Evaluating the Impact of Conservation Subdivision Implementation

“Assessing the Environmental Merits of Conservation Subdivision Design” by Z. Aslıgül Göçmen

Between those who extol the virtues of low-density suburban development (e.g. Kotkin, Cox, Gordon) and others who promote Smart Growth strategies (e.g. Talen, Ewing) lies the idea of the conservation subdivision. This policy strategy popularized by Arendt (1996) seeks to reconcile traditional suburban tract development with ecological principles.¹ More specifically, conservation subdivision design should promote:“(1) protection of environmentally sensitive and ecologically significant areas within a subdivision, (2) creation of a regional network of such land and open spaces, and (3) less runoff and less pollution in the region’s water resources” (2). Environmental conservation is achieved mostly through the clustering of housing within the subdivision. Using 26 conservation developments paired with 26 traditional suburban developments in Waukesha County, Z. Asilgul Gocmen asks whether those designed as conservation subdivisions under county regulations deliver on their ecological promises and goals.

Building on existing literature, Gocmen analyses whether conservation subdivisions actually does lead to 1) land preservation, 2) a network of interconnected open space, and 3) water quality benefits (through reductions in impervious surfaces). By matching subdivisions by gross density, size, and location, Göçmen isolates the impact of the conservation design through comparison with similar conventional developments.

Several key indicators tested failed to show statistically significant correlations (See Table). That said, “conservation subdivisions protected significantly more land (50 percent) than did conventional subdivisions (11 percent). However, the proportion of land left natural versus mown in these open spaces was similar.” Interviews conducted by the author confirmed that developers and planners do not give formal consideration the ecological values of which open spaces are conserved. Instead, they try to guarantee that there is a minimum of land set-aside.

In terms of water, conservation subdivisions did not have wider riparian buffers and did not decrease impervious surfaces. They did, however, include better designed storm-water retention ponds.

While conservation subdivisions do represent some improvements, they do not as currently practiced in Wisconsin offer a greatly improved environmental model for development.

Given these findings, should planners ask if site-based strategies are appropriate for landscape-scale conservation goals?

SAGE and ACSP have kindly granted access to the full article until 1/21/2014

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Göçmen, Z. Aslıgül. 2013. Assessing the Environmental Merits of Conservation Subdivision Design.Journal of Planning Education and Research: 0739456X13512526.

Summary by Tom Douthat