This chapter shall establish tree canopy standards for properties undergoing development to promote the incorporation of trees into future development in the urban growth areas of unincorporated Kitsap County. A healthy tree canopy contributes to physical and mental health, safety, aesthetics, and overall welfare of the public. Trees may also mitigate the effects of urban development including the loss to native wildlife biodiversity, increased temperatures, airborne particulates, carbon dioxide, noise, and stormwater runoff caused by increases in impervious surfaces and vehicular traffic. The retention of existing trees is encouraged by these regulations.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

A.    Tree canopy requirements shall apply to subdivision of land or single-family and multi-family development creating four or more developable lots or units or on a property of one-half acre or more within unincorporated urban growth areas.

B.    Tree canopy shall be determined based on the required tree density of a property expressed as tree units per acre.

C.    Trees or vegetation required by other regulations (e.g., landscaping, critical area buffers) may count towards these standards.

D.    Retention of trees greater than eighteen inches at diameter breast height (DBH) is encouraged.

E.    Tree retention is preferred to tree replacement.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

A.    A minimum tree density, expressed as a tree unit credit per acre, shall be maintained on the gross acreage of the lot as specified in Table 17.495.030-1. Only healthy trees can count toward the required minimum tree density per Table 17.495.030-2. If the number of trees required includes a fraction of a tree, any amount equal to or greater than one-half shall be rounded up. Tree density may be achieved through use of the replacement or retention standards of this chapter, or a combination of replacement and retention.

1    Example: To calculate the minimum tree unit credits for a seven thousand five hundred square foot lot in the ULR zone: 7,500/43,560 × 20 = 3.44, rounded down to three.

2    Trees growing on a property line shall count towards the tree credits listed.

B.    The following process shall be used for calculating the required minimum tree unit credits. The required tree credits shall be multiplied by the gross acreage of the lot.

C.    Tree density requirements for a lot can be met by trees located within shoreline jurisdiction, critical areas, and their associated buffers. Tree management and protection within critical areas and their buffers are regulated by Title 19, Critical Areas Ordinance, and trees within shoreline jurisdiction are regulated by the shoreline master program.

D.    Lots under development subject to the tree density requirements of Table 17.495.030-1 shall meet the required minimum tree density through the planting of replacement trees and/or by retaining existing on-site trees.

E.    “Diameter at breast-height (DBH)” means the diameter of a tree trunk measured at four and one-half feet above average grade. DBH is used in determining the diameter of existing trees. For trees located on a slope, the diameter is measured from the average of the highest and lowest ground points or, on very steep slopes where this is not possible, the lowest practical point on the uphill side. Where a tree splits into several trunks close to ground level, the DBH for the tree is the square root of the sum of the DBH for each individual stem squared (example with three stems: DBH = square root [(stem1)2 + (stem2)2 + (stem3)2]).

F.    Existing on-site tree unit credits shall be calculated according to Table 17.495.030-2.

1 Diameter at breast height (DBH) is used in determining the diameter of existing trees. For example: On a seven thousand five-hundred-square-foot lot in ULR zone (three credits needed) with one twenty-four-inch DBH tree, one twelve-inch DBH tree, and two six-inch DBH trees, the minimum tree unit credits are met by retaining the twenty-four-inch DBH tree only, or retaining the twelve-inch DBH tree and one of the six-inch DBH trees, or remove all trees on site and plant six new deciduous or three new conifers to meet the minimum tree density units for the lot.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

Existing, healthy trees to be retained on site shall meet the following minimum standards, as verified by a certified arborist, to be credited toward the tree unit density requirements of this chapter:

A.    Post-development life expectancy of greater than ten years; and

B.    Sound and solid trunk with no extensive decay or hollow and no trunk damage that would cause mortality; and

C.    No major insect or pathological problem; and

D.    Individual trees and groves of trees proposed for retention shall be wind-firm in their post development state; and

E.    Trees greater than eight inches DBH located within a critical area or shoreline and associated buffers may be credited toward the tree unit density requirements; and

F.    No species included on a state or county invasive, nuisance, or species of concern list may be retained for credits and native varieties are preferred.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

A.    Any trees planted to meet the landscaping requirements of Chapter 17.500, Landscaping, shall count towards the required minimum tree unit credits provided they meet the planting specifications outlined in Section 17.500.030, Installation and maintenance.

B.    Trees planted in public rights-of-way or areas to be dedicated as public right-of-way classified as arterials or collectors by the Kitsap County road standards shall not count toward a development’s existing or replacement tree unit credits. Trees that are retained or replaced within local and minor collector rights-of-way are counted toward tree unit credits.

C.    Each replacement tree proposed for planting must meet the following minimum standards to be credited toward satisfying the tree density requirements of this chapter:

1.    Minimum Size. The required minimum size of a replacement tree shall be six feet tall for native or other conifer species and two-inch caliper for deciduous or broadleaf evergreen trees. Additional credits may be awarded for larger sized trees, as determined by the director;

2.    Health and Condition. Trees shall be free from injury, pests, diseases, and nutritional disorders and must be fully branched and have a healthy root system.

3.    Species Selection and Form.

a.    Replacement trees proposed to be planted within open space, greenbelts, native buffer areas, and landscape areas, such as internal street trees, must be compatible with the intended growing location and conditions, allowing them to thrive with little or no irrigation, fertilizer or pesticide and provide appropriate habitat. Conditions should include light, soil, pH, moisture and hardiness;

b.    Individual species of nonnative replacement trees planted shall not exceed thirty-five percent of the total number of all replacement trees unless approved by the director due to site-specific conditions. Nonnative replacement trees shall not be listed on the approved state noxious weed list or county noxious weeds of concern list; and

c.    Trees planted to form a clipped or sheared hedge, such as but not limited to arborvitae or cherry laurel, shall not be counted toward tree unit credits.

4.    Tree Location.

a.    Replacement trees shall be planted within the proposed development;

b.    When tree credits are required by this chapter a minimum of twenty-five percent of the required trees shall be located in protected tracts, such as roadway, tree conservation, recreation, stormwater tracts, and critical area tracts;

c.    Trees may be planted on a solitary basis or within clusters to form stands or groves.

5.    Installation and Maintenance. Replacement trees shall follow maintenance and installation standards outlined in Chapter 17.500, Landscaping.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

A.    At the time of application, information regarding a property’s required tree density, tree protection measures, existing tree unit credits, and required replacement planting shall be shown on the site plan to support the design and location of the proposed development. Tree density and credit calculations as well as required replacement trees may be shown on a required landscape plan per Section 17.500.020. Tree replacement plans shall be prepared, submitted, and approved prior to the approval of site development permits.

B.    The plans shall be drawn to the same scale as the site plan, show approximate locations of trees to be retained or planted, shall meet the applicable standards of this chapter, and shall include:

1.    Trees with a DBH between one inch, but under eight inches shall be inventoried and located if the trees are intended to be used to meet tree unit density requirements;

2.    Where a sampling method is proposed for heavily treed project sites, standards shall follow accepted industry methods as determined by a professional forester or licensed landscape architect. Trees on the site counted towards the requirements shall be identified and labeled on the plan with species name and diameter at breast height (DBH);

C.    Protection fencing and other tree and soil protection measures shall be shown on the plan when any potential impact, including clearing and grading, is proposed within the critical root zone of retained trees.

D.    The plan shall include a permanent protection mechanism. This legal protective mechanism may include protection of trees within an open space, recreational or buffer tract; or a recorded covenant indicating the location and credit for each tree. Should a protected tree need to be removed in the future, replacement with like credits will be required.

(Ord. 637 (2024) § 7(D) (App. D), 2024)

Prior to land clearing or grading associated with a development project, retained trees, vegetated areas, and soils to be preserved shall be protected during construction. Protection measures shall include the following:

A.    Trees to be retained shall have readily visible temporary protection fencing at their critical root zones.

1.    Temporary fencing must be adequate to protect the critical root zones of trees designated for retention, vegetation, and native soil. At a minimum, fencing shall be installed at the drip line of the retained tree or six feet from the trunk, whichever is greater.

2.    Where circumstances warrant, the director may require more substantial tree protection, as necessary, to protect intrusion of construction into the critical root zones.

B.    No person shall conduct any activity within the tree protection fencing of a retained tree.

1.    Machinery and storage of construction materials shall be kept outside of the critical root zones of trees designated for retention.

2.    The code administrator may require fencing beyond the critical root zones if, in the code administrator’s determination, such additional protection is needed to protect the tree from damage.

3.    Trees designated for retention shall not be damaged by scoring, grading, compaction of soil, dumping concrete washout or other chemicals, attaching objects to trees, altering drainage, or other activities that may cause damage of roots, trunks, or surrounding vegetation.

4.    The director may allow certain activities to be approved by and under the supervision of a qualified tree professional at the expense of the applicant.

C.    When feasible, applicant shall shore basements and other extensive excavations to avoid impacts within critical root zones and cantilever structures over critical root zones.

(Ord. 637 (2024) § 7(D) (App. D), 2024)