There is hereby created a City Tree Advisory Board which shall consist of five members....The members shall be lay citizens and others with established professional competence in a pertinent discipline, and the following characteristics or attributes may serve as guidelines in making appointments to the Board:
1. Members of the public interested in trees as a major component of Carpinteria's physical and aesthetic environment.
2. Arborists, ornamental horticulturists, and landscape architects and designers, or those with a technical background in a related field. At least two members of the Board shall have such a professional background... [Carpinteria, CA: City Code Section 12.28.080]
There shall be a beautification or tree commission in the city consisting of 7 members, appointed by the mayor, subject to approval of the city council. Their terms of office shall be 3 years and until their successors are appointed and qualified... The members shall serve without compensation, but all necessary expenses shall be paid by appropriate council action.
The city council may remove any appointed member of said commission from office prior to the expiration of their term, with or without cause by an affirmative vote of not less than three-fifths of the members of the city council. Vacancies on the commission, ... , shall be filled by appointment by the mayor, subject to approval of the city council.
The commission shall hold regular meetings at least once each month, and may hold such addition meetings as it deems necessary. A majority of the commission shall constitute a quorum for the purpose of transacting the business of the commission. The commission shall, as soon as practical after the time of the annual appointment of a member to the commission, elect a chairman, vice-chairman, and a secretary thereof...
The secretary of the commission shall keep a record of all proceedings, resolutions, findings, determinations and transactions of the commission, which records shall be a public record, and a copy of which record shall be filed with the city clerk as clerk of the city council...[Burlingame, CA: City Code Chapter 3.28]
A. The Public Works Department shall notify the Parks and Recreation Department of any applications for new curb, gutter, sidewalks or driveway installations, or other improvements which might require the removal of or cause injury to any street tree, or interfere with the fulfillment of the street tree plan.
B. Any public utility maintaining any overhead wires or underground pipes or conduits shall obtain permission from the Director before performing any maintenance work on the wires, pipes, or conduits which would cause injury to street trees. The public utility shall in no way injure, deface, prune, or scar any street tree until their plans and procedures have been approved by the Director...[Modesto, CA: City Code Section 12-5.08]
In order to provide for coordination and the maximum feasible use of all public lands, areas and funds, plans and specifications for city street and public area planting proposed by the landscape supervisor shall be submitted to the city engineer, traffic engineer, planning director, and where appropriate, special district directors and managers, for their recommendations, and such recommendations shall be made within thirty days after receipt of such plans and specifications. To facilitate the planting and maintenance of trees in new subdivisions, developments, streets and public areas, the planning director shall advise and cooperate with the landscape supervisor in carrying out the provisions of this chapter. [Camarillo, CA: City Code 13.12.080]
Some elements to be considered in the management plan include:
See also The Urban Forest Management Plan Toolkit.
Within three years of the adoption of this Ordinance, the Director with the advice and participation of the Tree Board shall adopt an Urban Forest Management Plan. The Division thereafter shall use its best efforts to insure that activities of the Division are guided by such plan. The plan shall incorporate the following elements:
(a) A clear, concise, and comprehensive Statement of Policies and Objectives for urban forestry management in the City, which statement is to be developed by the Director with the advice and participation of the Tree Board through a process of at least three public hearings;
(b) A designation of proposed urban forestry treatments for major traffic routes and districts within the City consistent with the City's Master Plan, together with a program, schedule, and suggested budget for implementing such treatments;
(c) An inventory of every street tree and any other trees deemed necessary by the Division, which inventory shall include, as appropriate, species, age, condition, maintenance records, names of adjacent property owners, record of fees and fines, and any other information necessary or usable in the long-range planning or day-to-day planting and maintenance of the City's urban forest;
(d) A Street-Tree Renewal Plan, based on an evaluation of species characteristics and performance as recorded in the inventory, providing for rotational reforestation of diseased or declining trees and break-up of potentially problematic monocultures;
(e) A set of Standards for the Division, and the public for street-tree installation, landscape-tree installation, pruning and maintenance, acceptable tree species and any other standards, criteria, or administrative procedures deemed necessary to carry out the purposes of this Ordinance and the Urban Forest Management Plan;
(f) A process for continual update and improvement of the Urban Forest Management Plan elements.[San Francisco, CA: Public Works Code Section 806]
Management program. In consultation with the parks commission, planning commission and public works department, the director of parks and recreation or his/her designee, shall develop and implement a public tree policy consistent with other city regulations designed to provide an orderly program of tree management. Such program shall include all public property and rights-of-way including parks, public greenbelts and other city-owned property except Lake Chaplain. The development of such a program include the following objectives:
A. The setting of standards for the planting, maintenance, protection, preservation, removal and replacement of existing trees;
B. Planning and planting of trees for future benefit of the citizens of Everett;
C. Approval of all tree plantings, maintenance, and removal of trees on city-owned property and rights-of-way; and
D. In the short term, no net loss of forest canopy cover on city-owned public lands and right-of-way; in the long term, measurable gain. [Everett, WA: City Code Section 8.40.040]
Purpose: To set priorities for solving conflicts between trees and street improvements.
Notes: Tree-related damage to street improvements is common in many communities. Although tree roots are blamed for the cracking concrete and invading sewer lines, it is equally valid to point out that these structures fail because they have not been properly engineered to function in a landscape that contains growing trees and their roots. Unfortunately, the approach in too many cities has been to remove trees rather than to find a way to redesign structures to be compatible with trees. This provision can be used to establish the priority of trees over hardscape. Individual property owners normally do not have the resources or expertise to develop satisfactory solutions to tree- hardscape conflicts on their own. Therefore, the responsibility for correcting conflicts between trees and street improvements should not be assigned to the property owner. However, if the conflict results from actions by a property owner which violate municipal tree planting standards, the city may require the property owner to bear some or all of the cost of corrective action.
- Priority of trees over street improvements (hardscape)
- Responsibility for approving corrective measuresA. When roots of a tree planted within the planting area damage city curbs, gutters and sidewalks (including driveway ramps), the city shall be responsible for appropriate corrective measures which are least damaging to the tree. [San Luis Obispo, CA: City Code Section 12.24.150]
Where sidewalk or curb damage due to tree roots occurs, every effort shall be made to correct the problem without removing or damaging the tree. The city forester shall be responsible for developing or approving corrective measures in consultation with the city engineer. [Example code by the authors]
Purpose: To exempt a local jurisdiction from the provisions of the California Solar Shade Control Act.
Notes: The original Solar Shade Control Act of 1979 (California Public Resources Code Section 25980 et seq.) declared that it was a public nuisance for a landowner to permit trees or shrubs on their property to shade (more than 10% shade between 10 am and 2 pm) a solar collector on another person's property. The 1979 version of this code had at least one problem to which many jurisdictions objected: trees that were in place before a solar collector was installed could come to be in violation through further growth. The original ordinance allowed cities and counties, by majority vote of the governing body, to exempt themselves from the provisions of the act.
As the result of a court case related to this Act, it was superseded by the California Solar Shade Control Act of 2009 (Public Resources Code section 25980-25986). This revised Act has a number of provisions that reduce its impact on trees. The Act does not apply to:
(a) trees or shrub planted before the solar collector was installed
(b) trees planted, grown, or harvested on timberland or on land devoted to the production of commercial agricultural crops
(c) the replacement of a tree or shrub that had been growing prior to the installation of a solar collector and that, subsequent to the installation of the solar collector, dies, or is removed for the protection of public health, safety, or the environment.
(d) a tree or shrub that is subject to a city or county ordinance (such as a tree protection ordinance).
In addition, solar collectors that are designed and intended to offset more than the building's electricity demand (i.e., providing a profit to the solar collector owner) are not covered in the act. In addition, violations of the Act are classified as private nuisances (as defined in Section 3481 of the Civil Code), rather than public nuisances.
The 2009 Act indicates that local (city or county) ordinances specifying requirements for tree preservation or solar shade control have precedence within the jurisdiction. As in the original Act, a city or county can pass an ordinance to exempt themselves from the Act.The city is exempt from the provisions of Chapter 12 (commencing with Public Resources Code section 25980), Division 15 of the Public Resources Code which chapter is known as the Solar Shade Control Act. [Carmel-By-The-Sea, CA: City Code 12.28.050]
Purpose: To set forth any responsibilities for maintenance of trees, either public or private, assigned to property owners.
Notes: In many communities, residents are responsible for some types of tree maintenance, particularly for trees which extend over public rights-of-way. In such cases, it is the responsibility of the municipal tree program to provide information on the types of care to be provided and complete instructions on proper methods. For example, if residents are responsible for tree trimming to maintain clearance for pedestrian and vehicular traffic, standards for clearances and information on proper pruning methods should be readily available to residents. Even if standards are set and distributed, the municipality may still have little control over the quality of maintenance performed by residents. As an alternative, the municipality may simply require residents to notify the tree program when problems occur, and have work done by municipal crews or contractors. This allows for greater control over the quality of tree maintenance.
- Designation of responsible parties
- Assignment of responsibilities
- Performance standards for maintenance activities(a) It shall be the duty and responsibility of all property owners to maintain the grounds of maintenance strips on the owner's property, regardless of whether such property is developed. This maintenance shall include watering as needed and keeping such strips free from weeds or any obstructions contrary to public safety. Property owners shall be responsible for watering mature city street trees whenever landscaping of the property is changed in such a manner as to deprive the tree of its normal source of moisture. Such watering shall be continued during dry weather until the street tree becomes acclimated to the new environment, but need not exceed three years. All watering requirements shall be waived to the extent they are inconsistent with governmental restrictions on water use.
(b) It shall be the duty and responsibility of every person owning or occupying any real property within the City of Sacramento, to keep all trees on that property trimmed in such a manner that there is a clearance of at least fourteen feet above any street or alley, and a clearance of at least seven feet over any sidewalk. It shall also be the duty and responsibility of every person owning or occupying any real property within the City of Sacramento to keep all trees on that property trimmed in such a manner that they do not obstruct the view of any traffic sign or device for vehicle traffic in the direction controlled by that traffic sign or device. [Sacramento, CA: City Code Section 45.5]The owner or occupant of any corner lot or premises in the town shall keep trees, hedges and growth at the corners of intersecting streets, whether between the curb line and the private lot line, or within the private lot or premises, so trimmed that the height of the same shall not exceed three feet above the curb level for a distance of thirty feet measured horizontally in any direction from the point of intersection of the property lines at street corners; provided, that trees whose main trunks are exposed to a height of seven and one-half feet above the curb need not be so trimmed or cut. [Los Gatos, CA: Town Code Section 31-15]The duty is imposed upon a property owner to notify the parks and recreation department when any tree, palm, shrub or plant in a public street adjacent to his property is injuring or damaging any public sidewalk... [Carlsbad, CA: City Code Section 11.12.120]
Purpose: To assist citizens in meeting requirements mandated by the local government.
Notes: Some street tree ordinances contain a provision which allows the city to assist citizens with street tree maintenance, if the citizen reimburses the city for the work it performs. The following example is typical of such provisions.
- Types of assistance to be provided
- Method of applying and qualifying for assistance
- Authority charged with granting assistance...On application of any person to whom there has been issued a permit to trim, prune or remove a tree from a City right-of-way, the City Engineer may trim, prune or remove such tree described in such permit provided the cost thereof is paid by the permittee and provided there shall first be deposited with the City Engineer a sum determined to be the estimated cost of such work. All such deposits shall be placed in a trust fund. Following completion of the work the City Engineer shall determine the actual cost of the work and transfer that portion of the deposit to the appropriate City fund and return the balance to the depositor. Should the original deposit be insufficient to cover the actual cost of the work the permittee shall be liable to the City for the unpaid balance and shall promptly pay such amount to the City upon demand of the City Engineer. [San Carlos, CA: City Code Section 6504]The City of Visalia, California, tree ordinance authorizes the Director to require that citizens hire a professional to trim their oak trees. To offset this burden, the city provides financial assistance to help low income residents hire professional tree trimmers. The ordinance creates a special "Oak Maintenance Fund" to finance the assistance program. The fund derives its income from fines and penalties assessed for violations of the tree ordinance.If the Director determines that a property owner who has submitted a Notice of Intent to Prune an Oak Tree, cannot properly prune his or her Oak Tree without the assistance of a professional tree trimmer, and that said property owner cannot afford to hire a professional tree trimmer because he or she does not have the financial resources to pay for such services, the Director may provide financial assistance to said property owner for the purpose of pruning the tree or trees, if the following conditions are met:
(a) The property owner uses the property where the tree(s) are located as his or her principal place of residence;
(b) The aggregate gross income of all persons eighteen (18) years of age or older residing on the property does not exceed the minimum amount as may be set from time to time, by resolution of the City Council, pursuant to this subdivision; and
(c) The Director determines that it is necessary to prune the tree to remove hazardous conditions, remove disease, rot, pests, other harmful conditions, or promote healthy growth of the tree(s). Such financial assistance shall include, but not be limited to, low interest loans, work done by the City with the cost borne in part or in whole by the property owner, work done by the City with the cost borne by the City to be repaid by the property owner upon such terms as the City and property owner shall agree, or any combination thereof. [Visalia, CA: Ordinance Code Section 2349]
Purpose: To prohibit the practice of topping and/or other especially destructive maintenance practices in public and private trees.
Notes: A community's investment in its tree resources, which are accrued over many years, can be rapidly squandered through poor tree maintenance practices even if the trees are not actually removed. Poor pruning practices such as topping (aka hat-racking, stubbing, dehorning), i.e., cutting back large diameter branches of a mature tree to stubs, are particularly damaging. The excessive removal of canopy associated with topping is often stressful to mature trees, and may result in reduced vigor, decline, or even death of the tree. In addition, new branches that form below the cuts are only weakly attached to the tree, and are in danger of splitting out. Topped trees require constant maintenance to prevent this from happening, and it is often impossible to restore the structure of the tree crown after topping. Unfortunately, many people believe that topping is a proper way to prune a tree, and this destructive practice is very prevalent in some communities. In such cases, a vigorous program of public education should be pursued in combination with the ordinance.
- Definition of topping and other prohibited practices, if not included in provision 4 (Definitions)
- Classes of trees covered by the provision
Ordinances that restrict topping may apply to public trees only, or may extend to all trees, both public and private, within the community. For example, the City of San Juan Capistrano, California, has detailed regulations regarding topping. The regulations define topping (as "severe trimming"), prohibit it in certain zoning districts, and describe the type of pruning which is to occur.
Rather than including detailed specifications in the ordinance itself, we recommend that the ordinance authorize the preparation, adoption, and enforcement of tree pruning standards by the tree program manager (see provisions 15 - Designate administrative responsibilities and 18 - Develop a comprehensive management plan). This allows for greater flexibility and easier updating of the standards when necessary...."Severely trimmed" shall mean the cutting of the branches and/or trunk of a tree in a manner which will substantially reduce the overall size of the tree area so as to destroy the existing symmetrical appearance or natural shape of the tree in a manner which results in the removal of main lateral branches leaving the trunk of the tree in a stub appearances as shown is Exhibits A and B... ...No property owner or his agent in the Tourist Commercial, ... or any residential zoning district located within 500 ft of a scenic highway or drive ... shall cause any tree on his property to be severely trimmed ... ...The following standards identify trimming methods which will give maximum benefits to both trees and people:... [San Juan Capistrano, CA: City Code Section 9-3.625]
The following example includes selections from a portion of an ordinance that restricts topping ("hatracking") and several other destructive practices under the general term "tree abuse". The code includes specific definitions of what practices are and aren't prohibited, a mechanism for waivers and appropriate penalties, which include remedial maintenance or, if necessary, replacement (see also provision 11).
(a)Declaration of intent. The city commission (city) finds and declares that regulation of the cutting, trimming, and pruning of trees within the city will help ensure that the health, function and value of trees are protected, and will help to prevent dangerous branching conditions that may result in danger or injury to citizens or property...
(a.3) Tree abuse means:
a. To hatrack a tree; or ..,
c. Cutting upon a tree which destroys its natural habit of growth [as defined herein]; or
d. Pruning that leaves stubs or results in a flush cut; or splitting of limb ends; or ...
f. The use of climbing spikes, nails, or hooks, except for the purpose of total tree removal or as specifically permitted by the American National Standards Institute; or ...
(5) Violator means a person who abuses a tree or otherwise violates this section. The owner of property upon which the abused tree is located shall also be deemed a violator if the tree abuse is undertaken by the owner's employee, agent or person under the owner's control...
(b.1) No person shall abuse a tree unless one (1) of the following exemptions applies:
a. The abuse is necessary to alleviate a dangerous condition posing an imminent threat to the public or property,
b. Franchised utilities may obtain a permit form the city, renewable on an annual basis, authorizing the pruning of trees in a manner that may be defined herein as tree abuse provided such pruning is necessary to prevent service interruptions.
(b2) Any person may apply to the planning and development department for an administrative waiver from the terms of this section, provided that:[Sunrise, FL: City Code Section 16-173]
a. The application is made before any actions for which a waiver is sought have been undertaken;
b. Any alleged hardship is not self created by any person having any interest in the property. A hardship shall not be considered self created if the subject tree was installed prior to the effective date of this section;
c. There are unique and special circumstances or conditions applying to the subject tree or the property upon which it is located, that do not apply generally to other trees or properties.
d. The waiver proposed is the minimum variance necessary to alleviate the hardship.
e. That the granting of the waiver will be in harmony with the general intent and purposes of this section and will not create a dangerous condition that threatens the public or property.
While it is probably impossible to construct a concise list of all the ways that trees may be damaged, restricting the most common damaging practices may be of value if combined with an ongoing campaign of public education on proper tree care practices. Another approach to improving tree care, targeted at individuals and firms that perform tree work for hire, is discussed under provision 28 - Licensing of private tree care firms.
Purpose: To ensure that street tree selection and placement conforms with municipal standards.
Notes: In order to avoid future maintenance problems, conflicts with overhead utilities, and potential sidewalk damage, local governments usually reserve the right to control plantings in the public right-of-way. The tree program manager should be given authority over such plantings in provision 15 (Designate administrative responsibilities ). Acceptable tree species and planting specifications should be described in the comprehensive urban forest management plan (see provision 18).
- Permit process for planting in the public right-of-way
- Prohibition of planting in conflict with established standards
- Remedies to be applied in case of violationNo person shall plant any street tree except according to policies, regulations and specifications established pursuant to this chapter... [San Luis Obispo, CA: City Code Section 12.24.130 F.]Although some ordinances require removal of any tree planted without a permit, it may be preferable to require removal of only those trees that do not conform with standards. Some jurisdictions will allow nonconforming trees to remain, but require the property owner to accept all financial responsibility for tree maintenance and damage that may be caused by the tree.
All trees planted in the public street or sidewalk area and all tree planting required by this code shall be located and planted under the supervision of the city forester, who shall supervise such planting and locating. In the performance of such work, consideration shall be given to the following factors; provided, that setbacks permit and considerations of safety do not interfere. These factors are determined to be of primary importance in maintaining the city forest.
A. Trees that must be removed shall be replaced by new planting, except in unusual circumstances.
B. Wherever feasible, trees shall be planted near old and dying ones in anticipation of their removal.
C. Unnatural regularity of spacing and arrangement shall be avoided; staggered, or irregular locations or a simulated forest arrangement being preferred.
D. Species selected may vary, depending on location; however, the preference of native species is urged; the Monterey pine is to be perpetuated as our dominant forest tree within the city.
E. The coordinating of tree planting on public ways with landscaping on private property so as at achieve the above purposes is deemed desirable.[Carmel-By-The-Sea, CA: City Code Section 12.28.230]Whenever any tree is planted or set out in conflict with the provisions of the Article, it shall be lawful for the Parks Superintendent to remove or cause removal of the same. The cost of removal of such tree may be charged to the property owner responsible for the planting thereof. [San Buenaventura, CA: City Code Section 8421.2]If one of your goals is to encourage tree planting, the permit process for planting should be as simple as possible, and no permit fee should be charged. We highly recommend a program to educate the public on appropriate tree selection and siting for local conditions to complement this provision. It is more productive to spend time and effort encouraging proper tree selection and planting than removing offending trees.
Purpose: To ensure appropriate tree planting in new developments, including parking lots.
- Performance standards for tree planting and maintenance during establishment
- Designation of responsibility for planting and maintenance
- Protocol to ensure that planting complies with the comprehensive management plan (see provision 18) or other standards
- a mechanism to provide for monitoring of tree establishment unless specifically addressed elsewhere (e.g., provision 13)
Notes: Some communities include tree planting requirements in a separate landscape ordinance, or in the zoning code under various development standards. However, in many cases, tree planting requirements are appropriately placed in the tree ordinance or at minimum should be cross-referenced in the tree ordinance. It is very important that basic performance standards be set in this provision. The provision can specify minimum tree densities (e.g., numbers of trees per street mile) or canopy standards (e.g., amount of canopy cover or shading to be provided within a set period of years). The tree program manager should then be given the latitude to develop appropriate implementation standards and approve specific plans.
Responsibility for planting and maintenance varies by community. If developers do not perform the actual planting, they are normally required to pay in-lieu fees and tree planting is handled by the local government.
The building permit approval process is frequently used to ensure compliance with tree planting regulations. Communities may withhold occupancy permits until trees have been satisfactorily installed, and require performance bonds to ensure establishment. Performance bonding should be for at least three years to guarantee good long-term survival. Furthermore, unacceptable tree growth or condition, as well as actual tree death, should be grounds for bond forfeiture. Trees that are of poor quality when planted or are maintained poorly may not actually die within three years, but their future survival and performance may still be unacceptable.No subdivision shall be approved unless it is found to include planting of official, approved street trees within the adjacent parkways in conformity with the Street Tree Management Plan and under the Director's supervision...
In-lieu fees, which are established by resolution of the City Council, may be deposited by the developer or applicant upon the recommendation of the Director. In cases when a subdivision is being approved, and the building process may be over a prolonged period of time, in-lieu fees may be required...
In the event a subdivider desires to plant trees within the parkway adjacent to a new subdivision, he may apply to the Director for a permit. Such permit may be issued by the Director only after the subdivider has posted a a bond pursuant to Chapter 2.17 of this Code, guaranteeing the planting of all street trees, and paid the estimated cost of all irrigation and maintenance for a three-year period. All such planting shall be done in accordance with the Street Tree Master Plan, as shall any necessary replanting which would be required should any of the planted trees die within [or be deemed unacceptable by the Director at the end of] the three- year period.
The costs of planting and the first three years of maintenance, including irrigation, of all street trees in a new subdivision, shall be borne by the subdivider. The Director shall determine the cost involved for each subdivision, which shall be paid to the City prior to City Council approval of the final map of the subdivision. The Director shall plant, maintain, and irrigate such trees at such times and places as the development of the subdivision, its occupants, and other conditions make feasible.[Carpinteria, CA: City Code Section 12.28.160]
B. Before planting, all street trees must be inspected and approved by the city arborist or his designee...
F. So the city arborist can determine the tree requirements for site development, any subdivider or developer shall submit to the city a plot plan of the proposed subdivision which shall:
[San Luis Obispo, CA: City Code Section 12.24.100]
- show clearly all existing trees, noting location, species, diameter and condition
- note whether existing trees will be retained, removed or relocated
- show proposed utilities, driveways, street tree locations, and the size and species of proposed street trees.
Parking lot shading provisionsEspecially in warm climates, unshaded parking lots become extremely hot, contributing to both the urban heat island effect and increased air pollution through enhanced volatilization of reactive hydrocarbons from parked vehicles (Scott et al 1999; Center for Urban Forest Research 2001a). Hence, many communities require that newly constructed or reconstructed parking lots be shaded by incorporating tree plantings into the parking lot design. Requirements for tree planting in parking lots are sometimes enacted though a specific parking lot shading ordinance, but the code may be incorporated into the city code related to trees, landscaping, parking lots, or elsewhere. Key elements:
- basic performance standards related to the amount of shade or tree planting required. The most common types of standards include:
- shading standards based on the amount of shade to be provided by trees after a set period of time, such as 50% of pavement shaded in fifteen years.
- minimum distances from any parking stall to a tree,
- tree to parking stall ratios
- minimum landscaped area as a percent of paved area in conjunction with tree density standards in the landscaped area.
- methods used to calculate tree shading and determine the amount of shaded and nonshaded area to be counted in calculations or assess tree planting ratios provided on parking lot plans
- person or body responsible for determining that a plan complies with the standards
- a mechanism to provide for periodic monitoring of parking lots to assure that tree maintenance is adequate and that standards are met
Based on their analysis the Center for Urban Forest Research (2001b) notes several additional factors that should be considered when developing parking lot tree shade ordinances. These include:
- provisions to deal with the common conflicts between parking lot trees and business signage and parking area lighting
- refining calculations for tree shade provided in the plan to include only partial credit for trees that are located on the periphery of the lot because only a portion of the canopies of these "edge" trees actually shades pavement
- requirement that removed trees be replaced according to a replacement schedule based on equivalent size or value
- funding compliance monitoring through fees paid at the time of construction.
As discussed under the special topic Evaluating parking lot shading, the success of parking lot tree shade provisions depends on good implementing regulations or guidelines. The Center of Urban Forest Research (2001b) suggests guidelines for tree planter size, irrigation, and planting methods to ensure good tree growth. Local empirical data on tree growth in parking lots is needed to develop realistic estimates of tree canopy cover after various time intervals. Technical information and specifications, such as lists of tree species and their respective canopy spread after a set number of years, examples of shade calculations, and construction details, are needed to implement this and other planting provisions. However, these technical details are better placed in accompanying guidelines and regulations. Inserting such technical details into the ordinance code not only clutters it unduly, but can interfere with routine updating needed to keep specifications up to date.
Finally, even with monitoring, the ordinance must provide for enforcement of the provision, either as part of the provision or under a synoptic enforcement provision (provision 12). Enforcement is somewhat problematic because the party that submits the original planting plan is typically not the eventual owner of the parking lot, and ownership of the lot may change periodically. Hence, one enforcement method (e.g., withholding of occupancy permits) may be appropriate for the planning stage whereas another enforcement method (e.g., fines, abatement orders) may be appropriate for the long-term maintenance of required plantings.
At least 50% of the paved area surface [of parking areas] shall be shaded by tree canopies within 15 years of acquisition of building permits. Trees to be planted to develop such a canopy shall be in accordance with the City's Master Street Tree Plan and the requirements of the Director of Parks and Trees. Plans submitted to the Development Review Board shall show the estimated tree canopies after 15 years of growth, the specific names, sizes and locations of trees to be planted, and the total area in square feet of the area shaded by tree canopies. In determining the area shaded, the following methodology shall be used:
i. Measure the shaded area on the pavement assuming that the shaded area is only that area directly under the tree canopy or dripline.
ii. Landscape planters under the canopy may be counted as shaded area.
iii. Paved areas shaded by structures (such as second stories of buildings, carports) may be deducted from the total paved area.[Oroville, CA: City Code Section 26-49.k.10)
Tree Shading. Trees shall be planted and maintained throughout the surface parking lot to ensure that, within fifteen (15) years after establishment of the parking lot, at least fifty (50) percent of the parking area will be shaded.
1. Surface Parking Lot. Except as provided below, all surfacing on which a vehicle can drive is subject to shade calculation, including all parking stalls; all drives within the property, regardless of length, and including drive-through lanes; and all maneuvering area, regardless of depth. The following surfaced areas are exempt from this shade requirement: (i) truck loading area in front of overhead doors; (ii) truck maneuvering and parking areas unconnected to and exclusive of any vehicle parking; (iii) surfaced areas not to be used for vehicle parking, driving or maneuvering, provided they are made inaccessible to vehicles by a barrier such as bollards or fencing; (iv) automobile dealerships, display/sales/service/vehicle storage areas (required parking for auto dealerships is still subject to shading); and (v) existing surfaced areas.
2. Shading. Shading should be calculated by using the diameter of the tree crown at fifteen (15) years. Each planting area shall be of adequate size for the landscaping approved and shall have adequate irrigation for that landscaping. All landscaping (trees, shrubs, and turf) in these planting areas shall be properly maintained. The city landscape architect shall establish a list of species appropriate for providing shade in parking lots, and shall review site plans of each parking lot to determine whether or not the lot complies with this chapter. Trees planted in order to comply with the regulations of the chapter shall be selected from the list prepared by the landscape architect. The city landscape architect shall have the discretion to modify tree shading requirements under power lines and other obstructions which prohibit strict compliance with shading requirements, and to give shading credit for photovoltaic arrays, off-site trees and structures, sidewalk canopies, and other structures, where appropriate. [Sacramento, CA: City Code Section 17.64.030.H.]What levels of parking lot shading are realistic to include in a parking lot shading provision? The answer depends not only on the eventual size that trees will attain under parking lot growing conditions but on the amount of space set aside as growing space for trees. We used Peper et al's empirical crown projection data numbers to calculate how much of the interior paved area of a parking lot would need to be set aside for trees in order to reach a 50% pavement shading goal after 15 years. We made the following assumptions in these calculations;
(d) Interior parking areas shall be landscaped in addition to the required landscaped strip. Trees must be provided in each parking lot at a minimum average density of one (1) shade tree (three inch caliper minimum) for each fifteen (15) parking spaces provided, or any fraction thereof. In the case of mini warehouses, such parking spaces shall be determined by the number of parallel parking spaces contained in the required loading and unloading lanes. Additionally, interior parking lot landscaping shall be provided in accordance with the following table...
Total Parking Area Interior Landscape Area 0 - 24,999 square feet 5% 25,000 - 49,999 square feet 8% 50,000 square feet and larger 10%
(e) Except for customer and employee parking, parking lot landscape requirements do not apply to storage or standing parking spaces incidental to uses, such as sales and rental of motor vehicles, mobile homes, boats, trailers or other similar uses.
(f) To calculate the total parking area and the subsequent percentage of required interior lot landscaping, total the square footage of parking spaces, planting islands, curbed areas and all interior driveways and aisles except those with no parking spaces located on either side. Landscaped areas located outside the parking lot may not be used to meet the interior landscaping requirement.
(g) The required landscaping for parking lots shall be more or less evenly distributed throughout the parking lot, although adjustments may be approved by the Community Development Department where the shape or size of the parking lot, the location of existing trees or other natural constraints reasonably prevent such distribution.
(h) All landscaped areas, including the permeable areas and drip lines around trees and planting beds used for visual screening which abut any parking lot or vehicular travel area, shall be protected with curbs, parking blocks or similar barriers sufficient to protect them from vehicular intrusion.
(i) An automatic irrigation system is required for all landscaping. Water conservation is encouraged. [Lewisville, TX General Development Ordinance Sec 6-103]
- Landscaping consists of shade trees individually planted in 6 foot by 8 foot planter islands located within the parking lot (i.e., all of the trees' canopy is over the parking lot).
- The shade trees used reached an average crown diameter of 21 ft after 15 years (according to Peper et al, this is the average size of London plane trees in Sacramento, CA, parking lots after 15 years).
- Planting islands are configured so that there is no overlapping shade from adjacent trees
- All planted trees survive and trees are not topped or otherwise pruned to reduce tree canopy development
- Canopy over the planters counts toward the 50% shading requirement even though planters are not actually paved areas.
If we assume that trees are also planted at the edge of the parking lot to provide at least partial shading, less than 7% of the parking lot are would need to be devoted to tree planters to reach 50% shading in 15 years, again assuming that fast-growing trees with relatively large crowns are used. If tree crown diameter is only a bit smaller after 15 years (17.5 ft), a full 10% of the paved area will be required for tree planters to attain 50% canopy. Good data on actual sizes trees attained in parking lots under local growing conditions are essential for developing planting specifications that will result in desired levels of canopy cover. Further information and technical considerations related to parking lots and shade trees can be found at Center for Urban Forest Research website at http://wcufre.ucdavis.edu/parkordinances.htm.
Percent of interior paved area occupied by 6 ft by 8 ft planters (1 tree/planter) Projected parking lot shading after 15 years (average crown diameter= 21 ft) 5% of paved area 35% 7% of paved area 49% 10% of paved area 70%