system
is, finally, a judgmental act.
The most important point to realize is that an area does not have
a single, fixed carrying capacity. The capacity of a system is a
function of existing technology, economic resources and acceptable
quality -of -life levels. A system's capacity may be changed by altering
these determinants. The capacity of many systems (particularly infra-
structure) can be expanded by additional investment. Advances in
technology may also permit sudden expansions in capacity, such as
the increase in available water supply that would accompany the in-
vention of an economical desalination process. The available capacity
of a resource may stretch much farther if the per capita consumption
is reduced. This may be through voluntary or enforced conservation
measures.
61

The result is that, for most systems, there exists a series of
capacities. Each one requires a shift in the parameters that define
it (technology, investment level, acceptable quality) before it can
be surpassed. Godschalk and Axler (1977) explained this concept as
follows:
The picture that will emerge from this analysis will not
be that of a single, fixed carrying capacity limit, but rather
• a series of limits imposed by different critical resources.
Each one defines the carrying capacity of a particular resource
in the light of certain assumptions about technology and economics.
In some cases these limits may coincide. In most cases they will
not, but instead will define a series of thresholds for growth.
Many of these thresholds can be crossed, if there is an invest-
ment in new technologies or new approaches to ameliorate the
particular resource constraint. Where the threshold can be
crossed, it will frequently not be feasible to do it incremen-
tally, because the technology for doing so will demand large
blocks of investment (as in going from individual waste disposal
to central collection and treatment).
Whether it is desirable to make the necessary investment to
cross one threshold may well depend on the proximity of other
threshold limits imposed.by other resources. If these are con-
siderably less restrictive than the carrying capacity limit of
the first resource, then the plan may be justified in making the
investment to cross the first threshold. If the carrying capac-
ity limit of the second resource is close to that of the first,
then an investment to cross the first threshold would only lead
to an immediate need for further investment to cross additional
ones. The extent to which carrying capacity is an absolute
limit on growth may well depend on whether there is such a con-
junction of limits imposed by different resources.

CHAPTER II.
The Carrying Capacity Process
While the various concepts of the carrying capacity are easily
explained, selecting a single concept and making it operational is
far more difficult. A basic approach to making operational a carrying
capacity project, as outlined by Godschalk and'Parker (1974), consists
of the following steps:
"l. Gathering existing data and conducting resource inventories
where existing information is insufficient;
2. Defining the relationships between each resource and the ex-
pected or potential use of that resource (e.g., per capita rates
of water use and waste production). Ideally, the result would
be a series of graphs indicating how much each resource would
be consumed by each increment of population and activity.
3. Predicting the carrying capacities of the different resource
systems. These carrying capacities are thresholds beyond which
a qualitative change occurs..In terms of environmental, perceptual
and institutional capacities, a particular threshold may represent
a point beyond which a different order of public investment is
needed to prevent degradation, a different type of experience
results, or an institution fails to perform adequately."
While this three step process provides the general direction of
a carrying capacity study, most small units of government need a more
detailed outline to conduct this type of work. One characteristic that
is consistent among all carrying capacity studies described in the
existing literature is that each study is highly individualistic. The
studies vary tremendously in that different levels of resources are
Y
used to address needs that are unique to the community conducting the
study. The lack of a common, workable format may be the biggest single
reason that such studies are not more commonly found. Until a more
universal approach to carrying capacity is developed from experience,
this diversity among approaches will continue.
7

The general approach described below is designed to guide a
community through the basic steps of developing a carrying capacity
study. It should be understood, however, that this approach would
likely need modification to fit the needs, resources and expectations
of a local community wishing to use it.
Step One. Review the general literature on carrying capacity
studies. Much information has been collected on carrying capacity
studies around the country leading to numerous published articles.
Before one launches into a carrying capacity analysis, some research
should be done to gain a thorough understanding of the concepts, def-
initions and previously tried approaches. Understanding can be
acquired only from reading selected articles. The articles by
Bishop et al. (1974), Godschalk and Axler (1977) and the book, Design
with Nature, by Ian McHarg, contain vital information and are vital
reading for anyone interested in pursuing a carrying capacity analysis.
Step Two. Determine the concept of carrying capacity most suited
to the community. The young field of carrying capacity has not seen a
single concept that rises above all others. Consequently, anyone
wishing to undertake an analysis must give careful consideration to
the various concepts in determining the one most suited for his situ-
ation. In making such a decision, one should consider the type of
information the community's decision -makers will find most useful and
the quantity and caliber of resources available for the project.
Much of the value of carrying capacity is in the approach to de-
cision -making that it encourages. Representatives of small units of
governments tend to require practical information before they will con-
sider the study totally worthwhile. The analysis would be considered
useful, by even the most critical of judges, if it identified points
in time at which decisions must be made to alow growth or increase
capacities of systems. This is particularly helpful to local govern-
ments planning capital improvements or wrestling with questions of
density. This concept of identifying thresholds, furthermore, can be
accomplished for many systems with calculations and inventories. Metho-
dologies using calculations and inventories generally are within the
capabilities of local government staffs or can be provided by consul-
tants at a cost suitable for small town budgets.
E3

Step Three. Collect copies of all studies, plans and reports
done for the community by consultants, public agencies and in-house`
staff. From these documents determine what data have been collected,
examine critical issues and relationships that have been identified,
and explore what work, if any, has been done toward a carrying capac-
ity approach. For most communities, there has been considerable
planning done in conjunction with projects funded by grants from the
Department of Housing and Urban Development, the Economic Development
Administration, Farmers Home Administration or various state agencies.
A useful, early step in any planning process is to inventory all past
planning that has been undertaken for data, issue and goal identifi-
cation. The data gathering and planning that has been previously
completed may influence the choices of issue and methodology selection.
Step Four. Select the issues to be addressed by the carrying
capacity study. As described above, the newness of the carrying
capacity field has resulted in tremendous diversity among the various
efforts. Consequently, any planner attempting to do a carrying capac-
ity study is going to be treading on some new ground that can produce
many different directions in which the study may go. This requires
that great emphasis be placed on keeping a sharp focus and a clearly
defined direction, while undertaking the analysis. An important begin-
ning toward maintaining a sharp focus is to state clearly and concisely
the issues to be studied. The study's usefulness is maximized if the
community's most pressing issues are addressed. Chapter Three is de-
voted to describing a detailed procedure for selecting the Issues for
study.
Step Five. Define the study area. Boundaries of the study area
can be drawn once the issues for study have been chosen. The objective
of this step is to recognize other units of government that should be
consulted, if not included in the carrying capacity study. If a
single governmental entity is undertaking the study, the study area
very likely will extend beyond its jurisdictional boundaries. In
this case, neighboring governmental units should be asked to join in
the project, if the analysis is to provide useful results. The study
may involve forces that are within the jurisdictional boundaries of
the locality, but are the responsibility of a different level of
government. Ideally, these agencies should join in the project.
7

Step Six. Select the methodologies to be used. Once the issues
are chosen, methodologies need to be selected to analyze the systems.
It is important to choose methodologies that will produce information
that will be considered useful and valuable to the decision -makers.
Data and resource availability should be considered and the steps of
the methodologies must be logical and understandable. Chapter Four
describes methodologies for selected systems that appear within the
capabilities and time restraints of local governments. They should
be considered as examples of methodologies that are available or
which can be divised and should be used only if they provide the type
of analysis desired.
Step Seven. Develop a framework for using the results in the
decision -making process. One should be concerned with the usefulness
of the study's results during each of the prior steps of the process.
Proper issue selection will lead to results that are considered impor-
tant. Nevertheless, one.should have a specific method in mind for
using the results in the decision -making process. Chapter Five sug-
gests one such method.
Operational Considerations and Pitfalls.
A carrying capacity analysis may produce very useful and valuable
information for a local government, making the time and effort spent
on the project worthwhile. Before a unit of government decides to
embark upon such an analysis, however, it should recognize basic con=
siderations and potential pitfalls. One of the most fundamental and
difficult concerns is the need.for inter -governmental cooperation.
Practically every local unit of government has some dependency on
sources of supply and demand located beyond its jurisdictional bound-
aries or beyond its scope of authority. Consequently, in order for
the results of a carrying capacity analysis to be relevant, it must
not stop at jurisdictional boundaries. For example, if a single aqui-
fer supplies water for three communities, the entire three -community
area should constitute the study area for an analysis of the water
supply and demand. Policies or programs that result from the analysis,
furthermore, should be implemented in the three communities if the
issue is to be fully addressed. Such inter -governmental cooperation
is not easily achieved when different philosophies and attitudes exist
10

.
.
among neighboring communities. Few units of government are isolated
to the degree that they can conduct a carrying capacity study on their
own. A carrying capacity analysis, at its outset, faces the stiff
challenge of inter -jurisdictional coordination.
The expenditure of time and/or money required for a carrying
capacity study should be considered before a decision is made to under-
take such a project. Small communities would have a difficult time
completing such a study with its in-house staff unless they were cap-
able of assigning one individual to work on the project between one-
half and full-time. If daily functions compete with the carrying capac-
ity project for the staff's time, the daily functions will tend to win
out most of the time. This means the carrying capacity analysis would
be put aside from time to time, causing a loss of continuity, concen-
tration and possibly information. Three to four days of uninterrupted
time are needed to make significant headway when work is being done on
the methodologies described in Chapter Four. The analysis may be
accomplished with in-house staff if the project can be divided into a
series of tasks, each designed to take three to four days. If the
staffing level does not allow sufficient amount of time to be devoted
to the project the use of consultants should be considered. Other
sources of assistance that may be available free of charge to a local
government are the staffs of the local regional planning agency, the
North Carolina Department of Natural Resources and Community
Development and university faculties. University faculties often
seek practical experience for classes and individual students. Many
students also are required to fulfill internship requirements. A more
direct relationship between local governments and the state's univers-
ities may provide student assistance.
Becoming overwhelmed with data and information is a pitfall to
avoid. As stated, careful consideration should be given to the se-
lecting of issues to be addressed development of the project's focus.
Efforts should be made to collect and concentrate only on that infor-
mation and research data that are directly pertinent to the carrying
capacity project. A way of helping to keep one's focus throughout
the project is to contract a small amount of time with someone who has
experience with carrying capacity studies. Such a�consultant that is

willing to serve as a sounding board for those conducting the study
will be very valuable.
The absence of clear and concise methodologies is another hurdle
to be cleared. Once the systems to be analyzed have been chosen, per-
tinent agencies at the local, state and federal levels should be con-
tacted in an attempt to uncover ways that will produce the type of
information desired. Telephone interviews and research have identified
the following sources of information.
Transportation - Planning Division, Department of Transportation,
Raleigh
Administrative Capabilities - Professors in the Public
Administration Department at Duke and North
Carolina State University
Hurricane Evacuation - The article by John R. Stone
Water Quality - The most pertinent information is being developed
in research projects by professors at the
University of North Carolina, East Carolina
University, North Carolina State University
Water Supply - The community's water superintendent, water depart-
ment records,'and reports by consultant engineers
Recreation - Division of Parks and Recreation, Department of
Natural Resources and Community Development,
Raleigh
Water System - The local water superintendent, water department
reports, and reports by consultant engineers
The lack of data is another stumbling block. A common problem
is that the data does not exist in the form or level of analysis
needed for the study. Much data, however, can be found in plans, re-
ports and studies done by consultants, state agencies and local staff.
The Bureau of the Census in Charlotte, N. C., and the State Data Center
in the Office of Management and Budget in Raleigh, N. C., can provide
much data as well. Credible information must be used if the analysis
is to be useful and valuable. If it is anticipated that useful data
can not be found, sufficient resources should be budgeted for the
proper research and data gathering to be needed.
12

CHAPTER III.
Issue Selection Process
One of the critical steps in planning and executing a useful
carrying capacity analysis is the selection of issues for study.
The concerns of a community, regarding growth, -can identify numerous
natural and manmade systems for studying a carrying capacity con-
text. Table 1, Potential Systems for Carrying Capacity Analysis,
depicts the vast array of potential systems and their measurable
indicators. Before embarking upon the process of methodology devel-
opment and data gathering, one should carefully select from the
systems for analysis. A systematic and comprehensive approach should
be used in this selection process. If the most critical concerns
are addressed, the usefulness and value of the study's results are
enhanced.
The selection of too many systems for study should be avoided.
It is easy to attempt to analyze too many issues for the time and
resources available. When undertaking a carrying capacity analysis,
one should attempt an in-depth analysis of a few issues rather than
touch upon several and risk inconclusiveness.
A three step process, similar to that used by the Hawaii
Department of Planning and Economic Development, is suggested for
identifying the issues to be addressed. The first step, as shown in
Figure 1, consists of initial screening of issues, relying on general
knowledge, documents, plans and reports. Discussions with represen-
tations of pertinent agencies, technical experts and the planning and
governing boards should also be used to develop a list of potential
issues for study.
Exploratory analysis, the second procedural step, consists of
exploring each potential item on the list in order to assign prior-
ities to the various issues. The concerns or issues of the community
should than be translated into a list of systems with quantifiable
indicators as shown in Table 1. The exploratory analysis also includes
13

an assessment of the data, expertise and time needed to analyze each
system. The community's plans and projected population growth should
be reviewed for their impact on various systems. Interrelationships
among the different systems should be considered as well.
The third step of the process, selecting issues and focusing the
analysis, consists of deciding upon the systems for study. If the
community wishes to develop criteria, such as percentage of population
affected, it should be utilized in its selection process. The number
of systems chosen should reflect the urgency of the issues as well as
the resources available for the project.
For more detailed discussion of an issue selection process, refer
to Chapter IV of Carrying Capacity Action Research: A Case Study in
Selective Growth Management, Oahu, Hawaii. This document has been
prepared by the State of Hawaii, Department of Planning and Economic
Development in 1978.
14

Potential Systems
for Carrying Capacity Analysis
Table 1.
SYSTEMS
INDICATORS
Water Supply - Quantity
Water use
Water Supply - Quality
Pollutant concentrations
(coliform, nitrates)
Estuarine Water Quality
Pollutant concentrations,
algae growth
Air Quality
Pollutant concentrations
Geologic Hazards
Risk of development, area
Sensitive Environments
Development density, area
Transportation
Traffic volumes
Evacuation
Time
Developable Land Area
Area
Police Protection
Population adequately protected
Fire Protection
Population adequately protected
School System
School population'
Health Delivery System
Population adequately served
Open Space
Area
Parks and Recreation Areas
Area, density of use
Aesthetic Character
Design features
Institutional Capacity
Numbers of department employees
Fiscal Capacity
Tax Base
15

Y
Figure 1. Outline of Issue Selection Process
INITIAL SCREENING
. General Knowledge
• Review of Plans, Reports and Studies
• Consideration of Demand/Supply Relationships
. Discussion with Planning and Governing Board
SET OF POTENTIAL ISSUES FOR I
EXPLORATORY ANALYSIS
EXPLORATORY ANALYSIS
. Review of basic background information relative to
future land use plans and projected population growth.
• Quantification of each issue into systems/indicators
as needed to diagnose potential imbalances between
demand and supply.
• Issue characterization in terms of key assumptions
and parameters.
. Review of studies and reports.
• Presentation of results to Planning and Governing
Board for debate.
(REFORMULATION OF POTENTIAL GROWTH ISSUES I
WITH IDENTIFIED SYSTEMS/INDICATORS
SELECTING THE ISSUES AND FOCUSING THE ANALYSIS
• Update of exploratory analysis results based on
comment from Planning and Governing Boards
• Criteria for selecting priority growth issues.
. Reformulation of issues and systems to capture
interdependencies.
SELECTION OF GROWTH ISSUES
FOR RELATED SYSTEMS AND IN-DEPTH ANALYSIS
Note: Adapted from: Carrying Capacity Action Research: A Case
Study in Selective Growth Management, Oahu, Hawaii.
16

CHAPTER IV.
Selected Methodologies
One step termed fundamental to the carrying capacity process is
a comparison of potential future population of a community with the
community's capacity for growth. Methodologies for deriving a
community's future population from land use, septic regulations and
market analysis are discussed below. The means of determining the
potential capacities of systems within the community, notably water,
hurricane evacuation and recreation are also described below so that
a.comparison of the data can be made.
While some of the methodologies for systems and population growth
have been taken from published sources, others have been derived for
this report. These methods are presented as examples and should be
applied by a local community only if appropriate for its specific needs.
Planners are encouraged to explore publications, plans and relevant
state and local agencies for methodologies to supplement or replace
the ones presented here prior to undertaking a carrying capacity
analysis.
17

Land Use Regulations
Many dimensional requirements of local ordinances, including
minimum lot sizes and density allowances, are somewhat arbitrarily
determined. Most local officials would be shocked at their community's
population if the town were built to the maximum denity allowed by
local ordinances. Carrying capacity analysis will provide a basis -
for reviewing the local zoning and subdivision ordinances. Density
allowed under these ordinances can be compared to the capacity of
systems already existing in the community. Certain tools are needed
in order to review ordinances to make such a comparison, as follows:
zoning map and ordinance; aeriel photography or land use inventory
map showing vacant land and development by land use; a map showing
unbuildable areas; and current population estimates.
The density allowed by local ordinances can be analyzed by
following a simple process delineated below:
Step 1. Determine the number of vacant acres in each zoning
district of the community.
Step 2. Determine and subtract the number of acres considered
unbuildable (either by ordinance or topographic features).
Step 3. For zoning destricts that allow mixed uses, such as
commercial and residential, assume all land will be residentially
developed.
Step 4. Determine the maximum residential density allowed in
each zoning district, and apply this density to each district's
vacant acres. This process will project the number of units that
are allowed on the vacant land.
Step 5. The average number of people per household, either from
a local survey or the census date, multiplied by the projected number
of units will estimate the maximum population allowed on the remaining
vacant land.
18

Step 6. The projected population allowed on the vacant land,
added to the existing population, will estimate the community's
total population if the town is built to'the allowed densities.
Step 7. This population total can be compared to the population
levels that can be accommodated by the community's extant systems.
Many communities do not have local ordinances that set out maxi-
mum densities. These communities can estimate their maximum populations
based upon the market demand and/or septic tank regulations.
W

Sewage Treatment
Alternative methods of sewage treatment make it impossible to
determine exactly the number of people that can be accommodated by
a community's sewage treatment system. If no public sewer exists
land area requirements for septic systems and package treatment plants
can be analyzed to determine the number of systems the community's
soils can receive.
The county health department administers regulations that state
minimum lot size and the maximum number of bedrooms for developments
using septic systems.. The procedure outlined in the section on Land
Use Regulations, with a minor change, can be used to determine the
maximum population allowed under the septic regulations. The density
of bedrooms per acre, instead of the density of units, can be applied
to the number of vacant acres remaining in town. Assuming an average
• of two people per bedroom, as do health departments when designing
regulations, the maximum allowable population under septic regulations
can be derived.
If one wished to determine the population for a community using
package treatment plants, the land area requirements can be obtained
from the North Carolina Department of Natural Resources and,
Community Development, Division of Environmental Management. The
same process as mentioned above can be used.
One must realize, however, that this procedure will produce
general estimates. The actual capacity of land to accept sewage is
determined only after on -site inspections. The standard requirements
will be adjusted to accommodate features of individual sites.
Communities with public sewer systems may assess the system's
capacity with a procedure described below for water systems. This
procedure itemizes the various components of the system and enunciates
each part's capacity. These capacities are then compared to the
projected demand based on projected population. Please refer to the
Section below on Water Systems for a more detailed description of the
process.
20

Market Demand
One of the basic principles in developing a growth management
policy for a community is to balance the demand for development with
a capacity for development. Early in the carrying capacity project
the demand for development of the community should be determined.
In order to project this demand, one would require a map indicating
an inventory of developed land by land uses, a map of undeveloped land,
the existing population and the projected population. A formula for
determining the demand for land follows:
L90 - L80 + P80-90 (Kh + Kr + Kc + Ki + Kp + Kt)
L90 equals land required for'1990 population or some other date
in the future.
L80 equals land required for 1980 population or some other past
date for which there is land use data..
P 80-90 equals population added to the community between 1980 and
1990.
Kh equals standard, or per capita, acres of land required for
residential use.
Kr equals standard, or per capita, acres of land required for
recreational use..
Kc equals standard, or per capaita, acres of land required for
commercial use.
Ki equals standard, or per capita, acres of land required for
industrial use.
Pequals standard, or per capita, acres of land required for
public and semi-public use.
Kt equals standard, or per capita, acres of land required for
transportation use.
The first step in determining the demand is to inventory the
number of acres developed by the various land uses, such as housing,
recreational, commercial, and so forth. The date of the inventory
should coincide with the date of the population used for the P80
21

factor. If the 1980 Census data, for example, is to be used for this
baseline population figure, an inventory should be done of the acres
developed by each of the land uses as it existed in 1980. If aerial
photography or land use data do not exist to allow the 1980 inventory
to be obtained, the inventory can be undertaken for a more recent
year or the current year. The 1980 population figures, however, would
need to be updated to the same year as the inventory.
The inventory of the various land uses will provide the number of
acres developed as residential, recreational, commercial, industrial,
public and semi-public and transportation. The population figures
for the time period in which the inventory was conducted will allow a
ratio of acres per person to be developed for each of the above men-
tioned land uses. If a community's population, if instance, is 100
and the land use inventory indicated that 300 acres of land had been
developed for housing, the ratio of people to land developed for housing
will be one to three, or .33. The decimal equivalents of the acres -to -
people ratios will be inserted in the above equation as the standard
land requirements.
When the projected population standard land requirement factors
and the total acres developed for the baseline date are inserted in
the above equation, the demand for land for the year 1990 can be deter-
mined. If a more detailed explanation is needed for developing space
requirements in the various land uses, please consult Urban Land Use
Planning by F. Stewart Chapin. National standards of land requirements
for various land uses are found in other texts as well. If the local
trends derived from the space inventory are not preferred..these sources
can be used for obtaining the national standards. One such source,
although dated, is an article written by Larry Smith in the American
Institute of Planning Journal, February 1961, that provides per capita
floor area for selected activities. The activities include retail
office, parking, public, quasi -public, wholesale, industrial and
residential uses.
Once the number of acres needed for the projected population has
been determined, one can derive the total number of acres available
for development by subtracting from the community's total vacant acres the
land not suitable for development. Such unsuitable land can include
wetlands, flood hazard areas, steep slopes, watershed areas and woodlands.
22

The total number of acres suitable for development is then compared
to the demand for acres as determined in the formula above. If
the demand for acres exceeds the available acres, the community will
experience pressure to overdevelop.
Maps and aerial photography of the community can assist in deter-
mining the acres of land restricted or unsuitablefor development. .
The land use maps adopted as part of the local land use plan under the
Coastal Area Management Act identify forest land, water, wetland and
beaches which should be excluded from the total of developable acres.
The local Soil Conservation Service can provide soil survey maps of
the community. These maps, available for most counties, indicate
slope of land, soil type and classification of land according to its
use suitability. U. S. Geological Survey topographic maps may be used
to indicate flood plains, wetlands and wooded areas. Also, State
Geological Survey Department has topographic quantrangle maps that
indicate the locations of wetlands. A plant and wildlife inventory
can be developed with the assistance of the Soil Conservation Service,
Cooperative Extension Service, or State Wildlife agencies.
23

Water Supply
The ability to deliver water is clearly a limiting factor to
development. This factor reflects both the capacities of the water
source and the delivery system. One of the first steps inassessing
the capacity of the water supply and system is'to tabulate past water
consumption. Local water plants file monthly reports with the Water
Supply Branch of the Division of Health Services in Raleigh, which
aid in evaluating water supply. N. C. State Form 1399 is filed by
plants that do not process their water while Form 1940 is filed by
the processing plants. Each of the forms indicates the number of
gallons of water per day that pass through the plant with the peak
and average uses shown. Figures 2 and 3 depict examples of the forms.
Population counts, whether from Bureau of Census data or local
estimates, can be compared with the water consumption totals for the
corresponding time period. If a time period can.be determined for
which the community is assured of its population, the water consumption
for this period divided by the population will derive a per capita
consumption of water. The per capita consumption estimate will allow
future water demands to be projected based upon the community's popu-
lation estimates.
Local and regional planning documents generally contain.population
projections. If census data is unavailable, population projections
can be derived by the use of several standard projection techniques.
Techniques such as the linear model, growth curves, the comparative
method and the cohort -survival model are referenced in several planning
texts. 'One readily available work is Urban Planning Analysis: Methods
and Models by Donald Krueckeberg and Arthur Silvers (1974). Applica-
tion of such techniques requires someone who is familiar with planning
techniques and statistical analysis. The North Carolina Department of
Natural Resources and Community Development (NRCD) field office or the
Regional Council of Goverment may be able to provide staff assistance
to a local community wishing to derive population projections.
24

FIGURE 2.
(a) CHLORINATION PLANT AT
REPORT OF OPERATION TO THE
DEPARTMENT OF HUMAN RESOURCES
DIVISION OF HEALTH SERVICES
ENVIRONMENTAL HEALTH SECTION
Month
/ Year
Total
Water
Treated —
Thousands
of Gallons
Cost of Chlorine or Hypochlorite, per lb. ......... $
Total cost of operation ........................... $
Total precipitation for Month ..................... inches (Signed) _
i
DRS Form 1399 (Rev. e/73)
Motor Supply 25

FIGURE 2. INSTRUCTIONS FOR FILLING OUT IHE CHLORINATION PLANT REPORT
(b )
Duplicate copies of this report should be made. One copy should be mailed.direct to,
the Division of Health Services, Water Supply Branch, Raleigh, N. C. at the end of each
month, and one copy should be filed with the proper local official as a permanent record,
COLUMN (1): The dates are printed. No entries are to be made -in this column. All
other entries are to be made to correspond with the date, horizontally across the report.
COLUMN (2): Water plants should be equipped with a meter in order that the total water
treated, in gallons, per 24 hours may be determined. The total amount of water treated in
24 hours should be indicated in this column. In case there is no meter, the quantity of
water treated should be estimated as accurately as possible on the basis of capacity of pump,
reduction in level of water tank, or from calculated flows. Inexpensive weirs can often be
installed to determine the water flow.
COLUMN (3): Where liquid chlorine is used, the cylinder should be kept on platform
scales. Record the loss in weight at the end of the day'.s run, to the nearest decimal or
fraction of a pound of chlorine used. In case HTH,.Perchloron, chlorinated lime, or other
form of hypochlorite is used the amount put in the solution tank should be accurately weighed
and the proportionate part of the tank used up during the day utilized as a basis of calcu
lating.the number of pounds or fraction of a`pound of the chemical used. This figure should
be entered under this column.
COLUMN (4,5 &6): These columns are left blank for the purpose of indicating other
chemicals used or results of other tests.
COLUMN (7): Chlorinator meter reading.,
COLUMN (8): The total number of hours the plant was in operation for the 24 hour period
should be recorded in this column. If the plant was in operation 24 hours, that figure
should be recorded. 4
COLUMN (9): The temperature of the water being treated should be recorded in this
column. The temperature should.be determined at the same time tests are made for residual
chlorine. If more than one determination is made, the indicated result should be the
average of the several determinations.
COLUMN (10): In case a water runs perfectly clear all of the time "0" should be entered
in this column. If there is an appearance of turbidity, a turbidity, a turbidimiter or
turbidity rod should be secured in order that determinations can be made and the results
recorded in this column.''
COLUMN (11): This column should be used to record the results of the orthotolidine
tests for residual chlorine. This test should be made at least once daily. -If more than one
test is made the average results should be recorded in this column. Test to be made at water
plant.
COLUMN (12): This column should be used to record results of samples collected from
distribution system.
COLUMN (13): Under remarks should be included any troubles experienced with the chlo-
rinator, any stoppages for repairs, any complaints made of tastes and odors, turbidity, or
any out of the -ordinary occurances.
In case the chlorinator gets out of order and cannot be repaired, the Division of
Health Services should be notified promptly.
If any further explanations for filling out this report form, or information on,plant
operation is needed, advise the Water Supply Branch of the Division of Health Services of
your difficulties, in order that they may give you the needed information or assistance.
26

Projections for counties are derived by the Officecof Budget and
Mangement of the North Carolina Department of Administration. These
estimates are commonly used in local and regional planning documents
and can be obtained for years ending in 0 and 5.
A paramount concern in planning a community's future is to insure
that the water supply can provide for the projected population. If the
projected water use derived from per capita consumption and population
projections exceeds the capacity of the water service, the community must
seek a new water source and/or ways to curb future growth.
Engineering methods for determining the quantity of available
water are fairly straightforward. Such a project is usually done by an
engineering firm using test wells for underground aquifers or flow cal
culations for surface water sources. This report will not set out a
description of these methods, but rather will discuss the application
of the results of such a study.
If the maximum capacity of the water source is determined the upper
population limits of a community can be derived. The maximum capacity
of the water source devided by the estimated per capita consumption, as
discussed above, will produce the maximum population that the water
source can support. The community must plan for ways to curb population
growth as it approaches this limit or identify other water sources and
budget for the necessary costs of tapping the sources.
If water consumption can be determined for various land uses,
such as retail establishments, restaurants and residential units, con-
clusions may be drawn regarding the optimal composition of land uses
for a community. Development standards"may be adopted that limit the
number of high water users and encourage the low water users.
An engineering study of the water supply can produce more than
an assessment of the quantity of water available. It can also identify
the type of water source and the particular hazards to it. If an under-
ground aquifer is the source, the study can identify the boundaries
of the primary recharge area and the amount and rate of infiltration
• necessary to maintain its water yield. Once this information has been
determined, a local regulatory program may be developed to protect the
source. Another important part of the study would be to determine the
a-s

necessary amount of land area needed to provide for sufficient recharge.
Once this has been determined, a regulatory strategy can.be developed
for protecting land area.
Critical information from the study of the community's water supply,
if its supply is in fact ground water, is the rate in which the source
is replenished. This rate has particular significance in the coastal
areas in that salt water intrusion may occur if the wells are pumped out
at a rate greater than that at which they are replenished. Where fresh
ground water aquifers are adjacent to saline ground water, overpumping
of fresh water results in the intrusion of salt water. If this occurs,
the fresh water wells must be abandoned until the fresh water reservoirs
are adequately replenished and the boundaries between fresh and salt water
are reestablished.
There are natural limits upon the amount of water which can be
extracted from the aquifer. While many aquifers are replenished or re-
charged by seepage from adjacent underground formations, all aquifers
depend upon infiltration of surface water. The amount of water which
enters the aquifers yearly, whether directly from perculation, or in-
directly from adjacent formations, determines the amount of water that can
be withdrawn annually without severly depleting the reservoir. Failing
to consider the natural limits of the recharge process can result in
overuse and waste of the resource. A community must insure that its
growth rate does not cause the withdrawal rate of water from the aquifer
to exceed the rate of recharge.
29

C
Water Systems
The capacity of a community's water processing and distribution
system is equally as important as that of the water source. While.the
water source must provide the needed quantity of water, the water system
must be capable of delivering the water to the community. The following
steps can be used. to assess the system's capacity and compare it to the
projected water demand:
Step 1. Determine the per capita consumption as described in the
section of this report on water supply.
Step 2. Project water consumption by multiplying the per capita
consumption and the projected population. Sources for population
estimates also are set out in the section of this report on water supply.
Step 3. Identify the individual components.of the water system,
listing the capacity of each. The system may consist of at least the
' following: (1) transmission line from the water supply, (2) raw water
pumps, (3) primary clarifier, (4) finished water reservoir, (5) finished
water pumps, (6) chlorinators, (7) transmission line to storage tanks,
(8) storage tanks, (9) distribution lines.
Step 4. Develop a graph, as shown in Figure 4, in which the
vertical axis is titled "Gallons of Water Per Day" and the horizontal
axis represents "Population." The capacity of each component of the
system is then graphed as a horizontal line according to the maximum
number of gallons as identified on the vertical axis. Each horizontal
line is identified as the capacity of pumps,'transmission lines, etc.,
as shown in Figure 2.
Step 5. Graph the curve of projected water demand based upon
per capita consumption and projected population.
• Step 6. Where the curve depicting water use intersects horizontal
lines identify points at which the demand for water will exceed the
capacity of the individual components of the system.
30

Thousands
of gallons
1000
750
ca
A
t�
vl
U
Cd
cd 500
U
44
O
to
O
O
r-1
r-1
Cd
0 250
0 0 0 0 0 0 CD
0 0 0 0 0 0
Ln n m w w w
Population r+ rq r-1
��
31

Hurricane Evacuation
Components of Evacuation Time
.A good estimate of total evacuation time is one of the most
important keys to hurricane preparedness.. Too long an estimate may
lower public credibility in the plan; too short an estimate could
mean disaster. Only with good estimates of evacuation time can local
officials know when to issue the order for their community's resi-
dents to abandon their homes and businesses in order to save their
lives.
"Evacuation time" represents the minimum amount of time that
local decision -makers must allow for safe evacuation of an area
which is faced with eminent danger. Different hurricane situations
• require different evacuation times. For example, if the National
Hurricane Center forecasts that the eye of a low intensity, Category
I hurricane is to reach a community's shores by 6:00 p.m., then local
authorities may officially order the evacuation to begin no later
than 10:00 a.m. For a more intense hurricane, the evacuation time
will likely be longer because of earlier roadway flooding or the
earlier arrival of gale force winds. The evacuation should begin
even earlier than 10:00 a.m.
Several measurable components make up evacuation time as shown
in Figure Three-1. The transportation related components, "clearance
time," is dependent upon the attitudes of the evacuating population
and on the carrying capacity of the community's transportation net-
work. Clearance time is defined as the amount of time necessary for
the relocation of all evacuees to their respective shelter destinations,
once the official evacuation order is issued. The clearance time con-
sists of three main subcomponents: "mobilization time," "travel time,"
and "queuing delay time."
Source:
John R. Stone, Hurricane Emergency Planning: Estimating Evacuation
Times for Non -Metropolitan Coastal Communities
32

Mobilization time is that period of time between the issuance
of the evacuation order and the departure of the last vehicle from
the vulnerable area. This period greatly depends on the attitudes
and response time of residents. Travel time is the period necessary
for the vehicles to travel the length of the evacuation route at an
anticipated operating speed (assuming no traffic delays). Queuing:
delay time is defined as the time spent by vehicles in traffic jams
which result when the capacities of the evacuation routes are ex-
ceeded.
These three components of clearance time result from analyzing
the transportation characteristics of the evacuation route and the
behavior of the evacuees. If a vulnerable area is relatively isolated
and evacuation behavior (mobilization time) is assumed to be relatively
constant, clearance time will tend to remain the same, regardless of
hurricane intensity. However, the clearance -time may vary depending
upon hurricane intensity and whether vulnerable areas share the same
evacuation route. As the storm intensity increases, storm,surge
builds. More areas become vulnerable and more people must evacuate.
As more vehicles crowd the evacuation routes, clearance time will
increase.
33

Figure Three-1
COMPONENTS OF EVACUATION TIME
(Source: Ref. 7)
Clearan,Ge Time
(TRANSPORTATION
MODELING) Mobilization Time Travel T Queuing Delay Time
u, (HAZARD ANALYSIS) Surge
Roadway
Inundation
Time
(HAZARD ANALYSIS) Arrival of
Gale Force Winds!
Time
L
Pre -landfall
Hazards Time
Evacuation Time
Issuance of '. Hurricane
Local Evacuation Order Eye Landfall
time in hours
* Also includes rainfall roadway inundation time.

Besides clearance time and its three subcomponents, total
evacuation time depends on the "pre -landfall hazards time." It is
this period of time, before the eye of the hurricane reaches the
coast, that either (a) evacuation routes become inundated and impass-
able by storm surge, or (b) sustained gale force winds arrive from
.. the approaching_ hurricane. The larger of (a) or (b) represents the
pre -landfall hazards time or "cut-off" time. The "hazards time com-
ponent" is not available for vehicle movements from the vulnerable
areas. All vehicles must leave the evacuation zones by the end of
the clearance time or they will be estranged from safety. Generally,
the cut-off time occurs earlier during hurricane increased intensity.,
At this time, evacuees must leave in order to reach shelter.
In summary,'total evacuation time depends upon the category and
characteristics of the hurricane being considered; the hazards from
storm surge, winds, and flooding; characteristics -of the evacuees and,
the transportation network. Figure Three-2 illustrates the major
steps in a methodology to determine evacuation time. The details of
each step are discussedin the insuing sections of this chapter.
Scenario Development
To formulate distinct evacuation times and plans for all possi-
ble hurricane conditions would be impossible for a community. A
plan must be based on probable conditions, and it must also be geared
to cope with "worst -case" hurricane hazards. Consequently, lesser
hazards will be covered by evacuation times and plan recommendations.
Usually evacuation planners consider five scenarios for vulner-
able areas. The primary hurricane parameter which distinguishes
different scenarios is "intensity." This term is defined by the
Saffir/Simpson Scale shown in the appendum to this section. Re-
lating the scenarios to this scale is necessary because the National
• Hurricane Center uses it when reporting the expected time and location
of hurricane eye landfall. Local planners should also include in the
scenarios probable storm size, direction of approach, and landfall
location as suggested by a study of past storms in the study area.
The various combinations of hurricane parameters define worsen-
ing evacuation scenarios which in tern identify, as a result of .the
hazards analysis, successively more vulnerable areas which must be
35'

Figure Three-2
Scenario Development
Hazards Analysis to Cut -Off Time
Transportation Modeling
W
Community Response Analysis - Mobilization Time
Free -flow Traffic Analysis Travel Time
W
Traffic Queue Analysis Queueing Delay Time
Evacuation Time = Cut -Off Time + Mobilization Time + Travel Time +
Queueing Delay Time
A Methodology for Estimating Evacuation Time
36

evacuated. As a result of choosing specific evacuation scenarios
for planning purposes, planners can calculate cutoff times and traffic`
clearance times for the vulnerable areas. For each evacuation sce-
nario, a different evacuation time may -be subsequently estimated for
each evacuation zone.
Hazards.Analysis
As discussed earlier, the "pre -landfall hazards" time depends
upon storm surge, high winds or flooding from rainfall which cut off
evacuation routes. Storm surge isparticularly dangerous. It is
during this time that most of the damage and 90% of all deaths occur.
The height of water that an evacuation area experiences during
a hurricane does not necessarily have to correspond to the Saffir/
Simpson Scale. If there is a high shoaling factor (shallow water and
gradual slope of the bottom off the immediate location of hurricane
landfall) then surge heights can be higher than those indicated on the
Saffir/Simpson Scale. Also, the surge height can be higher than ex-
pected if the surge travels into a bay or river. These enclosed
bodies of water entrap the surge and, through a funneling effect,
amplify its height.
Estimating the surge height requires the analysis of numerous
factors which describe the storm and the local physical characteristics
of the shoreline. The most practical way of accomplishing this anal-
ysis is through computer simulation. The results of the computer
analysis are in the form of "space-time" plots of predicted storm
surges. The plots indicate how high the water level will be at a
particular point along the coast and for.times.relative to actual storm
landfall or closest approach. Knowing the history of surge heights
and the elevations of low points along the evacuation routes allows
for calculation of roadway inundation "cut-off times."
The computer simulations for surge height also predict space-
time information for gale force winds. This information will indi-
cate when and where it will be hazardous, if not impossible, to
operate a vehicle on an evacuation route due to hazardous winds.
Cut-off times depend on hurricane conditions and local character-
istics as discussed above. However, typical hazard analyses suggest
that gale force winds may arrive up to six hours before the hurricane
37

eye. Also, low roadways may be inundated five hours before eye land-
fall.
Community Response Analysis
A significant fraction of the total evacuation time is repre-
sented by the time required for mobilization. Residents need to be
warned that evacuation preparations must be made and a traffic control
system must be established to insure optimum utilization.of the evac-
uation routes. For typical communities, it has been estimated that it
will take one hour for all evacuees to learn of the evacuation order,
another hour to establish traffic control procedures, and at least one
hour will be necessary for residents to make their preparations to
depart. Consequently, a total mobilization time of three hours.may
result before significant numbers of evacuees are moving away from
the vulnerable areas. The three-hour figure may vary somehwat from
community to community depending on its size, preparedness, and espe-
cially, the behavior of the evacuees.
To obtain more precise evacuation behavior data, planners often
use telephone and mail -back questionnaires to ask residents what,
actions they will take, when they will begin evacuating, and where
they will go in event of such an emergency. Questionnaire results not
only help to determine mobilization time, but also how to model the
traffic flow on the evacuation routes. Typical surveys have suggested
the following types of community response: ,
-Up to 80% of the vehicles in an area may be used in an evacuation;
-As many as 20% to 30% of the residents will leave before the
evacuation order is given, while up to 20% of the residents will
delay four or more hours.after the order; '
-Public shelters will be used by at least 35% of the evacuees and
the remainder will go to friends, relatives, motels, etc.
Such community response data is very important in the evacuation plan-
ning process. Unfortunately, the questionnaries are answered by a
very small percentage of the potential evacuees. Therefore an accu-
rate community response may not be derived.
Free Flow Traffic Analysis
Travel time is calculated by assuming "free -flow," uninterrupted
traffic movements. Delays from traffic jams at intersections and other
38

bottlenecks are accounted for in the traffic queue analysis.
Assuming that a known evacuation route consists of several road-
way sections and that the anticipated free -flow operating speeds during
the evacuation can be estimated, then the free -flow travel time is
• determined by the following formula:
Travel Time = f (Length of section i / Operating speed on section i)
The section lengths can be estimated from maps and the anticipated
operating speeds can be estimated from experience or trial runs. Usu-
ally such speeds will vary between 25 and 45 miles per hour (mph) with
35 mph being the mean. This range of speeds reflects capacity operating
conditions that evacuation routes are likely to experience.
For networks that have few evacuation zones and routes, the above'
formula provides a simple method for calculating travel time. However,.
as evacuation networks become more complex, providing alternative routes
to safety and allowing many evacuation zones to share sections of the
same evacuation route, more sophisticated methods are required.
If the community is small to medium size, the non -computerized
traffic assignment procedures discussed in Chapter 7 of a publication
by A. B. Sosslau, et al. may be used to determine the travel times and
• traffic volumes on the various sections or "links" of the evacuation
network. The site of this article is in the bibliography. If the
shelter assignments of the evacuation zones are not known, the trip
distribution procedures in Chapter 3 may be used to supply this infor-
mation.
For large metropolitan areas with many evacuation zones'and`routes,
computerized traffic assignment and trip distribution algorithms are
used to determine the optimum, shortest and quickest routes to safety.
The algorithms require extensively coded descriptions of the evacu-
ation networks including the distances, assumed operating speeds, and
capacity characteristics of each roadway section. The traffic demands
from each evacuation zone are then placed onto the coded network. The
algorithms then determine the optimum routes and travel times. The
analytical details of computer methods are often the proprietary in-
formation of consulting firms.
39

Traffic Queue Analysis
Estimating the queuing delay time is the final step in esti-
mating the components of total evacuation time. This is the delay
that occurs when evacuating vehicles encounter queues or lines of
stopped or slow moving vehicles.
For unrestrained traffic flow, where the total volume assigned to
a link is less than its capacity, traffic encounters normal travel
time. As previously stated, link travel time is the distance divided
by the estimated operating speed. When the traffic demand assigned
to a link during a given time period exceeds the capacity of that link,
however, a queue will form and the evacuating traffic will experience
additional delay.
For simple evacuation networks, traffic demand comparisons can
be easily made to link capacities. Where demand exceeds capacity,
queuing delay time can be estimated by the following formula: .
Queuing Delay Time = (Queue Length / Queue Dissipation Rate)
The queue dissipation rate is approximately equal to the capacity
of the traffic impediments, i.e., the maximum flow of vehicles per
hour through the bottleneck. The queue length during a particular
time period is estimated as follows:
Queue Length = (Rate of Queue Growth X Length of Time Period)
The rate of queue growth is proportional to the difference in capac-
ities of the approach link and the bottleneck.
For complex networks in which many evacuation zones may share
evacuation links, the same formulae as above are used to determine
traffic demands. However, the bookkeeping procedures for the links
become more complicated, especially as the traffic from different
evacuation zones will tend to reach the links at different times.
For small to medium size cities, the manual traffic assignment proce-
dures in the Sosslau article may be applied for successive time
periods in the evacuation. For large metropolitan areas, computer-
ized techniques are the most practical.
40

North Carolina
• OUTDOOR RECREATION FACILITY STANDARDS
Introduction
This document recommends outdoor recreation facility standards
for North Carolina. Statewide standards measure the quantity of
recreation services ideally available to the public and can help
describe the quality of recreation services. These standards
emphasize local discretion and should not be used as absolute
guidelines that cannot be altered. While they provide a goal to
achieve, they do not imply that each communityshould choose to pro-
vide identical services. Communities with different interests and
socio-economic characteristics will naturally want different
recreation opportunities. The standards should be used as part of
a comprehensive planning effort to satisfy the community's pref-
erences for outdoor recreation. The planning effort should consider.
• public preferences, socio-economic characteristics and financial re
sources along with recreation supply and demand information.
The document consists of three sections. The first section
describes outdoor recreation in terms of experiences, activities
and facilities.. The second section presents the recreation facility
standards and how they can be used to estimate the recreation:ser-
vices needed to serve a community. The third section describes how
this information can be applied to common recreation management
decisions.
Source:
North Carolina Statewide Comprehensive Outdoor Recreation Plan

Section I. Outdoor Recreation Experiences
Whether it's the satisfaction of making a good golf shot, com-
pleting a 10-kilometer race, or hiking a scenic trail; it is the
recreation experience that motivates people to participate. The pur-
pose of operating carefully planned and maintained recreation facil-
ities is to provide experiences that satisfy the people who use them.
It is therefore advantageous to describe the need for recreation
services in terms of the experiences they provide. This section
describes two main categories of recreation experiences; natural
resource oriented recreation and physically -athletically oriented
recreation. Each type of experience can be provided by many different .
activities and therefore, a community has many options in deciding
how they will satisfy the demand for each recreation experience.
Figure 1 defines the two recreation experiences and presents examples
of the facilities and activities that provide these experiences. It
is not intended to provide a complete list of facilities and activities.
Figure 1.
OUTDOOR RECREATION EXPERIENCES, ACTIVITIES AND FACILITIES
Natural Resource Oriented Recreation
Definition: Experiences in which enjoyment, observation,
and/or skill development in a natural setting
are the primary motivations for participation.
Activities Related Facilities
Camping, Tent
Campsite
Camping, Trailer
Campsite
Canoeing
Streams
Cross country skiing
Trails
Fishing
Streams
Hiking
Trails
• Horseback riding
Trails
Hunting
Hunting land
Off -road vehicle driving
Trails
Picnicking
Tables
Power boating
Large water surface area
Rock climbing
Climbing areas
Sailing
Large water bodies
Swimming, lake or ocean
Beaches
42

Figure 1 (continued)
Physically/Athletically Oriented Recreation
Definition: Experiences in which physical activity and/or
skill development are primary motivations
for participation. Activities can involve
various levels of competition, physical
endurance, and social interaction.
Activities. Related.Facilities
Archery
Basketball
Field Hockey
Football
Golf
Handball
Horse shoes
Lacrosse
Playground activities
Shuffleboard
Soccer.
Softball
Swimming Pool
Target Shooting.
Tennis
Trap and Skeet
Volleyball
Targets
Courts
Fields
Fields
Courses
Courts
Courts
Fields
Tot lots
Courts
Fields
Fields
Pools
Targets
Courts
Traps
Courts
43

Section II. Recreation Facility Standards
All recreation standards express a desirable balance between
the supply and demand for recreation services. While most standards
express the need for a particular recreation area or facility, supply
and demand can also be explained terms of recreation experiences.
Recreation demand is described as the total number of visits per year
to recreation sites that the people in an area will want to make.
Recreation supply is the capacity of the existing facilities such as
ball fields, picnic tables and trails to accommodate visitors. It
is important to consider public, private, and commercial recreation
facilities when measuring recreation supply in order to get a true
picture of the opportunities available to a community.
Recreation demand is expressed as a participation rate estimating
the number of times each person in an area will want to visit an out-
door recreation site. The participation rate is multiplied by the
total population to estimate the total demand for visits to outdoor
recreation sites. Annual supply capacity is best understood by de-
scribing the factors that can change the number of visitors served by
the facility. These factors include:
Factors Influencing Supply Capacity
1. Unit.of measurement.
2. Average number of people using the facility at one time.
3. Average number of groups on a peak day.
4. Number of peak days per year.
5. Proportion of annual use occurring on peak days.
A peak day is a day in which the recreation facility is used con-
tinuously such as a summer weekend day or a holiday. An example showing
how to calculate a facility supply capacity using these factors is
presented in Firgure 2.
44

Figure 2.
ANNUAL SUPPLY CAPACITY CALCULATIONS
Annual Supply Capacity _ (group size) x (group/day) x (peak days/year)
Per Unit Percentage of annual use occurring on peak days
Example: Basketball
1. Unit of measurement One full court
2. Average number of people using
facility at one time 10
3. Average number of groups per peak
day 6
4. Number of peak days per year 34
5. Percentage of annual use occurring
on peak days .50 or 50%
Annual Supply Capacity = (10) x (6) x (34)
Per Basketball Court .50
Annual Supply Capacity __ 2,040 = 4,080 visitors
Per Basketball Court .50
The total capacity of all existing outdoor recreation facilities
to serve visitors in an area is estimated by combining the individual
facility supply capacities. If the total supply is greater than the
total demand for recreation visits, then there are sufficient facilities
to serve the people who will want to use them. However, if the total -
demand exceeds the total supply, there are people in the community or
county who are not able to participate because of a lack of facilities.
Using the concept of recreation experiences, this means there is a
shortage of opportunities to participate in either physically/athleti-
cally oriented or natural resource oriented recreation.
45

DEMAND INFORMATION
Figure 3 presents participation rates estimating the demand for
the activities providing the two recreation experiences. The partici-
pation rates were determined using five recreation demand studies per-
formed in North Carolina and surrounding states. Surveys include
three studies from North Carolina, one from Georgia, and one from
Tennessee. The total participation rate for each recreation experience
group represents the sum of the participation rates for activities
within it. The experience group participation rates represent the
median estimate from the 5 surveys using activities that all the sur-
veys had in common to define the experience groups.
Figure 3.
Experience Annual Participation
Rate
• Natural Resource Oriented 32.3 visits per . capita
Recreation
Physically/Athletically 25.7 visits per capita
Oriented Recreation
SUPPLY INFORMATION
Figure 4 presents the annual supply capacities for selected
facilities within each experience group. The supply capacities were
estimated in studies involving recreation managers in North'Carolina
and Georgia. Figure 4 shows the range of estimates received,including
a low, medium and high supply capacity for the facilities in the North
Carolina study. While not all facilities have been included in the sur-
vey, the supply capacity for the other facilities can be estimated by
_ following steps shown in Figure 2.
The supply capacities are presented in ranges because communities
and recreation managers can control the number of people served by a
recreation facility as a management strategy. Choosing a high capac-
ity by allowing more people to use the facility per day makes it
possible to increase the number of people served each year. However,
this will also increase the maintenance costs and may cause the facility
46

to depreciate more quickly. Maintenance cost, maintenance practices,
staff requirements, user preferences, and user fees should therefore
be taken into account when making this decision. Generally, lower
supply capacities will require less maintenance and fewer staff but
may cost more per user to operate.
Figure 4.
Natural Resource Oriented Recreation
Facility
Supply Capacity
Activity
(Unit of Measurement)
(Annual Visitors)
Camping, Tent
Campsites (one site)
408
Camping, Trailer
Campsites (one site)
272
Canoeing
Streams (one mile)
2011
Cross Country
Skiing
Trails (one mile)
Fishing
Streams (one mile)
Hiking
Trails (one mile)
1450
Horseback riding
Trails (one mile)
4883
Hunting
Hunting land (one square
mile)
Nature Walks
Trails (one mile)
2454
• Off Road Vehicle
Driving
Trails (one mile)
1283
Picnicking
Tables (one table)
544 - 2040 - 3400
` Power Boating
Water surface (one acre)
39 - 183
Rock Climbing
Designated area (one acre)
Sailing
Water surface (one acre)
Swimming, Lake
Beach (one acre)
15,504 - 65,484
Physically/Athletically
Oriented Recreation
Facility
Supply Capacity
Activity
(Unit of Measurement)
(Annual Visitors)
Archery
Targets (one target)
Basketball
Courts (one court)
1,632 - 3,400 - 8,160
Field Hockey
Fields (one field)
Football
Fields (one field)
2,176 - 5,400 - 8,976
Golf
Courses (1-18-hole course) 7,140 - 8,160
Handball
Courts (one court)
Horseshoes
Courts (one court)
Lacrosse
Fields (one field)
Playground
Activities
One tot lot
• Shuffleboard
One court
Soccer
One field
2,448 - 6,392 - 10,200
Softball
One field
3,264 - 6,800 - 10,608
Swimming, pool
One sq. ft. of water surface 2 - 4
Target shooting
One target
Tennis
One court
544 - 1,360 - 2,720
Trap & skeet
One trap
Volleyball
One court
47

APPLYING THE STANDARDS
A manager can use the estimates provided in Figure 4 to calculate
supply and the estimates in Figure 3 to calculate demand for the
• recreation services in a community, county, or region. One can them
determine if the existing outdoor recreation facilities are suffi-
cient to serve the population by comparing supply and demand. The
three -step process is shown below using a hypothetical example:
Step 1: Estimate total annual demand.
Use the community's population and the participation
rates supplied in Figure 3 to estimate the total
number of visits to outdoor recreation facilities the
people will want to make yer year.
a. Physically/Athletically Oriented Recreation
Population x Participation Rate = Total Demand
10,000 people x 25.7 annual visits per person = 257,000 annual
visits
B. Natural Resource Oriented Recreation
Population x Participation Rate Total Demand
10,000 people x 32.3 annual visits per person = 323,000 annual
visits
Step 2: Calculate supply capacity
Select a supply capacity for each existing outdoor recreation
facility to estimate the number of visitors it serves. Selecting an
appropriate supply capacity using the information in Figure 2 and Figure 4
should take several factors into account. These include the amount of
crowding at current facilities, maintenance requirements, resources
available for building additional facilities, community preferences, and
staffing requirements. The sum of supply capacities for existing rec-
reation facilities represents their total capacity to accommpdate visitors.
It is important to note that some recreation facilities that are
outside a community or county can be counted as serving the population.
Facilities such as campsites, fishing streams, and hiking trails that
are normally used on weekend trips are examples. These weekend trips
oriented facilities within about one hour driving distance can be
counted as part of the community's or county's supply of recreation
facilities.
48

1. Select supply capacities for each facility in the area using
the process in Figure 2.
Example: Tennis
a. Unit of measurement One tennis court
b. Average number of people
using the court at one time 3 people
c. Number of groups/day 10 groups
d. Number of peak days/year 34 peak days
e. Percentage of annual use
occurring on peak days .50 or 50%
Annual Supply = (group size) x (groups per peakday) x (peak days/year)
Capacity Percentage of annual use occurring on peak days
Annual Supply =
Capacity
(3) x (10) x (34) .5 = 2,040 visits
2. Multiply the annual supply capacity for each type of facility
in the area.by the number of facilities available to calculate
the total number of visitors served. For example, if each
tennis court serves 2,040 visitors annually and there are eight
tennis courts, then the eight tennis courts can serve a total
of 16,320 visitors annually. Repeat the process for each type
of facility in the experience groups and add results together
to determine the total capacity of the facilities to accommodate
visitors.
Natural Resource
Oriented Recreation
Annual
Facility
Number of Units
Supply
Capacity
Interpretive Trails 3 miles x
2450
visitors
= 6,950
Hiking Trail
15 miles x
1450
visitors
= 21,750
Swimming Beach
2 acres x
45000
visitors
= 90,000
Total annual supply capacity =
118,700
visitors
Physically/Athletically Oriented Recreation
Annual
Facility
Number of Units
Supply
Capacity
Tennis Court
8 courts x
2040
visitors
= 16,320
Basketball Court
10 courts x
5500
visitors
= 55,000
Football Field
4 fields x
6000
visitors
= 24,000
Softball Field
7 fields x
8000
visitors
= 56,000
Total annual supply capacity =
131,320
visitors
49

Step 3: Determine net demand.
Net demand is determined by subtracting the capacity of existing
.facilities to serve visitors from the population's total demand for
visits. Net demand represents the participation in outdoor recreation
activities that did not occur because of lack of facilities. If total
supply exceeds demand then the existing recreation facilities are
sufficient to serve the population.
a. Natural Resource Oriented Recreation
Total Annual Demand 323,000 visits
Total Annual Supply-1189700 visits
Net Annual Demand 204,300 visits
b. Physically/Athletically Oriented Recreation
Total Annual Demand 257,000 visits
Total Annual Supply-151020 visits
Net Annual Demand 105,680 visits
Step 4: Satisfying Unmet Demand
The hypothetical town with 10,000 people has greater demand for
recreation than its current recreation facilities can accommodate.
Specifically, the town should provide opportunities for 204,300
additional visitors to participate in natural resource oriented rec-
reation, and opportunities for 105,680 additional visitors to participate
in physically/athletically oriented recreation. The recreation manager,
working with representatives of the community, can explore alternatives
for eliminating these shortages and choose the most reasonable solution.
Alternatives might include increasing the number of visitors served
by current facilities, building additional facilities, or a.combination
of the two. The community should consider preferences, socio-economic
characteristics, and available financial resources when making its
decision.
Each alternative will have costs that can be identified, measured
and compared. For example, the cost of allowing more poeple to use
current facilities by adding lights and increasing organized use can
be compared to the cost of building and operating a new facility. In-
creasing the use of existing facilities will increase the maintenance
and staff requirements. By comparing the cost and public preference for
each alternative, -the recreation manager and community will be more able
to select the alternative that best fits their current situation.
50

Section III. Using Supply Capacity Information
The number of visitors an outdoor recreation facility can serve in
a year can vary accoring to the facotrs shown in Figure 2. A recre-
ation manager can help a community choose an appropriate supply capa-
city for each recreation facility and use the information in making
numerous decisions. Users can be asked, for example, whether a tennis
court is too crowded and if it is, which of several alternative solu
tions they prefer. Solutions could include adding lights to create
longer hours, limiting playing time, or using a reservation system.
The previous sections discussed how supply capacities are used in
determining how many recreation facilities are needed to serve a popu-
lation. Although this is the most obvious use of supply capacity infor-
mation its only use of many possible uses. Other uses include:
Site Design and Development Applications:
1. These guidelines can help the designer to determine the best
land uses in activity areas as they relate the site's natural
assets and limitations.
2. The guidelines can help determine the desired proximity of
activities to one another and at what levels of intensities they
can co -exist.
3. The guidelines can help a designer estimate site deterioration
and required maintenance and thus design the site with management
and cost 'in mind.
4. The guidelines can help insure that recreation facilities and
their supporting facilities such as parking lots and restrooms
are designed in a proper balance. For example, a picnic area
designed for 10 families or groups should not be accompanied by
a parking lot accommodating twice as many families or groups.
Administrative and Operations Application:
1. The guidelines can help in determining the level of recreation
use at which the administrator will exercise controls to dis-
courage or further restrict useres of the area.
2. The guidelines can help managers make more realistic attendance
estimates when actual counts cannot be made.
51

3. Optimum capacity guidelines can help predict the need to
expand support systems such as access roads, parking lots, water
resources and restrooms.
4. The guidelines can help the manager in conducting user preference
.surveys. He can then determine specifically how users feel about
y overcrowding or over use of a specific park and make a historical
record of the changing attitudes toward optimum carrying capacity.
52

Street Network
Every community has a transportation system that has a maximum
capacity. Obvious problems can occur when the load on this system
exceeds the capacity. In most small communities, the street network
consists of highway that are under the control of the North Carolina
Department of Transportation and smaller collector and local streets
that are under the control of the town or private entities. The
capacity analysis for streets appears more pertinent to the highways
in that they handle the vast majority of the traffic.
The collector and local streets are usually short streets that
provide access to a single subdivision or serve as connectors between
the highways. The methodologies for determining capacities of streets
and intersections, furthermore, are geared to urban settings. These
procedures are designed for addressing much larger, more heavily
traveled intersections than are found among the collector and local
streets of a small community.
The methodologies lend themselves to calculating the capacity of
highway.intersections. These methods have become very specific and
well defined and -have become the common tool of traffic engineers.
Many of the methods utilize graphs that chart traffic in thousands
of vehicles and allow adjustments for pavement widths, turning options,
various peak hour loads, street parking and bus stops. The complexity
of these methodologies require individual experience in traffic plan-
ning. In order to gain the fullest potential of the procedures it is
recommended that determining the capacities of major streets.and
highway be left to traffic engieers. If one wishes to explore further
the capacity methodologies of this area, however, refer to the Design
of Urban Streets, prepared for the U. S. Department of Transportation
in January 1980, by J. H. K. and Associates.
53

CHAPTER V.
Policy Implications
Throughout the design and implementation of a carrying capacity
analysis, planners should move toward presenting the results in a use-
ful format. Judgmental decisions, one must remember, are made in the
course of the analysis; the results, consequently, are not absolutely
scientific. If the data from the carrying capacity analysis is employed
to establish general guidlines rather than absolute maximums and mini-
mums about growth capacity the results can contribute significantly to
the community's decision -making process.
The results of the study can aid in framing development -related
questions by outlining a community's capacity for growth. While the
analysis will not replace policy decisions, it will aid decision -makers
by identifying critical thresholds.. A threshold is the point at which
the population growth reaches the maximum service capacity of a system.
At this point, a decision must be made either to increase the system's
capacity, or stop or redirect the population growth. The analysis can
help a community schedule its capital expenditures.
While the. type of output of the analysis and its presentation
depends upon the issues studied and the methodologies used, one way
the results of a threshold analysis can be presented is in the form
of a bar graph. A graph, as shown in Figure 5, can be devised once the
population totals that each system can accommodate have been determined.
The graph can allow the capacities of each system to be compared with
one another and with the projected population. The total population
allowed by the densities in local ordinances and the current pouplation
also can be graphed for comparison.
As shown in Figure 5, each bar can represent an individual system
with its height reflecting the maximum capacity of the system. The
population total, aligned with the top of the bar, represents the thres-
hold for the system. The shortest bar represents the system presenting
the first threshold. A decision must be made to increase capacity or
54

15,000
I �
14, 000
( 3 15 I
13,000
� I
1 i PROJECTED
12,000 2 - —� POPULATION
4 1 7
11,000
CURRENT POPULATION 6 I CURRENT POPULATION
10, 000"
9000
o
a
.o
'a
PRO
a)�
a
4
POPION
In
o
co
CO
Wr
to
b
b o
�w
v
8000
b 0
a, �
b0
a, a
-H
ca
0
M
0
-H
I C
0�
01
0 cd
N
0Cdd
0-H
�
0
0
00
0cd
0
r-+r-1
r-A-W
0
u
u
u u
u w
u 0
.-1 ;j
r-q 0
a v
u
u
u cd
u
u
7000
cd do
W
co .-4
0 0
cd
d >%
d
0
d
�
d� 1
d 4
1~ a
0
to
a
a
1-4a,
0 P.
0"
0
co
ci 0
0 0
P.
-° a1
-H a
0) A
-°
-° >,
1° 9
-° -°
44 4j
� 0
-WEn
41M
4
"41
" 0
6000
to
(d 0
u a.+
cd
cd
cd u
(d cd
cd -H
rI
:3 b
r-4,H
0 .0
WW
•n .14
r-4P
0 a)
r-1k
:j a)
r-A-H
:J 14
.-1W
0 P
r-4
:1
0
P.
H
C1,
o
0 M
P.
cad
aai
c�tl
cad
0 au)
as
wcn
w
w3
w3
ax
arx
w
5000
1. New well added
2. Additional storage tank
3. Bridge widening
4. New city park built
5. Bicycle path built
6. Staff increase of 10%
7. Computer added in billing office
FIGURE 5.
55

stop or redirect growth before the community's population passes the
population level aligned with the top of the shortest bar.
If future changes which would increase capacity of various sys-
tems can be foreseen, the bar may be extended in dotted lines to reflect
the new capacities. The dotted line portion of each bar, as shown on
Figure 5 would indicate the additions or changes that would increase the
capacity of the system, thereby raising the threshold.
Bar graphs may depict different situations for different commun-
ities. A potential scenario, as shown in Figure 6 is for several thres-
holds to cluster around a single population level. While this report
does not recommend that carrying capacity be used to determine a growth
cap, such an arrangement of thresholds may present a community with
overwhelming capital expenditures before additional growth can be
absorbed. A single alignment of several thresholds may.identify an
optimal population level for the community. Enacting a population cap
in lieu of incurring the high costs of absorbing additional growth will
be a policy decision.
A simple scenario may when a single threshold is encountered.
As shown in Figure 7, after passing one threshold, a community may be
free and clear of any other thresholds for a period of time. A community
would probably incur the costs of passing the first threshold in this
situation.
The staggering of thresholds, as shown in Figure 8,`will present
a community with a different decision. In such a situation, a community
will encounter thresholds every few years. Some may view this as a
staggering of expenses that can be absorbed. Others may see this arrange-
ment of thresholds as an unending series of expenses. The reaction to
such an arrangement of thresholds will be a policy decision.
In summary, the results of a carrying capacity study will not remove
the burden of decision making from local officials. The study will,
however, provide policy makers with better and more comprehensive infor-
mation on which to base their decisions. In a more general sense the
results of the carrying capacity study would provide a framework for
decision -making - a way of analyzing questions and alternatives. The
analysis defines questions and issues about the capacities of the man-
made and natural systems of the community and the community's ability
56

to absorb further growth and development. Carrying capacity studies
provide local leaders not with certainties but with insights into.
the issues surrounding the growth and development of a community.
57

151
14,
131
12,
11
CURRENT POPULN
10
FIGURE 6.
58

I
14
1:
CURRENT POPULi
11
FIGURE 7.
59
SIT POPULATION

1?
12
1]
CURRENT POPULI
1(
f
FIGURE 8.
60

APPENDIX
THE SAFFIR/SIMPSON HURRICANE SCALE
The Saffir/Simpson Hurricane Scale is used by the National
Weather Service to give public safety officials a continuing assess
ment of the potential for wind and storm -surge damage from a hurricane
in progress. Scale numbers are made available.to public -safety
officials when a hurricane is with 72 hours of landfall.
Scale numbers range from 1 to.5. Scale No. 1 begins with hurri-
canes which have maximum sustained winds of at least 74 miles per
hours, or which will produce a storm,surge 4 to 5 feet above normal'
water level, while Scale No. 5,applies to those in which the maximum
sustained winds are 155 miles per hour or more, or which has the
potential of producing a storm surge more than 18 feet above normal.
The Weather Service emphasizes that the scale numbers are not
forecasts but are based on observed conditions at a given time in a
hurricane's life -span. They represent an estimate of what the storm
would do to a coastal area if it were to strike without change in
size or strength. Scale assessments are revised regularly as new
observations are made, the public -safety organizations are kept in-
formed of new estimates of the hurricane's disaster potential.
The Saffir/Simpson Hurricane Scale indicates probable property
damage and evacuation recommendations as listed below:
Category 1. Winds of 74 to 95 miles per hour. Damage primarily
to shrubbery, trees, foliage, and unanchored mobile homes. No real
damage to other structures. Some damage to poorly constructed signs..
And/or: storm surge 4 to 5 feet above normal. Low-lying coastal
roads inundated, minor pier damage, some small craft in exposed
4 anchorage torn from moorings.
Category 2. Winds of 96 to 110 miles per hour. Considerable
damage to shrubbery and tree foliage, some trees blown down.. Major
damage to exposed mobile homes. Extensive damage to poorly con-
structed signs. Some damage to roofing materials of buildings; some
window and door damage. No major damage to buildings. And/or:
storm surge 6 to 8 feet above normal. Coastal roads and low-lying
61

escape routes inland cut by rising water 2 to 4 hours before arrival
of hurricane center. Considerable damage to piers. Marinas flooded.
Small craft in unprotected anchorages torn from moorings.
Category 3. Winds of 111 to 130 miles per hour. Foliage torn
from trees, large trees blown down. Practically all poorly constructed
signs blown down. Some damage to roofing materials of buildings; some
window and door damage. Some structural damage to small buildings
Mobile home destroyed. And/or: storm surge 9 to 12 feet above normal.
Serious flooding at coast and many smaller structures near coast
destroyed; larger structures near coast damaged by battering waves and
floating debris. Low-lying escape routes inland cut by rising water
3 to 5 hours before hurricane center arrives. Flat terrain 5 feet or,
less above sea level flooded inland 8 miles or more. Paralleling
hurricanes reveal hazard characteristics that can be correlated to a
landfalling hurricane. The passage of a hurricane paralleling from 25
to 100 miles from the coast would require approximately the same response
as a Category 3 landfalling hurricane. Evacuation can be upgraded upon
short notice.
Category 4. Winds of 131 to 155 miles per hour. Shrubs and trees
blown down, all signs down. Extensive damage to roofing materials,
windows, and doors. Complete failures of roofs on many small residences.
Complete destruction of mobile homes. And/or: storm surge 13 to 18
feet above normal. Flat terrain 10 feet or less above sea level flooded
inland as far as 6 miles. Major damage to lower floors of structures
near shore due to flooding and battering by waves and floating debris.
Low-lying escape routes inland cut by rising water 3 to 5 hours before
hurricane center arrives. Major erosion of beaches.
Category 5. Winds greater than 155 miles per hour. Shrubs and
trees blown down, considerable damage to roofs of buildings; all signs
down. Very sever and extensive damage to windows and doors. Some
complete building.failures. Small buildings over -turned or blown away.
Complete destruction of mobile homes. And/or: storm surge greater
than 18 feet above normal. Major damage to lower floors of all struc-
tures less than 15 feet above sea level within 500 yards of shore.
Low-lying escape routes inland cut by rising water 3 to 5 hours before
hurricane center arrives.
62

BIBLIOGRAPHY
Bishop, A. B., H. H. Fullerton, A. B. Crawford, M. D. Chambers and M. McKee.
Carrying Capacity in Regional Environmental Management. Environmental
Protection Agency, Washington, D. C., 1974.
Godschalk, David R., and Francis H. Parker.
The potential of carrying capacity as a planning concept. Ch. 5 in
David R. Godschalk et'al. Carrying Capacity: A Basis for Coastal
Planning. Department of City and Regional Planning, Univ. of
North Carolina, Chapel Hill, 1974.
Godschalk, David R., and Francis H. Parker.
Carrying capacity: A key to environmental planning? J. Soil Water
Cons. 30:160-165, 1975.
Godschalk, David R., and Norman Axler.
Carrying Capacity,Applications in Growth Management: A Reconnaissance.
U. S. Department of Housing and Urban -Development, Washington, D. C.
1977.
Hawaii Department of Planning and Economic Development.
Carrying Capacity Action Research: A Case Study in Selective
Growth Management, Oahu, Hawaii. Chapter IV: Case Study
Descriptions: A Basis for_Selective Growth Management. Pp. 52-97,
1978.
Krueckenberg, Donald A. and Arthur L. Silvers.
Urban Planning Analysis: Methods and Models.. John Wiley, Inc.,
New York, 1974.
McHarg, Ian L.
Design With Nature. Natural History Press, Philadelphia, 1969.
North Carolina Statewide Comprehensive Outdoor Recreation Plan, N. C.
Department,of Natural and Economic Resources, 1979.
Pizor, Peter J. et als.
Managing Growth in Developing Communities (New Brunswick, N. J.:
New Jersey Agricultural Experiment Station), 1982.
Schneider, Devon M., David R. Godschalk and Norman Axler.
The Carrying Capacity Concept as a Planning Tool. PAS Report
No. 338, 1978.
Sosslau, A. B. et al.
Quick Response Urban Travel Estimation Techniques and Transferable
* Parameters: User Guide. NCHRP.Report 187, Transportation and
Research Board, Washington, D. C. 1978.
Stone, John R.
Hurricane Emergency Planning: Estimating Evacuation Times for
Non -Metropolitan Coastal Communities. -UNC Sea Grant College
Program, 1982.