Take even a passing glance at an aerial picture of any urbanized area and it is amazing how much of it is paved over to provide for the various highways, arterials, feeder roads, alleys, drive ways, parking lots and roadside parking spaces that our car clogged cities require. Look more closely and one quickly discovers that a significant portion of this paved over space devoted to the car and getting around is comprised of parking lots as well as the ubiquitous curbside parking strips so common in almost all urban settings.
This three part series looks at the problems that parking lots, curbside parking strips and other non road paved areas exacerbate; it then goes on to illustrates various ways in which we can make these facilities greener and how doing so can improve the urban environment; lessen its impact on waterways and beautify the urban spaces all at the same time. Promoting the adoption of green parking lots and roadside parking strips is win-win scenario.
Check out our five part article series to get an in depth look at the many facets and aspects of green (or sustainable) buildings design. To read the first article in the series: The Green (or Sustainable) Building: Part I – What Is the Green Building DNA?
There Are Some Serious Problem With Paving
Typically nowadays parking lots as well as curbside parking on the street margins are paved over with impermeable asphalt or concrete. These impervious urban spaces are the source of some large problems and also contribute to what many would say are an aesthetic impoverishment of the urban space. The first two problems, namely runoff and the heat island effect are quantifiable and serious issues associated with urban built up that have large deleterious effects on the urban as well as the water systems downstream from storm drains.
The aesthetic issue of ugly barren asphalted spaces are harder to quantify, but most people will, I think, agree when I say that they are do not add any great beauty to our world. Besides often being eyesores parking lots can make a city pedestrian unfriendly by cutting street pedestrian traffic off from buildings, creating barriers between the street and the buildings that are ringed by large lots. Anyone who has had to trudge across a large parking lot in the heat of summer, with heat shimmering off the black asphalt lot and little or nor shade or any pedestrian friendly walkways knows of what I speak.
Stormwater Runoff Pollutes Our Water
Because the typical parking lot (or curbside parking strip) is paved over with an impervious paving material like asphalt or concrete any rain that falls on these surfaces cannot seep into the ground, as it would on natural green earth. Because of this the water runs off flowing towards the lowest area, which in traditional lots rapidly funnels water into the city’s storm-drain systems. Storm water runoff can be defined as water from rain or melting snow that “runs off” across the land instead of seeping into the ground. As runoff water flows over hard paved surfaces it can pick up and carry many substances that pollute water, including petrochemical pollutants such as motor oil and gasoline residues. In fact impervious parking lots are recognized as one of the a largest sources of Nonpoint Source Pollution, which is a term for polluted runoff and other sources of water pollution that are hard to pinpoint, unlike say the discharge from a factory tailpipe that leaves a traceable plume.
Furthermore because the runoff is moving very rapidly as it gushes into and also out of the storm drains it also picks up and carries with it any fine particles in suspension and this can lead to silting problems in streams, rivers and other bodies of water. These rapid pulses of storm water rapidly shed from the large areas of hard urban surfaces, which besides roads and parking space also notably include roofs, can also lead to problems of urban flooding in low lying areas. In natural ground cover much of this water would have infiltrated into the ground and be released much more slowly into aquifers.
To give you an idea of the difference a hard surface makes, consider the difference between one inch of rain falling onto a meadow and a parking lot. The parking lot sheds 16 times the amount of water that a meadow does. In another example a study in Washington State by the City of Olympia’s Public Works Department found, that parking lots account for 53% of imperviousness on a commercial site and 15% of multi-family sites. That is a lot of runoff and in fact urban storm runoff is a very serious environmental problem.
Parking Lots Contribute to the Urban Heat Island Effect
Parking lots and the surprisingly large portion of road surfaces that are devoted to parking are major contributors to the urban heat island effect. Paved over areas, which include parking lots, roads, etc. comprise nearly 30–45% of land cover in urban areas based on an analysis of four geographically diverse cities by the Lawrence Livermore Berkeley National Laboratory. And given their thermal characteristics – as anyone who has ever had to walk barefoot across an asphalt parking lot on a hot summer day can surely tell you – they contribute to making urban areas less livable harsher environments.
What Is an Urban Heat Island?
The EPA provides the following description of the heat island effect and quantifies how dramatic it can be.
“As urban areas develop, changes occur in their landscape. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry. These changes cause urban regions to become warmer than their rural surroundings, forming an “island” of higher temperatures in the landscape.”
“Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F (27–50°C) hotter than the air, while shaded or moist surfaces—often in more rural surroundings—remain close to air temperatures. Surface urban heat islands are typically present day and night, but tend to be strongest during the day when the sun is shining.”
“In contrast, atmospheric urban heat islands are often weak during the late morning and throughout the day and become more pronounced after sunset due to the slow release of heat from urban infrastructure. The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. On a clear, calm night, however, the temperature difference can be as much as 22°F (12°C).”
As a rule of thumb, energy use in medium and large cities due to the increased demand for cooling from air conditioning increases by approximately 1.5-2% for each 1 degree (F) increase in summertime temperatures. Therefore, a City’s peak utility load may increase by 7.5 to 10% as a result of a 5 degree urban heat island effect.
What Can Be Done To Make Parking Lots Be Green
In the next post in this three part series we will examine the various techniques that can help make parking lots become much greener than they are. In addition to remediating existing parking lots and designing new ones to have as little an impact as is possible consideration should also be given to how much parking space a project actually requires. Look for: Green Parking Lots: Part II – How Alternate Paving Helps scheduled for publishing two days from now.
© 2009, Chris de Morsella. All rights reserved. Do not republish.