A common question that we get when designing site plans and evaluating sites with our clients is “Are there any regulations on which trees I must keep, and which I can remove on my site?” The short answer is probably. This issue really depends on which jurisdiction your property is located and under what zoning ordinance it must abide. For the sake of this article, we will explain the requirements in one of the more stringent jurisdictions…Austin, TX.
Which trees on my site are protected?
The first step is always to ask the jurisdiction what sizes and species of trees are protected. Most jurisdictions with tree protection ordinances will determine the trees protection level according to species and size of the tree. We will go through the types that are protected from removal in Austin, TX. There are 4 types of trees according to the City of Austin.
Heritage Trees – Heritage trees are usually the very big and beautiful trees on your site. The technical determination for a heritage tree is one that is over 24” in diameter (measured from 4 ½ feet from the ground) AND is of one of the following species listed:
- Texas Ash
- Bald Cypress
- American Elm
- Cedar Elm
- Texas Madrone
- Bigtooth Maple
- All Oak species
- Arizona Walnut
- Eastern Black Walnut
Protected Trees – A protected tree is any tree (regardless of species) that is 19” or larger in diameter.
Trees that Require Mitigation – Any tree that is 8” (regardless of species) or larger in diameter must be mitigated if removed.
Trees that are allowed to be removed – Any tree that is under 8” in diameter may be removed without mitigation or jurisdictional permitting
What all are the trees protected from?
With any jurisdiction you have to ask what constitutes removal. In some cities it can only mean actually cutting the tree down. In Austin removal is defined by these 4 acts:
- Uprooting the Tree
- Severing the main trunk (cutting it down)
- Damaging the root system
- Excessive pruning
The main requirement to pay attention to here is the damaging of the root system. Any construction within the “Critical root zone” or CRZ will damage the tree. The CRZ is defined by the size of the tree’s trunk. It is one foot for every 1” of the tree’s diameter. For instance, if the tree is 20” wide than the CRZ is 20 feet total from the trunk of the tree. The diagram below outlines how close you can get before you are damaging the root system, and therefore removing the tree. This can be a huge part of site planning as the design team will have coordinate where not only the building, but any paving can be placed in relation to the trees.
As the diagram shows, within the first ¼ of the CRZ there can be no impact at all. Within the first ½ of the CRZ there can be no digging more than 4” down. Within the outer ½ of the CRZ you must preserve at least 50% of the outer ring of CRZ for the tree not to be damaged.
What if the Tree must be removed?
If any tree 8” in diameter or larger must be removed for any reason (at least in the City of Austin) there are some things that you can do depending on the type of tree as listed above.
Heritage Tree Removal – The only way to remove a heritage tree from your site is to apply for a variance to the zoning code. Normally the City of Austin will only consider the variance if the heritage tree:
- Is dead
- Is a hazard to life or property
- Is diseased and contagious or restoration isn’t an option
The City Arborist will come inspect the conditions. It is rare to get a variance to remove a heritage tree for any other reason than the above.
Protected Tree Removal – While easier to remove than a heritage tree, one must still apply to remove a protected tree. The application is not a variance, but will be inspected by the City Arborist. Normally the City of Austin will only consider the application if the protected tree:
- Prevents reasonable access to the property
- Prevents reasonable use of the property
- Is a hazard to life or property
- Is dead
- Is diseased
Mitigated Tree Removal – If you want to remove a tree 8” or larger, that is not a protected or heritage tree, all you have to do is mark its removal on the site plan. The City of Austin may require (depending on your site) that you mitigate any trees removed. This includes replanting a tree in place of the tree to be removed. You may be required to put down a deposit at the time of the approved site plan to ensure that the trees get planted.
If you are looking to purchase a property for development, the best way to determine that it is feasible for your use, any protected trees on the site can be designed around, and the property is ultimately a good fit for your development, is to consult a design professional that is well versed in the local requirements.