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Thread: Tree canopy ordinances

  1. #1

    Tree canopy ordinances

    Working on a rewrite of our Tree/Landscape ordinance and I've become pretty interested in canopy ordinances that require parking lots to have a certian percentage shaded... does anybody have any good ideas or examples?

    Thanks

  2. #2
    Cyburbian hilldweller's avatar
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    Quote Originally posted by Tree Planner View post
    Working on a rewrite of our Tree/Landscape ordinance and I've become pretty interested in canopy ordinances that require parking lots to have a certian percentage shaded... does anybody have any good ideas or examples?

    Thanks
    I don't think this is a such a good idea because it would be too hard to enforce.
    Stick to the basics like landscape types, quantity of trees/shrubs, landscape island sizes, etc. That way the applicant will know exactly what is expected of them rather than trying to measure the angle of the sun and all that entails.

  3. #3
    Actually in looking at a few different places that do this it seems pretty easy. An engineer shows the shading pattern on the plans and viola it's done. I think it's done in a much more theoretical manner, rather than an after the fact empirical evaluation. Seems like anything else on a site plan, the inspector just goes out an makes sure they plant the trees, which he already does. The benefits are way too beneficial to write it off based on your criteria.

  4. #4
    Cyburbian
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    In three communities I do landscape plan review work, landscape ordinances require between 15% and 25% of the parking lot surface area to consist of landscaped parking islands. This includes islands at the ends of each row of parking, including a double landscaped island for two rows of parking. Intermediate landscaped islands and continual landscaped planting islands (perpendicular to a parking row and similar to a landscaped perimeter yard).

    In other communites, landscaped islands are requried at the ends of every parking row, with additional landscaped islands every 20-21 spaces.

    Hope this helps-

  5. #5
    Cyburbian boiker's avatar
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    Quote Originally posted by Tree Planner View post
    Actually in looking at a few different places that do this it seems pretty easy. An engineer shows the shading pattern on the plans and viola it's done. I think it's done in a much more theoretical manner, rather than an after the fact empirical evaluation. Seems like anything else on a site plan, the inspector just goes out an makes sure they plant the trees, which he already does. The benefits are way too beneficial to write it off based on your criteria.

    Shading pattern based on what angle of light (i.e. what time of day). I think that can be a difficult sticking point. Also, how is the shading pattern determined? By an average species shade pattern? and where would the engineer get that information? Also, trees don't grow completely uniform so it would be difficult to assess the effectiveness of the % shaded cover.

    I'm not against the proposal, I'm just trying to think like a developer and poke holes in it.
    Dude, I'm cheesing so hard right now.

  6. #6
    Cyburbian craines's avatar
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    I believe land cad has the ability to calculate coverage.
    Looking for Sanity
    In this Crazy Land Of Ours

  7. #7
    Cyburbian
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    You might consider potential overlap of tree canopy shading, if allowed, how much, etc. No clustering, minimum distance between trunks, variation allowed or encouraged.

  8. #8
    Cyburbian Richi's avatar
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    Requiring trees in parking lots does make the lots larger and the area less dense. Other than making the lots pretty, I think that attempting to get much canopy from parking lot trees often doesn't work well because of the limited space for the roots, etc. I would rather see a more massed effect that would have a better chance to grow some really big trees and better support at least some bird life.

  9. #9
    Dan Staley's avatar
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    Quote Originally posted by boiker View post
    Shading pattern based on what angle of light (i.e. what time of day). I think that can be a difficult sticking point. Also, how is the shading pattern determined? By an average species shade pattern? and where would the engineer get that information? Also, trees don't grow completely uniform so it would be difficult to assess the effectiveness of the % shaded cover.

    I'm not against the proposal, I'm just trying to think like a developer and poke holes in it.
    First, this is the best compendium of ordinances.

    Second, Davis, CA has one of the better shading ordinances, as one of the top urban forestsers (Greg McPherson) helped write it. IIRC section 37.

    Shade coverage is unenforceable in my view, unless one chooses between, say, 1-2 PM on a date not at solstice.

    With respect to root volume, this is easy enough to do if you make minimum planter width 8' (or stall width). Canopy cover over pavement has multiple benefits, contra a comment below - pavement longevity, fewer VOCs from parked cars, aesthetic, etc. Besides, many places are overparked, so reducing a few spaces generally won't hurt.

    Shade ordinances are an excellent idea.

    DS (B.S. Env Hort and Urban Forestry UCD)
    Last edited by Dan Staley; 14 Oct 2008 at 7:44 PM. Reason: clarification

  10. #10
    It isn't that difficult to design something based on the angle of the sun during the daytime... You just need a sun chart, which is easy to get on the internet.

    Usually during the summer, the sun (as we all know) is more directly overhead at noon. The hottest part of the day is also about 3pm-5pm.

  11. #11
    Dan Staley's avatar
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    Quote Originally posted by HeartlandCityBoy View post
    It isn't that difficult to design something based on the angle of the sun during the daytime... You just need a sun chart, which is easy to get on the internet.

    Usually during the summer, the sun (as we all know) is more directly overhead at noon. The hottest part of the day is also about 3pm-5pm.
    Agreed. You still get volatilization of fuel in shoulder months, which requires shade to ameliorate. The easier enforceability is in the canopy, as this can be done at any time with aerial orthophotos.

    Also, the language required to define when the canopy shades, say, 50% of the pavement is necessarily complex. That is: how do you keep developers from saying that at 0900 the shade is 80% of the pavement and they exceeded minimums - the reverse of solar access ordinances.

  12. #12
    Cyburbian abrowne's avatar
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    Quote Originally posted by boiker View post
    Shading pattern based on what angle of light (i.e. what time of day). I think that can be a difficult sticking point. Also, how is the shading pattern determined? By an average species shade pattern? and where would the engineer get that information? Also, trees don't grow completely uniform so it would be difficult to assess the effectiveness of the % shaded cover.

    I'm not against the proposal, I'm just trying to think like a developer and poke holes in it.
    And at what age for the trees? 1 yr? 3yr? 5yr? "maturity"?

    I agree, tough one to even understand.

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    That sounds like an incredibly 'fiddly' thing to impose on a developer. Far too many variables & almost definitely unenforceable, as has been mentioned previously.

  14. #14
    I think many of you are viewing my question as an enforceable after fact development criteria. That's not what it is at all it's more of an effort to encourage "greener" and more energy efficient development practices. We know that in all cases we aren't going to reach a measured shade cover area, however by providing a standard diameter an AutoCAD program can do 'little circles' to note the projected tree canopy coverage... the standard diameter is assigned to each tree specie so all we are asking the developer to do is mark the plans.. our numbers are quite liberal, given the changing times we don't feel this is infringing on development in the least. In fact we already require a tree in a landscape island, with a maximum of 10 spaces together before an island is required. By using a larger shade tree our developers should be able to easily meet this requirement. Again, barring all of the technical jargon, this is more of a good development practice.

  15. #15
    Dan Staley's avatar
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    Quote Originally posted by Tree Planner View post
    I think many of you are viewing my question as an enforceable after fact development criteria. That's not what it is at all it's more of an effort to encourage "greener" and more energy efficient development practices. Again, barring all of the technical jargon, this is more of a good development practice.

    [snipped]
    Absolutely. A great thing to do. Please, everyone out there do this. And IME often you have to have something enforceable/incentable to get them to do it right.

    Be careful though with large-canopied trees, as they need ~250-400 cu ft of root volume to ensure viability - hard to do in a parking lot where the entire expanse is compacted, then little slices are dug up to throw a few trees in. This is why coverage requirements are often stated as 10 or 15 years running with the deed, as this encourages best practices at design & installation.

  16. #16
         
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    can't you just impose/suggest better landscaping treatment for car parks, rather than go through what still sounds like a rather onerous ordinance regarding tree canopies?

    apologies for being awkward, but i'm interested in ordinances - to someone outside US planning looking in they do look to be very very detailed guidance, almost anally so.

    we have supplementary planning guidance that are published by individual planning authorities but none i have come across have ever addressed some of the subjects i've read on here!

  17. #17
    I don't disagree with how detailed this tree ordinance is but you would be amazed how, I've had to "fight" with people over trees. 20 years ago, our code book was 1/3 of what it is now and probably more in-line with what you're are thinking... a large part of what I do, I would consider in the "protection" realm of thinking, in that I have to protect things from going sour. As you can see from the discussion here, we constantly have to justify ourselves against good sound logical thinking and hence this is why our code books get so large.. we not only have to be prepared to set policy but we also have to defend it, long before it ever gets attacked. Our City, and its residents have decided to protect the canopy and now as a planner, it's my job to see that it's done. Can it be overbearing? Probably a little, but is it needed? You betcha.

  18. #18
         
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    We require a photometric plot showing footcandle measurements around a property's perimeter. It seems that a canopy/shade requirement could be based on some numeric standard similar to that.

  19. #19
    Cyburbian Streck's avatar
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    What is the goal by having a tree canopy rule?

    Is it to keep the cars and pavement from getting too hot? Cars have relatively instant air conditioning cooling. Does it matter if the pavement gets hot? It seems like this should be a matter of owner concern - to make his parking lot more inviting - not a city government enforcement concern.

    It does seem to be more of a city concern as to appearance of the lot from the public street. This affects adjacent property values and city image. Along those lines, it would seem that continuous shrub type planting along the ROW would be more beneficial. The shrub selection should be evergreen, about 3 feet high (to cover most glaring chrome), varied in grouping of species, and occasional flowering types or low flowering plants in front. And yes include some relatively small ornamental flowering street trees (so as not to interfere with overhead powerlines or requires severe pruning which never enhances the city).

    Of course it is agreed that there should be some planting islands in the lot to break up the apparent concrete desert - but major tree roots tend to break up pavement after awhile. And their canopy tends to block light from pole mounted fixtures at night.

  20. #20
    What is the goal by having a tree canopy rule?

    Is it to keep the cars and pavement from getting too hot? Cars have relatively instant air conditioning cooling. Does it matter if the pavement gets hot? It seems like this should be a matter of owner concern - to make his parking lot more inviting - not a city government enforcement concern.

    Dr. Kathleen Wolf sums up one of our concerns… “Some paving materials cause heat build up over a parking lot on hot days. The effect over an entire city is that temperatures rise, leading to increases in air pollution and ozone.” Not withstanding the broader political or philosophical argument, the private sector has failed to maintain a parking lot canopy, in our city. In many cases they have requested to clear lots or destroy all of the trees on a particular lot.. and our city has deemed this an unacceptable practice. Our tree ordinance, authored in 1985, was established to maintain the canopy.. we are working on the parking lot shade ordinance to further establish the canopy and avoid the further blight of these parking lot deserts.

    It does seem to be more of a city concern as to appearance of the lot from the public street. This affects adjacent property values and city image. Along those lines, it would seem that continuous shrub type planting along the ROW would be more beneficial. The shrub selection should be evergreen, about 3 feet high (to cover most glaring chrome), varied in grouping of species, and occasional flowering types or low flowering plants in front. And yes include some relatively small ornamental flowering street trees (so as not to interfere with overhead powerlines or requires severe pruning which never enhances the city).

    Ornamental trees and a “shrub line” just doesn’t cut it in our Tree City. While traveling out West and seeing many of the growing pains in cities that exploded growth-wise the last few years, I was shocked to see parking lots with very little trees covering them. I’m sure it’s what our city looked like before the establishment of a tree ordinance. We already keep our trees from the powerlines, minimum 25-35 feet, so this isn’t an issue when working on new development. Also, a shrub does very little for the environment and often dies as the private sector fails to maintain it. Besides, we address buffering with shrubs, so it’s already a requirement that we adhere to. Again, it just isn’t enough.

    Of course it is agreed that there should be some planting islands in the lot to break up the apparent concrete desert - but major tree roots tend to break up pavement after awhile. And their canopy tends to block light from pole mounted fixtures at night.

    Major root damage is more often associated with trees that have a shallow root zone a landscape island that doesn’t have enough square footage. These are things we review during the site plan process, and in doing this we rarely have problems. Given the site plan review process, I couldn’t kill this ordinance based on this premise. Problem easily avoided with good planning.

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    landscape stds

    Leon County Florida has some stds you may want to check - here is the main part...you can review more on municode.com web site or call our office at 850-606-1300. We find that these kinds of requirements are very helpful to mitigate the heat island effects of the parking lots and to mitigate the general poor aesthetics associated with large parking areas (parsley on a pig?)

    Sec. 10-4.347.* Landscape design standards for perimeter and interior landscape areas.
    Off-street parking facilities and other vehicular use areas shall meet the following minimum requirements:
    (1)***Perimeter landscape area requirements.* *
    a.***Front perimeter landscape area.* A 20-foot wide strip of land along the entire front perimeter of a site, located between the front property line and any vehicular use area, shall be landscaped. Corner parcels where any two streets intersect shall be considered to have perimeter frontage on two sides of the site. Width of sidewalks shall not be included within the 20-foot wide front perimeter landscape area.*
    b.***Side and rear perimeter landscape areas.* A six-foot wide strip of land along the entire side and rear perimeter of a site, located between the side and rear property lines and any vehicular use area, shall be landscaped, except that where a perimeter landscape area is between a side or rear property line and a vehicular use area used as an access way, only a four-foot wide strip of land shall be required to be landscaped.*
    c.***Joint landscape areas for adjacent properties.* When side or rear perimeter landscape areas are required on adjacent properties, the owners of such adjacent properties may agree to the installation of only one such landscape area on the adjacent boundary, as long as such agreement is binding on both property owners and their successors in interest and is approved as part of the permit application by the county administrator or designee.*
    d.***Vehicular overhang areas.* Vehicle wheel stops or other design features, such as curbing, shall be used so that parked vehicles do not extend more than two feet into any required landscape or buffer area.*
    e.***Access ways.* All access ways through the perimeter landscape areas shall meet the standards established by the county for driveways pursuant to section 10-7.506 Separation between any one-way drives shall be no less than ten feet. If it is determined that access way separation minimum, or aisle width maximum, requirements will create a safety hazard or unreasonably limit safe access to and from the development, or will significantly impact protected trees, such requirements may be waived or modified by the county administrator or designee.*
    f.***Cross-visibility standards for perimeter landscape areas.* A sight triangle shall be provided at all points where an access way intersects the right-of-way easement line of any street and also where the right-of-way or easement lines of any two streets intersect. The area within the sight triangle shall be constructed and maintained in accordance with sections 10-4.211(4) and 10-7.506.*
    g.***Grass ditches in perimeter landscape areas shall have back slopes no steeper than 3:1 for support of the required landscaping materials.
    h.***Perimeter landscape areas shall not count as landscape islands.
    i.***Perimeter landscape areas shall not be used for garbage or trash collection or any other functional use.
    j.***No use shall be made of, nor development activity permitted in, the perimeter landscape areas except for:
    1.***Planting material approved as part of the landscape plan.
    2.***Completely underground utilities and essential, specifically approved, overhead or above-ground utilities which do not interfere with the mature growth of required plant material.
    3.***Grass ditches, with back slopes no steeper than 3:1, which can support the required landscaping materials.
    (2)***Interior landscape for vehicular use areas.* *
    a.***Size.* In vehicular use areas within the interior of a site, one 400 square foot (eight percent) natural or landscape planted area shall be required for every 5,000 square feet of vehicular use area, or major portion thereof. Interior planting areas shall be located to most effectively relieve the monotony of large expanses of paving, reduce heat inversion, and contribute to orderly circulation of vehicular and pedestrian traffic, and shall be no less than 12 feet in width, exclusive of curbing. Whenever linear medians at least 50 feet long having shade trees spaced no greater than 15 feet on center are used, the minimum width may be reduced to eight feet exclusive of curbing. There shall be an additional 400 square feet of planting area for every eight parking spaces above the minimum number required in Article VI (zoning).*
    1.***Landscape area credit availability.* As an incentive for preserving forest communities, landscape islands within the vehicular use area encompassing urban forest shall count on a square foot to square foot basis toward the interior landscape island requirement, when preserved in a natural state. To qualify for such a waiver, the preserved natural areas must be a minimum of 800 square feet in size (which would qualify as 800 square feet of interior landscape) and be approved by the county administrator or designee as meeting the objectives of this division.*
    b.***Vehicular overhang.* Vehicle wheel stops or other design features, such as curbing, shall be used so that parked vehicles do not extend more than two feet into any required landscape or buffer area.*
    c.***Grass ditches shall have back slopes no steeper than 3:1 for support of the required landscaping materials.
    (3)***Landscaping functional waiver.* When an applicant demonstrates to the satisfaction of the director that strict application of this section will interfere with the function of vehicular use areas, the county administrator or designee may permit relocation of required landscaping or other substitutions which will improve functioning provided that the intent of this section is met by such modifications.*
    (Ord. No. 07-20, § 2, 7-10-07)

    The Doctor

  22. #22
    Cyburbian Plan-it's avatar
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    You can do the same exact thing by mandating tree placements for landscape islands in your ordiannce and have a list of approved trees (shade producing trees) with minimum size requirements. This will take out all of the arbitrary, if it blooms at full in winter during a solar eclipse mumbo jumbo, and in the end does the same exact thing as the shade ordinance (shades the parking lot to reduce the heat island effect).
    Satellite City Enabler

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