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May 19, 2007
Small Parks Could Cool Big Cities
A little bit of greenery in urban areas can cool off the hotter and stickier summers that city residents face as a result of global warming, new research show.An additional 10 percent more green space could reduce surface temperatures by 7 degrees Fahrenheit, according to a team of British scientists. Extra parks and green roofs could counteract the predicted rise in temperature until 2080 when summers are expected to be hotter and drier and winters wetter.
The notion of planting trees in England is a good idea to offset the heat bubble that forms around major metropolitan areas. But I found their concerns about their inability to deal with the larger amounts of water in the winters a bit, I don't know, overblown.
Although Ennos' models suggest green space will decrease temperatures, it will not be able to absorb the rainfall from the more frequent and 50 percent larger winter storms predicted to hit Manchester by 2080, he said. Left unabsorbed, the rainwater is expected to flow to city drains and travel to streams and rivers, ending up in the ocean."Unfortunately, increasing the amount of green space only has a limited effect in reducing run-off, and so flash flooding will become an increasing problem in our cities," Ennos said.
Floods could be prevented with more rainwater storage, he said, which might keep the city's green space irrigated during the droughts expected in summer months.
It seems like the logical solution is to start using permeable paving techniques in their cities to help with the absorption of water. I swear I've talked about this before, but I can find no record of it on the blog, I must have used another title or I wrote it up and never published it. Anyway, basically using this technique your able to create city surfaces that allow water to pass through them into the ground like they normally would on a natural surface. Then the cities could absorb massively increased amounts of water that they would get. Not only that, it would allow that water to make it's way into the ground water per the normal natural cycle. Anyway, you can make all sorts of different version of this, even make large parking lots with it. Most versions don't hold up to massive weights of semi's for example, but it works fine for regular cars and foot traffic. This also allows you to save money on construction because the water run off is a lot easier to manage because it's mostly being absorbed. By combining these two technology, I think they can mitigate all their problems at once. It's definitely the future.
Read more over at Live Science.
Posted by Jamison at May 19, 2007 9:23 PM
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Comments
Their are down sides to using this type of pavement.
If the soil is saturated at the time of the rain event the water stays in the pavement. When the ground is frozen the water that is melted by the sun during the day is subject to re freezing at night which breaks up your pavement. Also the salt and other chemicals that filter down into the pavement tend to eat it up thus reducing you pavement life cycle. For low volume roads, walkways and secondary parking lots that are not used during snow and storm events this is a good ideal. Yet main arterial and collector routes this is a maintenance problem waiting to happen.
Also one needs to review the road base of an existing route before retro-fitting to see it the existing mateial is suited to dealing with the extra water. Water in the base and sub-grade of most current roadway is a ticket for self destruction. If the fines from the base(Rock)are
washed away by water it leaves voids in the base which allows the pavement to form a pumping (suction) problem (first sign is a crack in the surface with white "lime stone" or Brownish "river rock" around the location after the water has dried up from a rain event) as loads travel over the area which pulls water and sub grade materal up in to the base material corrupting its ability to support the loads applied to the pavement above.
This results in Gator Cracking (Little square looking pattern like the scales on the reptiles back) on the pavement on the surface.
Posted by: Royal at May 26, 2007 9:01 AM