The Valley's Urban Heat Island Effect

[traal]

According to an article in today's AZCentral.com, temperatures in the valley have risen recently by as much as 10

[colin]

That's one issue that consistently comes up: green building does not work well with aesthetic design standards. Homeowners associations often have rules which effectively prohibit various green building additions.

Foresightful urban planning is, I think, the best and most simple way to counteract the heat island effect. Reservation of open space (like what San Diego's done) works well. But I don't see any Valley municipalities doing that in the near future. It doesn't seem to be a concern for anyone there.

[nuplanner]

Good topic guys. One of the reasons for this is the construction/development industry is running everything in this state. Its about the economy and so forth, not the enviroment. Last week, I had a lecture from Dean Brennan with Phx urban form project. They have some pretty innovative ideas to combat the heat in the downtown area.

Just to name a few, green streets. Native vegetation that goes along the streets. The city has found that when air temps is 110 outside, due to the materials used in the area it actually feels like 135 outside. That is really sick! But by using different materials, providing shade and native vegetation and open space, they have found they can actually lower the temps to feel like 95 instead of 135. thats big and will help downtown with a 24/7/12 a year atmospher.

First, our streets are so big and wide that is makes the heat island effect worst. Most of our streets are ugly and unfriendly to other mods of transportation such as pedestrians, bicycles, mass transit and so forth. Next, there are no trees or medians in most streets, and our sidewalks are right up against the street which is unsafe. We have a lot of problems with our streets.

Also, the life line of the desert is desert washes. Development that sprawls out just covers these areas up which could be a valuable resource to urban flooding, native vegetation and open space trails etc. It regenerates the ground water, higher vegetation and helps combat pollution and heat in the summer.

I have just did a research paper on this subject in the great northwest and how it can be applied here in the desert.

Here

[traal]

Phoenix weighs plans for cooler downtown.

Phoenix is pitching a seductive idea to lure more people to downtown: shady, cooler sidewalks lined with canopies, mini parks, fountains and public art.

[convulso]

^ anything helps. the one complaint i have about the weather in southern AZ is that sunny days there are absolutely blinding, especially when they monotonously repeat for weeks on end. i wish the cities would offer some way for providing refuge from it, but i haven't really experienced that feeling of being sheltered from sun & heat, as a pedestrian, in either phoenix or tucson. hats & sunglasses, for now.

maybe this is just a personal complaint not shared by others, owing to my sensitive eyes. but the heat aspect - all it takes to mitigate the feel of scorching heat is shade (except during monsoon, when the humidity ruins outdoor tarrying whether you're in the shade or not). palms aren't the greatest for this, since their canopy is far too small and too high to be of efficient respite. but people love the palm tree image, no matter that the ubiquitous palms we see in the cities aren't native to the area (then again, few wide-canopy shade trees are, outside riparian zones.)

[traal]

I guess the general term for the downtown Phoenix revitalization effort is the "Downtown Phoenix Urban Form Project". Apparently, Proposition 207 which was approved by voters last November is going to make things difficult:

Under the new law, owners must be compensated if a city acts without their OK and the move hurts their property values. When owners sign Proposition 207 legal waivers, it helps cities avoid lawsuits.

[nuplanner]

Damn prop 207. They used the old bait and switch on AZ voters. It also did not help that there were 21 props on the ballet either.

all this does is make things harder to improve the valley as a whole. Stupid ignorant people.

[traal]

More news: More people, more concrete, and lots more heat in Phoenix

In the 1950s... the temperature rose to 110 or higher an average of 6.7 days per year... in the 2000s (through Aug. 21, 2007), 21.9 per year, according to the National Weather Service.

[clarebear]

is it possible that the introduction of man made lakes and streems could help with that? i know it sounds crazy but theres not that much above ground water flowing through phx right now, maybe that could help?

[traal]

I think evaporation from them might have a cooling effect on surrounding areas, but only on non-humid days.

[clarebear]

dang, oh well. it was worth a shout out

[colin]

Vegetation tends to increase humidity because of evaporation whereas open space tends to lower temps because of the lack of concrete and other materials that retain heat better than natural desert terrain. The former can actually make it feel cooler when it's cool and hotter when it's hot.

Phoenix has quite a bit of vegetation (about 90% of it fake) including lawns, farms and various non-native trees like palms and citrus, but almost no open space, which is really part of the problem with the heat island there.

Or am I way off on this and getting my high school geography confused?

There will be fringe open space though. For instance, a large part of Phoenix is surrounded by Indian reservations which, for the most part, are somewhat undeveloped and open (except for the northeast ones, which have quite a bit of farmland), the White Tank Mountains on the west side, South Mountain on the south side, the Superstations/Tonto National Forest to the east and Lake Pleasant and lots of state and federal land to the north. Unfortunately though, there's currently little, if any, between developed areas.

[traal]

Whereas vegetation is better than concrete for keeping the environment cool, concrete is still better than asphalt and other dark-colored roofs and gravel. So, replace asphalt with concrete wherever convenient and try to shade as much as possible with trees.

If Phoenix were to tear down buildings and create more open space within city limits, wouldn't the lower population density be worse for the environment? If you tear down an office building to make a park, a person who worked in it and lived next to it would have to get a new job further away, requiring more resources (like gasoline) to get to work.

[colin]

I don't necessarily mean that every city should just start destroying buildings to create open space. I think San Diego did a pretty good job on simply preserving open space. Like Tecolote Canyon, Mission Trails, and the little river that runs into Sweetwater Reservoir.

And I don't know that open space necessarily facilitates sprawl. I see your point, but I feel like pushing development out will just speed up the inevitable process of developing that land. But, as far as actually increasing sprawl, I think you still have that "How far are people actually willing to go" and "How inconvenient are people willing to make their commutes" questions that dictate when in-fill and gentrification begin to start up and sprawl slows or outright ceases. But you also have to couple this open space planning with other planning, like for transportation (especially public).

I'm just a big fan of the New Town concept though that incorporates all of this. Not necessarily saying it's the best school of thought.

Either way, Mesa has done zero planning and it's too late to engage in a proactive approach. But I'd love to see some of those abandoned strip malls razed for smarter development or, yes, added open or park space.

[traal]

Here is a picture I was looking for, comparing heat emanated from vegetation, concrete, and asphalt.

Looking at thermal imagery maps here and here, it appears that the mountains, desert, and the asphalt expanse of Sky Harbor are some of the warmest spots in the valley, while the surrounding farms are the coolest. So it appears that open space isn't enough to cool down the valley. Those open spaces also need vegetation.

Some places encourage green roofs. That's one thing Mesa and Phoenix could do at this stage. There are plenty of roofs that could be greened!