Cluster development also called open space development or conservation development, attempts to achieve balance between growth and preservation of open space in rural and suburban settings. It is done by clustering homes on a smaller proportion of land. The additional land, which would normally be allocated to individual lots across the entire subdivision, becomes protected as common space. Depending on the site, the common space may protect wetlands, floodways, steep-grade slopes, farmland, wildlife habitat, woodlands, archaeological, historic or cultural resources, or groundwater resources.
Beyond achieving site-specific goals of open space preservation, cluster development attempts to connect open space areas from one development to the next, creating an interconnected network of farmland and conservation land. Conventional development patterns fragment open space into disconnected parcels, severely limiting the amount of suitable wildlife habitat and doing little to create a visual sense of contiguous open space.
By contrast, cluster development places dwellings in areas hidden from existing roads, in order to preserve view corridors and the countryside aesthetic. In many cluster developments, municipal trail networks are included in developments, the goal being for them to someday connect to each other to form a regional trial system for the public.
The vast majority of cluster development is achieved through incentive- based approaches. The most common incentive tool is to award developers zoning density bonuses for higher proportions of open space in their developments. For example, if in a rural context typical density is 80,000 square feet per housing unit, protecting 60% of a multi-parcel subdivision as open space would result in a density allowance of 60,000 square feet per housing unit; protecting 70% of a subdivision would further reduce the density to 40,000 square feet per unit.
Advantages of Cluster Development
In addition to the obvious environmental benefits of increased open space and protection of critical areas, cluster development creates many economic advantages for developers. The design review process is generally much smoother, because the more thoughtful, site-specific design process often anticipates many of the potential problems that arise during the design review period. Often, developers incur lower infrastructure and engineering costs because utilities, roads, water and septic systems are streamlined to accommodate homes located close together. Finally, cluster development inherently creates a marketing and sales advantage, because greenways, open space, common areas and wildlife are attractive amenities for potential home buyers.
Beyond economic and environmental benefits, an argument can be made for the social and recreational advantages of cluster development. Preservation of critical areas and site-specific attributes gives a development a greater sense of place. Trail networks provide more frequent opportunities for casual interaction between residents than exist in a typical subdivision. Largely because of these two factors, residents of cluster development communities often report an increased sense of community.
Challenges to Cluster Development
Though cluster development has been generally well-received when implemented, there are a number of barriers keeping it from becoming a widespread practice. In many communities, current zoning regulations require conventional building patterns and may include restrictions that prohibit cluster development. A developer often must convince local zoning boards to approve variances for a cluster subdivision, forcing he or she to spend time educating planning commissions and potentially delaying the project timeline (Ohio State University Factsheet: Cluster Development).
One of the commonly perceived obstacles to cluster design in areas outside of water and sewage service areas is the disposal of wastewater and the availability of drinking water. In reality, cluster development provides more options for effective well and septic location for two reasons. First, because developers usually work with smaller lots, they have much more flexibility in locating housing sites and septic and well sites on areas with most suitable soil types. Second, these systems can be located off lots in common areas, especially if they are done in environmentally sensitive manners.
Another potentially negative aspect of cluster development is that homeowners’ associations and fees are normally required to maintain open space for the community. (Ohio State University Factsheet: Cluster Development). Though the costs may be equal or less to costs that landowners would incur if they were to live on an individual rural parcel, the idea of communal dues (or perhaps the perceived lack of control or excess of bureaucracy) is off-putting to some people.
Still others are put off by preconceived notions that smaller lots, an important characteristic of cluster development, are undesirable; and that homes on smaller lots are not attractive and will disrupt community character. Indeed, some earlier cluster subdivision models did not provide very much open space, which resulted in negative perceptions of cluster development in general. These criticisms are best addressed through thoughtful site design and architectural standards. For example, in The Fields of St. Croix, a cluster development in Lake Elmo, Minnesota, the site planner utilized “single-loaded streets,” a technical term for streets having houses on only one side. By single loading the project’s streets, the site planner created vital visual connections to open space from every residence and for users driving, biking, or walking through their neighborhood on a daily basis. The project has been extremely well- received and home prices reflect the public’s acceptance of the project. In addition to the visual connections created by single-loaded streets, their use in open-field situations create visually appealing foreground meadows, treating people entering the development to views of wildflowers or horses grazing.
Finally, cluster development has been criticized as a tool that promotes sprawl, just a different form of sprawl than conventional development. Such criticism is valid, and it is important to note that this tool best helps to protect open space when used in conjunction with other tools, such as Urban Growth Boundaries.
Successful Large-Scale Implementation: A York, Maine Case Study
Because cluster development is largely implemented through incentive-based policies, and not all developers (and not even the majority, at this time) choose to develop in clusters, cluster development is not yet a widely successful tool for the large-scale creation of farmland and wildlife habitat preservation corridors. The success of cluster development as a large-scale corridor protection tool depends largely on the buy-in of local communities. A community exhibiting such buy-in is York, Maine, where the York Planning Board works closely with the York Land Trust to ensure that significant percentages of rural developments remain as permanent open space (Arendt, Growing Greener, p. 104). As of 2005, over seven hundred acres of designated open space in twenty-six development projects had been preserved (York Land Trust Descriptions of Property). In this arrangement, the Trust is routinely included in the town’s subdivision review process, participating from the outset. The Trust identifies potential conservation areas and trail linkages before any layout patterns are proposed, making recommendations to the planning commission about their findings. This process has resulted in widespread acceptance among the development community, as added value and greater marketability of areas in compliance with Trust recommendations are realized.
One of the keys to York’s success is the Planning Board’s commitment to integrating their vision of permanently protected open space into their development policies and procedures. Indeed, Arendt recommends that communities integrate large-scale cluster development visions into their communities by weaving it into a community’s Comprehensive Plan. He believes that a Comprehensive Plan should include specific recommendations for adopting clear standards in subdivision and land development ordinances that address land conservation issues as squarely as development issues. Specifically, in the background information and the resource inventory stages of Comprehensive Plan development, Arendt suggests inventorying potential conservation lands in a community and creating an official community-wide map of these lands. This map goes beyond inherently unbuildable lands to include lands with resource value—woodlands, open agricultural lands—that are developable, so that planners may more effectively target areas in which the community’s vision supports cluster development. As planning agencies work with developers to show them the marketability and enhanced value of creating developments in line with the community’s vision, cluster development easily could become an effective tool for wide-scale wildlife and farmland corridor protection.