Mapping Urban Tree Canopy in Virginia Localities

Transcription

1 Mapping Urban Tree Canopy in Virginia Localities Jennifer McKee 1, Jim Pugh 2, John McGee 1, Randy Wynne 1 Virginia Tech Department of Forest Resources and Environmental Conservation 1, Virginia Department of Forestry 2

2 Mapping Tree Canopy: Overview What is the Virginia Urban Tree Canopy (UTC) Project What is UTC and why is it important What is UTC analysis and why is it important Potential applications and limitations Lessons learned

3 Virginia Urban Tree Canopy Project Partnership between: Chesapeake Bay Program Virginia Department of Forestry Virginia Geospatial Extension Program at Virginia Tech Participating Localities

4 Virginia UTC Project: Locality Requirements Signed agreement from locality political figure agreeing to participate Must set a minimum 5% canopy cover increase to be achieved in 20 years Canopy cover goal must be adopted by some form of locality government Locality must create report about urban forestry with canopy cover goal implementation plan

5 The Geospatial Extension Specialist A Geospatial Extension Specialist (GES) acts as a knowledge broker, or the two-way conduit between research, applications development and practice. The tasks / focus areas of a GES vary from state to state to reflect local needs. Typically based at a land grant institution.

6 Geospatial Extension Specialist Status of the National Program Puerto Rico Geospatial Extension Program States Interested States In limbo

7 Our community of practice -

8 What is Urban Tree Canopy? Urban tree canopy (UTC) is the layer of leaves, branches, and stems of trees that cover the ground when viewed from above

9 UTC provides many benefits such as: improving water quality reducing air pollution saving energy lowering city temperatures enhancing property values mitigating stormwater runoff costs providing wildlife habitat facilitating social & educational opportunities providing aesthetic benefits tourism

10 Why UTC is Important Urban land in the US is projected to increase from 3.1% in 2000 to 8.1% in 2050 (~392,400 km 2 ) Urban land (2000 US Census def): block groups & census blocks with a min pop density of 500 ppl/mi 2 & less densely settled blocks that form enclaves or indentations or connect discontinous areas Nowak, DJ and JF Walton, Projected Urban Growth and its Estimated Impact on the US Forest Resource. Journal of Forestry. 103 (8):

11 Why UTC is Important By 2050, 4 states (RI, NJ, MA & CT) are projected to be more than ½ urban land On average, 20% of subsumed forests will remain as forest within the urban boundary Nowak, DJ and JF Walton, Projected Urban Growth and its Estimated Impact on the US Forest Resource. Journal of Forestry. 103 (8):

12 Fairfax County, VA Example *UTC Analysis performed in house Lost 38% canopy in last 32 years 85,600 acres lost since 1973 = 2.4 million lbs of potential air pollution removal lost with an approximate value of $6.8 million / yr Tree Canopy Percentage Source: Tree Action Plan - Fairfax County, VA -

13 What is a UTC Analysis? Assessment of the amount & type land cover of a locality Time of assessment is determined by date of imagery used Using the assessment a baseline estimate of canopy cover is derived Canopy cover for entire area as well as by zone or parcel Provides areas that could theoretically support an increase in tree canopy Locality provides GIS data: Corporate boundary Building footprints Parcel data Zoning data State provides: Aerial Imagery

14 Urban Forest Planning Model Inventories (What do we have?) UTC Analysis helps determine what you have Feedback Management Goals (What do we want?) Management Plans (How do we get what we want?) VDOF assists here

15 Why is a UTC Analysis Important? To educate the public about the urban forest resource The current amount & where it could be improved Guides urban forest conservation and policy Allows for goal setting and future management

16 Baseline Assessment VDOF UTC project assessment process Use 2008 NAIP imagery (public domain data) Subset to buffered locality boundary Use imagery & remote sensing software to create a 4 class land cover map Water, Impervious, Non-Tree Vegetation, Tree Canopy Single trees as small as 9 m 2 detected Conduct accuracy assessment Must be >90% accuracy

17 Aerial imagery used to derive land cover

18 Resulting 4 Class land cover map

19 UTC Summarization Run 4 class land cover results through UTC Toolbox to summarize UTC by parcel and zones Results: Land cover map with 5 classes: Water, Non-Tree Vegetations, Non-Building Impervious, Building Impervious, & Tree Canopy Table - UTC metrics by Property Parcels Table - UTC metrics by Land Use Zone

20 Land Classes Acres % Total Land Tree Canopy 6,353 43% Non-Tree Vegetation Non-Building Impervious Buildings Impervious 2,504 17% 4,101 28% 1,632 11% Water 73 1% Total Area 16, %

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22 UTC Parcel Metrics Definitions Parcel land: All land area (not including water areas) within parcel boundaries Existing UTC: Amount of UTC within parcel boundaries Possible UTC: Amount of land theoretically available for the establishment of tree canopy within parcels. This excludes areas covered by tree canopy, buildings and water. Split into two classes: Possible UTC Vegetation: Amount of land theoretically available for the establishment of tree canopy in non-tree vegetation areas within parcels. This excludes areas covered by tree canopy, impervious surfaces and water. Possible UTC Impervious: Amount of land theoretically available for the establishment of tree canopy in impervious areas within parcels. This includes impervious areas (roads, parking lots & sidewalks) except for buildings.

23 Property Parcel Summary UTC Parcel Metrics Acres % Parcel Land Area Parcel Land 10, % Existing UTC 5,174 48% Possible UTC 4,009 37% Possible UTC -Vegetation 1,899 18% Possible UTC -Impervious Not Suitable for UTC* 2,110 20% 1,627 15% Summarizing all LAND area within parcel boundaries (excludes any areas covered by water) *Not suitable for UTC includes all Building Impervious areas within parcel boundaries

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26 Land Use Zoning Summary- Top 5 Land Use Apartment Dwelling District: RA14-26 One-Family Dwelling District: R-6 One-Family Dwelling District: R-8 One-Family Dwelling District: R-10 Special District: S-3A Land Area % Land Existing UTC Possible UTC-Vegetation Possible UTC-Impervious % Zoning Category % UTC Type % Land % Zoning Category % UTC Type % Land % Zoning Category 759 2% 42% 5% 1% 16% 5% 1% 20% 7% % UTC Type 4,319 15% 49% 34% 6% 18% 32% 3% 11% 22% 563 2% 55% 5% 1% 16% 4% 0% 9% 2% 2,025 8% 54% 18% 3% 18% 15% 1% 8% 8% 2,894 10% 48% 22% 4% 21% 25% 1% 7% 10% % Land = Area of UTC type for specified land use Area of all land % Category = Area of UTC type for specified land use Area of all land for specified land use % UTC Type = Area of UTC type for specified land use Area of all UTC type

27 Land Use Zoning Summary Top 5 Apartment Dwelling District: RA14-26 One-Family Dwelling District: R-6 Possible UTC (Veg+Imp) Possible UTC-Vegetation Possible UTC-Impervious Existing UTC Land Area One-Family Dwelling District: R-8 One-Family Dwelling District: R-10 Special District: S-3A Acres

28 What is Provided to the Locality UTC Report via DVD containing: All data used & created GIS summarization model Digital copy of report Read_Me file

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30 Current Virginia UTC Progress

31 Potential Applications Use UTC analysis to help guide the creation of: canopy cover goals policies urban forest management plan Re-summarize UTC by neighborhood or study area Use UTC to locate possible new/additional greenways

32 Limitations Consider accuracy when setting canopy goals If 92% accuracy then (8% margin of error) setting a goal that increases within the MOE makes it difficult to determine if an increase has been obtained Possible UTC areas of increase need to be scrutinized *These are theoretical amounts of increase in an area Do potential UTC areas need to be removed due to restrictive uses? recreational fields, land fills, utility line ROWs, etc Static measure of tree canopy Reassessments must be conducted to determine changes in canopy over time

33 Lessons Learned Get local buy-in before the first pixel is ever processed Set consistent method across the region / state Work with jurisdictions to develop management plans / targets and goals

34 Summary Tree Canopy is important for many reasons Increasing urban areas, loss of unmanaged canopy, benefits provided increase the healthier the urban forest is Knowing what you have is essential for planning UTC assessment is a baseline estimate of canopy coverage (as of imagery date) Know the limitations of your data/analysis

35 Questions?