Agenda - Planning Commission - 09/07/2006

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Woodland protection/percent tree cover. Another technique for delineating which resources to protect focuses less on individ- ual trees and more on entire stands or wood- lands. While only a few ordinances written prior to 1990 took this approach, it has become the method of ch'oice in many juris- dictions with comprehensive tree protection programs and often is combined with protec- tions for specimen trees. There are various ways of implementing a percent cover require- may be counted toward buffer yard landscap, ing requirements. Speeal area and habitat protection_ A growing number of communities are focusing - their tree and vegetation protection activities on what might be called "special areas": lands with important aesthetic or environmental values that warrant special protection. One of the advan- tages of this approach is that it is usually easier to gamer political support for strong protection .. measures in areas with unique qualities. ment. Lake County, Illinois, requires that a flat 70 percent of mature woodlands and 50 per- cent of young woodlands on a site be pro- tected as open space. Other jurisdictions have adopted a more flexible approach with a sliding scale that takes into consideration the proposed type of development (e.g., residen- tial vs. industrial) and the amount of existing tree cover on a site (where the amount of tree save area is inversely proportional to the amount of site under tree canopy). Many communities incorporate such techniques into comprehensive protection schemes. For instance, a system could be developed in which a minimum percentage of trees and natural vegetation is preserved, subject to the sliding scale requirements, and supplemented by a requirement that all sig- nificant trees over a certain size be preserved. Distance/buffer requirements. Another common technique used in determining what to protect involves establishing distance or buffer requirements. For example, some com- munities adopt regulations requiring a buffer zone (e.g., 100 feet) between major roadways and any buildings on adjacent private prop- erty. Within the buffer ail trees and vegetation must be retained, with certain limited excep- tions. Existing trees and vegetation retained 102 Natural areas such as rivers and coastal zones are targeted for protection in some commu- nities. In Fulton County, Georgia, the Chatta- hoochee River Corridor Tributary Protection Act requires active tree protection in an area "exten- ding outward 35 'horizontal feet from the tops of the banks on both sides of all flowing tributaries of the Chattahoochee River." Disturbed areas within the buffer must be replanted to county standards using indigenous riparian vegetation. In Sanibel, Rorida, native vegetation that contributes to beach stability cannot be removed seaward of a coastal construction control line. Strict controls also are placed on vegetation trimming and stump removal. Where undesirable, nonnative species such as Australian pine are removed a revegeta. tion plan must be submitted to reduce soil move- ment caused by wind or water. Many states regulate tree preservation by protecting the habitat of endangered species. Numerous cases have come out of the Pacific Northwest in recent years regarding timberland preserved as spotted owl and eagle nesting sites. Habitat protection is one of the most compelling reasons to save trees, especially where the habitat of an endangered species is at issue. Replacement/mitigation standards. Another increasingly common feature of local tree preservation laws are provisions requir- ing on-site replacement of trees removed during development or other mitigation measures such as off-site planting or cash- in-lieu contributions. Most such require- ments are based on very specific numerical standards governing the number of trees to be replaced. Fulton County offers specific guidance regarding replacement and mitiga- tion. The quantity of replacement trees must be sufficient to produce a total "site.tree density factor" of no less than 20 units per acre pursuant to administrative guidelines. Detailed standards are provided for trans- planting and selecting quality replacement stock. Specimen trees must be replaced by species with potentials for comparable size and quality. To the extent that these replanting requirements bear some reasonable relation- ship to the number of trees removed (for - example, smaHer replacement trees, some of which may die, may be required in greater numbers to compensate for removal of larger trees), they should withstand challenge. However, planners should be careful not to be overly vague about the size and location of the replacement trees. From a practical stand- point, each community should carefully con. sider what constitutes a rational replacement standard in light of the species involved, spec- imen size, local survival rate of smaller stock, time required for trees to grow to maturity, and similar considerations. This may vary markedly depending on the region of the country. Construction protection measures. Most sophisticated local governments have come to realize that designating trees for protec- tion by strong standards is only half the bat. tie. The best standards being implemented by the most sympathetic developer can be undermined in an afternoon of careless con- struction activities on a site. Bulldozing near a large tree's roots, digging utility trenches, or dumping construction waste close to a tree can' result in the de facto removal of a tree that was designated for preservation. The death may be slower, but it can be just as sure. For example, a few years ago, it was a commonly accepted practice to protect a tree by forbidding any construction activities or excavation'within its so-called dripline (a vertical line extending from the outermost edge of the tree canopy to the ground). Today, the latest thinking is that this old standard may not be sufficient given the fact that most trees do not have a single large tap root, but rather a large network of ZONING PRACTICE 7.06 AMERICAN PLANNING ASSOCIATION I page 6