Monday, December 12, 2011

Constraint-Based Spatial Planning


INTRODUCTION
Note: this paper was published in the online journal, Practicing Planner, in September 2011. Be warned: If you are not a professional planner, the paper is likely to be boring beyond relief.
Creating spatial plans for local political jurisdictions, business and educational campuses, military installations, or other districts is, by its very nature, a complex endeavor characterized by difficulties and uncertainties. To manage those challenges, planners apply a variety of analytical approaches to the planning process. Some of those approaches were originally created in disciplines related to urban and regional planning. Others came from unrelated fields, such as finance and business, and were modified to address planning needs. In either case, the nature of those analytical efforts is to apply objective, rational procedures to help achieve operational improvements.
As applied to land-based planning, those approaches are characterized by various advantages and disadvantages. The key for practicing urban and regional planners is to evaluate various approaches and choose one that produces results that, in their judgment, most effectively address the contextual needs of the client-community.
Professional planners are familiar with one or more of the following acronyms used to describe analytical techniques that have been applied to many urban planning and community development projects throughout the United States. See Table 1 below.

Table 1: Analytical Techniques Used in Urban Planning
Acronym
Analytical Technique
ABCD
Asset-Based Community Development (Planning)
ASCOT
Assets, Challenges, Opportunities, Threats
PIC
Problems, Issues, Concerns
SWOO
Strengths, Weaknesses, Opportunities, Obstacles
SWOT
Strengths, Weaknesses, Opportunities, Threats

Most of those planning approaches focus on recognizing and building on strengths, skills, and capacities to overcome the weakness, threats, or needs that are often said to characterize a community or spatial district. Fundamentally, those approaches foster the capacity to see, cultivate, and use asset-based or strength-based characteristics the community may not have known or fully realized it possessed or known how to apply those strength-based factors to its benefit. Those methods are about seeing the world and approaching the planning process from a position of internal strength rather than from one of perceived needs or weaknesses. Those analytical approaches typically focus on and celebrate the community’s (or other geographic district) positive characteristics rather than on what is wrong or what supposedly requires repair or restoration before the community can achieve a higher level of functionality.
I believe those approaches contain significant difficulties that affect the planning process and that may adversely influence potential outcomes. Typically, those approaches ignore or fail to fully recognize and develop the complex interrelationship between constraints and opportunities and the multi-faceted effects of constraint analysis and mitigation on development suitability. In this paper, I present a new constraint-based approach to spatial planning that constitutes an alternative to asset-based, SWOT-based, and needs-based models. Although analysis of constraints has played key roles in business/management and scientific endeavors, to this point it has been applied infrequently to fields related to urban planning.1
The Constraint-Based Planning Process that is proposed to guide development of spatial plans2 as described below is an integrated, problem-solving analytical tool. That Process is summarized diagrammatically below in Figure 1. Please note that this paper focuses only on the first three phases in that Process since the unique aspects of the proposed technique are most fully developed in those segments. Other phases required in that planning process, and illustrated for informational purposes in Figure 1, are not part of this discussion. Those excluded phases are:

  • Phase 4 — Basis of Planning/Planning Drivers
  • Phase 5 — Development Alternatives
  • Phase 6 — Preferred Alternative
  • Phase 7 — Land-Based Plan/Implementation Strategy

PHASE 1: SETTING THE STAGE
The materials in this section examine in some detail the three initial planning phases that are critical to Constraint-Based Planning. In order to move forward in creating a land-based plan, a community must first establish an open public involvement effort to ensure the resulting plan incorporates citizen/stakeholder input throughout the planning process. The foundation for that step is best laid in the Request for Proposals issued by the client/community in setting the required performance parameters that will inform the entire planning process.
The next step in the initial phase is to articulate the community’s vision of the future and the mission of the client with respect to that future. That visioning process, in which a clear visualization of the range of possibilities and development of the guiding vision statement will be articulated, constitutes the framework on which the community’s future will be built.
Only then can overall planning process goals that will shape future planning and development scenarios be created. Once those primary goals have been established, the community then must determine how to bridge the gap between current realities and the vision by identifying specific project-related goals that characterize varying stages in the plan. For each of those secondary goals the community then must specify precise and obtainable objectives, tasks, and priorities that can be monitored and evaluated. The five major elements comprising Phase 1 are:

  • Public Involvement (Citizens/Stakeholders)
  • Vision and Mission Statements
  • Overall Planning Process Goals
  • Specific Project-Related Goals
  • Objectives/Tasks/Priorities
PHASE 2: REALITY CHECK
The second phase involves collecting detailed information on the area’s historical development and analyzing the present situation with respect to existing conditions, issues, and trends. The critical aspect of what I term a “Reality Check” is not to focus most of the planning team’s efforts on data collection but to organize/position relevant data as the launch pad for the analysis component. A web-based Geographic Information System (GIS) is proposed as the key organizational and analytical tool for the Constraint-Based Planning process. That system should be in place and functional prior to the start of the data collection effort.
Each individual data element should be discussed carefully, spatially characterized, and rank ordered with respect to the vision and overall project goals established previously. Those efforts should be part of the public involvement process, with the public fully engaged in each task. Then, the implications of each specific task with respect to its potential effects on the planning process must be documented, mapped, and analyzed. An example would be the effects of one-way traffic flows in a specified area on local traffic operations, site accessibility, connectivity, safety, and neighborhood functionality.
Materials developed in this Phase, which constitute the critical local or regional community characteristics (many principal elements are listed below in Table 2), will become the basis of the work performed in Phases 3 through 7. Please note that the following list is meant to be suggestive of topics to be investigated and is not all-inclusive.

Table 2: Data Gathering/Analysis Elements

Major Element
Sub-Element
Socioeconomics
Demographic Variables

Income Characteristics

Crime Rates

Physical Infrastructure/Rights-of-Way
Transportation/Circulation

Utilities

Social Infrastructure
Education

Public/Quasi-Public Institutions

Police/Fire/Emergency Services

Community Facilities and Services
Parks and Recreation

Public Buildings/Other Public Spaces

Other Services

Building Conditions (Specified Sub-Districts)


Environmental Features
Open Space

Water/Wetlands

Topography/Slope

Sub-Surface Conditions

Habitat

Endangered Species

Hazardous/Toxic/Radiological Wastes

Weather/Climate

Housing Characteristics
Public

Private

Quasi-Private (subsidized)

Regulatory and Legal Systems
Zoning

Land Use

Restrictive Covenants

Lands with Protected Status

Others (as appropriate)


It is important to note that the participation of community citizens and stakeholders could potentially be more influential in the planning process if their input was empowered by a system that presented easy to understand visual images that showed the nature, location, and extent of each element that affected the plan, beginning with the Reality Check. Implementation of a web-based Geographic Information System (GIS) is a critical element of Constraint-Based Planning for numerous reasons, including its geospatial integration of appropriate data, analytical tools, and powerful visualization/presentation capabilities. But, GIS is much more than an efficient technical tool since it plays a key role in a collaborative citizen/stakeholder involvement effort in which incorporating public feedback in each step of the plan is an integral part of the process.
I believe that a GIS is the most appropriate geospatial mapping tool to accomplish that task because it enables construction of a number of geographical layers that, when overlain, produce a visual representation of areas that show geospatial relationships between and among a variety of data elements and, later in the planning process, constraints to opportunities and the varying potentials of specific areas for future development or growth. As an essential part of the planning process, a GIS map inventory and evaluation of existing natural and man-made development would be prepared in the Reality Check Phase with construction of a geodatabase. Layers contained in that database should include a variety of vector and raster data, such as slope, elevation, environmental elements, surface and subsurface drainage, transportation, structures, utilities, boundaries, and various regulatory data — including land use, zoning, parcel characteristics, building condition, etc. — as well as remotely sensed imagery, data from tabular databases, digitally scanned property records, GPS coordinates, and geo-referenced site or area photographs as appropriate.
Recent desktop applications provide the capability to seamlessly interact with the above types of geographic information as data layers on a 3D globe. Using ArcGIS 3D Analyst 9, Map 3D, and similar software, the consultant can introduce a revolutionary technology that enables citizens/stakeholders to visualize in three dimensions geographic data from a local or global perspective. For example, citizens/stakeholders can see what a proposed 12-story building might look like in a neighborhood with low-rise structures in terms of height above the existing skyline, facades, shadow effects throughout the day, whether views are obstructed, etc. That technique has the ability to stimulate intense public discussion and generate additional development options through the public involvement process.
A GIS links data observations and measurements to specific locations and indicates actual or inferred relationships between data points. A GIS can also pull together different types of data and allow quantitative analysis at whatever scale is specified in the plan, whether large-scale — showing individual sites/parcels — or a smaller scale presenting a district or even the entire cityscape. For example, information on soils, water resources, habitat, and vegetation might be combined in analyses of wildlife habitat needs. That same data set could be used in determining constraints and opportunities for the restoration of damaged ecosystems or for the potential of land to be developed for a variety of urban uses.
GIS also facilitates the integration of remotely-sensed images, such as collected by Landsat or aerial photography, with data gathered through more traditional techniques, such as census data or field surveys. And it permits extrapolation from limited sample locations to larger areas. Because of its ability to handle complex analyses at varying geographic scales, GIS has become an indispensable tool for land use planners and forms an essential part of constraint-based analysis and the public involvement program.
PHASE 3: CONSTRAINTS/OPPORTUNITIES ANALYSIS
Brief Definitions
A constraint restricts the degree of freedom urban planners, client staff, and citizens/stakeholders have in providing solutions within the setting of a land-based plan. Thus, constraints are limitations that inhibit the way a plan can be developed and implemented. Constraints in the context of urban planning can be economic, environmental (natural and built), financial, infrastructure, legal (regulations and ordinances), political, social, or technical and pertain to project resources, schedule, mutual exclusions, conditional effects of actions, precedence relationships between activities, or other limitations to the system itself.
An opportunity is a suitable condition or combination of suitable conditions or an advantageous, favorable, or suitable circumstance or combination of circumstances and time (schedule) that promotes progress or advancement. Like constraints, opportunities in the context of urban planning can be economic, environmental (natural and built), financial, infrastructure, legal (regulations and ordinances), political, social, or technical and pertain to project resources, schedule, a specified environment, or other limitations to the system itself.
Both constraints and opportunities may be characterized by major type, such as those that are resource-based (environmental) and non-resource-based (socioeconomic or cultural). In this paper I refer to those types respectively as Biogeophysical and Cultural. Typically, Biogeophysical Constraints/Opportunities are physical in nature, such as slope, topography, wetlands and waterways, surface and subsurface conditions, natural and man-made hazards, vegetation zones, wildlife habitat, view sheds, etc. Cultural Constraints/Opportunities include legal, regulatory, policy, institutional, demographic, timing/scheduling, and financial and budgetary concerns, etc.
By their nature, land planning projects are characterized by significant amounts of spatial information. Geographic Information Systems are capable of managing and manipulating large quantities of spatially related information, integrating multiple data layers, and deriving additional information. That evaluation is capable of incorporating such Biogeophysical Constraints as topography, surficial and bedrock geology, groundwater conditions, and historic geologic hazards with such Cultural Constraints as archaeological and historical resources, land use-zoning-site-building restrictions, and urban/suburban land-use data that are categorized according to the types of use and projects planned. Multi-criteria analysis would then be performed to evaluate the suitability of a specified location for each development alternative according to appropriately measured and weighted factors.
Constraints before Opportunities
Information developed in the Reality Check phase of a spatial planning project leads directly to the identification of constraints and opportunities. Please note that the word order in the title of Phase 3 provides a critical clue as to the nature of the analysis. In planning for facilities, sites, or larger geographic areas, constraints — also variously referred to as obstacles, obstructions, weaknesses, disadvantages, restrictions, conflicts, problems, needs, issues, limitations, or challenges — must always be considered before opportunities.
The old adage, Know Your Weaknesses, applies directly to constraints and to spatially-based planning. If strengths or assets were the first order of business and the key focus of analysis, planners and citizens/stakeholders involved in a planning process would start by identifying potentially beneficial situations for development only to find out later that those situations may be limited or adversely influenced by one or more restrictive factors and could not play the role that was initially anticipated.
Dealing with significant constraints encourages and even forces those involved in the planning process to focus on identifying creative, purpose-driven solutions. Few planning professionals or committed citizens/stakeholders are willing to throw their hands up in frustration and leave in place a significant constraint that could adversely affect the outcome of the planning process and the future of the entire community without first expending considerable effort to find appropriate mitigation options.
Consequently, many experienced planners adopt what amounts to a turn-your-weaknesses-into-strengths position: “Show me a constraint and I’ll show you an opportunity.” Thus, even in the act of accepting a constraint, planners may be rewarded with an opportunity. That position is only a seeming paradox because the act of confronting constraints and understanding their salient characteristics can become the very source of creative solutions.
An in-depth understanding of the complex interrelationships between constraints and opportunities is the foundation from which development alternatives are created and on which the resulting plan is based. If those relationships are inadequately addressed at the beginning of the analysis, planners have little chance to recover without extensive back-tracking and re-work.
The primary elements and sub-elements comprising Phase 3 are listed below in Table 3. All three primary elements contain explanatory narrative and multiple GIS map overlays.

Table 3: Constraints/Opportunities Analysis
Primary Element
Sub-Element
Constraints Analysis
Biogeophysical and Cultural Constraints

Constraints Continuum (Ranking Process)

Mitigation Strategies (for each identified constraint/sub-constraint)

Opportunities Analysis
Biogeophysical and Cultural Opportunities

Opportunities Continuum (Ranking Process)

Development Suitability


Constraint-Opportunity Relationships
The following materials elucidate the nature of constraint-opportunity relationships.
Owing to their nature, constraints are limiting factors in whatever environment is under examination, whether biogeophysical, cultural, or varying combinations of both. Therefore, in identifiable ways constraints adversely affect those environments and restrict subsequent opportunities with respect to development and other planning and design-related actions.
Although constraints range from minor to nearly absolute, upon close examination they also may present significant development opportunities. Frequently, constraints can be mitigated in whole or in part so that they can be developed into short- or long-term benefits to the environment in question and thus become development opportunities. For example, if a large rock outcrop poses a major constraint to building or roadway construction, it may form an opportunity for development as a natural resource element that can be integrated into other adjacent landscape features, such as open space, greenways and nature trails, pedestrian walkways and bikeways, physical training trails, or as a visual buffer. Or that outcrop may serve as a platform on which to exhibit large-scale art, such as an exhibit presenting permanent or temporary sculpture. In other words, if constraints are carefully analyzed and their natures and characteristics fully understood, they may be altered or transformed into competitive advantages and opportunities and be fully integrated into the planning process.
Through an in-depth analysis of the nature of each constraint, planners and citizens/stakeholders may be able to creatively transform that adverse condition, turning it into an opportunity to accomplish the desired end in a totally different and previously unforeseen manner. In other words, opportunities may in fact be generated by constraints through a creative planning process. In short, what may initially be seen as a disadvantage may indeed become advantageous.
Constraint Analysis
Organizing the planning process around constraint analysis not only gives planners the freedom to be less cautious and take greater risks, but also, and perhaps most importantly, encourages all those involved in the planning effort to consider cutting edge ideas and themes outside narrow but more traditional approaches. That exploration of a wider and less predictable range of potential solutions is beneficial because it leads planners and citizens/stakeholders outside their comfort zones and into unchartered territory.
Implicit in the constraint analysis is the potential for a specific constraint to be decomposed or deconstructed into component variables, some or all of which may be addressed individually. That deconstruction may result in identification of a series of mitigating techniques that could alter the nature of the sub-constraints or the ways in which they may affect the planning process. Deconstruction and mitigation of individual sub-constraints may also result in such substantial alteration of the parent issue that that constraint may be effectively neutralized or transformed into a previously unrecognized opportunity.
The process of analyzing a constraint may also reveal interrelationships (either previously known or unsuspected) with seemingly dissimilar or unconnected constraints. As a result, a specified mitigation technique may positively affect multiple other constraints. Thus, determining connectivity between or among constraints and subsequent connectivity with regard to mitigation techniques should be a goal of constraint analysis.
Also implicit in the analysis is that not all constraints are equal in terms of potential adverse effects on the planning process if not appropriately mitigated. It should be recognized that certain constraints have major implications and others have adverse effects that range in significance from minor to moderate. That recognition leads to a ranking or weighting along a Constraints Continuum that reflects how individual constraints can potentially affect the vision, goals, and priorities established in Phase 1.
As stated previously, one of the main goals of this planning process is a public involvement effort open to all citizens/stakeholders. Therefore, it is critical that that ranking procedure be conducted as an integral part of the participation effort and that analytical measures of low to moderate complexity are used wherever possible rather than such cutting edge techniques as regression analysis or even neural computing and evolutionary programming that are difficult for most citizens/stakeholders and many planners to understand and use wisely. An initial ranking of constraints — perhaps as simple as using low, moderate, and high values or a more ambitious but easily understandable matrix of four or five variables to which objective scores have been assigned — may be performed by the consultant team working closely with client staff. That initial ranking would then be presented to a workshop of citizens/stakeholders who, in conjunction with the consultant and client staff, would prepare the final ranking of constraints. Because higher points would be awarded to potential development that has fewer constraints and greater opportunities, it is possible to assign priority evaluations for individual projects and areas. How that process actually would function is treated in more detail below in the section on Development Suitability/GIS Analysis.
Consequently, the constraints weighting or ranking process will also reflect the imperative for planners and citizens/stakeholders to address appropriate mitigation strategies, especially for those constraints that have the highest potential for adversely affecting the community’s functioning and its future. Creating innovative and targeted mitigation strategies not only requires application of traditional planning concepts but also innovative or outside-the-box approaches to design and development.
The constraint type (Biogeophysical or Cultural) and its spatial characteristics must also be considered in the ranking process since they may influence various strategies that may be applied to mitigate potentially adverse effects. For example, a seismic hazard zone in a densely populated urban area should be dealt with in a different manner than the same hazard zone located in a sparsely settled district with few buildings and little infrastructure.
Once constraints are catalogued, analyzed, and their effects on the biogeophysical and cultural environments and the planning process made explicit, opportunities for growth and development can then be identified and examined. Consciously choosing to analyze and understand the nature and specific attributes of constraints before looking at opportunities presents planners with the potential of developing more powerful and productive insights. The effort to resolve those difficulties typically leads to a deeper understanding of the spatial context in which planning is performed.
Role of Mitigation Strategies
Development of the constraint analysis leads to the identification of mitigation strategies and the critical question concerning how constraints are mitigated or turned into opportunities. To put it another way, in an urban planning context the question is whether it is possible to systematize the mitigation or transformation of constraints into opportunities. I believe that systemization is possible and propose the following operational elements to guide that process.
First, each constraint should be identified within the context of a specific category of the Reality Check Phase, such as socioeconomics or physical environment.
Second, the precise nature and relevant spatial and non-spatial characteristics of the constraint must be analyzed and understood. For example, if the constraint is environmental in nature, such as a seismic hazard zone, its key attributes must be established through search of available documents, data, or interviews with recognized authorities. Those attributes should include location, size, geographic extent, event severity (high, medium, and low), event periodicity, past and potential effects on surrounding uses or facilities, and planning implications, etc.
Third, the analysis then must determine if the constraint can be deconstructed into component parts that can be examined separately. That analysis may lead to the identification of sub-constraints, ranging from minor to major, that are subject to mitigation.
The fourth element is to establish the precise manner in which the constraint may affect the planning process and the community’s vision, mission, goals, objectives, and priorities. That step certainly is one of the most important aspects of the analysis. The potential implications of each constraint and sub-constraint must be addressed in specific detail so that a comprehensive range of mitigation strategies that are appropriate with regard to the future can be identified and explored.
Fifth, the various identified mitigation strategies should contain solutions that will accomplish the following:

  • Eliminate, transform, alter, buffer, exploit, or block adverse effects of the constraint or otherwise optimize its positive aspects.
  • Identify alternative actions that will neutralize or modify the constraint.
  • Reduce or eliminate long-term risk and adverse effects for people and property affected by the constraint.
  • Meet development needs in a sustainable manner by maintaining the health and integrity of the biogeophysical or cultural environments being considered.

Sixth, it is critical to note that in considering and selecting the most appropriate mitigation strategies, it may be necessary to analyze sequentially the effects of specific individual mitigation strategies on an individual constraint. For example, the first mitigation strategy may buffer one specific type of adverse effect but not others. The second mitigation strategy may reduce several of the risks not mitigated by the first strategy but may not affect additional adverse conditions. Consequently, a range or variety of mitigation strategies should be identified and examined in detail until the maximum positive outcome is obtained. As a result, individual constraints may be moderated or ameliorated by multiple mitigation strategies, not merely one. That point is especially pertinent when the specific constraint being analyzed is complex and may be deconstructed into numerous components, each of which may feature distinctive elements that can be mitigated individually, or when the constraint is related to other constraints.
Mitigation Strategies and Public Involvement
Creation of mitigation strategies is the essential function that connects constraints to opportunities and therefore is a crucial element in the Constraint-Based Planning Process. Conceptualization and discussion of those strategies must take place within the context of the public involvement effort. The precise manner in which that creative procedure occurs should, at minimum, be addressed by consultant teams after receipt of the Request for Proposals in the proposal preparation stage. But, in my opinion, the necessity to integrate those strategies into the public involvement effort is sufficiently critical to be specified by the client in the official scope of work contained in the request for proposals issued to qualified firms.
Naturally, the consultant team should have the experience and expertise to identify and propose mitigation solutions appropriate to individual constraints. However, residents and other local stakeholders know their communities in ways outsiders never can or will, no matter how detailed their experience or expertise. The input of citizens/stakeholders to the creation of mitigation strategies constitutes a significant element that must not be minimized.
Therefore, my strong recommendation is for the constraint mitigation strategy process to occur in citizen involvement workshops led by the consultant team/client staff. Even if no specific mitigation strategies are proposed by citizens/stakeholders in the workshop(s) that have not been identified previously through the efforts of the consultant (which is possible but in my experience more than somewhat unlikely), their participation in that effort creates buy-in that otherwise would be difficult to generate. For that reason alone conducting the mitigation strategy workshop(s) with citizens/stakeholders is a key tool in Constraint-Based Spatial Planning.
Development Suitability/GIS Analysis
One of the main challenges facing urban/regional planners is how to actively engage the public in the land use planning decision-making process. As has been noted previously in this paper, I believe that the public involvement effort begins at the very initial stage of a spatial plan. But, since most members of the public have little training or professional expertise in the minutia of the planning process, the real challenge is to identify and employ techniques that are relatively simple to understand yet have genuine analytical and explanatory power.
Incorporation of GIS as an analytical tool in the planning process allows citizens/stakeholders to quickly access existing conditions, constraints, opportunities, and development suitability maps to determine potential uses for land anywhere in the community. For most citizens/stakeholders, that proposed level of involvement in the planning process provides an unparalleled opportunity to have direct input into their community’s future because geospatial information provides a snapshot of what the community looks like now and, more importantly, what it might look like in the future given certain inputs. Specifically, that information is invaluable in the planning process in assisting planners and the public in determining where new development and re-development can be encouraged or discouraged, or where new services will be needed. By using GIS overlays of varying citizen/stakeholder land use preferences, the locations where those preferences conflict in the present and future can be identified and the nature of the conflicts can be analyzed and mitigated.
If the specific planning project allows the consultant to use a web-based GIS and circulate maps via the Internet, citizens/stakeholders would be able to provide almost instant feedback at every critical stage in the planning process, making it possible to record and publish citizen/stakeholder data online, including positive and negative comments and questions. GIS would then be used to create a number of the highest ranked development scenarios and to generate maps that show citizens/stakeholders what each course of action would look like, where it would be located on the ground, the people and areas it would affect most directly, and how it would help move the community in a positive direction.
GIS scenario analysis can demonstrate the effects of applying different priority levels to specified projects or locations. For example, in certain opportunity areas development priorities ranging from higher to lower may be assigned to economic uses or to mixed use development. Subsequently, those areas can then be assigned a different development priority, such as environmental sustainability. The outcomes of combining those different priority assignments and others would then be included in the public participation effort. Potential conflicts in proposed resource use, for example between specialty agriculture (such as high value flowers in western Maricopa County, Arizona) and encroaching urban or suburban uses (residential/retail/office), can be mapped and described using a GIS system that combines biophysical and socio-economic characteristics for land use evaluation. A multi-criteria evaluation tool can be developed to support decision-making in terms of potential trade-offs between and among different stakeholder interests over time.
A full range of development opportunities should also be identified and mapped in the planning area. Those opportunities may be Biogeophysical or Cultural in nature. Biogeophysical Opportunities may include level ground with soils that are capable of bearing loads or potable quality water in underground aquifers in sufficient quantities for human consumption. Cultural Opportunities may result from local policies or regulations or arise from land use relationships and adjacencies, such as locating aviation-related uses like Fire/Rescue or aircraft maintenance in close proximity to hangers, aprons, taxiways, or runways on an airfield. A key point is that specific conditions that have the potential of becoming beneficial can only be identified and mapped as opportunities suitable for development if the community has or will have in the foreseeable future the capacity (internal resources) to take advantage of those conditions.
Planning-related constraints and opportunities mapped as part of the previous analysis should lead directly to the identification of locations as being suitable, partially suitable, or unsuitable for various types of development. That Development Suitability Map then becomes the foundation for the next phases that guide the land use planning and decision-making process, especially Planning Drivers, Basis of Planning, and Development Alternatives that lead directly to the draft and final spatial plans.
That mapping step involves compiling a list of factors that restrict or encourage future development. Once the list of those factors has been developed, weights need to be assigned to each negative or beneficial limitation. After the factors have been identified and weighted, conducting the analysis is a fairly simple process with the use of GIS software. A layer can be created for each factor. That process builds up a number of separate data layers to produce a visual representation of geographical areas that demonstrate more or less potential for future growth or redevelopment. Each layer can then be assigned a score depending on the degree to which the constraint or opportunity is likely to limit or benefit future development. A final constraints map, which overlays all constraints within the study area, is produced using GIS and a grid-based data model. A final opportunities map should also be produced to show areas with greater or partial opportunity. The combined constraints and opportunities map would then identify areas that have:

  • Fewest to greatest constraints that cannot be mitigated
  • Fewest to greatest opportunities (ranked primary, secondary, marginal)
  • Range of opportunities to constraints (highest to lowest)

Use of GIS in a planning project that applies constraints analysis is an example of “better information resulting in better decisions” by using geospatial data to create maps that help determine whether constraints or opportunities are related spatially and if a separate set of mitigation strategies can be developed for two or more constraints or opportunities that may be geospatially related. Questions critical to the success of the plan — such as is sufficient land available for a given use or how much land is required to buffer a controversial facility from sensitive receptors — can be modeled and the best options identified through GIS and presented through the public participation effort.
The ability to interactively analyze and quickly view the available geospatial data allows the consultant/client staff to engage in a series of highly informative and productive citizen/stakeholder workshops and discussions throughout the entire planning process and especially during the Development Suitability Analysis. The complex task of creating a spatial plan may be democratized by providing citizens/stakeholders easy access to public data and the means of decision-making through a web-based GIS and also by giving them meaningful and functional roles throughout the planning process.
Finally, use of GIS as a tool to empower meaningful public involvement would largely refute the cynical view that various elite power groups control the land use decision-making process for their own benefit and the exclusion of the affected citizenry and stakeholders who may view themselves as having little political power or clout. Which is another reason to ensure that the Constraints-Opportunities and Development Suitability Analysis process always be entirely open, and that all professional players in the planning process — public officials and agency staff as well as consultants — are knowledgeable and forthright about why and how specific socioeconomic or biogeophysical factors may influence on-the-ground planning decisions.
CONCLUDING THOUGHTS
The proposed Constraint-Based Spatial Planning process is an innovative integration of several traditional elements common to many land-based planning techniques — Public Involvement, Vision/Mission/Goal Setting, and Data Collection-Analysis — with a new focus on Constraints Analysis, Mitigation Strategies, and Development Suitability/GIS Analysis. That new approach involves a critical re-focusing that demands all those involved in the planning process address goals and objectives, problems and solutions, policies, procedures, and evaluation measures in a different way. That new approach encourages planners to engage in the activities presented below in Table 4.

Table 4: Summary — Constraints-Based Planning Process

Major Elements
Sub-Elements
Document the specific nature and relevant characteristics of individual constraints.

Employ GIS to map and analyze existing conditions, land-based constraints, and opportunities

Establish the precise manner in which each constraint may affect the planning process and the community’s vision, mission, goals, objectives, and priorities.

Rank constraints along a continuum that reflects how individual constraints can potentially affect the elements established in initial project phases — vision, mission, etc.

Fully explore the spatial nature of constraint-opportunity relationships and specific ways those relationships may affect the planning process.

Deconstruct constraints into sub-components to facilitate mitigation.

Select mitigation strategies containing solutions that would:
Eliminate, transform, and block adverse effects of each constraint

Optimize the constraint’s positive aspects and reduce long-term risk and adverse effects for people and property

Meet development needs in a sustainable manner by maintaining the health and integrity of the biogeophysical or cultural environments being considered.

Provide the following GIS maps in the Development Suitability Analysis:
Constraints that cannot be mitigated

Primary, secondary, and marginal opportunities

The range of opportunities to constraints (highest to lowest)

I believe that the planning process proposed in this paper avoids numerous potential pitfalls associated with other approaches by creating a tightly interwoven decision-making fabric comprised of three principal components:

  • In-depth public involvement throughout the project that provides multiple opportunities for genuine and meaningful input using a web-based GIS
  • In-depth GIS overlay analysis of existing conditions, issues, and trends
  • GIS mapping and analytical techniques to help determine the spatial components of constraints, opportunities, mitigation strategies, and development suitability.
The combined result is a powerful collaborative tool that, when applied appropriately, can connect citizens/stakeholders with decision-makers and result in dynamic solutions to complex urban and regional planning challenges. I also firmly believe that, due to its inherent characteristics, appropriate application of constraints analysis is not limited to the field of urban and regional planning. This constraint-based technique may be employed profitably in a wide range of spatially based and other endeavors, such as real estate management, land development, community-based and economic development, transportation project planning, infrastructure planning, natural resource and ecosystem management, recreation planning, and emergency planning, etc.

Endnotes

1 One professional paper that addresses constraint-based spatial planning, but without discussing the various interrelated components, is that of Ronald Milam and Kendra Breiland, “A New Transportation Planning Paradigm: Constraints-Based Planning in Response to the Continuing Decline in Transportation Funds.” Practicing Planner, September 29, 2009. Jeremy Frank and Ari Jonsson of the NASA Ames Research Center have developed a constraint reasoning technology, “Constraint-based Attribute and Interval Planning (CAIP)” to address real-world problems involving space operations (2002 Kluwer Academic Publishers; 06/14/2002; 16:58; p.1). In The Goal: A Process of Ongoing Improvement, (Great Barrington, Massachusetts: North River Press, 3rd edition, 2004), Eliyahu Goldratt, an Israeli physicist who became a well-known specialist in business management science and system dynamics, proposed the Theory of Constraints (TOC), a management technique that is marginally related to the ideas proposed in this paper. In addition, dealing with capacity constraints is a critical element in advanced planning and scheduling (APS), a manufacturing management process in which raw materials and production capacity are optimally allocated to address demand; see Kenn Steger-Jensen and Hans-Henrik Hvolby, “Constraint Based Planning in Advanced Planning and Scheduling Systems.” 8th International Conference on Concurrent Enterprising. Rome, Italy, 17-19 June 2002 (accessed February 22, 2011: http://www.ve-forum.org/projects/408/ICE2002/Enterprise%20modelling/16_Steger-Jensen_Hvolby.pdf). Constraint-based scheduling has also become the dominant form of modeling and solving scheduling problems for many complex construction and industrial applications; see: Markus P.J. Fromherz, “Constraint-based Scheduling,” (invited tutorial paper at the American Control Conference, Arlington, VA, June 2001, accessed February 22, 2011: http://www2.parc.com/isl/members/fromherz/publications/cbs-tutorial-local.pdf); also see: Ian Flood, “Foresight Versus Simulation: Construction Planning Using Graphical Constraint-Based Modeling,” Proceedings of the 2010 Winter Simulation Conference, B. Johansson, S. Jain, J. Montoya-Torres, J. Hugan, and E. Yücesan, eds. accessed February 22, 2011, http://www.informs-sim.org/wsc10papers/279.pdf). Complex temporal constraints have also been addressed in a variety of studies in artificial intelligence and operation research/decision theory, for example: Tsamardinos, Ioannis; Vidal, Thierry; Pollack, Martha E.; (2003). “CTP: A New Constraint-Based Formalism for Conditional, Temporal Planning.” Constraints 8 (4): pp. 365-388 and Nareyek, A.; Fourer, R.; Freuder, E. C.; Giunchiglia, E.; Goldman, R. P.; Kautz, H.; Rintanen, J.; and Tate, A. 2005. “Constraints and AI Planning.” IEEE Intelligent Systems, 20(2), pp. 62-72.

2 Although Constraint-Based Planning may be applied to any number of spatial projects, for the sake of simplicity in this paper I assume that the project being described is a comprehensive plan prepared for a local political jurisdiction.

3 It is important to realize that the initial Vision/Mission Statement may be revised or amended as a result of feedback from later phases in the planning process.

4 A number of the ideas presented in this section were informed by a critical reading of János Kornai, (2007) By Force of Thought: Irregular Memoirs of an Intellectual Journey. Cambridge, MA: MIT Press, a work by a noted economist that focuses on opportunities provided by constraints.

5 In Eliyahu M. Goldratt’s Theory of Constraints, constraints dictate system performance and if the goal is to increase that performance those constraints must be identified and fully explored.

6 Not all cutting edge ideas are productive or beneficial. But, exploration of potential solutions outside more traditional approaches increases the chances of constraints being dealt with in creative ways that may not have been considered under other circumstances.

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