Tree density is a quantitative measure of the number of trees or amount of tree cover per unit area.
In tree ordinances that regulate trees during the process of land development, a minimum amount of tree density is required on a per acre basis. This minimum tree density requirement takes one of four common forms–number of trees, tree density units, DBH inches or tree canopy cover. These forms of tree density requirements are described in detail in the November 2107 Focus on Issues page describing Tree Density Requirements.
The community’s goals for its community forest should be reflected in the method chosen for requiring tree density. Once community priorities and goals are set, then trees can be required in specific priority areas, such as in parking lots and buffers, or along road frontages, or in a certain concentration or configuration on a lot or within a development.
NUMBER OF TREES
Many ordinances require a specific number of trees along street frontages, in parking lots, and in buffers. For street trees, these requirements may say 2 trees must be planted in the front yard of a residential lot, or 1 tree must be planted for every 25 to 40 feet of road frontage, .some ordinances require a specific number of trees
TREE DENSITY UNITS
The communities listed below have adopted a requirement for a minimum number of tree density units per acre. A few are highlighted with links to Municode.
Most commonly, 15 to 40 tree density units are required per acre and these may, but don’t always, vary by zoning district. The number of TDUs given to a tree of a certain size varies from one community to the next, however, as communities have adjusted the basic values that were originally developed based on the cross-sectional area of a tree.
The communities listed below require a minimum amount of DBH inches on a property upon development.
TREE CANOPY COVER
See our Tree Ordinance of the Month page, and the Athens-Clarke County Community Tree Management Ordinance as an example of a tree canopy ordinance.
Based on a Municode search, there are at least 15 communities in Georgia, both large and small, that use tree canopy cover as either their primary tree density requirement or as a secondary requirement on certain sites. A list of these communities follows, with a few communities highlighted with links to Municode.
- Athens-Clarke County
- Gwinnett County
- Richmond Hill
- Sandy Springs
- St. Marys