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Trees need water: they grow root systems that often extend horizontally far beyond their branches' reach in order to get that water.
Parking lots, on the other hand do *not* need water; they're usually laced with expensive-to-build storm-drain outflows.
So, the solution is obvious: Design a parking
lot with enough trees in it to soak up the water...
A Parking Forest is built with an especially deep bottom layer of large gravel. It has various pavement-level slopes to drain rain/meltwater from the ashphalt into Funnels.
Funnels are stainless steel cageworks open at the top and wide enough at the bottom(narrow end) to accomodate a mature tree: picture a wide-mouthed badminton birdie minus the rubber bouncy bit. Stone crenellations at the top of each Funnel keep vehicular incursions to a minimum; a layer of topsoil and shade-grass along the sloping sides help keep the system clean and looking pretty. Spacing of the Funnels is determined such that the roots of the Trees, when mature, will soak up all available groundwater.
Tree Types are determined by the probable longevity of the zoning of the area as a parking lot; a native species tree is chosen which will sequester the most carbon per areal measurement of root system based on complete uptake of precipitation at maturity during the projected time period. You may want to mix'n'match with nitrogen-fixing species... whatever floats your boat.
As a self-sustaining symbiotic arrangement, rain/meltwater flows into the Funnels from the Parking Lot which keeps parkers happy. The water flows into the funnels, through the shade-grass and then runs freely through the extensive layer of gravel, thus *not* drowning the tree or leaving it open to fungal infection. The roots sop up as much water as they need and grow and do *not* poke their heads up above ground level since the tree has been planted a metre below the pavement level and the layer of gravel won't contain enough water generally to encourage growth upwards through it.
Through the life-cycle of the parking lot, the "off funnel" points will slowly subside due to erosion and the funnel-points will also slowly...err.. upside because of root growth, but that's taken into account when the original slopes are calculated.
Upshot ? a maximal-carbon-sequestering Parking Forest.
Feel free to imagine dumping compost into the Funnels as long as you can also freely imagine cleaning it out every once-in-awhile, too.
Tree in a hole
http://www.flickr.c...r_goleta/207730474/
I can't find a photo of it above ground, but the main part of the tree is actually above ground, just the roots and trunk are down a level in the tunnel. [Zimmy, Feb 18 2009]
[link]
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[21Quest]sorry I was editing our lengthy conversation and deleted one anno too many; I saved the gist of it, though
//You'd end up killing the trees//
I can't think of any automotive compound that's a natural herbicide in the dilution you'd get when the rain washed it into the funnel... and any amount that got in when it isn't raining (for instance your radiator exploded while you were parked) would be trapped by the grass/topsoil. |
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And even if pollution was a problem, you could plant Plane trees. The reason London's streets are planted with Plane trees is because they're very tolerant of pollution. |
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Wouldn't the roots destroy the asphalt though? I don't know if this is the case with most trees, but I've seen entire houses brought down by rampant roots. |
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+ Tree roots do tend to do that, but if paving squares were used you could pull up the pavers every 25 years and fill with sand to smooth it out. Plus the pavers would let the water soak in through the joints.
I think I have some sort of 1/2B block right now. Any good idea I come up with tends to already exist after googling, so I guess I'm reduced to adding comments. What a bummer. |
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I would be worried about limbs falling on my car. |
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But I would park here anyway, because it would be shady and
pretty. + |
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//I can't think of any automotive compound that's a natural herbicide in the dilution you'd get when the rain washed it into the funnel// |
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This statement has me thinking... what about light showers? Wouldn't be such a heavy dilution rate, I wouldn't think, and the risk of Toxic Root Syndrome rears its ugly head again. I'm gonna stay neutral on this one, and I'm gonna do some research. I wonder what the EPA would think of it, though, because all that pollution, even if it doesn't harm the trees, may leach into groundwater and make people or animals ill. |
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[placid] as noted the trees are planted a metre down from the surface of the lot: you'll still get some "bunching up" accounted for in the design, but the roots won't try to make their way to the surface since only the bottom bit of gravel will be getting wet. |
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[21Q] I imagine the EPA would think about as much of it as they would any other parking lot. To start your research you might note that most cities' modern stormwater systems are separate from their septic systems (makes it easier to treat the septic systems) and are left untreated... not sure where you're going with the fake disease name, though. :D |
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Yeah, I made up the disease name. Sounded kinda cool, I thought. |
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//The roots sop up as much water as they need and grow and do *not* poke their heads up above ground level since the tree has been planted a metre below ground-level and the layer of gravel won't contain enough water generally to encourage growth upwards through it.// |
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You may want to edit this part. I don't know of any tree that can grow when there's a meter of gravel between it's leaves and the sunlight... |
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the pavers are a good idea though. I don't know why more people won't use them instead of cement and asphalt. |
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//I don't know of any tree that can grow when there's a meter of gravel between it's leaves and the sunlight//
Me either... [post edited] does "below pavement level" work for you ? |
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[ye] yeah I know, they look great: Pavers would be (are) a good solution for a high-class personal or small business lot; you can adjust them "on the fly", but I think for something like a mall parking lot they'd require too much maintenance... also you couldn't use the large snowplow that such sized lots needs. |
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I'm neutral on this. Shade is handy in carparks too - I'm all for integrated water capture and root management systems, but let those trees' heads rise proud and high |
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[BH] the trees are going to be below pavement level no matter what: gotta get the water off of the ashphalt; envisioned is a metre deep hole, 1.5 - 2m wide (at the top). The goal is to eventually have trees whose root systems pull in *all* the rain/meltwater in the lot: I'm not sure 3' is going to make that much difference to a 50' tall tree. |
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/Parking lots, on the other hand do *not* need water; they're usually laced with expensive-to-build storm-drain outflows./ |
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Replace the parking lot with a multi level parking garage, and stick a green roof on top of the building. |
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Am I going to need to bring my car cover to keep the birds off? |
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//green roof//
In what way would that provide more carbon sequestration than the post idea ? |
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[RS] yup but we don't mention that in the flyer. |
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Not sure what all the fuss is. Several cities have plants and trees next to parking lots and streets to mitigate groundwater runoff. Don't believe the flora has buggered off yet. |
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recap :) a parking lot constructed with integral trees that, when mature, shade the entire lot (not because it needs shade especially, but because that's the way to get maximum C sequestration). And the trees sop up all the rainwater, obviating the need for stormdrains. From above it will look like a densely packed forest. |
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A full grown oak will shade, I would think about 4 cars at most, there might be other trees with more coverage, but I wouldn't think you'd ever get more than about 6. Assuming the space a tree takes up is 1/2 parking space ( I suspect it would be closer to 1 at full growth, but we'll try 1/2), you're looking at an 8% increase in lot size, with equivalently greater land use. A parking garage with green roof has no increase in land use, and probably has a decrease relative to an open parking lot. This allows denser development which creates less total travel distance and less energy use. |
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Unless you want 30ft deep dirt/gravel as the last "floor" (and the attendant structure), your options for greenery type are limited to shrubs and itty-bitty trees with little or no eye-appeal. |
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//8%// as compared to how much for support beams and ramps ? |
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Bear in mind that for this idea, I'm thinking of suburban malls, not inner-city lots. |
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Remember 8% was the minimum under some generous assupmtions, and while you do lose space to columns and ramps, adding an extra level regains it. |
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Many tree types, including fruit trees, will grow happily with 5-10 ft of dirt (not that I'm saying you go that way, but 30ft is exessive), dwarf varieties can be pot grown in about 2-3. I'd love to have a nice apple orchard on top of my parking area. |
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I don't hate the idea, but mall parking lots are already absurd, I'm not a fan of anything that increases sprawl. Admittedly a 2-3 layer parking garage with trees growing from the base up might work as well. You'd either need mirrors at the top while the trees were growing (to get them enough light) or build layers of the garage over 50-70 years while the trees were growing. |
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//adding an extra level// means longer shadows: your 2-3 layer garage may have a neighbourhood shade footprint three times it's areal size... I'm not sure but I don't think any decent carbon-sequestering tree will be happy in a mere five foot depth of soil. |
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Given that most malls parking lots are between a road and
the mall, an increased shade footprint is not a major
concern. |
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And again, if you're purely going to build this for carbon
sequestration, the best I've heard of is bamboo, and it does
quite nicely in 1-2 feet of soil. Dwarf variety trees, which are
mostly ornamental or fruit bearing can do quite well in fairly
shallow soil. |
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//Given that most malls parking lots are between a road and the mall, an increased shade footprint is not a major concern.//
... so your requirements are for a mall that has roadways on three sides and the mall on the fourth? |
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bamboo vs. other trees' carbon-sequestration: I haven't been able to find a comparison chart, have you ? (seriously). Bamboo grows fast, but is quite light. |
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The major factor in carbon sequestration is below ground growth, not above, as above eventually returns to the air, below stays in the soil. Bambo's root growth is incredible. |
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Even if you look at total growth, bamboo is one of the highest tons per unit area, followed I believe by various trees under a coppicing plan which doesn't require huge root systems. I forget where I found the numbers, but I did track them down for another discussion on here relating to radial cutting wood fired power plants. |
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Most suburban malls are surrounded by roads, often a purpose built ring road, or at a major intersection. Those that aren't are rountinely adjacent to other development that won't be greatly harmed by shading. Only rarely does a mall have many of it's sides surrounded by natural growth, with resedential development maybe being only slightly more common. |
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//bamboo// *numbers* not numbing. |
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This is my entry for "large radius power plant". Several on-line sources seem to confirm numbers in this range depending on conditions: |
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"The sources I find recommend about 5 years for bamboo growth, with a biomass production of 86 tonnes per hectare, with an additional 43 tons of carbon sequestered as underground growth (roots and such). Fast growing willow coppiced at 5 year intervals will run as high as 48 tonnes/hectare, depending on environment. " |
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This assumes harvest and utilization of the stalks. Leaf litter biomass is unkown. |
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gotta wonder what they mean by "biomass" though: to my mind that means hydrocarbons... and water. If the entries read "sequestered carbon", that'd be different. |
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Biomass is everything that grows, but is (I believe) relatively consistent among woody plants as far as atomic make-up even if it varies slightly in chemical. Thus while comparing tonnes of grown material may not be perfect, it's probably pretty close. |
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<meh> still can't find a comparison of "wet weight" vs. "dry weight" or "green vs. seasoned" for bamboo. |
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