Tuesday, June 09, 2009

depaving our cities!

I recently read about a great non-profit organization called "depave", based in Portland, Oregon. Their mission is to work away at de-paving the many unnecessary urban concrete areas to instead create useful, living, healthier spaces with many practical benefits such as reducing city temperatures, decreasing impact of storm water run-off, and offering new places for urban food products.

Vancouver's "green infrastructure program" has a somewhat similar project called "country lanes" where the pavement of backlanes is removed in order to plant grases. These green lanes are set up primarily to help decrease the impact of storm water run-off into the city's sewage system, but also offer a beautiful alternative to regular pavement. See:

From the depave website here is their statement on the benefits of depaving (

Impervious surfaces such as concrete and asphalt can be useful for providing access for pedestrians, bicyclists, wheelchair users, and cars. However, the paving over of millions of acres of land and vegetation have contributed to numerous economic and environmental problems. In many cities, over half of the urban land is paved for roadways and parking lots. While we may need sidewalks and roadways, we can minimize the pavement we use for driveways and parking areas, and thereby restore the natural environment. Ideally, we shouldn’t be paving over habitat and farmland to accommodate auto-centric development, but through depaving, we can reverse the damage!

Firstly, impervious surfaces prevent rainwater from entering the soil and instead divert it to nearby waterways. Along the way, the rainwater carries pollutants such as oil, antifreeze, plastics, pesticides, and heavy metals from the roads into local streams and rivers, devastating riparian habitat and polluting local waterways. In places like Portland, Oregon, which uses combined sewer overflows, the high volume of stormwater runoff forces untreated sewage into the rivers.

Pavement also increases the summertime temperatures in cities and suburbs. This “heat island effect” in urban areas often increase temperatures by about 10 degrees (F) higher than surrounding rural areas. This in turn increases the need for electricity to power fans and air conditioning units. The elevated temperatures also contribute to the formation of ground-level ozone – the main constituent of smog.

The removal of pavement allows for the revegetation of land with trees and plants.

The benefits of urban vegetation include:

  • Cooling of homes and offices by shading the sun’s rays and the protection against harsh winds
  • Ambient cooling from evapotranspiration of rain on the leaves
  • Aesthetic enhancement to areas and psychosocial benefits associated with greenery
  • Enhancing air quality by removing particulate pollutants and carbon dioxide from the air while producing oxygen
  • Visual privacy and reduction of noise from the street
  • Traffic calming when trees are planted along urban streets
  • Restoration of local habitat for birds, insects and other wildlife
  • And if the previously-paved land is used for farming, this provides food and nutrition for local residents.
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