Trees are routinely lost from publicly owned and maintained areas for many reasons, including infrastructure maintenance and new construction. Removal or replacement of trees within rights of way associated with private development are governed by provisions within the County Code, site plan conditions, or other County policies and/or procedures.
Street Trees
A number of street trees will be designed into each County street improvement project to reforest or afforest the appropriate sections of the right of way based on spacing and other conditions, regardless of the number of trees removed. Appropriate species, quantities and sizes will be suggested by the Department of Parks and Recreation (DPR) in accordance with Administrative Regulation 4.3 or its addenda.
An evaluation of potential tree loss will be made prior to removals to determine if this reforestation or afforestation represents reasonable compensation for the total value of the lost resource. To assist in that evaluation, the following criteria will be used:
- As a minimum, trees with a caliper of 10 inches or less that are removed from the rights of way will be replaced on a one-for-one basis.
- Significant trees (caliper greater than 10 inches) will be replaced at a rate derived from a formula of the International Society of Arboriculture.
Replacement Tree Types and Equivalents
Large shade trees generally provide greater ecological benefit than do smaller ornamental trees. Therefore, the number of shade trees and ornamental trees proposed as replacement trees should be comparable to the number of trees that are to be removed from the site.
- One-for-One Basis: One new shade tree or large evergreen tree will fulfill the replacement requirement of one replacement tree per the tree replacement calculations.
- Three-to-One Basis: Three deciduous ornamental or small evergreen trees will fulfill the replacement requirement of one replacement tree per the tree replacement calculations.
Where there’s not adequate room in the rights of way to replace the required number of trees within the project limits, the trees that cannot be accommodated will be provided in a monetary amount to the Tree Canopy Fund of at least $2,400 per tree coordinated with DPR.
Parks, Open Spaces and Other Public Properties
The guidelines are identical to the ones above, with the exception that shrubs and ground cover will also be designed into the reforestation, and replacement trees that can’t be placed at the project site will go back into parks, open spaces or other public properties (as opposed to rights of way) from a DPR priority list.
Private Property
Trees removed from private property as part of a project will be replaced in accordance with the Chesapeake Bay Preservation Ordinance.
Tree Replacement Formula
| Definitions | |
| Diameter | Trunk diameter at 4 1/2 feet above the ground. |
| Species | All tree species given a value from 1 to 100, which is expressed as a percentage of 100 (e.g., 40 = 40 percent = .4). This is a value assigned to a species according to a number of factors including longevity, durability and appropriateness to the growing zone. |
| Condition | Rating from 0 (dead) to 100 percent (perfect) and is expressed as a percentage of 100 (e.g., 100 percent = 1; 60 percent = .6, etc.). |
Procedure
Scoring is determined by the multiplication of diameter and species and condition. Shown below are three applications of the formula.
1. A 10-inch American holly is automatically replaced with one tree, according to the above policy.
2. A 40-inch silver maple (species rating of 40), rated at 60 percent condition, is scored as 40 X .4 X .6 for a total score of 9.6.
3. A 36-inch white oak (species rating of 80), rated at 70 percent condition, is scored as 36 X .8 X .7 for a total score of 20.16.
Application to Replacement Policy
Trees are replaced at the following rates, based on the overall scores:
- 1-4.9 = One tree
- 5-9.9 = Two trees
- 10-14.9 = Three trees
- 15-19.9 = Four trees
- 20-24.5 = Five trees
- 25+ = Six trees
In the examples above, the American holly is replaced with one tree, the silver maple with two trees and the white oak with five trees.
The formula should only be used by qualified individuals, like professional arborists, with the knowledge of tree condition determinations and species factors.
Practical Examples
| Example 1 | ||||||
| Species | Number | Diameter (“) | Condition | Species Rating | Total Score | Replacements |
| Maple | 1 | 4 | 1 | |||
| Oak | 1 | 12 | .8 | .7 | 6.72 | 2 |
| Dogwood | 1 | 6* | 1 | |||
| Sycamore | 1 | 8* | 1 | |||
| Sycamore | 1 | 30 | .4 | .7 | 8.40 | 2 |
| Locust | 2 | 6* | 1(x2) | |||
| Locust | 5 | 8* | 1(x5) | |||
| Locust | 1 | 10* | 1 | |||
| Locust | 1 | 12 | .4 | .6 | 2.88 | 1(x2) |
| Locust | 1 | 15 | .4 | .6 | 3.60 | 1 |
| Ash | 1 | 8* | 1 | |||
| Mulberry | 1 | 4 | 1 | |||
Note: The diameters with an asterisk (*) denote trees with 10 inches DBH and smaller, which are automatically replaced at a rate of one-for-one according to the policy.
In this example, 18 trees are lost (1,173 caliper inches) and 20 trees replaced, since two of the trees being removed warrant greater than one-for-one replacements. However, a 36-inch sycamore is also at risk; if it dies, it would be replaced with four trees:
| Sycamore | 1 | 36 | .7 | .7 | 17.64 | 4 |
| Example 2 | ||||||
| Species | Number | Diameter (“) | Condition | Species Rating | Total Score | Replacements |
| Cedar | 1 | 20 | .5 | .4 | 4.00 | 1 |
| Cherry | 1 | 18 | .5 | .4 | 3.60 | 1 |
| Holly | 1 | 4* | 1 | |||
| Linden | 1 | 27 | .8 | .6 | 12.96 | 3 |
| Ash | 1 | 18 | .7 | .6 | 7.56 | 2 |
| Ash | 1 | 24 | .7 | .4 | 6.72 | 2 |
| Am. elm | 1 | 15 | .4 | .6 | 3.60 | 1 |
| Am. elm | 1 | 27 | .4 | .3 | 3.24 | 1 |
| Am. elm | 1 | 27 | .4 | .3 | 3.24 | 1 |
| Am. elm | 1 | 8* | 1 | |||
| Linden | 1 | 21 | .8 | .6 | 10.08 | 3 |
Note: The diameters with an asterisk (*) denote trees with 10 inches DBH and smaller, which are automatically replaced at a rate of one-for-one according to the policy.
In this example, 11 trees are lost (209 caliper inches) and 17 trees replaced, since four of the trees being removed warrant greater than one-for-one replacements. However, the trees listed below are also in the project area and are considered to be at risk; if they die before construction is completed, they would be replaced as follows:
| White Pine | 1 | 24 | .4 | .6 | 5.76 | 2 |
| Holly | 1 | 16 | .4 | .6 | 3.84 | 1 |
| Magnolia | 1 | 20 | .8 | .8 | 12.80 | 3 |
| Maple | 1 | 10* | 1 | |||
| Magnolia | 1 | 24 | .7 | .8 | 13.44 | 3 |
| Crab | 1 | 16 | .7 | .8 | 8.96 | 2 |
Note: The above examples are for illustrating the application of the formula and don’t necessarily represent an actual project.