PLAN-IT GEO LLC
AN ASSESSMENT OF URBAN TREE CANOPY IN AKRON, OHIO November 2013
Plan -It Geo LLC | 5690 Webster Street, Arvada, Colorado, 80002 | www.planitgeo.com
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Urban Tree Canopy Assessment in Akron, Ohio Prepared By
Acknowledgements Funding for this project was provided by the USDA Forest Service through the Ohio Department of Natural Resources and the Project Clean Lake grant.
Core partners included the U.S. Forest Service and the City of Akron. In addition, thanks go specifically to City Arborist and Horticulturalist Bill Hahn, City Landscape Technician Jon Malish, the City of Akron Engineering Bureau GIS Administrator Darren Rozenek, and Director of Public Service John Moore for their invaluable assistance at many stages of this project. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, sexual orientation, marital status, family status, status as a parent (in education and training programs and activities), because all or part of an individual’s income is derived from any public assistance program, or retaliation. Prepared For City of Akron Akron Engineering Bureau Akron Parks Maintenance Division GreenPrint Akron
“We are caretakers of our land, our water, and our environment. We must make wise choices today, so that our grandchildren and their children’s children have a safe and clean city and a prosperous community.” Donald L. Plusquellic, Mayor of Akron
CONTENTS Executive Summary
1
Urban Forest Assessment Approach
1
Urban Tree Canopy In Akron
1
Ecosystem Services Analysis
2
Potential Tree Planting Sites
2
Goal Setting
2
Recommendations and Summary
2
Project Background
3
Major Findings
5
Project Fundamentals
6
Mapping Land Cover and Urban Tree Canopy 6 Terminology
8
UTC Assessment Boundaries
9
Ecosystem Services Analysis
10
locating and Prioritizing Potential Planting Sites
11
Goal Setting by Zoning District
12
Assessment Results and Products
13
Land Cover in Akron
14
Policy & Planning
15
Street Trees
18
Stormwater Management and Tree Canopy 19 Ecosystem Services
21
Prioritizing Potential Planting Sites
22
Suggested Canopy Cover Goals
24
Recommendations
25
Summary
27
Appendix
29
EXECUTIVE SUMMARY The City of Akron’s urban forest is comprised of trees, forests, gardens, green spaces and other natural areas. This urban forest provides numerous benefits by making environments cleaner, safer, and more livable, therefore contributing directly to public health and reducing the costs associated with many required services. To manage, monitor and enhance the quality and stream of benefits received from its urban forests, the City of Akron initiated this study assessing the extent of Urban Tree Canopy (UTC) across the city. This report presents results for current land cover and UTC distribution and offers data analysis, potential planting locations, custom maps and tools, and broad recommendations for setting and achieving canopy goals.
URBAN FOREST ASSESSMENT APPROACH Natural resource managers use top-down (aerial imagery) and bottom-up (field-based) approaches to measure land cover, trees and other green infrastructure, and associated ecosystem services. Terms and methods for UTC assessment are presented within Project Fundamentals on page 7.
URBAN TREE CANOPY IN AKRON This study encompasses 39,816 acres (62 square miles) defined by the city limits of Akron, Ohio. Based on a land area (after excluding water) of 39,357 acres, the City has 14,647 acres (37%) of existing tree canopy, 17,292 (44%) of total Possible Planting Area, or PPA, which is defined as non-building, non-road land area where tree planting is possible. Additionally, 7,878 acres (19%) of Akron is unsuitable for tree planting. The land cover data was used to assess similar metrics for the City’s wards, watersheds, neighborhoods, zoning districts, census blocks, parcels, and street rights-of-way. See Results section on pages 14-25.
Unsuitable UTC Area: 19% Plantable Area (Impervious): 18% Plantable Area (Vegetation): 26%
37%
UTC: 37%
Figure 1: Distribution of UTC Metrics
Akron City Limits
39,357
Land area in acres for this assessment
44
Percent of Akron Available for Tree Planting
55
Highest canopy cover percent in a Ward (Ward 4)
25
Percent of Citywide UTC from the City of Akron Watershed
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ECOSYSTEM SERVICES ANALYSIS Urban trees and forests in communities provide many “ecosystem services”, or direct and indirect economic and environmental benefits such as removing air pollutants, storing and sequestering carbon, mitigating stormwater runoff, conserving energy through shade and wind block, improving public health, and providing wildlife habitat. Akron’s tree canopy currently provides an estimated $4.2M in air quality services each year, $1.4M in annual carbon sequestration benefit. An increase in tree canopy to 45% would increase the stormwater benefit by 22%, while a decrease in tree canopy to 30% would reduce the stormwater benefit by 21%. See Ecosystem Services section on page 22.
POTENTIAL TREE PLANTING SITES Planting locations were generated from the land cover data using a GIS model, resulting in 237,175 potential sites citywide. To help the City prioritize locations for plantings that achieve specific benefits, numerous attributes were joined based on proximity overlay to the GIS points. Examples (with a count of sites) include parks (14,644), schools (2,103), within floodplains (8,212), near streams (10,165), on city owned property (17,279), near major roads (5,529), near residential homes (112,656), and near wildlife habitats (57,000) where associated tree benefits impact social well-being, environmental health, and economic vitality. See Planting Sites Prioritization on pages 23-24.
GOAL SETTING To support and facilitate future tree planting and canopy preservation policies, UTC goals were analyzed using GIS methods and a Canopy Calculator tool. A suggested city-wide canopy cover goal of 40% (an additional 1,095 acres of tree canopy) is presented along with goals for individual zoning types. These should be used as a starting point for an interdisciplinary goal setting process. See Suggested Canopy Cover Goals on page 25.
RECOMMENDATIONS AND SUMMARY To balance future development and growth with effective urban forestry planning, city officials must value Akron’s canopy cover in environmental, social, and economic terms during planning processes. Maintaining and enhancing this green infrastructure will involve ongoing care and protection, strategic canopy increases, and education to increase the awareness of UTC benefits. This will ensure that trees appreciate over time and that their contributions toward addressing environmental issues and improving community health are maximized. Akron exhibits an impressive 37% UTC; a laudable achievement and contribution towards the City's overall sustainability and greening efforts. This study provides hard data required for natural resources planning, monitoring, and decision-making. See the Recommendations and Summary sections on pages 26-28.
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PROJECT BACKGROUND In recent years, the City of Akron has made great strides to improve the natural and built environment to ensure a sustainable community for future generations. Many aspects of this effort relate to improving the quality of the City’s urban forests, including annual tree plantings, passing initiatives to improve air and water quality, and developing action plans within the GreenPrint Akron framework to conserve natural resources. The City of Akron, Ohio, covers approximately 62 square miles, and has a population of 198,549 (2012 census). The City of Akron contracted with Plan-It Geo to conduct Akron’s Urban Tree Canopy (UTC) Assessment. Using Geographic Information Systems (GIS), the process measures existing canopy cover, provides a baseline of information for increasing environmental services from the urban forest, strengthens local/state partnerships, builds awareness of urban forest benefits, and enables Akron and State of Ohio to establish canopy goals and strategies.
Figure 2: City boundary of Akron, Ohio and the study area for the UTC Assessment.
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Using color-infrared 2011 aerial photography, this assessment mapped five primary land cover classes listed below. Land cover was further categorized by using additional local GIS data layers to separate impervious surface types (buildings, roads, and others).
Urban Tree Canopy: Tree cover, when viewed and mapped from above Vegetation: Irrigated and non-irrigated vegetation Impervious: Surfaces: roads, buildings, sidewalks, parking areas and other impervious surfaces Soil: Dry vegetation/ bare soil Water: All water bodies, including lakes, rivers, and streams The land cover data is used to examine area and percent metrics for existing tree canopy, possible planting areas, and areas unsuitable for planting. These metrics were calculated for the following GIS assessment boundaries: (1) City Limits, (2) Zoning Districts, (3) Wards, (4) Watersheds, (5) Neighborhoods, (6) Street Rights-of-Way by Neighborhoods, (7) Census Blocks, and (8) Parcels (see Table 1 on page 10). Finally, a GIS model is used to locate and create priority attributes for potential planting sites. This information serves as the basis for all maps, summaries, and potential planting sites presented in this report. Akron’s UTC Assessment is a top-down approach which provides data and tools to enhance planning, management, and value received from the City’s urban forest. Additional bottom-up inventory and assessment can ground-truth viable planting areas as well as provide data on species composition, condition/quality, safety, and forest structure to augment this assessment. The products and outcomes will support developing and monitoring of canopy goals, data-driven resource management plans, refinement of policies and ordinances, and help to foster a greater understanding of urban forest benefits.
What the UTC Assessment provides: This project provides maps and statistical quantification of existing urban tree canopy, possible planting areas and other land cover classes across the City of Akron, and targeted areas for tree planting and forest preservation.
Why the UTC Assessment is necessary: This assessment provides an up-to-date benchmark of tree cover, a critical component for effective urban forest management planning and a key measure of environmental sustainability in urban areas.
How Akron will use this UTC Assessment: The tools and information resulting from this analysis should be used by planners, resource managers, and community members to understand, improve, and promote forest management across the City.
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MAJOR FINDINGS LAND COVER: Akron has 37% (14,647 acres) urban tree canopy and 44% (17,292 acres) of additional area available for tree planting. 18% (7,022 acres) of Akron is covered by possible plantable space over impervious surfaces (PPA Impervious).
CANOPY BY WARDS: Of Akron’s 10 Wards, Ward 8 has the highest UTC at 55% (3,405 acres), while Ward 3 has the lowest at 28% (991 acres). Ward 1 has the lowest possible planting area (PPA) acreage at 1,371 (38%), while Ward 8 has the highest acreage of PPA Vegetation 2,020 acres (33%).
CANOPY BY ZONING DISTRICTS: Residential zoning comprises of 64% (21,465) of the total land area, and with 10,024 acres of UTC, makes up 68% of all tree canopy. Additionally, residential districts have 8,631 acres (40%) of additional possible planting area. Commercial and industrial zoning districts have 18% (585 acres) and 25% (853 acres) UTC, respectively. Tree protection and preservation should be a focus in these areas.
CANOPY BY WATERSHEDS: Of Akron’s 9 Watersheds, Boston Run-Cuyahoga River has the highest UTC at 60% (3,151 acres), while Portage Lakes - Tuscarawas River has the lowest at 29% (2,577 acres).
CANOPY BY NEIGHBORHOODS: Akron’s 21 neighborhoods range from a high of 60% UTC (1,859 acres) in Northwest Akron to a low of 14% UTC (162 acres) in Downtown.
ECOSYSTEM SERVICES: The current urban forest removes nearly 993,827 pounds of air pollutants from the air annually, valued at $4.2 million per year. Akron’s canopy provides $1.4 million in carbon storage and sequestration benefits annually. Existing trees mitigate 1.8% of stormwater runoff. An increase of 3% canopy to 40% overall UTC increase the stormwater benefit by 8%.
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How Are UTC Results Used? To set and implement canopy cover goals To prioritize areas for tree planting and preservation To analyze and visualize tree planting opportunities To work with multiple, diverse partners to achieve and maintain goals
PROJECT FUNDAMENTALS This section describes: Mapping Land Cover & Urban Tree Canopy UTC Terminology Assessment Boundaries Urban Forest Ecosystem Benefits Potential Planting Sites Prioritization Goal Setting
The “top-down” UTC assessment conducted for Akron provides an accurate evaluation of canopy cover within the desired boundary. The following section describes the data and methods used for land cover classification, the terminology for defining and assessing Urban Tree Canopy (UTC) and Possible Planting Areas (PPA), and the boundaries (geographic units of scale) that were assessed.
MAPPING LAND COVER AND URBAN TREE CANOPY Aerial photography (2011 National Agricultural Imagery Program) at 1-meter pixel resolution was used as the basis for this UTC assessment. Object-based image classification results were combined with GIS data provided by the City to produce a five (5) class land cover layer. Numerous GIS layers from the city, county and state were used to map the following five land cover classes in Akron: (1) tree canopy, (2) other low-lying vegetation, (3) impervious surfaces, (4) bare soil/dry vegetation, and (5) water. Roads and buildings were included in the analysis and added to eliminate areas that are unsuitable for planting. Once finalized, the land cover data was the input to assessing boundaries to provide UTC metrics at multiple scales.
Figure 3: Accurate land cover mapping is the foundation of a UTC assessment.
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URBAN FORESTS GIVE BACK Urban forests are an integral part of the character for many residents and policy makers in the City of Akron. Benefits of trees are referred to as “ecosystem services” and describe the ways that urban forests impact our lives and the environment. The information below outlines and justifies the many reasons to promote, establish, manage, and maintain a robust, “working” urban forest in Akron.
A Better Place to Live, Work, and Play: Environmental Air Quality – Trees absorb, trap, offset and hold air pollutants such as particulate matter, ozone, sulfur dioxide, carbon monoxide, and CO2. Water Quality and Stormwater Runoff Mitigation – Soil aeration, evapotranspiration, and rainfall interception by trees increases water quality and reduces stormwater flow. Erosion control – Tree roots hold soil together along stream banks and steep slopes. Increased wildlife habitat – Increases biodiversity in urban areas.
Economic Property value –Residential homes with healthy trees add property value (up to 15%). Energy conservation – Trees lower energy demand through summer shade and winter wind block, additionally offsetting carbon emissions at the power plant. Stormwater facilities – Trees and forests reduce the need for or size of costly gray infrastructure .
Social Public health – Trees help reduce asthma rates and reduce UV-B exposure by about 50%. Crime and domestic violence – Urban forests help build stronger communities. Nature and trees provide settings in which relationships grow stronger and violence is reduced. Noise pollution – Trees reduce noise pollution by acting as a buffer and absorbing up to 50% of urban noise (U.S. Department of Energy study).
Resources to Manage Tree Inventory and Monetize Urban Forest Benefits: i-Tree Tools: Software suite from the USDA Forest Service that delivers urban forestry benefits and analysis assessment tools. http://www.itreetools.org/
The UF Cloud: With tools such as Canopy Tracker, Simulate Canopy, Prioritize, and Update Metrics, Plan-It Geo’s Urban Forest Cloud applications, allow users to design and print maps of tree planting plans. This can increase volunteerism and community outreach, and tree’s environmental services. For more information, visit: http://www.planitgeo.com/
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TERMINOLOGY Land cover classes were grouped into UTC Types for the assessment. UTC types categorize the landscape so that metrics can be summarized across spatial scales consistently for different applications. These terms are the metrics used in the project, and the following page illustrates the boundaries they were used for. The metrics also target land uses, neighborhoods, natural areas, or individual properties for tree planting activities and policies.
UTC Types assessed in this Report: Existing UTC comprises forests and individual trees when viewed and mapped from above.
Possible Planting Areas - Vegetation are area of grass and open space where tree canopy does not exist and it is biophysically possible to plant trees.
Possible Planting Areas - Impervious are non-road, non-building hardscape surfaces that contribute to stormwater runoff where establishing tree canopy is biophysically possible.
Unsuitable UTC - the combination of bare soil, roads, buildings, and water, where it is not feasible to plant trees.
UTC types were mapped across GIS boundaries, described on the next page. From the city to the parcel-level, the area and percent of these UTC Types was calculated for map-making and tabular summaries.
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UTC ASSESSMENT BOUNDARIES Assessment boundaries provide geographic units linked to where we live, work and play. Metrics for UTC Types were assessed for the GIS boundaries in Table 1. These summaries provide data for resource managers and planners at different spatial scales. Table 1: Seven (7) assessment boundaries examined Assessment Boundary
# of Features
Description
City Limits
1
Akron City Limits
Wards
10
Districts designated by City officials in which specific structures are allocated to each zone.
Watersheds
9
An area or ridge of land that separates waters flowing to different rivers or basins.
Neighborhoods
21
A group of residents or property owners who advocate for or organize activities within a neighborhood.
Zoning Districts
7
Commercial, Industrial, Institutional, Planned Development, Residential, Other, Street ROW
Census Blocks
4,637
2010 U.S. Census data provides demographic data at the tract, block group, and block level.
Parcels
98,983
Tax lots from the county assessors property database
An Assessment of Urban Tree Canopy in Akron, Ohio
Map
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ECOSYSTEM SERVICES ANALYSIS Urban forests are an integral part of the character of Akron. Trees are often appreciated for their aesthetic appeal; however, they greatly contribute to the health and vitality of resident’s daily life. This report quantifies some of the benefits of urban trees, referred to as “ecosystem services.” While the net benefits of urban trees are usually positive, costs are also part of this study’s ecosystem service evaluation and scenario tools for managers. i-Tree Hydro (beta) and i-Tree Vue software were used to estimate the benefits of Akron’s existing urban tree canopy and scenarios with decreased and increased canopy cover. i-Tree Vue benefits related to carbon storage and sequestration and air pollutant removal. i-Tree Hydro was used to calculate stormwater runoff mitigation benefits of urban forests. See complete details below and on page 42 in the appendix. Current and future values were estimated for the following three ecosystem service types: o o
o
Air Quality—Trees naturally remove pollutants and lower air temperature Stormwater mitigation—Trees intercept stormwater, reducing runoff and filtering out pollutants that would otherwise enter rivers and lakes Carbon sequestration and storage—Through photosynthesis, trees absorb atmospheric carbon and use it for new growth (stems, branches, roots and leaves), acting as a natural carbon sink
http://www.itreetools.org/resources/reports/Corvallis_ Urban_Tree_Assessment.pdf
City Budget: Green vs. Grey Infrastructure According to the EPA, gray infrastructure refers to traditional practices for stormwater management and wastewater treatment, such as pipes and sewers, while green infrastructure refers to sustainable pollution reducing strategies that also provide ecosystem services, such as bioretention swales, rain gardens, and urban forests (EPA 2013). When gray infrastructure drains excess water from the landscape, pollutants such as chemicals, heavy metals, oils, and fertilizers, enter our water treatment plants and drinking water system. The City of Akron is currently spending $900 million to build massive holding tanks for sewage and stormwater during periods of heavy rain to slowly release water into the treatment plant, preventing overflows into Cuyahoga River. Allocation of funds to increase the urban forest budget may save taxpayers money on costly infrastructure repairs in the future, and help filter out harmful pollutants. Regional Cities such as Cleveland, Cincinnati, and Philadelphia, have highly progressive green infrastructure policies, and may be used as models for future budget planning. For more information, visit: http://www.cuyahogaswcd.org/euclidcreekfiles/EC_ClevelandWPCGreenInfrastructureProject.htm, http://projectgroundwork.org/benefits/, and http://www.phillywatersheds.org
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LOCATING AND PRIORITIZING P OTENTIAL P LANTING SITES Potential planting sites were identified, prioritized, and analyzed within all Akron’s possible planting areas as part of this assessment. The resulting GIS points will assist the City in targeting areas to plant trees, summarizing the quantity and quality of planting opportunities, identifying partners, and evaluating canopy goals. To get a more realistic estimate of where trees could be practically planted, exclusions and constraints were applied to a sophisticated GIS model to automate the mapping of potential tree planting sites. The land cover data, UTC results, zoning and infrastructure data provided from the City were inputs to the model. The complete list of these constraints and exclusions with their definition is provided in Table 2 below. Figure 3 illustrates the input at left, constraints/exclusions in the middle, and final outputs at right. Table 2: Constraints/exclusions in generating potential planting sites
GIS Layers
Rule Applied
Reason
Non-Tree Vegetation
Plant only in these areas
Where tree planting is feasible
Tree Canopy Polygons
Buffered by 4 meters
To allow room for spacing and growth of existing trees
Building Footprints
Buffered by 2 meters Remove Sites from golf courses and airports
To avoid tree and building conflicts
Unsuitable Areas
Tree planting will not occur in these areas
Figure 3: Input areas, exclusions and final planting sites, viewed from left to right.
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GOAL SETTING IN AKRON In the 2013 revision of Akron’s Master Tree Planting Plan, the goals set forth to promote a sustainable urban forest included: Maintain the health and vigor of all trees in the urban forest Plant the largest suitable tree for each site selected Achieve a fully stocked urban forest. To support and facilitate future tree planting and canopy preservation policies, GIS and statistical methods were used to provide UTC goals for the City and generalized management districts (Residential, Street ROW, Parks & Recreation, and Institutional). Plan-It Geo’s canopy goal-setting process uses current canopy and potential planting sites to provide Akron with goals that are appropriate and attainable in the future. The citywide goal-setting process is described below. UTC metrics are calculated for all parcels. Legitimate parcels are selected for the goal-setting process by eliminating polygons in the parcels dataset that are not truly tax lots. Parcel areas with less than 100 square feet are omitted from the analysis. An appropriate and attainable goal is selected using the 75th Percentile Rule. Parcels within each land use category are ranked from lowest to highest by UTC percent. The 75th percentile takes into account Akron’s current resources by looking at current UTC percent, is attainable (25% of areas have already attained the goal), but are meant to promote urgency in the UTC process (75% of parcels are below the goal) (Poracsky 2004). Once the citywide goal was determined, the Canopy Calculator was used to determine number of trees needed to reach specific management goals. The City may use the citywide goal as a starting point for an interdisciplinary goal setting process throughout zoning classes, and other management districts.
Figure 4: Steps used for suggested goal setting
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ASSESSMENT RESULTS AND PRODUCTS The UTC boundaries assessed in Akron are governed, owned, managed, and used in different ways by diverse constituents in the community. Therefore, the UTC data and analysis results are presented for multiple scales and purposes to inform planners, managers and citizens alike. The following sections present canopy cover and planting potential across geographic assessment boundaries and describes how the City can use the data to develop ways to manage this important resource.
Tree Canopy in Akron
Land Acres: 39,357 UTC Acres: 14,647 UTC: 37% Potential Planting Sites: 237,175
This study encompasses 39,816 acres defined by the City limits of Akron and provides a snapshot of land cover based on 2011 aerial imagery. Tree canopy covers 14,647 acres (37%) of Akron (based on total area including water). The predominate land cover types for the study area are vegetation (grass and open space) at 11,230 acres (28%) and impervious surfaces (roads, buildings, parking lots, driveways, patios, and other paved surfaces) at 7,190 acres. Water covers 1% of the City’s area (459 acres) and “bare soil/dry vegetation” covers 243 acres, or 0.6% of Akron. The results from this assessment are presented by each geographic boundary, and ‘drill-down’ approaches to identify areas where additional tree canopy would contribute greatest to overall environmental services (mitigating the urban heat island effect, managing stormwater, improved air quality, etc.). Similar areas for planting or canopy protection/preservation can be quickly generated across all boundaries.
We all Impact UTC: Within the City of Akron, the fate of urban forests relies upon City planners, council members, business owners, and residents alike. Sustainable community efforts must be met by all parties of Akron in order for the City’s urban forest to thrive. Local involvement includes: Establishing and enforcing tree preservation ordinances across all zoning types. Community outreach to educate residents of the economic and health benefits of trees and provide incentives to promote tree planting on private property. Preserving or offsetting existing tree canopy in areas at risk to forest loss (i.e. development pressures, storms, etc.), and planned maintenance of mature trees. Involvement from City council members in development of an urban forest management plan.
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459 Ac.
LAND COVER IN AKRON
243 Ac.
7,190 Ac. 14,647 Ac.
2,386 Ac. 3,661 Ac. 11,230 Ac.
Figure 4: Distribution of seven land cover classes in Akron.
= Total: 39,816 Acres
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TREE CANOPY BY ZONING Many of the policies, regulations, ordinances, and actions influencing tree canopy in Akron are dependent on zoning. To provide data that advances urban forest management, ten zoning categories were assessed for tree canopy and possible planting areas (Figure 8). Results can be queried and symbolized using GIS to drill down and identify specific planting opportunities in wards or zoning types. Table 3 provides complete results for UTC and PPA metrics by zoning.
2% %
10% 4% 6%
3% 7%
68%
Figure 6: Distribution of total UTC by zoning class. (Note: State Capitol, Agriculture and Planned industrial districts had no significant UTC percentages.
Table 3: UTC and PPA metrics by Zoning
Figure 5: Map of Zoning classes in Akron.
POLICY & P LANNING *Note: Area totals calculated with street ROW may differ from the City total.
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TREE CANOPY BY WARDS City council members have direct influence on development patterns and policies within their Ward. In Akron’s ten wards, UTC ranged from 28% (991 acres in Ward 3) to 55% (3,405 acres in Ward 8).
Figure 7 (Above): Percent UTC by Wards and drilling-down to Ward 5 where census blocks with less than 20% canopy cover and more than 50% total planting area are shown in red.
GreenPrint Akron The GreenPrint Akron initiative, developed in 2009, includes urban forest preservation and improvement as part of its campaign goals. This includes becoming a national leader in Urban Forestry. For more information, visit:
http://www.keepakronbeautiful.org/greenprint
Figure 8: Optimal planting sites within census block with low UTC.
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TREE CANOPY BY NEIGHBORHOODS There are 21 neighborhoods in Akron. These areas provide neighborhood-level planning data, with greater detail than at the ward level. Tree canopy in neighborhoods ranged from 14% UTC (162 acres) in Downtown Akron, to 60% (1,859 acres) in Northwest Akron. Overall, neighborhoods contain 13,325 acres of UTC, and 16,010 acres of total possible planting area, 9,306 acres of which are vegetated areas (PPA Vegetation) such as grass and open space.
Figure 9 (Above): Percent UTC by neighborhoods
Figure 10 (Above): Percent UTC by parcels in the East Akron Neighborhood
Community Outreach by Neighborhood: Residential zoning accounts for 55% of Akron. Within this area, 8,635 acres are available for tree planting. Community outreach and tree planting incentives for residents can dramatically increase citywide tree canopy.
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STREET TREES Tree Canopy in Street Rights-of-Way Akron’s urban forestry program plants, manages, and maintains trees in the street rights-of-way (ROW) where the City has the most direct opportunity to increase tree planting. Using the UTC assessment data, the city may target strategic areas to increase tree canopy in streets and highway corridors to improve aesthetics and air quality. ROW metrics were assessed for both wards and neighborhoods. Akron’s total ROW land area is equal to 6,601 acres (17%) of the City’s total land area. Key findings in Akron’s ROW are: Existing UTC in the ROW is 1,531 acres or 23% average cover. This represents 10% of all UTC Citywide. PPA – Vegetation totals 1,357 acres or 21% of the ROW, and PPA – Impervious totals 1,431 acres, or 22% of the ROW. ROW in Ward 8 has the highest UTC at 38%, or 18% of all UTC in Akron’s Street ROW
Figure 11: Percent UTC in Street ROW by ward. (Inset): Percent Total PPA in Street ROW by neighborhoods
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STORMWATER MANAGEMENT AND TREE CANOPY Stormwater Benefits of Trees Trees and forests play an important role in stormwater management. As new development occurs and impervious surface cover increases, less rainwater infiltrates into groundwater and more runoff enters nearby rivers, often resulting in greater flood damage. Tree canopy not only intercepts stormwater runoff and releases it back into the atmosphere through evapotranspiration, but also promotes infiltration into soil, reduces peak flows, and filters pollutants before entering streams. Ultimately, tree canopy helps to offset the need for costly stormwater infrastructure.
Watersheds and Tree Canopy Tree canopy in Akron’s watersheds ranged from 29% to 60% while PPA Impervious ranged from 7% to 22%. By assessing UTC within watersheds, the City may target watersheds with low UTC and high PPA and determine priority planting areas. Complete results are shown below in Table 4. Table 4: Complete UTC Assessment results by Watersheds Watersheds
Total Land Acres
UTC Acres
UTC %
% of Total UTC
PPA (Veg.) Acres
PPA (Veg.) %
PPA (Imp.) Acres
PPA (Imp.) %
Total PPA Acres
Total PPA %
Boston Run City of Akron Fish Creek Tuscarawas River Mud Brook Pigeon Creek Portage Lakes Wingfoot Lake Outlet Yellow Creek
5,220 10,755 1,516 725 856 5,227 8,869 5,931 258
3,151 3,589 655 217 383 2,093 2,577 1,881 101
60% 33% 43% 30% 45% 40% 28% 32% 39%
22% 25% 4% 1% 3% 14% 18% 13% 1%
1,172 2,560 308 270 292 1,510 2,568 1,499 91
22% 24% 20% 37% 34% 29% 29% 25% 35%
353 2,395 279 61 95 744 1,951 1,104 40
7% 22% 18% 8% 11% 14% 22% 19% 15%
1,525 4,955 588 331 387 2,254 4,519 2,604 130
29% 46% 39% 46% 45% 43% 51% 44% 51%
TOTAL
39,357
14,647
37%
100%
10,270
26%
7,022
18%
17,291
44%
Prioritizing Tree Planting for Stormwater Management Benefits: Within the City of Akron, 8,188 planting sites were derived from areas in mapped floodplains. Additionally, 10,124 sites fall within 100 feet of waterways. An emphasis on tree planting in these areas can help support stormwater management and water quality. The Urban Watershed Manual Part 1: Methods for Increasing Forest Cover in a Watershed, developed by the US Forest Service outlined techniques for maintaining and increasing current canopy within drainage basins (table of goals and techniques provided in appendix). To read more, visit: http://nemonet.uconn.edu/images/resources/FREMO/ completepart1forestrymanual.pdf
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The example here highlights the Portage Lakes Watershed. Possible planting areas from the land cover data are highlighted in parcels within 500 feet of a waterway where canopy cover is low (less than 30%) and PPA Impervious is high (at least 20%) as potential restoration areas to manage stormwater runoff.
Figure 13: Percent UTC by Watersheds.
Figure 12: Portage Lakes Watershed.
Figure 14: Planting sites near waterway to assist stormwater management.
Cuyahoga River Watersheds and Tree Canopy As part of the Project Clean Lake Grant, this assessment will highlight areas where the City and the Cuyahoga River Watershed would benefit the most in planting trees. An increase in tree canopy in these areas will reduce the amount of polluted runoff that enters tributaries, as well as increase the overall ecosystem sustainability and benefits provided.
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ECOSYSTEM SERVICES Assigning a dollar value to the benefits provided by Akron’s trees and forests can motivate leaders to preserve and enhance the urban forest. This is critical to understanding how trees impact our homes, communities, and overall environment.
Carbon and Air Quality Findings: Plan-It Geo’s environmental analysis reveals that existing canopy in Akron stores approximately 2.1 million tons of carbon, valued at $41.1 million, and each year sequesters Credit: approximately 70 thousand tons of carbon dioxide, valued at $1.3 million. An http://www.itreetools.org/resources/report increase in tree canopy to the suggested goal of 40% would result in 75 s/Corvallis_Urban_Tree_Assessment.pdf thousand tons of carbon stored, increasing the City’s annual savings to $1.5 million. Figure 15 below presents four tree canopy scenarios, and total ecosystem services savings. Findings from the i-Tree Vue software also reveal that tree canopy in Akron removes 994 thousand pounds of air pollution annually, valued at $4.2 million. Increasing tree canopy to 40% would remove 1.1 million pounds of air pollution annually; a value of $4.4 million.
Stormwater Mitigation Findings:
Monetary Gains
Tree canopy intercepts stormwater runoff and thus reduces stormwater infrastructure costs to the city. I-Tree Hydro scenarios show that existing trees mitigate 1.8% of stormwater runoff. An increase of 3% canopy to 40% overall UTC increase the stormwater benefit by 8%. Additionally, an 8% UTC increase to 45% would mitigate 2.2% of runoff; increasing stormwater benefits by 22%. A decrease in canopy cover to 30% would mitigate 1.4% of runoff; reducing stormwater benefits by 21%. $7,000,000 $6,000,000 $5,000,000 $4,000,000 $3,000,000 $2,000,000 $1,000,000 $0
Air Pollution
Existing 37% UTC
$4,160,068
Annual Carbon Sequestration $1,355,563
TOTALS
Increase to 40% UTC
$4,471,241
$1,456,959
$5,928,200
Increase to 45% UTC
$5,030,354
$1,639,147
$6,669,501
$5,515,631
Figure 15: Ecosystem benefits by canopy cover scenario.
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PRIORITIZING POTENTIAL P LANTING SITES The tables on the following pages present the planting sites prioritization criteria and results. These numbers may be used to collectively, or within each criterion to target specific tree planting benefits. Table 5: Planting site prioritization criteria.
Planting Site Attribute
GIS Criteria Used
No. of Planting Sites
Floodplain
Within mapped floodplains
8,212
Riparian Area
Within 100 feet of water or wetlands
10,165
Schools
Within a parcel that contains a school
2,103
Parks & Rec
Within a mapped park or greenway, or within 100 feet of trail/trailhead
14,644
City Owned
Within a city owned parcel
17,279
Air Quality
Within 50 feet of highway or major road
5,529
Energy Conservation
Within 50 feet of buildings Within 100 feet of forest tracts (contiguous tree canopy >25 acres)
112,656
Wildlife Habitat
57,000
237,175
CITYWIDE TOTAL Figure 16: Number of planting sites per acre within PNAs.
Figure 17: Planting site prioritization by criteria
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Planting sites within each ward ranged from 18,999 sites (Ward 1) to 29,151 (Ward 8). Schools criteria produced the least amount of planting sites (2,117), while planting sites for energy conservation totaled 151,704.
The City of Akron has developed a Master Tree Planting Plan, identifying specific tree varieties for specific locations. Using the data provided, tree planting in highpriority sites may be determined for each planting season. Figure 18: Number of total planting sites per ward Table 6: Number of planting sites per criteria in each ward.
Ward 1 2 3 4 5 6 7 8 9 10 TOTALS
Land Acres 3,610 3,879 3,547 3,482 3,101 4,534 3,621 6,155 3,662 3,738 39,330
Prioritization Factors Flood Plain
Riparian
Schools
Parks
City Owned
Energy
Air Quality
Habitat
652 208 665 715 31 519 1,743 874 2,403 402 8,212
1,325 317 606 771 281 802 1,560 1,375 2,386 742 10,165
52 224 150 209 160 269 270 251 205 313 2,103
1,433 896 1,676 1,787 936 993 1,817 1,900 1,622 1,584 14,644
2,037 674 2,117 1,410 1,575 866 691 5,314 1,789 806 17,279
5,108 11,218 10,503 12,508 10,068 13,387 13,317 12,106 12,732 11,709 112,656
300 295 1,052 491 698 742 614 192 739 406 5,529
7,708 5,608 2,491 4,518 3,769 5,536 2,784 15,430 3,738 5,418 57,000
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SUGGESTED CANOPY COVER GOALS A tree canopy goal should be physically, fiscally attainable and desired socially. UTC goal setting should be incorporated into landscape ordinances, tree preservation policies and planning documents, such as the comprehensive plan. Based upon the Master Tree Plan, revised in April 2013, a specific goal is to achieve a fully stocked forest. The City’s annual tree replacement program, funded with $100,000 generally affords to plant 310 trees citywide, which focuses on tree restoration. Based upon the 75th percentile rule, the suggested citywide goal for UTC is 40% (15,742 acres). This goal aligns with the suggested canopy goal of 40% for the region, as advocated by American Forests. Collective participation from the public works, residents, and business owners will be required to reach this goal. The following table demonstrates one of many possible planning scenarios to reach the suggested goal, incorporating diverse land management districts. Table 7 illustrates how each component of this assessment relates to the overall goal of increasing the health and resilience of Akron’s urban forests. Canopy goals are derived directly from mapped UTC within zoning categories. Percent goals are converted to acres using the Canopy Calculator to illustrate total area of canopy for meeting the goal. Planting site analysis identifies the potential for achieving a host of benefits provided by trees and forests. Table 7: Planning scenario to reach suggested UTC goal
UTC Existing Increase UTC % %
Total Goal Acres
Tree Planting Acres Supporting Plantings Sites Needed Benefits Needed Available
Land Use Type
Management
Street ROW
Parks & Maintenance
23%
7%
1,790
400
5,000
5,536
Air Quality
Residential
Private
47%
2%
10,569
545
34,290
151,704
Energy
Parks & Rec.
Parks & Maintenance
N/A
N/A
N/A
100
10,026
14,626
Habitat
43%
5%
559
50
1,751
2,117
Health
37%
3%
15,742
1,095
51,067
240,057
Institutional Public & Private CITYWIDE
Aspects of Increasing UTC: In order to effectively increase UTC in Akron, the City may consider incorporate 1) greater tree planting, 2) preservation of existing trees, and 3) establishing areas suitable for forest regeneration. Areas suitable for regeneration include:
Areas adjacent to large patches of tree canopy and forest Areas within a riparian buffer (i.e. public conservation lands along the Little Cuyahoga River) Where soils will experience conditions of flooding or high saturation Vacant or abandoned properties
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RECOMMENDATIONS PPA Impervious, primarily parking lots, covers roughly 7,022 acres (18%) of the City. This project mapped land cover across the City of Akron, identified 237,175 possible planting locations with extensive attributes, assessed benefit values of current and future canopy cover, and developed data and tools allowing managers to identify where urban trees can be planted for specific purposes. Based on the results of this work, the following broad recommendations are provided on how to best use these data, tools, and information to implement urban tree canopy objectives in Akron.
LAND COVER ANALYSIS Disseminate the land cover data to diverse partners for urban forestry and other applications while the data is current and most useful for decision-making and implementation planning. Re-assess canopy cover in no less than 10-year intervals, and use LiDAR data if available, aiming for 95% overall accuracy.
ECOSYSTEMS SERVICES & PRIORITY PLANTING SITES Overall Use the results to develop targeted presentations for city leaders, planners, engineers, resource managers, and the public on the functional benefits of trees in addressing environmental issues. Conduct i-Tree or similar ecosystem services analysis studies with local field data collection input to better understand and quantify forest structure, function and value. Air Quality This study identified 2,788 acres of possible planting area (Total PPA) within street rights-ofway. Officials can partner to target canopy increases in the corridors as an air pollution mitigation strategy. With 5,529 potential planting sites near major roads, tree planting and maintenance will help reduce the urban heat island effect and formation of ground-level ozone. Conduct tree planting along highways 76, 77 and 277 corridors where tree canopy is low, and where canopy would reduce the impact of noise pollution and enhance air quality. Energy Conservation Develop strategies to plant trees for energy efficiency. This study identified 112,656 potential planting locations near residential homes. 11 of 21 neighborhoods have less than 30% UTC and should be targeted for energy conservation from trees. Encourage the use of free online tools such as i-Tree Design to determine proper placement of trees around homes to maximize energy efficiency benefits. Encourage local electric utilities to partner with the Arbor Day Foundation and start an “Energy Saving Trees” program.
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Stormwater & Water Quality Field-verify and prioritize plantings in Watersheds, such as the City of Akron Watershed, where canopy cover averages just 33% and polluted stormwater runoff can enter the Cuyahoga River. 10,165 planting sites were identified in riparian corridors, prime areas where tree canopy can improve impaired water quality. Work with the Stormwater Management Program and others to prioritize areas for restoration. To determine the most up-to-date stormwater benefits, engage local experts to periodically utilize user-friendly i-Tree Hydro beta software as provided in the assessment. Involve the city’s stormwater engineers in this process to inform them further on the benefits trees have on stormwater mitigation, and the money it can save their department. Promote the use of trees and forests as stormwater Best Management Practices (BMPs), where appropriate. To reduce the flow of contaminated runoff into surface waters, develop, implement, and enforce programs and policies to plant and maintain large trees in parking lots.
GOAL SETTING Establish canopy cover goals for the city, wards, neighborhoods, watersheds and zoning in a collaborative, multidisciplinary planning process. Use data from this assessment along with PlanIt Geo’s “Canopy Calculator Tool” and suggested goals in this report to play with scenarios and drive discussions. Aim for tree species diversity in planting practices and determine desired levels of service in landscape design for new and redevelopment that result in a sustainable community forest.
PLANNING Work closely with the City of Akron Engineering Bureau, Parks and Maintenance, GreenPrint Akron, and other entities to enhance the existing Master Tree Plan. Increase UTC in Commercial/Industrial zones, which have 54% and 56% Total PPA, respectively. Host the UTC data and potential planting sites in a web-mapping application focused on urban forest planning. Use the tool to engage public/private partners to advance urban forest benefits.
Maximizing the Urban Forest: Community Objectives In order for Akron to successfully reach and maintain a higher tree canopy goal, collective commitments must be met by City officials, business owners, and residents. With the attainment of this UTC assessment, continuing objectives include: Involvement of large private and institutional land holders Citizen-municipality-business interaction and involvement in urban forest management Intense management and maintenance of publicly owned trees Municipality-wide funding for a comprehensive urban forest management plan
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SUMMARY Akron’s urban forest is a living resource that changes through natural and human processes. Managing UTC requires an understanding of where trees are, where they can be planted equitably to maximize benefits, and how to work within regulatory and physical restrictions to achieve goals. Akron’s UTC Assessment provides an accurate benchmark and tools to assist in the City’s near and long-term vision of urban natural resource management. Some highlights from this study include: 37% (14,647 acres) of Akron land area is covered by tree canopy with 44% (17,292acres) available for addition tree planting (Total PPA). Wards ranged from 28% UTC (991 acres in Ward 3) to 55% UTC (3,405 acres in Ward 8). Residential zoning comprises 55% (21,465) of total land area. With 10,024 acres of UTC, this makes up 68% of all UTC. Additionally, residential districts average 40% (8,631 acres) PPA. Commercial and industrial zones have 18% (585 acres) and 25% (853 acres) UTC respectively. Of Akron’s ten watersheds, Portage Lakes (Tuscarawas River) had the lowest UTC at 29% (2,577 acres) and Boston Run (Cuyahoga River) had the highest percent UTC at 60% (3,151 acres). Neighborhoods ranged from 14% (162 acres) in Downtown Akron to 60% (1,859 acres) in Northwest Akron. Akron’s tree canopy currently removes nearly 994,000 pounds of air pollutants annually, valued at $4M per year, and existing trees mitigate 1.8% of stormwater runoff. An increase of 3% canopy to 40% overall UTC increase the stormwater benefit by 8%. A detailed an accurate baseline of land cover has been thoroughly analyzed and presented in this report. An ongoing challenge will be to balance new development with the protection and conservation of environmental values related to forest cover such as energy conservation, air quality, and climate adaptation related to carbon storage and stormwater mitigation. The social, environmental, and economic benefits of urban trees and forests are an incentive to continue in this direction.
Figure 19: Average UTC in regional cities
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APPENDIX Additional details on the City of Akron’s 2013 urban tree canopy assessment are provided including supporting information on:
A1: Glossary of Terms A2: Comprehensive Assessment Boundary Results A3: Urban Forest Self Evaluation; Criteria & Indicators A4: Canopy Calculator A5: USFS Table for Increasing Forest Cover within Watersheds A6: Land Cover Classification Accuracy Assessment A7: i-Tree Hydro (beta) Methodology
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A1: GLOSSARY OF TERMS Air Quality – The quantity of particulates and other pollutants present in a volume of air relative to necessary compounds such as oxygen. Trees improve air quality by absorbing and trapping air pollutants such as particulate matter, ozone, sulfur dioxide, carbon monoxide, and CO2 and by decreasing volatility by lowering air temperatures. Carbon Sequestration – The rate that carbon is removed from the atmosphere by trees. Carbon is considered a very important element because of its recognized influence on climate regulation as a greenhouse gas. Carbon Storage – Cumulative amount of carbon stored in the stems, branches and roots of trees over time. Ecosystem Services – Direct and indirect benefits provided by natural systems. The most common ecosystem services associated with urban trees and forests are air quality improvement, carbon sequestration and storage, energy conservation, and storm water mitigation. Energy conservation – The amount of energy saved due to the presence of trees. Summer cooling through shade, and by wind blocking in the winter reduces total energy used. Geographic Information Systems – Computer mapping systems used to understand how resources are distributed across the Earth’s surface. Impervious Land Cover – Hardscape surfaces that do not allow rainfall to infiltrate the soil (Buildings, roads, parking lots). i-Tree Design– As part of the i-Tree suite developed by the USDA Forest Service, this tool calculates benefits of trees on a property PPA Vegetation – (Possible Planting Area) associated with vegetation and open space. These are areas where tree planting is possible. Urban Heat Island Effect – refers to developed areas that are hotter than surrounding rural areas due to the abundance of man-made materials which absorb the sun’s energy much more than trees or other plants, and in turn warm the air around them (Center for Environmental Studies, Brown University, “Trees and the Urban Heat Island Effect”, 2010). UTC – (Urban Tree Canopy) is defined as the layer of leaves and stems of trees that cover the ground when viewed from above. Stormwater Runoff Mitigation and Water Quality – Important ecosystem services related to precipitation events, hydrologic cycles, and urban forests. Trees reduce stormwater runoff and improve water quality by intercepting rainfall, increasing soil permeability, and evapotranspiration.
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A2: COMPLETE ASSESSMENT BOUNDARY RESULTS The following maps and tables on pages 32-39 provide more comprehensive results for each boundary assessed in this study.
UTC results by Wards
Figure 21: Percent UTC by Ward Figure 20: Percent Total PPA by Ward
Figure 22: Percent possible planting area Vegetation by Ward
An Assessment of Urban Tree Canopy in Akron, Ohio
Figure 23: Percent Possible Planting Area Impervious by Ward
31
Table 8: Complete UTC results for Akron Wards Ward
Total Acres
Total Land Acres
UTC Acres
UTC %
% of Total PPA (Veg.) PPA (Veg.) PPA (Imp.) PPA (Imp.) Total PPA Total PPA Uns. UTC Uns. UTC UTC Acres % Acres % Acres % Acres %
1
3,645
3,610
1,642
45%
11%
843
23%
528
15%
1,371
38%
632
17%
2
3,899
3,879
1,545
40%
11%
801
21%
831
21%
1,632
42%
721
18%
3
3,565
3,547
991
28%
7%
889
25%
902
25%
1,791
50%
783
22%
4
3,493
3,482
1,279
37%
9%
1,057
30%
540
16%
1,597
46%
616
17%
5
3,105
3,101
898
29%
6%
841
27%
688
22%
1,529
49%
678
22%
6
4,539
4,534
1,376
30%
9%
1,152
25%
863
19%
2,015
44%
1,147
25%
7
3,756
3,621
1,035
29%
7%
1,146
32%
643
18%
1,789
49%
931
22%
8
6,219
6,155
3,405
55%
23%
1,487
24%
533
9%
2,020
33%
794
12%
9
3,812
3,662
1,071
29%
7%
1,083
30%
800
22%
1,883
51%
858
19%
10
3,755
3,738
1,379
37%
9%
969
26%
693
19%
1,662
44%
713
19%
TOTAL
39,787
39,330
14,623
37%
100%
10,267
26%
7,022
18%
17,289
44%
7,875
20%
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UTC Results by Watersheds
Figure 24: Percent Total PPA by Watershed
Figure 25: Percent PPA Vegetation by Wards
Figure 26: Percent PPA Impervious by Wards
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Table 9: Complete UTC results for Akron Watersheds Watersheds
Total Land Acres
UTC Acres
UTC %
% of Total PPA (Veg.) PPA (Veg.) PPA (Imp.) UTC Acres % Acres
PPA (Imp.) %
Total PPA Acres
Total PPA %
Boston Run
5,220
3,151
60%
22%
1,172
22%
353
City of Akron
10,755
3,589
33%
25%
2,560
7%
1,525
29%
24%
2,395
22%
4,955
46%
Fish Creek
1,516
655
43%
5%
308
20%
279
18%
588
39%
Headwaters
725
217
30%
2%
270
37%
61
8%
331
46%
Mud Brook
856
383
45%
3%
292
34%
95
11%
387
45%
Pigeon Creek
5,227
2,093
40%
14%
1,510
29%
744
14%
2,254
43%
Portage Lakes
8,869
2,577
29%
18%
2,568
29%
1,951
22%
4,519
51%
Wingfoot Lake Outlet
5,931
1,881
32%
13%
1,499
25%
1,104
19%
2,604
44%
Yellow Creek
258
101
39%
1%
91
35%
40
15%
130
51%
TOTAL
39,357
14,647
37%
100%
10,270
26%
7,022
18%
17,291
44%
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UTC Results by Neighborhoods
Figure 28: Percent Total PPA by Neighborhoods
Figure 27: Percent PPA Vegetation by Neighborhoods
Figure 39: Percent PPA Impervious by Neighborhoods
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Table 10: Complete UTC results for Akron Neighborhoods
Neighborhood
Total Total Acres Land Acres
UTC Acres
UTC %
PPA (Veg.) Acres
PPA (Veg.) %
PPA (Imp.) Acres
PPA (Imp.) %
Chapel Hill
1,535
1,534
457
30%
338
22%
453
30%
Downtown Akron
1,168
1,162
162
14%
244
21%
401
East Akron
2,268
2,264
495
22%
705
31%
553
Elizabeth Park Valley
1,352
1,342
627
47%
273
20%
243
Ellet
3,654
3,652
1,011
28%
937
26%
691
Fairlawn Heights
890
890
530
60%
202
23%
Total PPA Total PPA Uns. UTC Uns. UTC Acres % Acres % 791
52%
287
19%
35%
646
56%
361
31%
24%
1,258
56%
514
23%
18%
516
38%
209
15%
19%
1,628
45%
1,015
28%
54
6%
256
29%
104
12%
Firestone Park
2,100
2,050
506
25%
591
29%
512
25%
1,103
54%
491
22%
Goodyear Heights
3,032
3,024
1,351
45%
782
26%
426
14%
1,208
40%
472
15%
Highland Square
1,036
1,036
427
41%
233
23%
172
17%
405
39%
204
20%
Kenmore
2,452
2,365
559
24%
703
30%
563
24%
1,266
54%
627
23%
Lane-Wooster
1,106
1,103
316
29%
305
28%
247
22%
552
50%
238
21%
Merriman Valley
3,227
3,148
1,850
59%
774
25%
221
7%
995
32%
381
10%
Middlebury
1,005
999
273
27%
227
23%
271
27%
498
50%
234
23%
North Hill
1,413
1,405
475
34%
330
24%
264
19%
595
42%
343
24%
Northwest Akron
3,126
3,115
1,859
60%
615
20%
238
8%
853
27%
415
13%
Rolling Acres
1,080
1,079
372
34%
335
31%
216
20%
551
51%
157
14%
South Akron
604
604
157
26%
152
25%
142
23%
294
49%
153
25%
Summit Lake
687
626
163
26%
179
29%
135
22%
314
50%
209
24%
University of Akron
844
844
164
19%
170
20%
265
31%
435
52%
246
29%
Wallhaven
1,010
1,001
434
43%
248
25%
192
19%
439
44%
137
13%
West Akron
3,082
3,080
1,137
37%
962
31%
445
14%
1,407
46%
538
17%
TOTAL
36,669
36,323 13,325 37%
9,306
26%
6,704
18%
16,010
44%
7,333
20%
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UTC Results in Street Rights-of-Way by Wards
Figure 30: Percent Total PPA in Street ROW by Ward
Figure 31: Percent PPA Vegetation in Street ROW by Ward
Figure 32: Percent PPA Impervious in Street ROW by Ward
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Table 10: Complete UTC metrics in street Rights-of-Way by wards
Ward
Total Acres
Total Land Acres
UTC Acres
UTC %
1
457
456
111
24%
7%
83
18%
111
24%
194
43%
152
33%
2
544
544
126
23%
8%
91
17%
131
24%
222
41%
196
36%
3
809
806
122
15%
8%
175
22%
214
27%
389
48%
298
37%
4
671
671
180
27%
12%
166
25%
114
17%
280
42%
212
32%
5
676
675
122
18%
8%
124
18%
167
25%
291
43%
263
39%
6
705
705
145
21%
9%
161
23%
153
22%
314
45%
245
35%
7
667
660
157
24%
10%
122
19%
142
22%
264
40%
246
37%
8
753
744
283
38%
18%
162
22%
99
13%
261
35%
209
28%
9
780
734
142
19%
9%
160
22%
159
22%
319
43%
319
43%
10
606
606
143
24%
9%
114
19%
141
23%
254
42%
209
34%
TOTAL
6,669
6,601
1,531
23%
100%
1,357
21%
1,431
22%
2788
42%
2,350
36%
% of Total PPA (Veg.) PPA (Veg.) PPA (Imp.) PPA Total PPA Total PPA Uns. UTC Uns. UTC UTC Acres % Acres (Imp.) % Acres % Acres %
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A3: URBAN FOREST SELF EVALUATION ; CRITERIA & INDICATORS The table below illustrates Criteria and Indicators (Clark 1997) to self-evaluate various components necessary for an effective and sustainable urban forest model. This is a useful tool in guiding the process of developing an urban forest management plan.
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A4: CANOPY CALCULATOR To assist in advanced UTC goal setting, Plan-It Geo’s Canopy Calculator (MS Excel) tool is provided as an advanced but easy-to-use tool to the City of Akron. The City may quickly and easily enter various goals and determine future tree canopy cover and tree planting scenarios.
Figure 33: Screenshots of Akron’s UTC Calculator
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A5: INCREASING FOREST COVER WITHIN WATERSHEDS Recommendations for maintaining and increasing forest cover, taken from the US Forest Service’s Urban Watershed Forestry Manual, Part 1: Methods for Increasing Forest Cover in a Watershed.
Figure 34: Goals, objectives and techniques to increase forest cover within watersheds.
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A6: LAND COVER CLASSIFICATION ACCURACY ASSESSMENT Akron Land Cover Classifications This report describes the methods used and generated results in mapping land cover types across the City of Akron. National Agricultural Inventory Program (NAIP) aerial photography from 2011 and GIS data were combined to map five land cover classes: (1) Tree Canopy, (2) Impervious Surface, (3) Green Vegetation, (4). Soil and Dry Vegetation, and (5) Water. Object-based image analysis (OBIA) was used to map trees, other vegetation, impervious surfaces and soil/dry vegetation areas. Impervious surfaces were augmented with existing buildings (provided by MS) and by buffering existing road centerlines. Water was mapped using features provided in addition to manual digitizing at a 1:1,000 scale. Additional Land Cover Products Two additional land cover products related to impervious areas have been prepared for the City. A Comprehensive Impervious raster was created by joining input data provided by Akron (Roads, Buildings, and Parking Lots) with impervious areas mapped in the image classification procedure. The dataset breaks impervious areas down by type and allows users to see the impervious extent independent of overhanging canopy cover.
The Canopy Cover over Impervious raster is comprised the three classes of interest: (1) Tree Canopy, (2) Classified Impervious, and (3) Tree Canopy over Impervious. Classes 1 and 2 are extracted directly from the five-class land cover, while class 3 is derived by overlaying tree canopy with the Comprehensive Impervious raster discussed above. This dataset is helpful for identifying where impervious surfaces are covered by existing tree canopy which is a large benefit for reducing stormwater runoff.
Leaf-on 2011 NAIP 4band aerial imagery
NAIP Natural Color with Trees
CIR (Color Infrared) NAIP with trees
Figure 35: This graphic depicts various imagery used in land cover classification.
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Accuracy Assessment Classification accuracy serves two main purposes: First, accuracy assessments provide information to technicians producing the classification about where processes need to be improved and where they are effective. Secondly, measures of accuracy provide information about how to use the classification and how well land cover classes are expected to estimate actual land cover on the ground. Even with high resolution imagery, very small differences in classification methodology and quality can have a large impact on overall map area estimations. The classification accuracy error matrix illustrated in Table 1 contains confidence intervals that report the high and low values that could be expected for any comparison between the classification data and what actual, on the ground land cover was in 2011. One thousand (1,000) sample points were randomly distributed across the study area and assigned a random numeric value. Sorting from lowest random value to highest, each sample point was referenced using the NAIP imagery and assigned one of the five land cover classes (Reference ID) mentioned above. Random values ensure sample points are geographically distributed across the entire study area. An automated script is then used to assign values from the classification (Evaluation ID). Misclassified points (where reference ID does not equal evaluation ID) and corresponding land cover are inspected for necessary corrections. The procedure was repeated until an acceptable accuracy percent and classification quality are achieved.
Reference Data
Classification Data
Tree Canopy Vegetation Tree Canopy Vegetation Impervious Soil / Dry Veg. Water Total
397 8 13 0 0 418
2 218 7 5 0 232
Overall Accuracy = Producer's Accuracy Tree Canopy Open Space / Grass Impervious Bare Ground / Soil Water
95% 94% 94% 78% 94%
Impervious
Soil / Dry Veg.
13 3 283 3 0 302
Water 2 1 2 21 1 27
Total Reference Pixels 0 414 0 230 1 306 0 29 17 18 18 997
94% User's Accuracy Tree Canopy Open Space / Grass Impervious Bare Ground / Soil Water
96% 95% 92% 72% 94%
Figure 36: Error Matrix Interpretation
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Sample Error Matrix Interpretation Statistical relationships between the reference pixels (representing the true conditions on the ground) and the intersecting classified pixels are used to understand how closely the entire classified map represents the Akron landscape. The sample error matrix represents the intersection of reference pixels manually identified by a human observer (columns) and classification category of pixels in the classified image (rows). The white boxes along the diagonals of the matrix represent agreement between the two pixel maps. Off-diagonal values represent the number pixels manually referenced to the column class that were classified as another category in the classification image. Overall accuracy is computed by dividing the total number of correct pixels by the total number of pixels reported in the matrix (392+204+352+4+10 = 962 / 996 = 97%), and the matrix can be used to calculate per class accuracy percent’s. For example, 394 points were manually identified in the reference map as Tree Canopy, but only 392 of those pixels were classified as Tree Canopy in the classification map, with 2 pixels misclassified as Impervious. This relationship is called the “Producer’s Accuracy” and is calculated by dividing the agreement pixel total (diagonal) by the reference pixel total (column total). Therefore, the Producer’s Accuracy for Tree Canopy is calculated as: (392 / 394 = 0.99), meaning that we can expect that 99% of all tree canopy in the Akron study area were classified as Tree Canopy in the classification map. Conversely, the “User’s Accuracy” is calculated by dividing the number agreement pixel total by the total number of classified pixels in the row category. For example, 392 classification pixels intersecting reference pixels were classified as Tree Canopy, but 19 pixels were identified as Impervious, 13 as Impervious and 3 as Vegetation in the reference map. Therefore, the User’s Accuracy for Tree Canopy is calculated as: (392 /414 = 0.95), meaning that pixels classified as Tree Canopy the classification were actual tree canopy in Akron. It is important to recognize the Producer’s and User’s accuracy percent values are based on a sample of the true ground cover, represented by the reference pixels at each sample point.
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I-TREE HYDRO (BETA) METHODOLOGY Methods: Plan-It Geo modeled the effects that Akron’s tree canopy has on the amount of total stormwater runoff within the city. I-Tree Hydro version 5.0 was used for this modeling. Version 5.0 of i-Hydro is new as of October 2013, it represents a complete overhaul of the application from version 4, and is still in the beta testing phase. I-Tree Hydro uses elevation, local weather, and stream flow gauge data combined with 20+ environmental parameters that can be defined by the user to fit the model to local runoff conditions. There are 5 steps to running an i-Hydro model: Step 1- Project Area Information (Choose Data Sources) – In the first step, basic information about the location of the project is entered along with the time period for which to run the model. User’s also choose which stream gauge to use for measuring actual observed flow, which weather station to use for precipitation and temperature data, and which elevation file they wish to use (either a digital elevation model that has been manually clipped to the AOI using GIS, or one of i-Hydro’s pre-processed topographic index files which exist for states, counties and municipalities in the US). Plan-It Geo used the time frame of Jan. 1, 2010 to Dec. 31, 2010, the stream gauge located at lock #1 on the Ohio & Erie Canal in central Akron, the weather station at Akron-Canton Airport, and the pre-processed topographic index for the city of Akron.
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Step 2 Enter Landcover Parameters – In step 2, users enter the percentage of landcover types across the AOI. User’s also input the percentage of tree canopy that overhangs impervious surfaces vs. pervious ones. Plan-It Geo used the landcover percentages that were obtained in the UTC assessment. It was assumed that 10% of Akron’s tree canopy overhangs impervious surfaces.
Step 3 – Hydrological Parameters (Calibrate Model) – The third step in running i-Hydro is to adjust the user-defined model parameters, there are 22 in all. This step is a trail-and-error process where the user adjusts any or all parameters and then calibrates them to compare the modeled base case flow to the actual observed flow. This can be time intensive, as there are many parameters to experiment with and getting a “good fit” can be difficult. The screen shot below shows the parameters that Plan-It Geo used. It should be noted that the model parameters in i-Hydro cannot be interpreted as measurable, realworld values. Discussions with the i-Tree environmental modelers yielded this reasoning: “i-Tree Hydro is a lumped parameter model. There is debate on whether the parameters of a lumped parameter model can be obtained by measurement and whether the calibration is necessary for this type of conceptual model. There is general agreement that the parameters of a lumped model cannot be directly measured in the field mainly because: a. It is almost impossible to generate a representative value for large heterogeneous area.
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b. Models, especially lumped models, generally cannot capture all the dynamic real processes, so the parameters are actually aggregates of all the processes (including those explicitly included in the simulation and those that are not). 2.) To get the best parameters for the system, calibration is necessary. However, the calibrated parameters should not be interpreted as the values that can be obtained in field measurement. It is best to use the calibration instead of applying the “indicative” values to the area. This relates to the lumped model limitations of mapping one value to an entire area.”
Step 4 – Define Alternative Scenario - The final step before running the model is to define the alternate scenario to model. Defining a scenario consists of entering the same landcover parameters as in step 2, but with different values in order to predict what might happen if changes occur. In order to isolate the benefit of trees alone, Plan-It Geo’s alternate scenario is a zero tree canopy scenario where all of Akron’s tree canopy has been removed. All tree canopy in the alternate scenario is assumed to be removed with no changes to the ground surface below the tree. In accordance with the assumed cover below tree canopy from step 2, the trees must be replaced with 90% pervious cover and 10% impervious cover. It can be seen below that the alternative case reassigned 90% of tree canopy area (33% of total
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city area) to herbaceous cover and 10% of the tree canopy area (4% of total city area) to impervious cover. Water, soil and shrub cover were unchanged from the base case to the alternative case.
Step 5 Run Model and Review Results – i-Hydro’s key results are three values, expressed in cubic meters of water, that represent the amount of total runoff within the city over the specified time frame. a. Actual Observed Flow – This is the actual amount of runoff that was measured by the stream gauge b. Base Case Flow – This is the amount of runoff the model predicts, based on the existing landcover conditions. c. Alternative Case Flow – This is the amount of runoff the model predicts, based on the no tree scenario Plan-It Geo did this “No tree replacement” process four separate times to create scenarios that predict the effects of changes in tree cover on stormwater runoff. The primary scenario modeled the effects of Akron’s current 37% tree cover. Three change scenarios modeled what would happen if Akron’s canopy cover decreased to 30%, increased to 40%, and increased to 45%.
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Results: Running the i-Hydro model as described above yielded the following values for total observed flow, total modeled flow in base case and total modeled flow in alternative case. These results reflect only the Existing 37% scenario, results for the three canopy change scenarios are very similar with only changes in the modeled base case flow and modeled alternative case flow Actual Observed
Modeled Base Case
Modeled Alternative Case
Net Benefit
Decrease 30%
11,108,689
14,482,764
14,688,277
205,513
Existing 37%
11,108,689
14,431,586
14,690,451
258,865
Increase 40%
11,108,689
14,410,610
14,690,451
279,841
Increase 45%
11,108,689
14,376,146
14,691,551
315,405
*all values are in cubic meters per year Modeled benefit of existing urban tree canopy on total runoff in Akron
15,000,000 13,000,000
Amount of disagreement between modeled runoff for existing conditions and actual measured runoff
11,000,000 9,000,000 7,000,000 5,000,000 3,000,000
1,000,000 -1,000,000
Actual Observed Modeled Base Case
Modeled Atlernative Case
Graphical representation of results for Existing 37% scenario
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Discussion of Results
The graph above compares the total amount of runoff in the one year time frame for the base case and the actual observed in the existing 37% UTC scenario. There is a significant disagreement between the measured amount of runoff at the stream gauge and what the model predicts for the base case. Discussions with the environmental modelers responsible for i-Hydro revealed several possible causes of this disagreement.
The fit is sensitive to a poor match in rainfall and runoff data. I-Tree is working to reduce this error by providing daily fit instead of hourly, and by using gage-averaged or radar rainfall We chose the "Ohio / Erie Canal" stream gauge data which entails manmade influences coming into this “system” because it’s a canal (rather than a pure functioning hydrologic watershed w/o diversions/etc.). We are unsure whether (or to what degree) that is influencing our fit.
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The graph above compares the total amount of runoff in the one year time frame for the base case and the alternative case for the existing 37% UTC scenario. When comparing the total modeled runoff in the current system (base case) to one in which all tree canopy has been replaced by 90% herbaceous cover and 10% impervious cover (alternative case) the net difference is 258,865 cubic meters per year.
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REFERENCES "Akron, Ohio Master Tree Planting Plan." Akron, OH, 2013. Clark, N. Matheny, G. Cross, V. Wake. "A Model of Urban Forest Sustainability." Journal of Arboriculture, 1997: 23: 17-30. EPA. Green & Gray Infrastructure Research. 2013. http://www.epa.gov/nrmrl/wswrd/wq/stormwater/green.html#green. Nowak, David J. Strategic Tree Planting as an EPA encouraged Pollutant REduction Strategy: How Urban Trees can Obtain Credit in State Implementation Plans. Syracuse, NY: Northern Reserach Station, n.d. Poracsky, Joseph. Urban Forest Canopy Cover in Portland Oregon. 2004. http://web.pdx.edu/~poracskj/Cart%20Center/psucc200404-047.pdf.
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