Tree Unit Replacement Proposal. DRAFT by Julie Weinstein

Transcription

1 Tree Unit Replacement Proposal DRAFT by Julie Weinstein

2 Background Our recommendations to the Board of Trustees regarding revisions to the tree ordinance included implementing site replacement standards Several methods were suggested including canopy, model-driven value (itree) & monetary equivalent This proposal deals with UNIT REPLACEMENT! Compares standards of 8 areas in the US & Canada Reflects findings of a SUNY Purchase study on legislation to protect and replace trees.

3 The majority of the communities adopted a Tree Unit Density value of 30 per acre. The range was We should be at the top or above since we are in the highest canopycover region. Greenburgh uses 30. I recommend a goal of First Step: Picking a Required Tree Unit Density (measured per acre) How to convert our Village in a Park tree coverage to a single number.. 35.

4 Two Types of Standards are Required to Meet Unit Density: Existing Tree Standards Assign a value to the trees that are left on the site during/after construction Goals: Maximize # of mature canopy trees remaining on lot Ensure that % canopy is maintained over time Replacement Tree Standards Assign a value to the trees that will be planted at the completion of construction Goals: Encourage a mix of evergreen and deciduous Encourage plantings that are appropriate for Scarsdale

5 Comparison of Existing Tree Valuation Tables Area 1 Unit 3 Units 10 Units Federal Way, WA 1-6 DBH 24 DBH NA Kenmore, NY 1-5 DBH 17 DBH 34 DBH Forsyth, GA 5-7 DBH 14 DBH 25 DBH East Point, GA 3 DBH 8 DBH 48 DBH Vancouver, BC 1-6 DBH 16 DBH 30 DBH Cherokee, GA 14 DBH 23 DBH 37 DBH Greenburgh, NY 3-6 DBH DBH DBH There s a wide range of values in each column. For Scarsdale, it makes sense to value the largest and well-established trees to encourage their protection on the site.

6 Comparison of Existing Tree Valuation Tables Area 1 Unit 3 Units 10 Units Federal Way, WA 1-6 DBH 24 DBH NA Kenmore, NY 1-5 DBH 17 DBH 34 DBH Forsyth, GA 5-7 DBH 14 DBH 25 DBH East Point, GA 3 DBH 8 DBH 48 DBH Vancouver, BC 1-6 DBH 16 DBH 30 DBH Cherokee, GA 14 DBH 23 DBH 37 DBH Greenburgh, NY 3-6 DBH DBH DBH PROPOSED 5-7 DBH 14 DBH 25 DBH

7 Density Factors for Existing Trees CONVERSION OF EXISTING TREE DIAMETERS (DBH) TO EQUIVALENT TREE UNITS Based on caliper measures in inches Diameter Equiv. Units Diameter Eq. Units Diameter Units Diameter Units

8 Simplified Existing Conversions SIMPLIFIED EXISTING CONVERSIONS DBH measured in inches Diameter Units Diameter Units Age = DBH in cm. (Lowenstein) so a 70-year old oak is valued at 10 times the value of a sapling. Seems low, but can t justify higher based on other municipalities.

9 Conversion to Equivalent Tree Unit by Tree Type and Region for Existing Trees Tree Type DBH in " Count Forsyth Federal Way Kenmore East Point Vancouver Cherokee Greenburgh Proposed Evergreen Evergreen River Birch 5 10* River Birch River Birch Sycamore Weeping C Oak Maple 20* Oak Oak Sugar Map Silver Mapl Locust Cherry Arborvitae Total % Evergreen 7% 31% 25% 18% 23% 0% 14% 7% % Trees 20"+ 68% 23% 41% 32% 47% 75% 54% 68% 1/2 acre requirement = ? % County Canopy Cover = NA NA 10-20? Comments Simplest Based on Basal Area

10 Comparison of Replacement Tree Municipality Federal Way, WA Kenmore, NY Forsyth County, Georgia East Point, GA Vancouver, BC Cherokee County, Georgia Greenburgh, NY Valuation Tables Replacement Trees Sig Tree Other Replacement 1 unit = 2.5 units Credit Criteria med canopy type NA Mix of trees from list min 2" min conifer size = 6' 6" deciduous NA If trees don't fit on property, 8-10' ht conifer NA off-site replacement. 6" 14" DBH 4 x value 60% Overstory Species 7 gal conifer =.4 18" DBH* Fewer 40% single genus 4" =.9 6" DBH =2.4 Trees chosen from list. 7 gal conifer =.3 $ to tree bank per density unit. 1" Deciduous NA Defferent values for commercial 3' conifer NA 6" NA Tree list provided.planting directions detailed.

11 Proposed Density Factors for Replacement Not Final still researching! CONVERSION TO EQUIVALENT TREE UNIT FOR REPLACEMENT TREES Deciduous Tree Caliper in Inches* Tree Units For Recommended Trees and greater Tree Units For Other Deciduous Coniferous Tree Height in Feet Tree Units For Non-Native Conifers Over Over Over Tree Units For Native Conifers

12 Comments on Replacement Chart: Based on Kenmore, NY Many municipalities didn t address the replanting of deciduous vs. evergreen, but those that did allocated more units to deciduous *Small replacement trees are measured differently: caliper in inches 4 above ground Height used for conifers This helps achieve a goal of planting trees deemed good for Scarsdale and I don t know which those are. Help! Lena?? Encourages planting larger trees resulting in larger canopy earlier

13 Canopy Category Small Canopy Species (Mature canopy area <450 SF) Medium Canopy Species (Mature canopy area 450 to 1,250 SF) Large Canopy species (Mature canopy area > 1,250 SF) Alternate Replacement Table Replacement Tree Units.5 tree units 1.0 tree units 1.5 tree units Where tree replacement is required in order to achieve minimum tree units per acre, the replacement trees shall consist of a mix of evergreen and deciduous trees with no more than 40% evergreen, suitable to specific site conditions. Replacement tree species shall be selected from a list of approved tree species. All species listed are suited to the climate conditions found in the Scarsdale. The list is for guidance only and is not intended to be allinclusive. Other tree species may be utilized where appropriate when recommended by a professional forester, certified arborist, or licensed landscape architect. Size of replacement trees. Replacement trees shall be evergreen trees a minimum of six feet in height and deciduous trees with a minimum two inches caliper.

14 . Density Calculations The density may be determined by counting existing trees to be preserved, planting new trees, or some combination of the two. Site Density Factor (SDF) = Existing Density Factor (EDF) + Replacement Density Factor (RDF) Site Density Factor (SDF) is calculated by multiplying the site to be developed by the Required Tree Unit Density (RTUD) of 35 units/acre. In some towns, this is affected by significant tree codes. Should we? Existing Density Factor (EDF) is determined by converting the diameter of individual trees to Equivalent Tree Units as shown on the above chart. Replacement Density Factor (RDF) is calculated by subtracting the EDF from the SDF.

15 Example Large Property A 2.5-acre lot is redeveloped. The Site Density Factor with no significant trees removed is 87.5 tree units calculated as follows: 2.5 acres x 35 units/acre = 87.5 SDF A total of 15 trees will remain on the 2.5 acre site as follows: 4-12 diameter pines 3 14 diameter maples 3-18 diameter oaks 1-21 hickory 1-30 oak Converting diameters (DBH) to density units, the EDF is calculated below DBH Units # Trees Total 12" 2.4 x " 3.3 x " 5.4 x " 7.2 x " 14.7 x EDF 57.6 The RDF is calculated by subtracting: RDF = = 29.9 replacement units required

16 Example cont d Sample Replacement Calc. 1 st Method Alternate Methods An example would be 10-3 native deciduous, 5-5 native deciduous and 11-6 native conifers. 10 x.9 = 9 5 x 2.0 = x 1.0 = 11 Total = 30 units An example would be 10 small canopy trees, 5 medium and 6 large replacement trees combined with 10 evergreens. 10 x.5 = 5 6 x 1.0 = 6 6 x 1.5 = 9 10 x 1.0 = 10 Total = 30 units