Title: Increasing Green Infrastructure in Compact Developments: Strategies for
providing ecologically beneficial greenery in modern urban built environments
Author: Daniel C. Staley ::
staley.dan@gmail.com ::
303.552.6623
Subject: This paper gives new, detailed strategies for providing high quality green
infrastructure in modern, ordered compact developments.
Keywords: designing communities, economic effects, government policies, mitigation
technologies, standards, urban planning.
Extended Abstract:
Urban forest canopies are generally declining in areal extent across the United States
(American Forests, n.d.). At the same time urban areal extent is increasing, with urban
areas in the conterminous United States having doubled in size between 1969 and 1994
(Staley 2004) and projected to increase another 50% by the year 2050 (Nelson 2006).
Eighty percent of North Americans are now living in urbanized areas, spending 90% of
their time indoors or in controlled microclimates (Staley 2004).
As a result of these and other concerns, the patterns of urban built environments are
subject to increasing scrutiny across many disciplines (Alberti and Marzluff 2004,
Glaeser and Kahn 2008, Jackson 2003, Ong 2003, Wells 2000, Zipperer et al. 2000).
Urban planners, politicians, public health officials and some developers are recognizing
that certain built environment patterns such as large-lot residential developments and
single-use zoning may have unintended and detrimental externalities on environmental
health (Frumkin 2003, Goldberg et al. 2007, Jackson 2003), receiving waters (Alberti et
al. 2007, Greenberg et al 1994, Tong and Chen 2002), urban heat islands (Stone 2001,
Stone and Rogers 2001) and municipal finance (Carruthers and Ulfarsson 2003, Soule
2006), among other effects.
Compact development is one strategy to address urban sprawl and its associated
environmental effects (Beatley 2004, Duany and Talen 2002, Speck 2007). Many cities,
concerned about sprawl and development costs, are approving an increasing number of
compact residential and commercial developments (Szold 2007). Compact developments
often feature medium- to high-density building footprints, small-lot development, shorter
building setbacks and greater emphasis on the public realm. Modern expressions of
ordered compact development (OCD) are variously named New Urbanist (NU),
Traditional Neighborhood Design (TND) or Smart Growth (SG) developments (Farr
2008, Staley and Olson 2007). Such OCDs eschew single-use zoning and massing
specifications in favor of mixed-use zoning and design specifications (Talen 2005,
Wickersham 2007). Code language in OCDs often requires easements that may constrict
both tree roots and tree canopies (Friedman 2007), providing insufficient room for
healthy canopy and root growth and creating a greater likelihood of infrastructure
conflicts. Potential social, economic and environmental benefits of urban green
infrastructure may be foregone.
The presence of a high quality, well-managed tree canopy is essential for a high quality
of life and for the delivery of environmental services in higher density areas and across
larger scales. This paper will present new design details, specific zoning and code
language, and best practices from multiple disciplines to frame a coherent set of strategies
to ensure attainment of recommended canopy cover levels in ordered compact
developments. This paper will also present strategies for integrating urban forestry within
built environments that may help cities remedy urban sprawl and return to positive,
supportive built environment patterns.
Zoning codes and design standards are not adopted equally or at the same time across
jurisdictions. This is due to multiple factors, mainly political will (Flyvberg 1998, Hoch
1994, Hoch, Dalton and So 2000,), economics (Heikkila 2000) and asymmetric learning
(Figures 1-3). This paper shall detail code changes that can expected to be adopted,
detailed according to the four categories of policy adoption (Figure 2) and along the
continuum of societal adoption (Figure 3).
Category I. Category I jurisdiction typologies (Figure 2) are Progressive and early
adopters of technology and innovation. Representative Category I jurisdictions are Davis,
CA and Boulder, CO. With respect to tree canopy, Davis has progressive parking lot
shading standards and Boulder has innovative solar access standards.
Zoning code language and design standards that can be adopted in Category I
jurisdictions include:
1. Required parking lot interior islands (Figure 4). Interior islands and peninsulas shall be
a minimum of 8 (eight) feet in width and 18 (eighteen) feet in length.
a. Islands and peninsulas shall be excavated post-paving and prior to planting in
accordance with the provisions in § x.y (z) to provide a minimum of 750 ft3
(cubic feet) per large-statured tree and 500 ft3 (cubic feet) per mediumstatured tree.
b. There shall be no more than 12 parking stalls between islands and/or peninsulas
(Figure 5).
2. Tree:stall ratio. There shall be a minimum of one tree for every 10 parking stalls. No
more than 25 (twenty-five) percent of total trees shall be on the landscaped perimeter
(viz. Wolf 2004).
3. Parking geometry. Parking geometry shall be according to the following table.
Exceptions to this section require a variance.
1-Way Aisle Width
2-Way Aisle Width
Maximum Stall Width
Maximum Stall Length
Parking Angle
0º
45º
13 feet 13 feet
19 feet 21 feet
8.5 feet 8.5 feet
20 feet 19 feet
90º
16 feet
24 feet
8.5 feet
17 feet
Returning to old built environment patterns challenges good horticultural practices to
ensure the health of woody plants in urban environments and delivery of ecosystem
services. This paper has presented design elements, specific code language and best
practices from the urban planning, transportation planning, urban forestry and landscape
architecture to frame a coherent set of strategies to ensure attainment of recommended
canopy cover levels in ordered compact developments.
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Figures
Figure 1.
Figure 1. Societal and group learning curves are similar to logistic growth curves (Bass
1965). Rapid learning occurs near the asymptote.
Figure 2.
Figure 2. This paper posits that decision-makers fall into categories similar to Bass
diffusion curves (Bass 1965) and Rogers Adoption curves (see Figure 3). As such,
decision-makers and their publics have asymmetric levels and times of acceptance of a
particular idea or solution set. The code language and design strategies and standards in
this paper are presented according to the groups arranged along this curve.
Figure 3.
Figure 3. Societies and groups do not accept ideas or policies symmetrically. This paper
posits that a slightly modified Rogers Adoption Curve illustrates how societies accept
ideas and policies for the purposes of this paper.
Figure 4.
Figure 4. Detail of interior islands typical in Category I developments. Note the smaller
parcel size and parking lot placement to the rear of the building envelope.
Figure 5.
Figure 5. Detail of a standard for spacing between interior parking lot islands. Note also
the placement of trees to ensure lesser likelihood of automobile damage and minimum
width requirement.