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Point System Background
A point system, or scoring system,
is a quantitative way to determine how important it is to
protect a parcel of land as openspace. This quantitative method
is used to create guiding policies to help land protection
occur in a systematic way. Many organizations participate
in openspace protection and have some sort of point system
that helps them evaluate properties. An example of this is
available on the Rhode
Island Department of Environmental Management's website.
GIS is a useful tool when prioritizing
land for acquisition in three ways. First, GIS can be used
to show parcels of land that are available for acquisition,
and provide information such as ownership, about each parcel
of land. This information allows policy makers to customize
their policies to fit their specific needs.
Second, GIS allows openspace scoring
systems to be applied to large geographic areas. This can
be used to quickly evaluated how well certain parcels meet
openspace acquisition objectives once these objectives are
established. Analyzing specific parcels to understand how
well they meet acquisition criteria gives policy makers the
ability to see how overarching policies impact individual
parcels. This section explains how this point system is created
in GIS, and gives an evaluation of every undeveloped parcel
in Charlestown.
Third, GIS provides information
about the potential consequences
of different openspace plans. By combining the tax assessors
database, a prioritization system, and buildout, it is possible
to see how openspace policies will change the condition of
the area at buildout. It is also possible to estimate how
much money is needed to achieve certain goals.
Recently, a study was conducted at the University
of Rhode Island to prioritize lands for acquisition statewide
entitled Critical
Lands for Conservation. This study developed a "a
simple analytical protocol that provide local conservation
organizations guidance in identifying the most important lands
for conservation" by using existing GIS data. The protocol
used in this study is presented in detail on the Critical
Lands website and will be discussed briefly on this page.
This study is used as a staring point to form a GIS openspace
prioritization scheme for Charlestown.
Critical Lands uses existing GIS data to identify
areas of co-occurring resources. Finding areas with
co-occurring resources is an axiom of most openspace prioritization
systems. It is based on the concept that the more desirable
attributes on a piece of land, the better. For example, if
a piece of land is potentially important for biodiversity
and groundwater, this piece of land is better overall than
another piece of land that is only important for biodiversity.
Critical Lands achieves this by creating four
themes: biodiversity, farmland, groundwater, and cultural.
All of these themes are weighted equally. In this system the
same value is given to land that has cultural significance
as land that is important to protect groundwater resources.
This system does not take into account varying
levels of importance within each theme. For instance, a piece
of land has four attributes that are important to biodiversity
is treated the same as another piece which has only one attribute
important to biodiversity. A more detailed discussion of this
is located in the methods
section of the Critical Lands website.
Another important aspect of Critical Lands is
its unit of organization. Critical Lands uses rasterized data.
The discussion of parcel level
methodology specifically deals with the difference between
raster and vector data, and its importance in this study.
The adaptation of Critical Lands to Charlestown
involves three major changes.
The first is parcel
level analysis, the score for a piece of land is determined
at the parcel level. Follow the link to parcel level analysis
for an in-depth discussion of this
difference.
The second difference is the weighting of resources.
Instead of analyzing for presence or absence of a certain
attribute of land, it is possible to weight the importance
of many different attributes. For example, in the scoring
system developed for Charlestown, a parcel of land with two
groundwater resources will get more points then a parcel with
just one groundwater resource. Additionally, these resources
can be weighed to reflect the different levels of importance
of the resources. For example, non-community wellhead protection
areas can be given fewer points then community wellhead protection
areas.
Third, more data is used then those included
in Critical Lands. Critical Lands only uses data that are
available state wide. More accurate town-wide data are substituted
when possible. Attributes of parcels such as the number of
units that can be built on the parcel which are not included
in Critical Lands are included in the Charlestown analysis.
The methodology section
discusses this in more detail.
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