Abstract

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Abstract

• This paper examines the relationship
  between urban form and impervious surface. Smart
  growth development (compact, mixed-use,
  pedestrian friendly, etc) has been held up as a
  solution to the negative consequences of urban
  sprawl. For example, smart growth has been hailed
  as a solution to traffic congestions, the loss of
  open space, the consumption of open space and
  other environmental impacts attributed to sprawl.
  This analysis explores the relationship of
  sprawl/smart growth to one very widely used
  indicator of water quality, impervious surface.
  The study first grades development in Gloucester
  County, NJ on a smart growth/sprawl scale
  utilizing a housing-unit density (Hasse 2004).
  The analysis evaluates impervious surface at a
  sub-watershed level as derived from NJ DEP land
  use/land cover data. A correlation evaluation is
  then made between sprawl/smart growth and gross
  as well as percentage amounts of impervious
  surface. The results indicate that while sprawl
  development actually has less intense impervious
  surface coverage per acre due to its dispersed
  nature, the total impervious surface contributed
  by sprawl is substantially higher than
  contributed by smart growth when calculated on a
  per-capita basis. The study concludes that smart
  growth is locally more impacting to water quality
  at the site-level due to its compact nature but
  overall less impacting on the regional-level due
  to its smaller total footprint compared to sprawl
  patterns of development.

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Sprawl has been claimed to impose greater impacts
to land resources (Hasse and Lathrop, 2003) than
compact development
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Urbanization results in the creation of
impervious surfaceParking lots, sidewalks,
buildings, driveways, etc.
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Impervious Surface Coverage and Water Quality
Arnold, Chester L Jr and Gibbons, C James
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Research Questions

1. Does Sprawl create more or less intense
   impervious surface than high-density growth?
2. At what scale?
3. Does sprawl create more or less total impervious
   surface per capita?
4. At what scale?

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Hypotheses

• Sprawl creates a lower total amount of
  impervious surface within a sub-watershed
• (Sprawl is good for water quality at the
  sub-watershed level)
• 2) Sprawl creates a greater total amount of
  impervious surface per capita
• (Sprawl creates a greater overall
  impervious surface footprint)

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Methods (1)

• Create a sprawl index related to density at
  housing unit level
• Identify housing units as point layer
• Assign the average housing population by census
  tract
• Created Sprawl Index
• Create Density Surface in Spatial Analyst (660 ft
  radius)
• Assign the density value back to the housing
  points

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Housing Units Graded for Sprawl (Density)

• Sprawl index represents density of population
  within ¼ mile of any given housing unit

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Methods (1 continued)

• Evaluate correlation of sprawl index with percent
  impervious surface per watershed
• Summarize the amount of Impervious Surface per
  watershed at different scales
• HUC 11
• HUC 14
• Sub Watershed

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(No Transcript)
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Gloucester County Impervious Surface
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Results - Basin
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Results - Watershed
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Results Sub-watershed
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Discussion

• Sprawl does create a lower total amount of
  impervious surface within a sub-watershed as
  compared to non-sprawling development
• Relationship is strongest at the basin level
  (largest scale)
• Many of the watersheds high sprawl values (i.e.
  low density) will receive more future development
  and can expect to increase I.S.

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Discussion cont.

• Sprawl creates more total impervious surface per
  person housed
• Relationship is strongest at the sub-watershed
  level
• Many of the watersheds have impervious surface
  not related to residential development
  (commercial and industrial).

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Conclusion

• Sprawl does have a relationship to impervious
  surface although it is a complex one.
• Scale is an important factor
• More research needed to determine the most
  appropriate scale of analysis
• More sophisticated measure of sprawl would make a
  stronger conclusion