land suitability analysis user guide

Land Sui tabi l i ty Ana lys is – User Guide

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N C D I V I S I O N O F C O A S T A L M A N A G E M E N T N C C E N T E R F O R G E O G R A P H I C I N F O R M A T I O N A N D A N A L Y S I S

Land Suitability Analysis User Guide

For ArcView 3.x and ArcGIS 9.x

December 2005


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Table of Contents

1.0 Background................................................................ 3 1.1 CAMA Requirements for Land Suitability Analysis in Land Use Plans .................. 4 1.2 GIS Approach ........................................................................................................... 5 2.0 GIS Tools for Land Suitability Analysis ................... 6 2.1 GIS and Spatial Analysis .......................................................................................... 6 2.2 Raster vs. Vector Approach...................................................................................... 6 2.2.1 Technical Issues with a Raster Data Model.......................................................... 8 2.3 Introduction to Spatial Analyst ............................................................................... 11 2.4 Introduction To Model Builder............................................................................... 11 2.5 Computer Requirements and Getting Started ......................................................... 13 3.0 Land Suitability Model............................................. 15 3.1 Define the Criteria................................................................................................... 16 3.2 Define the Data ....................................................................................................... 22 3.3 Determine the GIS Operations ................................................................................ 23 3.4 Data Preparation...................................................................................................... 26 3.5 Using ModelBuilder................................................................................................ 27 3.6 Running the Land Suitability Model....................................................................... 27 3.7 Evaluating the Results............................................................................................. 44 3.8 Modifying the Land Suitability Model ................................................................... 45 4.0 Environmental Composite Map .............................. 54 4.1 Description.............................................................................................................. 54 4.1.1 Criteria ................................................................................................................ 55 4.1.2 Setting Classifications in the Model ................................................................... 56 5.0 Images and Extensions ........................................... 61 5.1 Exporting Images .................................................................................................... 61 5.2 Note on ArcView 3.x Extensions ............................................................................ 61 Acknowledgements and Contacts......................................... 62

Figure 2-1 – Vector Data Example .......................................................................................... 7 Figure 2-2 – Raster Data Example ...................................................................................... 7 Figure 2-3 – Raster Overlay Example ................................................................................. 8 Figure 2-4 - Vector Polygon ............................................................................................... 9 Figure 2-5 - Raster Polygon; 209 ft Resolution.................................................................. 9 Figure 2-6 - Raster Polygon; 400 ft Resolution................................................................ 10 Figure 2-7 - Model Builder Example ................................................................................ 12 Table 1 – Criteria Table Example ......................................................................................... 19 Table 2 – Calculating Absolute Weight ................................................................................. 21 Table 3 - Environmental Criteria ........................................................................................... 55 Appendix 1 - Data Notes Appendix 2 - Data Processing for ArcView 3.x Models Appendix 3 - Data Directory


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1.0 Background The Land Suitability Analysis (LSA) project is a GIS-based process for evaluating the

suitability of land for development. The LSA project is a joint effort by the NC

Department of Environment and Natural Resources, Division of Coastal Management

(DCM) and the North Carolina Center for Geographic Information and Analysis (CGIA).

The project is an outgrowth of the 2002 Coastal Resources Commission (CRC) land use

planning requirements that place added emphasis on basing land use policies on natural

systems capabilities and limitations and a land suitability analysis. The CRC

requirements contain specific provisions for development-related analysis of natural

systems and land suitability. The LSA project makes it easier for local governments to

address these requirements. Also, the project increases the capacity of coastal

communities to consider land suitability in developing their land use plans and other

related policies and in making day-to-day decisions about land use and development.

The project also makes GIS technology and spatial information more accessible to local

governments in the coastal area. In this regard, the project utilizes ESRI GIS software

with the Spatial Analyst extension along with data layers available from DCM, CGIA and

other sources to evaluate natural features and existing development related to the

suitability of land for development. The project also allows local governments to add

their own spatial data.

The two major outputs of the LSA project are an environmental composite map and a

land suitability map. The environmental composite map shows the extent and overlap of

natural features and environmental conditions that indicate the capability and limitations

of natural systems for urban development. The land suitability map shows the relative

suitability of land in a planning area for urban-type development. Both of these map

outputs are consistent with current requirements for preparing Coastal Area

Management Act (CAMA) land use plans1.

The project team identified the following requirements for the application of GIS to land

suitability:

• The project must be capable of easily handling very large amounts of spatial data

1 Some of the information specifically identified by the CRC 2002 land use planning rules is not currently available. Appendix 1 details data that are included in the LSA project and those that are not included.


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• As new data are available, updating the project should be relatively easy

• The project should be capable of accommodating locally developed data

• The project should be interactive, enabling local decision-makers to modify the

weighting the factors used in the analysis

• The output of the LSA should be suitable for planning and policy development;

products should not be designed to apply to specific land parcels or sites

1.1 CAMA Requirements for Land Suitability Analysis in Land Use Plans

In the CAMA land use planning process, land suitability analysis is a mandatory

component of the local land use plan. It is a process for determining a planning area's

supply of land that is suitable for development. The analysis includes consideration of a

number of factors, including natural system constraints, compatibility with existing land

uses and development patterns, existing land use policies, and the availability of

community facilities. A key output of the analysis is a land suitability map that shows

vacant or under-utilized land that is suited for the development. This map is a major part

of the foundation for the development of local land use policies and the future land use

map. [CAMA Land Use Planning 15A NCAC 7B .0702 (c)(5)]

The CRC requirements for CAMA land use plans are the basis for identifying the data

that are used in the LSA project. In the CAMA planning requirements, there are six

categories of factors that must be considered in analyzing development suitability [.0702

(c)(5)]. These factors are listed below.

CAMA Land Use Plan − Land Suitability Factors

(A) Water quality;

(B) Land classes I, II, and III summary environmental analysis (see

further description below)

(C) Proximity to existing developed areas and compatibility with

existing land uses;

(D) Potential impact of development on areas and sites designated

by local historic commissions or the North Carolina Department


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of Cultural Resources as historic, culturally significant, or

scenic;

(E) Land use and development requirements of local development

regulations, CAMA use standards and other applicable state

regulations, and applicable federal regulations; and

(F) Availability of community facilities, including water, sewer,

stormwater, and transportation."

1.2 GIS Approach Land suitability analysis involves the application of criteria to the landscape to assess

where land is most and least suitable for development of structures and infrastructure. A

computer application is not essential for an analysis. A planner could generate a series

of maps on transparent media and overlay the maps so that each one fits over or under

each other and all the shading and labeling on each map is visible. By inspection, a

planner could see how a layer depicting environmentally sensitive areas relates to a

layer of sewer pipes, or how a layer showing flood hazard areas relates to roads. A

planner may be able to make an effective presentation of land suitability using the map

overlays. However, this method has several drawbacks:

1. the method has practical limits on the number of layers that the eye can interpret

at once;

2. all data on the maps are discrete, where some of the variables (e.g., distance

from a water line) are continuous;

3. the relative importance of each layer is not explicit or quantifiable; and

4. the results cannot be easily summarized or applied to other planning tasks.

A geographic information system (GIS) is an efficient tool for organizing, storing,

analyzing, displaying and reporting spatial information. GIS capabilities for spatial

analysis overcome the drawbacks of the paper map overlay approach. The system

enables planners to create and modify a land suitability analysis that makes the best use

of available data. GIS supports methods to apply guidelines and criteria set by coastal

management rules, and integrate value judgments of the planner’s jurisdiction into the

analysis.


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2.0 GIS Tools for Land Suitability Analysis

2.1 GIS and Spatial Analysis In addition to storing, retrieving, displaying spatial data, a geographic information system

enables the user to create buffers, overlays, intersections, proximity analysis, spatial

joins, map algebra, and other analytical operations. In the context of land suitability, GIS

helps the user determine what locations are most/least suitable for development. In this

way, the results of GIS analysis can provide support for decision-making.

The eight steps in Spatial Analysis include:

1. Define criteria for the analysis

2. Define data needed

3. Determine what GIS analysis operations should be performed

4. Prepare the data

5. Create a model

6. Run the model

7. Analyze results

8. Refine the model as needed

These steps are discussed in further detail in section three.

2.2 Raster vs. Vector Approach There are two possible data models that can be used in a GIS: vector and raster. Vector data

consist of discrete points, lines, and polygons. These feature shapes are defined by x and y

coordinates. There can be multiple attributes associated with each feature, for example road name

and pavement type for a given road segment.


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Figure 2-1 – Vector Data Example

The raster data model represents features as a matrix of cells (pixels) in continuous space. Each

layer represents one attribute (although other attributes can be attached to a cell). And most

analysis occurs by combining the layers to create new layers with new cell values.

Figure 2-2 – Raster Data Example

Raster data are used for land suitability modeling because analysis can be performed on several

raster layers at once. For example, raster data enable the user to perform a weighted overlay on

several layers. Vector data enable analysis on only two layers at a time in an operation that


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requires a great deal of computer resources. Raster data provide continuous coverage of a

geographic area and analysis is much more efficient.

Figure 2-3 – Raster Ove rlay Example

2.2.1 Technical Issues with a Raster Data Model

• Resolution

The cell size used for a raster layer will affect the results of the analysis and how the

map looks. The cell size should be based on the original map scale and the minimum

mapping unit. Using too large a cell size will cause some information to be lost. Using a

cell size that is too small requires a lot of storage space, and takes longer to process,

without adding additional precision to the map. For a given analysis, you will need to

decide the optimal resolution to maximize accuracy and performance. The higher the

resolution, the greater the accuracy; but performance suffers. The LSA project uses 1-

acre cells (209 feet per side—rounded from 208.7 feet) to represent base data that are

mapped at a scale of 1:24,000.


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Figure 2-4 - Vector Polygon

Figure 2-5 - Raster Polygon; 209 ft Resolution


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Figure 2-6 - Raster Polygon; 400 ft Resolution

• Pixels contain one value only Limiting a cell to one value can misrepresent spatial data. For example, the boundary of

two soil types may run across the middle of a cell. In such cases, the cell is given the

value of the largest fraction of the cell, or the value of the middle point in the cell.

• Only one item of information is available for each location within a single layer

Multiple items of information require multiple layers. If, in a soils vector layer, you have

two attributes—septic suitability and flood frequency--you will have to create two raster

layers: one that contains septic suitability information and one that contains flood

frequency information.


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2.3 Introduction to Spatial Analyst The ESRI Spatial Analyst extension enables the user to create, query, map, and analyze

cell-based raster data and to perform integrated vector–raster analysis. It is available in

both ArcView 3.x and ArcGIS 9.x platforms.

Spatial Analyst enables desktop GIS users to create, query, and analyze cell-based

raster maps; derive new information from existing data; query information across

multiple data layers; fully integrate cell-based raster data with traditional vector data

sources; and create sophisticated spatial models using ModelBuilder. For the Land

Suitability Analysis, users can rate areas according to several factors with varying

weights and values, and derive new information from existing data to determine land

suitability.

Additional capabilities available through the standard user interface include queries on

multiple grid themes, neighborhood and zone analysis, grid classification and display,

summary histograms, and more.

Operations available with Spatial Analyst:

• Convert feature themes (point, line, or polygon) to grids

• Create raster buffers based on distance from any raster or vector feature

• Create density maps of point features

• Perform Boolean queries and algebraic calculations on multiple grid

themes simultaneously

• Do neighborhood and zone analysis

• Display and reclassify grid data

2.4 Introduction To Model Builder ModelBuilder is a tool for creating and managing automated and self-documenting

spatial models. While ModelBuilder is an extension with ArcView 3.x Spatial Analyst, it

is provided as a common tool with ArcGIS, and thus can be used for other models not

requiring the Spatial Analyst functions. Modelbuilder enables users to create process-

flow diagrams and scenarios to automate the modeling process. Users can easily


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change the data sets used by the model, modify the influence of each data set on the

model, perform complex analysis functions, and generate maps that illustrate the results

of analysis. Data derived from one model can be used as input for another model.

Users can run a model with a variety of parameters to assess data sensitivity or to

evaluate geographically different but structurally similar data sets. Users can copy

portions of their models within a model and smaller models can be combined to build

larger models.

In the case of Land Suitability Analysis, the layer weights can be easily changed, and the

models may be re-run to evaluate the new results. ModelBuilder is ideal for this task

because it allows users to overlay multiple layers, rank order categories within each

layer, include a weight for each layer, and sum using map algebra.

ModelBuilder creates a process-flow diagram that displays the layers and operations.

For example, the land suitability model combines and classifies multiple GIS layers to

produce a land suitability map as illustrated in the figure below.

Figure 2-7 – ArcView 3.xModel Builder Example


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2.5 Computer Requirements and Getting Started The LSA project model is provided in both ArcView 3.x and ArcGIS 9.x GIS software

with the Spatial Analyst extension. Other software products are available, however

ArcView was chosen because of its intensive use in the Division of Coastal

Management, CGIA, the NOAA Coastal Services Center as well as numerous

municipalities and counties in the coastal region. CGIA implemented the land suitability

model on a laptop personal computer operating on Microsoft Windows 2000 with 256

Megabytes of Random Access Memory, a Pentium III 850 Megahertz processor, and a

20 Gigabyte hard disk. Documentation with ArcView 3.x and the Spatial Analyst

extension suggests that the minimum computer requirements include 32 MB of RAM, but

an amount approaching 256 seems more practical for good performance. Spatial

Analyst for ArcView 3.x is supported on Windows 2000, Windows 95/98, Windows NT,

Digital UNIX (4.0 or higher), Hewlett-Packard 700 and 800 series (HP-UX version 10.20

or higher), IBM RS/6000 (AIX version 4.1.4.0 or higher), SGI (IRIX version 6.2 or higher),

Sun (Solaris 2.5 or higher). ArcGIS 9.x minimum requirements exceed those of ArcView

3.x; however, suggested minimum requirements are not provided here.

To install the ArcView 3.x land suitability model for a county, copy the county folder from

the workshop CD to the C: drive of your PC at the root. If the C: drive is not available,

you will need to edit the .apr files to change the path. For example, if you want to install

the programs on your K: drive, open the first .apr file in WORDPAD or another editing

software and replace C:/ with K:/ (replace all) then save as a text file, being sure to

specify the .apr extension for the saved file so ArcView will recognize it as a project file.


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To install the ArcGIS 9.x land suitability model for a county, copy the county folder from

the workshop CD to the C: drive of your PC at the root. Relative paths have been

stored. For more information, please see the text file found on the CD.


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Define Criteria

Land Suitability Criteria

Define Data Needs

List of Data

Determine GIS Operations

I.e. Vector to Raster Conversions, Buffers, Overlays, Map Algebra Operations

Process Data As Needed

Input Data for Model

Create Model

Execute Model

Model Results

Evaluate Results Acceptable

Results?

No

Modify Model

Land Suitability Map

Yes

Steps in GIS Analysis

3.0 Land Suitability Model Figure 3-1 illustrates the steps necessary for performing a land suitability analysis. Each

step is described in further detail below.


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3.1 Define the Criteria The project team defined criteria for the Land Suitability Analysis based on the CAMA

Guidelines and modified criteria according to available datasets. The criteria for

suitability for development (high, medium, low, and least suitable) were identified as

follows:

Areas…

• Within Beneficial Non-Coastal Wetlands have low suitability

• Within Storm Surge Areas have low suitability

• With Severe Septic Limitations (based on soils data) have low

suitability moderate limitations have medium suitability; slight limitations have

high development suitability

• Within 100-year Flood Zones have low development suitability

• Within HQW/ORW Watersheds have low suitability

• Within Water Supply Watersheds have low suitability

• Within 500 feet of a Significant Natural Heritage Area have low

suitability

• Within 500 feet of a Hazardous Substance Disposal Site have low

suitability

• Within 500 feet of an NPDES Site have low suitability

• Within 500 feet of a Wastewater Treatment Plant have low suitability

• Within 500 feet of a Municipal Sewage Discharge Point have low

suitability

• Within 500 feet of a Land Application Site have low suitability

• Within 500 feet of an Airport have low suitability

• Within a half-mile of Primary Roads have high suitability; within a half-mile

to a mile have medium suitability; areas greater than one mile outside of

primary roads have low suitability

• Within a half-mile of Developed Land have high suitability; areas within a

half-mile to a mile have medium suitability; areas further than one mile away

from developed land have low suitability


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• Within a quarter-mile of Water Pipes have high suitability; areas within a

quarter-mile to a half-mile of water pipes have medium suitability; areas

further than a half-mile away from water pipes have low suitability

• Within a quarter-mile of Sewer Pipes have high suitability; areas within a

quarter-mile to a half-mile of sewer pipes have medium suitability; areas

further that a half-mile away from water pipes have low suitability

• Within Coastal Wetlands are LEAST suitable

• Within Exceptional and Substantial Non-Coastal Wetlands are

LEAST suitable

• Within Federal Lands and State Lands are LEAST suitable

• Within Protected Lands are LEAST suitable

• Within Estuarine Waters are LEAST suitable

According to these criteria, values for layers are quantitatively scored according to

suitability for development. For example, an area that is inside a storm surge area or

within 500 feet of a Significant Natural Heritage Area has low suitability. These areas

receive a score of –2 (negative 2). An area that is close to existing infrastructure (roads,

sewer lines, existing development, etc.) has high suitability for development. These

areas receive a score of +2 (positive two).

Note that the proximity concept is represented by a buffer in the model. A buffer should

not be smaller than the distance of one side of a cell. In this case, the smallest buffer is

500 feet and a cell has a width of 209 feet. Also, to account for proximity of features to

cells on the boundaries of the study area (county), themes that are subject to buffers are

clipped to a polygon of the county plus 2 miles (2-mile buffer of county boundary

including the county). The final map will be clipped to the county boundary (not

buffered).

Additionally, most the data layers are ranked according to how important they are to the

overall analysis. In the criteria spreadsheet developed by the project team (Table 1),

users may rank a layer as 1, 2 or 3, with 3 being very important. Other values may be

used, but keep in mind the advantage of keeping the factors relatively uncomplicated for

presentation and explanation in public meetings.


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The least suitable areas (protected lands, military areas, coastal wetlands, estuarine

waters, and exceptional and substantial non-coastal wetlands) are treated somewhat

differently. They are given scores of 0 or 1. Areas within protected lands, coastal

wetlands, etc., receive a score of 0. Areas outside of these sensitive areas receive a

score of 1. These layers will be discussed further below.


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The following is an example of the criteria used to assign values, and weight the layers.

Table 1 – Criteria Table Example

----------Criteria and Rating---------

Layer Name Least

SuitableLow

SuitabilityMedium

Suitability High

Suitability

0 -2 1 2

Coastal Wetlands Inside Outside

Exceptional and Substantial Noncoastal Wetlands Inside Outside

Estuarine Waters Inside Outside

Protected Lands Inside Outside

Beneficial Noncoastal Wetlands Inside Outside

Storm Surge Areas Inside Outside

Soils with septic limitations Severe Moderate Slight

Flood Zones Inside Outside

Water Supply Watersheds Inside Outside

Significant Natural Heritage Areas < 500' > 500'

Hazardous Substance Disposal Sites < 500' > 500'

NPDES Sites < 500' > 500'

Wastewater Treatment Plants < 500' > 500'

Municipal Sewer Discharge Points < 500' > 500'

Airports < 500' > 500'

Developed Land > 1 mi .5 - 1 mi < .5 mi

Primary Roads > 1 mi .5 - 1 mi < .5 mi

Water Pipes > .5 mi .25 - .5 mi < .25 mi

Sewer Pipes > .5 mi .25 - .5 mi < .25 mi

Total

Explanation of Table – Least, Low, Medium, and High Suitability are the four classifications available for this analysis. Values are assigned –2, 0, 1, and +2 respectively. Note that the first set of layers (green shading) are either least suitable (the value of zero will be multiplied by the results of the layers with white and gray shading for a product of zero) or medium suitability (the value of one will be multiplied by the results of the other sets of layers for a product equal to the score based on those other sets).


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The next step is to rank the layers from 1 to 3 with 3 representing the most weight in

land suitability. The spreadsheet included on the Land Suitability CD is ready for the

user to modify the default weights (see Table 2). Once a ranking is agreed upon, the

model requires that the user quantify the ranked layers from an ordinal scale (ranked 1

thru 3) to a percentage of the total (percent weight) to assign relative weights. The

relative weight for a layer is equal to 100 (percent) divided by the product of the sum of

all rankings times the ranking for that layer. In other words, it is the whole pie divided by

the number of pieces (yielding the size of a piece), times the number of pieces for that

layer. If all layers were assigned a weight of 1, the relative weight in percent for any one

layer would be equal to the 100 divided by the number of layers (one equal piece of pie

each). The far right column of the spreadsheet (see Table 2) expresses the relative

weights as a ratio (or “multiplier” required for the model, below). Note that these

numbers change for each county depending on the number of layers that apply. The

calculations are already set in formulas in the spreadsheet.


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Table 2 –Example of Rankings and Percent Weights

--------Criteria and Rating-----------

Layer Name Least

SuitableLow

SuitabilityMedium

Suitability High

SuitabilityAssigned Weight

Percent Weight Multiplier

0 -2 1 2

Coastal Wetlands Inside Outside

Exceptional and Substantial Noncoastal Wetlands Inside Outside

Estuarine Waters Inside Outside

Protected Lands Inside Outside

Beneficial Noncoastal Wetlands Inside Outside 1 4.348 0.04348

Storm Surge Areas Inside Outside 2 8.696 0.08696

Soils with septic limitations Severe Moderate Slight 1 4.348 0.04348

Flood Zones Inside Outside 2 8.696 0.08696

Water Supply Watersheds Inside Outside 1 4.348 0.04348

Significant Natural Heritage Areas < 500' > 500' 2 8.696 0.08696

Hazardous Substance Disposal Sites < 500' > 500' 1 4.348 0.04348

NPDES Sites < 500' > 500' 1 4.348 0.04348

Wastewater Treatment Plants < 500' > 500' 1 4.348 0.04348

Municipal Sewer Discharge Points < 500' > 500' 1 4.348 0.04348

Airports < 500' > 500' 1 4.348 0.04348

Developed Land > 1 mi .5 - 1 mi < .5 mi 1 4.348 0.04348

Primary Roads > 1 mi .5 - 1 mi < .5 mi 2 8.696 0.08696

Water Pipes > .5 mi .25 - .5 mi < .25 mi 3 13.043 0.13043

Sewer Pipes > .5 mi .25 - .5 mi < .25 mi 3 13.043 0.13043

Total 23 100.000 1.00000


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Our criteria are now defined in the form of a table. Be sure to use the excel spreadsheet

provided which contains all the formulas you need. If you change assigned weights (1,

2, or 3) the percent weights in the spreadsheet will be automatically updated. If you add

or delete layers, the spreadsheet should be updated as well (i.e., the number of pie

pieces will change).

As noted earlier, Coastal Wetlands, Exceptional and Substantial Non-Coastal Wetlands,

Military Areas, Estuarine Waters, and Protected Lands are treated differently. These are

the least suitable areas for development and are differentiated accordingly. Values are

assigned 0 for inside the area and 1 for outside the area. We will apply Boolean logic in

the land suitability model (by multiplying the ranked layers by 1 or 0) so we can

differentiate the least suitable areas from the rest.

3.2 Define the Data The data applied to this land suitability analysis are listed in Appendix 1. While the criteria

follow the CAMA requirements, the final determination of the factors included in the analysis

was influenced by the availability of digital data layers from CGIA or DCM. For example, map

data on several of the Areas of Environmental Concern (AEC) categories, such as Inlet Hazard

Areas, are not currently available. However, these areas are covered by storm surge and

velocity zone data, which are readily available from CGIA. Likewise, map data of local land

uses are not available and surrogates are used where possible. In another example, land cover

classified as developed is a surrogate used to determine proximity to existing development.

Appendix 1 provides a detailed description of the data that are used in the project and data

considered for inclusion but not used.

The majority of the data in the LSA project are available in GIS format on a statewide basis from

the Division of Coastal Management and the Center for Geographic Information and Analysis as

part of the North Carolina Corporate Geographic Database. The data are projected based on

the North Carolina state plane coordinate system, North American Datum 1983, English map

units. Most of the data are mapped at the national mapping standard scale of 1:24,000,

implying accuracy within 40 feet.


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3.3 Determine the GIS Operations

Based on the established criteria and data, the next step is to define what operations need to be

performed in order to determine land suitability. Many layers will have to be converted from

vector to raster. Once in raster format, each layer’s values need to be reclassified into either

the 1’s and 0’s scoring system, or the –2 thru +2 scoring system. Buffering will have to be done

on many layers to determine what values should be assigned inside/outside the extent of the

feature and it’s buffer. For example, airports are buffered by 500 feet. Any areas within that

buffer are assigned a value of –2; areas outside are assigned a value of +2.

Operations used in this analysis:

• Raster to Vector Conversion

• Buffer

• Reclassification

• Map Algebra – multiply by a constant (absolute weight)

• Map Algebra – add multiple layers

• Map Algebra – multiply layers

Vector to Raster Conversion: Layers must be converted from vector to raster to be used in the model. Some layers are

converted within the model itself. Others have already been converted outside of the model.

Buffer: Many criteria specify that areas within a specific feature have suitability; outside have high

suitability (and vice-versa).

Example: Areas within 500 feet of a Hazardous Substance Disposal Site have low suitability.

2 2 2 2 2

2 2 2 2 2

2 -2 -2 -2 2

HSDS => 500' => 2 -2 -2 -2 2

buffer 2 -2 -2 -2 2

2 2 2 2 2


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Reclassify: Some layers need to be reclassified. For example, the ‘Soils With Septic Limitations’ layer has

a ‘septic’ attribute that contains values, Severe, Moderate, or Slight. These values are

reclassified to –2, 1, and +2 respectively.

Mod Sev Sev Sev Slight Mod

1 -2 -2 -2 +2 1

Mod Mod Sev Sev Mod Mod

1 1 -2 -2 1 1

Mod Mod Mod Slight Slight Slight -> Reclassify -> 1 1 1 +2 +2 +2

Slight Mod Mod Mod Slight Slight

+2 1 1 1 +2 +2

Slight Mod Sev Sev Mod Slight

+2 1 -2 -2 1 +2

Slight Slight Mod Sev Sev Slight

+2 +2 1 -2 -2 +2

Map Algebra – Multiply by a constant: The weighted layers will each be multiplied by their respective absolute weight. For example, all

the values in the Storm Surge Areas will be multiplied by 0.08696 assuming the criteria listed in

section 3.2.

1 -2 -2 -2 +2 1

0.09 -0.2 -0.2 -0.2 0.17 0.09

1 1 -2 -2 1 1

0.09 0.09 -0.2 -0.2 0.09 0.09

1 1 1 +2 +2 +2 X 0.08696 = 0.09 0.09 0.09 0.17 0.17 0.17

+2 1 1 1 +2 +2

0.17 0.09 0.09 0.09 0.17 0.17

+2 1 -2 -2 1 +2

0.17 0.09 -0.2 -0.2 0.09 0.17

+2 +2 1 -2 -2 +2

0.17 0.17 0.09 -0.2 -0.2 0.17


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Map Algebra – Add Multiple Layers: After all weighted layers are multiplied by their respective constants, they will be added together

to get a suitability rating. The following example shows only two of the layers being added

(allow for rounding in addition). When all layers are added, the resultant layer has values from –

2 to +2.

0.09 -0.2 -0.2 -0.2 0.17 0.09 -0.1 -0.1 0.09 0.09 0.09 0.09 0 -0.3 -0.1 -0.1 0.26 0.17

0.09 0.09 -0.2 -0.2 0.09 0.09 -0.1 -0.1 -0.1 0.09 0.09 0.09 0 0 -0.3 -0.1 0.17 0.17

0.09 0.09 0.09 0.17 0.17 0.17 + -0.1 -0.1 -0.1 -0.1 0.09 0.09 = 0 0 0 0.09 0.26 0.26

0.17 0.09 0.09 0.09 0.17 0.17 -0.1 -0.1 -0.1 -0.1 -0.1 0.09 0.09 0 0 0 0.09 0.26

0.17 0.09 -0.2 -0.2 0.09 0.17 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 0.09 0 -0.3 -0.3 0 0.09

0.17 0.17 0.09 -0.2 -0.2 0.17 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 0.09 0.09 0 -0.3 -0.3 0.09

Map Algebra – Multiply Layers:

Layers that have features to be scored least suitable are classified with 0’s and 1’s, then the

layers multiplied together. The resulting layer shows all areas least suitable for development.

Military Areas Coastal Wetlands Least Suitable

1 1 1 1 1 1 1 0 0 1 1 1 0 0 1

1 0 0 1 1 1 1 0 0 1 1 0 0 0 1

1 0 0 1 1 X 1 1 1 0 1 = 1 0 0 0 1

1 0 0 1 1 1 1 1 1 1 1 0 0 1 1

1 1 1 1 1 1 0 0 0 1 1 0 0 0 1

1 1 1 1 1 1 0 0 1 1 1 0 0 1 1


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This type of operation is also used to clip the final model output to the county boundary.

Reclassify the county boundary. Gray represents ‘No Data’.

Cnty 1

Cnty Cnty Cnty 1 1 1

Cnty Cnty Cnty Cnty ->Reclass-> 1 1 1 1

Cnty Cnty Cnty Cnty Cnty 1 1 1 1 1

Cnty Cnty Cnty 1 1 1

Cnty Cnty 1 1

Multiply the reclassified county boundary with the land suitability. The No Data values will drop

out, clipping the land suitability map.

County Boundary LSA Map Clipped LSA

1 1 2 2 1 2 2

1 1 1 1 1 2 2 2 1 2 2

1 1 1 1 X 2 2 3 2 2 = 2 3 2 2

1 1 1 1 1 3 3 3 2 1 3 3 3 2 1

1 1 1 5 4 4 4 2 4 4 4

1 1 5 2 4 4 3 4 4

3.4 Data Preparation After the GIS operations are determined, the data must be prepared for the Model. This

includes clipping the data to the correct boundary; creating subsets of data such as coastal

wetlands versus all wetlands; and even converting some data to raster format before it is added

to the model. There is much difference in the ArcView 3.x and ArcGIS 9.x models regarding this

step. The ArcGIS 9.x models include most of the data preparation steps while the ArcView 3.x

models do not. In the ArcView 3.x models, the decision to run some processes outside of the

model was based on the amount of time those processes took to run. In the ArcGIS 9.x models,

the majority of the processes were included since when model modifications are made (i.e. the

changing of weights) only sections of the model effected by those changes need to be re-run.

The preparation for each layer for the ArcView 3.x models is described in Appendix 2 (in

contrast, these processes are included and viewable within the ArcGIS 9.x models).


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3.5 Using ModelBuilder

The next steps involve more work with ModelBuilder.

Open the ArcView project with the necessary data. Make sure Spatial Analyst and

ModelBuilder extensions are enabled. In the View window, you should see an Analysis menu

as well as a Model menu. If these extensions are not enabled, go to File -> Extensions, and

check the Spatial Analyst and ModelBuilder extensions.

To open ModelBuilder, click Model-> Start ModelBuilder.

A new window will open. This is the Model Builder interface.

Map document files (.mxd) are provided for the ArcGIS 9x models. The model is located in a

new Toolbox in ArcToolbox (LSA Model and Environmental Composite Model). To run or make

edits to the model – double click the Toolbox function and right click the model and select Edit.

A new window will open. This is the Model Builder interface.

3.6 Running the Land Suitability Model Land Suitability models have already been created for you. These were customized for each

county depending on the availability of data in that county. You may add layers and change

weights to the layers as you see fit. Do not change the ratings for the layers (-2 thru +2 values),

as this may yield unreasonable results.

The following screen captures display the Model Builder interface for both ArcView 3.x and

ArcGIS 9.x relating to reclassification and overlay functions. Note the values entered for

classes for the various themes and overlays included the weighted overlays for which the

spreadsheet multipliers are essential.


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ArcView 3.x: Arithmetic overlay for “least suitable” layers


29

ArcGIS 9.x: Arithmetic overlay for “least suitable” layers


30

ArcView 3.x: Setting a 500-foot buffer for some of the weighted layers


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ArcGIS 9.x: Setting a 500-foot buffer for some of the weighted layers AND Reclassification


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ArcView 3.x: Setting a 2,640-foot (0.5-mile) and 5,280-foot (1-mile) buffer for some of the weighted layers


33

ArcGIS 9.x: Setting a 2,640-foot (0.5-mile) and 5,280-foot (1-mile) buffer for some of the weighted layers AND Reclassification


34

ArcView 3.x: Setting a 1,320-foot (0.25-mile) and 2,640-foot (0.5 mile) buffer for some weighted layers


35

ArcGIS 9.x: Setting a 1,320-foot (0.25-mile) and 2,640-foot (0.5 mile) buffer for some weighted layers AND Reclassification


36

ArcView 3.x: Overlay of the weighted layers using multipliers from the criteria spreadsheet


37

ArcGIS 9.x: Overlay of the weighted layers using multipliers from the criteria spreadsheet


38

ArcView 3.x: Adding a constant (+3) to the suitability ratings


39

ArcGIS 9.x: Adding a constant (+3) to the suitability ratings


40

ArcView 3.x: Setting up the overlay of the “least suitable” (excluded) layers and the weighted layers


41

ArcGIS 9.x: Setting up the overlay of the “least suitable” (excluded) layers and the weighted layers


42

ArcView 3.x: Setting the last overlay that clips the results by the county boundaries


43

ArcGIS 9.x: Setting the last overlay that clips the results by the county boundaries


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3.7 Evaluating the Results

ArcMap permits the classification of results by natural breaks, equal intervals, etc. ArcView 3.x

ModelBuilder only has a default classification of the results: equal intervals. Natural breaks is a

better classification of the results.

• Natural breaks are best for comparing relative suitability of resources within specific

planning area within a county

• Equal intervals may mask subtle differences between suitability of locations within the

planning area

• Equal interval may mean that some areas have few or no areas suitable for development

• Significant research may be required to determine ranges or the ranges would be more

arbitrary than natural breaks

• Natural breaks appear to be more statistically valid than equal intervals

In order to classify by natural breaks in ArcView 3.x, convert the grid to points and classify the

new point theme. Turn on the Spatial Tools extension (under File -> Extensions). Next, convert

the grid theme to a point shapefile (Transformation -> Grid to Point). Classify the new points

theme by natural breaks using the Grid_code item as the classification field. Note the breaks.

Go back to the grid result theme and enter the noted breaks in the legend editor.

Verify the results by viewing the newly classified grid underneath the vector layers. The land

suitability pattern should be related to vector layers visually, though of course the model has

computed the spatial relationships in a way that the vector layers cannot.


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3.8 Modifying the Land Suitability Model

Users may modify the Land Suitability Model in two ways: (a) adding data layers not included in

the original model that add value to the analysis and (b) changing weights in the model to better

reflect land use planning priorities and perspectives in a particular jurisdiction. In both cases,

the user may start by saving the model to a new file. The following exercises illustrate ways to

modify the model.

Exercise A1: Modifying the Land Suitability Model by Adding Data and Processes (ArcView 3.x) Adding an exclusive dataset: If necessary, open the LSA model for the County ArcView project:

1. Open the County project in ArcView (<county name>_lsa.apr) 2. Make active the view to which you will be adding data and be sure the full extent of the

study area is showing in the view 3. Start ModelBuilder: Model -> Start ModelBuilder 4. Open the County LSA model:

• File -> Open… • Navigate to <county name>\lsaModel • Double-click on lsaModel.apr

Add a new shapefile and vector-to-raster conversion process:

1. Open Vector Conversion wizard: Add Process -> Data Conversion -> Vector to Grid…

Vector Conversion Wizard


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2. Click ‘Next >’

3. Select a shapefile as the input theme. Note: a theme must be a feature theme (point,

line or polygon), and it must be in the current ArcView project.

4. Select StFips as the input field (this is a common field that will need to be added to the

shapefile database prior to this step…after adding field, you can normally calculate all

values to equal 37). Note: the values of the input field are used to determine the output

theme cell values. The type of field chosen also determines the type of grid theme

created (continuous or discrete). Click ‘Next >’

5. Choose Categories as the type of data (categorized values represent a type instead of

a measurement). Note: this screen only appears when the input field is an integer.

Click ‘Next ->’

6. Set the new class value and label = 0. This sets the value of all cells inside the

shapefile’s features to ‘0’. Note: this screen only appears when the input field is a

character or integer. Click ‘Next ->’

7. Use the default color setting. Click ‘Next ->’

8. Choose cty_buffer as the extent theme. Click ‘Next ->’

9. Choose This cell size: and type 209 (if necessary). Note: the value entered represents

one side of the grid cell and must be the same units as the view map units (in our case

the map unit is feet). Each cell in the output grid represents one acre (208.7 feet–

rounded to 209 feet—per side which equals 43,560 square feet). Thus the grid

resolution is 1 acre. Click ‘Next ->’

10. Name the theme and file. Click ‘Finish’.

Example of Vector to Grid Conversion Process


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Enter function into the model process

1. Drop (add) a connection from the new function to the Arithmetic Overlay function for the excluded themes:

• Click the Add Connection Button • Click and drag the connection from the new derived data block to the “least

suitable” themes’ Arithmetic Overlay function (top)

Example of process connection

2. Set the ‘no data’ value = 1. This sets the value of all cells outside of the shapefile’s

features to ‘1’. • Double-click the Arithmetic Overlay function to open its Properties dialog box • Scroll to the newly derived shapefile and change the operator to multiplication

(note: the first theme has to be addition for a base, but the other least suitable themes are multiplying by 0 or 1)

• Change the Value for No Data to 1 • Click ‘OK’ • Save the model

3. Run the model: Click the Run button

Note: adding a “least suitable”/excluded theme will not affect the weighted layers, thus there is no need to alter the assigned weights. However, when adding a non-excluded factor/theme (those themes where weighting factors apply – soils, sewer lines, significant natural heritage areas, etc.), weights will need to be modified accordingly.


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Exercise A2: Modifying the Land Suitability Model by Adding Data and Processes (ArcGIS 9.x) The processes outlined in Exercise A1 regarding ArcView 3.x are generally the same for ArcGIS 9.x (with the primary differences being the interface and terminology). Thus, only a few points are noted below. To edit a model, Right-click a model in a toolbox and click Edit. The ModelBuilder window opens so you can add or modify the processes in the model. To build processes you add tools into the ModelBuilder window, then supply values for the parameters of each tool. Both system tools and custom tools can be dragged into the ModelBuilder window, or you can use the Add Data or Tools button in the ModelBuilder window. Elements representing the tool and the derived data the tool will create are added to the display window. The derived data element is a variable that can be connected to other processes in the model. Below is a dialog box for a vector to raster conversion displaying the required inputs.

You can drag input data from the ArcCatalog tree or from the table of contents of any other ArcGIS Desktop application, such as ArcMap, into the ModelBuilder window. If the value set for the variable is of the correct input data type, the variable will connect to the tool. When all required parameter values are set, the process will be colored in. Additional tips for using ArcGIS ModelBuilder are provided in a text file provided with the model CD.


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Exercise B: Modifying the Land Suitability Model by Changing Weights

To change relative weights in the model (or to change weights after adding or deleting a weighted layer from the model), first modify the Land Suitability Model Criteria Table. Open the Microsoft Excel spreadsheet file LSA Weighting Criteria.xls:

Two categories of data—exclusive and weighted—are present in the model. The least suitable areas are represented by the exclusive data sets: these are assigned values of 0 or 1 and are differentiated from the other data within the model logic. These areas are unlikely to be developed for reasons of environmental resource value or conservation ownership. The weighted data are rated according to their respective suitability for development. The layers are rated as -2, 1 or 2, with 2 being assigned to the conditions most suitable for development (within the model, a constant of 3 will be added to each rating so that the results will be positive). This rating scheme avoids zero values (used for the exclusive areas) and results in a reasonable comparison of less and more suitable areas. In addition to the rating, the user may assign variable weights to each layer to represent greater or lesser importance in the model. The default weights were assigned based on the best judgment of the modelers. The user may change weights and modify


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the land suitability model accordingly. (Refer to section 3.1 Define the Criteria for a more complete explanation of the LSA Criteria Table). Exercise:

1. Change the weight assignment of the layers as follows: • Beneficial Noncoastal Wetlands = 2 • Flood Zones = 3

Note the change in the Percent Weight column each time an Assigned Weight value is changed:


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2. Record the new weight percentages in the LSA model: • Double-click on the Arithmetic Overlay in ArcView 3.x and Single

Output Map Algebra in ArcGIS 9.x process for the weighted data layers.

ArcView 3.x

ArcGIS 9.x

• In ArcView 3.x, under the Overlay Table tab, change the Multiplier

value for each layer to reflect the new Multiplier value in the Criteria Table. Double-check the values before clicking ‘OK’.


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• In ArcGIS 9.x, change the Multiplier value for each layer to reflect the new Multiplier value in the Criteria Table.

3. Run the model and note changes in the output. Note, in ArcGIS 9.x, it is not necessary to re-run the entire model. It is suggested that you only re-run those processes effected by your changes.


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Note that you may exclude a theme from the model (for “what if” purposes or if data for

that theme are not reliable) by deleting the link from the theme to the next process in

ModelBuilder and leaving the theme in the model for reconnection later if desired. If the

theme is a weighted theme, you need to change the weights in the spreadsheet and in

the properties of the weighted layers arithmetic overlay.

Caution: check all classifications and weights before running the model. In some cases,

ArcView 3.x Model Builder changes values to defaults for no apparent reason. This is

not an issue with ArcGIS 9.x.


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4.0 Environmental Composite Map

4.1 Description Environmental Composite Map The environmental composite map is also a

required component of the CAMA land use plan [15A NCAC 7B .0702 (c)(2)]. This map

must show the location of three categories of land based on natural features and

environmental conditions:

1. Class I is land that contains only minimal hazards and limitations which can be

addressed by commonly accepted land planning and development practices.

Class I land will generally support the more intensive types of land uses and

development.

2. Class II is land that has hazards and limitations for development that can be

addressed by restrictions on land uses, special site planning, or the provision of

public services, such as water and sewer. Land in this class will generally

support only the less intensive uses, such as low density residential, without

significant investment in services.

3. Class III is land that has serious hazards and limitations. Land in this class will

generally support very low intensity uses, such as conservation and open space.

For the ArcView 3.x models, the environmental composite model was more problematic

than the land suitability model because of a bug in Model Builder that resets

classifications to default values for no apparent reason. The first set of environmental

composite models (January 2003) may not hold the intended class values in overlays.

In the last three sets (November 2003, November 2004 and December 2005), the

environmental composite models were revised to overcome the Model Builder bug.

Nonetheless, please check the classification values in overlay function boxes in Model

Builder before running the model. This bug is not an issue with the ArcGIS 9.x models.


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This version of the environmental composite includes some work-around classification

schemes. Like the land suitability model, the environmental composite model uses 1-

acre grid cells to represent the landscape. Conceptually, if a grid cell intersects a Class

III feature (the most environmentally sensitive), it retains the Class III value no matter

what other features also intersect that cell. If a cell intersects a Class II feature (but no

Class III) it retains the Class II value without regard to Class I (least sensitive) features.

Class I cells do not intersect Class II or Class III features.

4.1.1 Criteria

Table 3 - Environmental Criteria

Layer Class I Class II Class III

Coastal Wetlands ü

Exceptional or Substantial Non-Coastal Wetlands

ü

Beneficial Non-Coastal Wetlands ü

Estuarine Waters ü

Soils with Slight or Moderate Septic Limitations ü

Soils with Severe Septic Limitations ü

Flood Zones ü

Storm Surge Areas ü

HQW/ORW Watersheds ü

Water Supply Watersheds ü

Significant Natural Heritage Areas ü

Protected Lands ü

For a given cell, the computed value of the cell will be determined by the highest class

theme that contains the cell. For example, if a cell is in a coastal wetland (Class III) and

in a storm surge area (Class II) and intersects a soil with a slight or moderate septic

limitation (Class I), the cell value will be Class III. In other words, if a cell does not meet

the criteria for Class III, but qualifies as Class II, it has Class II for a value. If a cell does

not qualify for either Class III or Class II, then it may be Class I or contain no data from

the themes identified in the criteria.


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4.1.2 Setting Classifications in the Model

The model uses arbitrary classification values to produce reliable results as shown in the

excerpt from a spreadsheet:

Classes Outside

Polygons Inside

Polygons Breakpoints Class I 0 1 1 Class II 0 11 11

Class III 0 34 34

Combinations Total Class 0-0-0 0 0 1-0-0 1 Class I 11-0-0 11 Class II 34-0-0 34 Class III 1-11-0 12 Class II 1-34-0 35 Class III

11-34-0 45 Class III

1-11-34 46 Class III The breakpoints are set so that the possible combinations result in appropriate classes

assigned to grid cells.

In Model Builder, the screens should look like the following. When opening Model

Builder, please check to be sure the number of classes and class values have been

retained. If they do not look like the following, edit the values in the Model Builder

interface.


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ArcView 3.x

ArcGIS 9.x


58

ArcView 3.x

ArcGIS 9.x


59

ArcView 3.x

ArcGIS 9.x


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Run the model and evaluate the results as described above for the land suitability

model.

The resulting Environmental Composite Map is similar to the Land Suitability Map in that

Class III areas are consistent with the Least Suitable category and the Class I areas are

related to the Most Suitable areas. The primary difference is the absence of

infrastructure in the Environmental Composite Map that heightens the emphasis on

environmental sensitivity and relative land conservation value.


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5.0 Images and Extensions

5.1 Exporting Images For Powerpoint presentations and other digital reporting methods, ArcView can export

views or layouts as jpg format images or other selected formats. For an image from the

view, make the desired view active, then select File -> Export. In the dialogue box, set

the file type to jpg, name the file, select the options button and select the highest quality

and resolution available, then OK. For an image from a layout, prepare a layout and

with the layout window active, go to File -> Export and proceed as above.

ArcMap offers a much greater variety of exporting formats, including pdf, jpeg, bmp, tiff

and gif. To do this, select File -> Export Map. In the dialogue box, you can set the file

type, name the file, set the resolution, etc.

An image processing software may be employed to resize and sharpen jpg images, and

add a border if desired. Images are now ready to insert as pictures in word processing

and presentation software.

5.2 Note on ArcView 3.x Extensions

The Land Suitability CD contains the Spatial Tools extension for ArcView 3.x for use in

this and other projects. Add the file (spatialtools.avx) to your

ESRI/AV_GIS30/ARCVIEW/EXT32 folder. In ArcView, turn on the extension under File -

> Extensions. The ESRI website describes the tool as follows:

Spatial Tools is an ArcView extension that contains a collection of 18 tools that extend the capabilities of Spatial Analyst. The majority of tools are implementations of functions available in spatial analyst from avenue programming or awkwardly in the map calculator but not from the menu, button, or tool interface. These include functions to clean up, assemble, aggregate, warp and analyze grids.

This is used for converting a grid theme to a point vector theme. ArcView 3.x cannot

convert a grid theme to a polygon theme.


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Acknowledgements and Contacts The work of CGIA and William Farris on this project was funded by the Division of

Coastal Management with a grant from National Oceanic and Atmospheric Agency

(NOAA), Coastal Services Center. The Division of Coastal Management currently

provides maintenance and enhancement to the models.

CGIA efforts were led by Jeff Brown, Jamie Wharton, Nancy Guthrie, Shannon

McDonald, and Colleen Kiley. William Farris’ vital work on the conceptual design and

criteria kept a sharp focus on land use planning. From the Division, Kathy Vinson, John

Thayer, Steve Underwood, Sean McGuire, Ed Lynch, and John Vine-Hodge have

provided invaluable technical assistance and guidance throughout the project.

Contacts: Department of Environment and Natural Resources Division of Coastal Management 1638 Mail Service Center Raleigh, NC 27699-1638 919-733-2293 http://dcm2.enr.state.nc.us/ Department of Environment and Natural Resources North Carolina Center for Geographic Information and Analysis 20322 Mail Service Center Raleigh, NC 27699-0322 919-733-2090 www.cgia.state.nc.us William B. Farris, Inc. 1806 Grace Street Wilmington, NC 28405 910-762-3577 NOAA Coastal Services Center 2234 South Hobson Avenue Charleston, SC 29405-2413 843-740-1200 www.csc.noaa.gov


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APPENDIX 1—DATA NOTES

The following notes describe data (1) used in the draft map and (2) not used in the draft map. 1. Data used in the draft land suitability map

Coastal wetlands – Salt/brackish marshes (wetland type 1 from the Division of Coastal Management’s coastal wetlands data) and freshwater marshes (wetland type 2). Non-coastal wetlands – Wetlands, excluding coastal wetlands, that have exceptional or substantial functional significance; data are classified in DCM’s Coastal Region Evaluation of Wetland Significance (NC CREWS) database. Non-coastal beneficial wetlands – Using the non-coastal wetlands layer created above, the data were queried for “OWR = 1 or OWR = -1”. The value 1 represents beneficial wetlands, and -1 represents wetlands that were unable to be rated, but are still regulated by DCM. Estuarine waters – Salt waters classified as “SA”, “SB” or “SC” by the Division of Water Quality. The land suitability model uses water polygons (and intersecting 1-acre grid cells) as a proxy for the concept expressed in the coastal management rules--estuarine waters with a shoreline buffer of 75 feet. Protected lands – lands managed for conservation and open space (CGIA 2001) include federal, state, local and nonprofit property and easements that permanently preclude private development; does not include military lands, private forests, and incidental open space around public facilities. Other areas currently not suitable for development– large holdings of lands not likely to be developed including military lands, university campuses, and other public properties not permanently protected as open space. Storm surge areas – hurricane storm surge inundation areas, fast moving storm, from 1993 study, all hurricane categories. Soils (septic limitations) – detailed county soil surveys with septic limitation identified by soil type. Flood zones – all 100-year (A) and velocity (V) zones in Digital Flood Insurance Rate Map data (NC Dept. of Emergency Management – NC Floodplain Mapping Program & FEMA Q3 flood zone data). HQW/ORW Watersheds – High Quality Water/Outstanding Resource Water watersheds from Division of Water Quality (DWQ). Water supply watersheds – Among coastal counties, water supply watersheds apply to Camden, Pasquotank, and New Hanover counties only. Natural heritage areas – Significant natural heritage areas from NC’s Natural Heritage Program.


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Hazardous Substance Disposal Sites – Formerly called Superfund sites. Historic property – State-owned historic sites are available as a selection from state-owned property. NPDES sites – Major and minor NPDES sites from the Division of Water Quality. Wastewater treatment plants – Point locations from public water and sewer data (Rural Economic Development Center (REDC) program in late 1990s); may overlap with NPDES sites. Discharge points – Wastewater treatment plant discharge points (REDC); may overlap with NPDES sites. Land application sites – Point locations were wastewater is applied to land by a public system from (REDC) data. Airports – Airport boundaries from CGIA. Developed land – Land cover classified as developed based on percent impervious surface in satellite imagery, 1996 land cover; high intensity plus low intensity developed. Roads – Primary roads from CGIA; street centerlines are too dense for analysis. Water pipes – Water pipes from REDC data, not available in Tyrrell, Pamlico and New Hanover counties. Sewer pipes – Sewer pipes from REDC data, not available in Tyrrell, Pamlico and New Hanover counties. Community facilities and supplemental data – Data were furnished by the Division of Coastal Management (not converted to grids) to be used in conjunction with the land suitability map: public schools, hospitals, community colleges, public universities, hurricane evacuation routes, railroads, primary nursery areas, and marinas; county data may be added such as fire stations and fire districts.


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2. Data considered for land suitability, but not used in draft map

Public trust waters – Not mapped in digital format, but are adequately represented by estuarine waters for the land suitability model. Ocean hazard areas/ocean erodible areas – Not available in digital format, but the areas are covered by hurricane storm surge inundation areas and velocity zones in the floodplain layer. Inlet hazard areas – Not available in digital format, but the areas are covered by hurricane storm surge inundation areas and velocity zones in the floodplain layer. Historic districts – The only current data in digital format are state-owned historic sites, of which there is only one in the coastal region: the former US Coast Guard station on Hatteras Island; this area was not included in the model but could be added for Dare County if desired. Archeological sites – Current digital data not available; requires site-specific consultation. Maritime forests – Included in exceptional non-coastal wetlands in CREWS data. Mineral resources – Data not available in digital format. Shellfish areas – Most areas suitable for commercial harvest are included in HQW/ORW. Areas of Environmental Concern – Site-specific areas that are not mapped in digital format; areas are likely covered by other coastal environmental layers in the land suitability model. Soils with erosion hazards – Available in woodland management and productivity table in detailed soil survey; would require extra processing for those selected soil types. Un-vegetated beach area – Coincident with hurricane storm surge inundation areas and velocity zones in floodplain data. Wellhead protection areas – Data creation in process by Source Water Assessment Program; future use possible.


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APPENDIX 2—DATA PROCESSING FOR ARCVIEW 3.X MODELS Note: these processing steps were performed outside of the ArcView 3.x models and are thus outlined here. Most of these processes are included within the ArcGIS 9.x models and thus are viewable inside those models. Added State FIPS field (value = 37) to all layers for a numeric identifier in the model; any positive integer would work, but 37 was distinct in this context. Coastal wetlands – NC CREWS dataset was clipped to the county boundary and queried for Wetland Type = 1 or Wetland Type =2. Non-coastal wetlands – NC CREWS dataset was clipped to the county boundary and queried for Wetland Type <> 1 or 2 to create a layer of non-coastal wetlands. This layer was then queried for “OWR = 3 or OWR = 2”. (OWR is the Overall Wetland Rating; the value 3 represents Exceptional wetlands, and 2 represents Significant wetlands.) Non-coastal beneficial wetlands – Using the non-coastal wetlands layer created above, the data were queried for “OWR = 1 or OWR = -1”. The value 1 represents beneficial wetlands, and -1 represents wetlands that were unable to be rated, but are still regulated by DCM. Estuarine waters – The Division of Water Quality (DWQ) hydrography polygon layer was queried for “DWQ_class = SA* or DWQ_class = SB* or DWQ_class = SC*” The asterisk is included because there is often multiply modifiers per classification, such as SA ORW, SA NSW, etc. This layer was clipped to the county boundary. Protected lands -The Lands Managed for Conservation and Open Space (lmcos.shp) layer was clipped to the county boundary. Storm surge – Hurricane storm surge inundation areas were clipped to the county boundary and converted to grid prior to use in the model. Soils with septic limitations – For each county, CGIA created a table of septic limitations by soil type from the published soil survey and joined the table to the detailed soil layer. Data were converted to grid prior to use in the model. Soils for environmental composite map – The same soils with septic limitations were used for the environmental composite Flood zones – Flood zones newly furnished by the NC Dept. of Emergency Management – NC Floodplain Mapping Program, and in some cases, old Federal Emergency Management Agency (FEMA) Q3 flood data; selected 100-year flood zones and velocity zones as the high hazard areas. Converted to grid prior to use in the model. HQW/ORW watersheds -The Division of Water Quality High Quality Waters and Outstanding Resource Waters watershed layer was clipped to the county boundary.


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Water supply watersheds – DWQ’s water supply watersheds layer was clipped to the county boundaries. Significant Natural Heritage Areas – Significant Natural Heritage Areas layer was clipped to the 2-mile buffered county boundary. Hazardous substance disposal sites – Hazardous substance disposal sites layer was clipped to the 2-mile buffered county boundary. NPDES – The NPDES (National Pollution Discharge Elimination System) layer was clipped to the 2-mile buffered county boundary. Wastewater treatment plants – Municipal wastewater treatment plants layer was clipped to the 2-mile buffered county boundary. Sewer discharge points -- Municipal sewer discharge points layer was clipped to the 2-mile buffered county boundary. Land application sites – Land application sites (point location of application of sludge from wastewater treatment plants) layer was clipped to the 2-mile buffered county boundary. Airports – The layer of airport locations was clipped to the 2-mile buffered county boundary. Developed lands – 1996 land cover was used to create a layer of developed lands. The 1996 land cover is available by 1:100,000-scale tiles. CGIA selected the tiles that covered the CAMA counties and queried the tiles for “Description = high intensity development or Description = low intensity development”; the tiles were then merged to create a layer of high or low intensity land cover that covered the CAMA counties. A county plus 2-mile buffer was then used to clip the data for each county. Primary roads – The primary roads layer was clipped to the 2-mile buffered county boundary. Water pipes - The water pipes layer was clipped to the 2-mile buffered county boundary. Sewer pipes - The sewer pipes layer was clipped to the 2-mile buffered county boundary. Final county boundary - The county boundary was taken from the Corporate Geographic Database “cb100” file which does not include a detailed shoreline.


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APPENDIX 3—DATA DIRECTORY

GIS data layers are shown with theme name and descriptive name. The definition is a brief statement of the file contents. See the metadata for more detail (http://www.cgia.state.nc.us/cgdb/catalog.html or contact DCM for other data sources not located at this site.) Some files are supplied in grid format on the Land Suitability CD. Others are converted from vector to grid in the model.

Theme Name Descriptive Name Definition ap24_100 Airports Location of airports in NC. crews (source for Non-Coastal Exceptional & Substantial Wetlands and Non-Coastal Beneficial Wetlands)

NC CREWS Wetland significance determined by Division of Coastal Management - subsets by type and functional significance.

cty County boundary Areas depicting jurisdictional boundaries of counties in North Carolina; contains county line features only. The dataset includes the following attributes: arcs coded with type number; polygons coded with county FIPS code, county name, county abbreviation, acres, and population. This does not include a depiction of the shoreline.

cty_buffer 2-mile county buffer <county>_cty.shp with a 2-mile buffer devland Developed land High intensity developed and low intensity

developed land cover classifications as a subset of land cover classified from 1994-95 LandSAT TM satellite imagery, CGIA.

hy24 (source for Estuarine Waters)

Hydrography 1:24,000-scale hydrography – subset based on classification (SA, SB, or SC) is Estuarine Waters.

flo Federally owned land The boundaries of all types of land in North Carolina owned and managed by the United States government.

hqworwdwq HQW and ORW watersheds

Waters identified as having excellent water quality in association with an outstanding resource. Point and non-point source pollution management strategies are applicable to these waters. Polygons are assigned High Quality Water (HQW) and Outstanding Resource Water (ORW) designations.

hsds Hazardous substance disposal site

Locations of uncontrolled and unregulated hazardous waste sites (formerly called Superfund Sites). The file includes sites on the CERCLA Information System (CERCLIS) National Priorities List, the State Inactive Hazardous Sites list, the Sites Priority List, and some Department of Defense files. Polygons are coded with NC DENR, Division of Waste Management, Superfund Section ID; state or federal status; longitude and latitude coordinate; and a site name.


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Theme Name Descriptive Name Definition sdisch Municipal discharge points Location of municipal waste treatment plants,

derived from the water and sewer survey. lmcos Lands managed for

conservation and open space; or “protected lands”

Lands in NC managed for conservation and open space relating to many purposes including recreation, wildlife habitat, water quality, and farmland preservation. This is a composite layer from 13 sources, representing an integrated depiction of lands that have been permanently protected or designated for open space. Polygons are coded with owner name and type, manager name and type, acres, area name, whether it counts toward the Million Acre Initiative goal, and other attributes. Multiple legends display alternative groupings of properties. Key to field names: LAND_ID = Unique identifier for property based on the state plane coordinates of the center point, generated by formula in GIS. MANAGEMENT = Organization managing the land for conservation or open space purposes. MANAGER TYPE = Type of organization managing the land. OWNER = Organization that owns the land or holds the easement or development rights to the property. OWNER TYPE = Type of organization that owns the land or holds the easement. TRANS_TYPE Type of transaction for conservation or open space purposes. AREA NAME = Reference name for the land area. TRANSACTION YEAR = Year of initial transaction for conservation or open space purposes. MILLION_QU = Property qualifies toward the goal of one million additional acres of protected land beginning in 1999. PUB_ACCESS = Public access to the property (yes, no, or conditional) ACRES = Land area computed by the GIS; not the deeded acres. COUNTY = County in which the center point of the property falls. HECTARES = Land area in metric units, computed by the GIS. RIVER_BASIN = River basin in which the center point of the property falls. DENR_REGION = Department of Environment and Natural Resources region in which the center point of the property falls. COG REGION = Council of Government (lead regional organization) region in which the center point of the property falls. QUAD_NAME = US Geological Survey 7.5-minute topographic quadrangle in which the center point of the property falls.


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Theme Name Descriptive Name Definition npdes Major and minor NPDES

dischargers Surface water discharge locations as recorded on permits issued for National Pollutant Discharge Elimination System Sites (NPDES). Points are coded with owner of permit, name of stream receiving discharge, site latitude and longitude, number of discharge pipes, county of discharge, subbasin number, technician review date, and map index numbers.

prds Primary roads Interstate routes, US routes, and selects state routes in NC, to be used as a general-purpose roads layer. Arcs are assigned US, state and interstate route designations and numbers.

flood Flood zones Flood zones newly furnished by the NC Dept. of Emergency Management – NC Floodplain Mapping Program, & old Federal Emergency Management Agency (FEMA) Q3 digital files, NC Division of Emergency Management.

slandapp

Land application sites Locations where treated wastewater or sludge is applied to be absorbed into the soil. Points are coded with the following attributes: id, permit expiration date, construction date, renovation date, and estimated area.

snha Significant Natural Heritage areas

Areas containing ecologically significant natural communities or rare species. NOTE: Due to its dynamic nature, this data becomes out-dated very quickly. The Natural Heritage Program (NHP) MUST authorize release of this data, in writing, prior to distribution, access or hardcopy output of this layer. Polygons are coded with NHP site number, name, and acres.

soc State owned complexes Boundaries of all types of North Carolina state-owned complexes.

soil Detailed Soils Detailed soil surveys by county, including soil types with septic limitations, CGIA.

spipes

Sewer pipes Locations of pipelines for wastewater distribution. Arcs are coded with the following attributes: system id, material, diameter, type (pressure, gravity, vacuum), utilization type (interceptor, outfall, collection), construction date, and renovation date.

hss93f Hurricane storm surge fast Hurricane storm surge inundation areas, fast moving storm, from 1993 study, CGIA.


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Theme Name Descriptive Name Definition streat Municipal sewer treatment

plants Locations of facilities used to treat wastewater and the related appurtenant works. Points are coded with the following attributes: id, treatment plant location descriptor, permitted flow capacity, maximum daily flow, average daily flow, type of treatment technology, sludge disposal technology, infiltration/inflow, estimated area, installation date, and renovation date.

wets (source for Coastal Wetlands)

Wetlands Wetlands delineated by Division of Coastal Management - subset by type and functional significance.

wpipes Water pipes Locations of pipelines for water distribution. Arcs are coded with the following attributes: system identification number, original construction year, renovation year, material, and diameter.


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land suitability analysis user guide

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