| Land Use and Growth Management |
| Buildout analysis: Linking Land Use Planning
with Transportation and Infrastructure |
| By Allan A. Hodges, Boston, Massachusetts 1-617-426-7330,
hodges@pbworld.com and Timothy
A. Case, Boston, Massachusetts, case@pbworld.com
|
| The results of a buildout
analysis provide a useful basis for linking land use, transportation
and infrastructure planning because the buildout totals set the outer
limits of growth. This article describes the buildout analyses performed
for five Massachusetts towns. |
|
Figure 1: This sequence of maps show the development pattern
in Kingston, Massachusetts over the past 200 years. |
The purpose of a buildout analysis is to construct a view of the future
that describes community development when permitted densities are
fully realized under the existing zoning and sub-division bylaws.
The buildout totals should be considered only as a mathematical calculation,
however, not as an opinion or projection of how the development must
or will actually occur.
Buildout analyses have proven to have great value for land use planning
because the buildout totals:
- Should alert local decision-makers as to
legally allowable future developments, of which they may not be
fully aware
- Provide a quantifiable basis on which to
intervene and change the legal framework, if required or desired,
so that development occurs in a way that supports the overall
objectives of the towns' residents
- When combined with the consequent cumulative
impacts on transportation facilities and services, provide compelling
scenarios upon which to launch, support or develop a comprehensive
planning program for the town.
Changes to local zoning bylaws and subdivision regulations are two
of the most immediately available and effective tools that local officials
and citizens have to shape their future. For zoning to be an effective
tool, however, the land uses and the densities allowed by the various
districts must reflect their land use plans. Moreover, land use plans
should be part of a comprehensive plan that reflects current local
goals and objectives regarding future development. Clearly, those
two documents must be consistent and compatible if agreed-to future
outcomes are to result.
Analyses Conducted for the Five Towns
In 1999, our Boston staff completed buildout analyses for five communities
in fast-growing southeastern Massachusetts for two clients.
- For the Old Colony Planning Council (OCPC)
located in the City of Brockton, we prepared buildout analyses
for Kingston, Plymouth and Plympton as part of the Transportation
Induced Growth Impacts Study.
- For the Commonwealth of Massachusetts' Executive Office of Environmental
Affairs, we prepared buildout calculations for Plymouth (using
different assumptions than in the OCPC study), Hanson and Westport.
The buildout totals in all five towns were much greater than projections
from other local and regional sources. The differences were because
the zoning district maps and the allowable densities in each district
were inconsistent with the towns' land use plans, if they had such
plans, which usually reflect desired outcomes that are much less dense
than full buildout.
We found in the OCPC study that none of the towns had a land use plan.
Only Kingston had a recent townwide comprehensive plan, for which
PB prepared the transportation element. Yet, all towns had zoning.
Methodology
The methodology for developing the buildouts included a careful review
of each town's zoning bylaws and subdivision regulations, which provided
our consultant team with:
- The total amount of buildable land area
- The maximum permitted housing unit densities
and commercial and industrial building floor area ratios for each
zoning district.
Figure 2: This map shows the Kingston/Plymouth/Plympton study
area with undevelopable (light gray), potential development
(grey), currently developed (dark grey) and significant subdivisions
in the 1990s (black) |
Other factors that affect the amount of land that is buildable were
not necessarily specified in the bylaws, ordinances and subdivision
regulations. These factors are important to understand for the buildout
analysis, however. Accordingly, a series of assumptions were developed
in discussions with local officials, the regional and town planning
staffs, review by the technical advisory committee (OCPC study), and
a review of similar studies.
The assumptions considered in the OCPC study were aimed at deleting
land area from buildable totals in order to reduce the amount of buildable
land to a more realistic total. These assumptions included the following:
- Internal Roadway Rights-of-Way. Ten percent
of developable acreage is used for internal circulation (e.g.,
roadway right-of-way).
- Wetland and Floodplain Constraints.
No area of a floodway is developable. Floodplains (usually a larger
area) were assumed to be developable in Plymouth, however, because
building can take place in a floodplain if certain engineering
standards are met, and some building lots will border and include
some floodplain and are allowed for use in establishing minimum
lot size requirements.
- Steep Slope Constraints.
All lands with slopes of up to 5 percent are developable, 15 percent
of all lands with slopes of between 6 percent and 24 percent are
developable, all lands with slopes of 25 percent and greater are
undevelopable.
- Preserved and Protected Open Space
Constraints. Publicly owned and land trust-preserved
open spaces are undevelopable.
- Infrastructure Factors. Water
and sewer service areas in each town are built to their maximum
extension as shown on local Capital Improvement Plans, in the
Plan of Development or other pertinent documents.
The suitability of the soil for septic systems was not a limiting
factor in estimating development densities in unsewered areas.
In general, the study area is underlain by very sandy soils that
provide suitable permeability for siting septic systems, provided
the lots meet established minimum lot sizes.
- Development Density Constraints. The maximum
height limit is two stories for any commercial or industrial building.
This assumption was consistent with height limitations imposed
as site design requirements in the local zoning bylaws. Where
a floor area ratio was specifically provided, however, that ratio
was used to determine maximum square footage of commercial or
industrial space per building lot.
The density of development for a planned unit development (PUD)
was assumed to be the same as the underlying zone. (Plymouth and
Kingston have adopted PUDs to allow variations in the design/
layout for development rather than for variations in densities
in a zoning district.)
- Population and Employment Factors. The number
of persons per dwelling unit for Kingston was based on the projections
made and documented in the Kingston Master Plan. For Plymouth
and Plympton, that number was based on the 1990 census.
The total number of dwelling units allowed by current zoning on
buildable land in each town was used to calculate the total population
that would be derived at buildout.
The number of employees per square foot of commercial and industrial
building space was based on the most recent estimates available
in the Institute of Traffic Engineers' (ITE) Trip Generation
Handbook. These estimates were used to calculate the total
number of employees who would be accommodated if commercial and
industrial zoned land were fully built out.
- Other Assumptions. All residential development
will be for year-round residency. (The buildout analyses did not
include any factors to account for seasonal residents.)
Conclusion
The buildout analyses did not include any influences related to how
regional or national housing or commercial or industrial building
market conditions might affect the attractiveness of the study area
for development. They represented a theoretical level of development
based upon what the current zoning bylaws will permit.
The buildout totals calculated for the five towns reflect official
development policy of each town according to its adopted bylaws, not
a recommendation of how land should be developed. The buildout totals
were intended for use as planning tools in the analysis of growth
in the five towns as it relates to needed community
infrastructure, including transportation facilities and services. |
|
Allan A. Hodges, has more than 30 years experience
in urban, environmental and transportation planning. He has been with
PB for 20 years, and served for more than 3 years as Coordinator of
the Urban and Land Use Practice Area Network (PAN). He was Project
Manager for the two studies described in the article and for other
master planning projects for a multi-modal industrial park including
a container port, a marine-oriented urban redevelopment site and a
conservation and recreation area. In 1996, Allan established a planning
practice in the Boston office after returning from a 10-year stint
as environmental documentation manager for the Central Artery/Tunnel
project.
Tim Case is a Senior Analyst who specializes in geographic information
systems, graphic design and land use analyses. He has worked on projects
for clients in New England and throughout the U.S. A member of the
Coordinating Committee of PB's GIS PAN since 1996, Tim has developed
a GIS Service Center in the Boston office. He managed all the GIS-based
activities for both studies referred to in this article and for projects
in disciplines such as water and sewer facilities; facility asset
management; roadway, airport and transit planning; and land use and
master planning. |
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