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Mitigating the Heat Island Effect

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Mitigating the Heat Island Effect MITIGATING THE HEAT ISLAND EFFECT ANALYSIS COMPLETED BY PROFESSIONAL ENVIRONMENTAL SERVICES, LLC STRATEGIC TREE PLANTING PLAN This project and the following report was made possible through funding from the Massachusetts Executive Office of Energy and Environmental Affairs’ Municipal Vulnerability Preparedness (MVP) Grant Program. t 27 Rt 9 and R iangle/ ection Golden Tr Inters ll Natick Ma HEAT ISLANDS IN Land Surface Temperatures along Route 9 in Natick NATICK N Compromised human health and comfort, Increased energy consumption, Impaired water quality, and Urban areas are commonly known for being Elevated pollutants and greenhouse gases. warmer than their rural counterparts, due to a phenomenon called the “heat island effect.” Unfortunately, climate change is expected to Heat islands are caused when an abundance of compound the heat island effect. Annually, buildings and pavement result in conditions Natick and other communities in the Charles that cause land surface temperatures to exceed River Basin can expect 10 to 35 more days air temperatures (Wong, 2014). with daily maximum temperatures over 90 °F by 2050, and 15 to 76 more days over 90 °F by However, heat islands are not limited to big 2100 (Northeast Climate Science Center, cities. An analysis using satellite imagery from 2018). Higher temperatures will mean hotter August 30, 2010 (a day when the high at Logan heat islands. Airport was recorded at above 90 degrees) found significant variation in land surface temperatures across the Metro Boston region, with hot spots extending into the suburbs. Climate change will compound the heat In Natick, where more than 25% of the Town is considered impervious surface (MassGIS, 2017), island effect. a clear connection between the built environment and surface temperatures was found. Areas including the complex along Charles River Basin communities are also Route 9 and Natick Center, where large black expected to experience an increase in heavy roofs and parking lots abound, were found to rainfall events. Days with more than an inch of have surface temperatures reaching near 130 precipitation are expected to increase from degrees Fahrenheit —"hot enough to fry an approximately 7.6 days/year to 10.6 days/year egg". (MAPC, 2015). by 2050 (Northeast Climate Science Center, 2018). In these events, the same impervious The negative impact of heat islands and their area that contributes to high surface corresponding high temperatures include: temperatures will carry a higher concentration of stormwater pollution into local water bodies. Page 1 LAND SURFACE TEMPERATURES IN NATICK LEGEND Land Surface Temperatures High: 140 in degrees, Fahrenheit Data Sources: MAPC, MassGIS Land surface temperatures created Low: 64 from LANDSAT images from 2010 Natick Town Line N Page 3 HOW TREES CAN HELP Trees and vegetation reduce heat islands by containers direct stormwater runoff to a tree providing shade and through box, where it is filtered by vegetation and soil evapotranspiration. before entering a catch basin. Shade from leaves and branches can reduce When planting near buildings, deciduous trees surface temperatures below the tree should be located on the western side, with a canopy by 20-45°F (Akbari, 1997). These goal of shading windows and portions of roof. cooler surfaces, in turn, reduce the heat transmitted into the atmosphere and nearby buildings. ADDITIONAL BENEFITS OF PLANTING TREES Evapotranspiration lowers air temperatures Trees bring benefits beyond mitigating heat by using heat from the air to evaporate islands including: water. This process can reduce peak temperatures by 2–9°F (Kurn, 1994). Reduced energy use: Trees that directly shade buildings decrease demand for air Trees can also reduce runoff by intercepting conditioning. rainfall and absorbing water that would otherwise be diverted to municipal storm Improved air quality and lower greenhouse drains. In Sacramento, trees in full leaf were gas emissions: By reducing energy demand, found to capture more than 35 percent of trees decrease the production of associated rainfall that came in contact with their air pollution and greenhouse gas emissions. canopies (Xiao, 1998). They also remove air pollutants and store and sequester carbon dioxide. MAXIMIZING IMPACT Reduced pavement maintenance: Tree The most effective heat island mitigation shade slows the deterioration of street plans focus on planting trees and vegetation pavement, decreasing the amount of in strategic locations to shade pavement and maintenance needed. buildings and reduce runoff. Improved quality of life: Trees and Trees can be planted around and in medians vegetation provide aesthetic value, habitat inside parking lots or along streets. Tree box for many species, and reduce noise. filters are another option in areas where ground surface is sparse. These in-ground (Taken directly from Wong, 2014) Natick Mall and Speen St Page 4 Add Rich's Impervious surface map South Natick Page 5 TREES IN NATICK According to the Massachusetts Urban & Community Forestry program, Natick has a forest canopy density percentage of 44%. The majority of these trees are located on private property. While Natick's tree canopy is strong versus NATICK IS A TREE CITY peer communities, it is vulnerable. The town continues to experience a high rate of Natick has received the Arbor Day development, which can have an adverse Foundation's Tree City USA designation, for effect on tree preservation. Pests and more than ten years. To receive this pathogens and the impacts of climate change designation, Natick must demonstrate it meets are also real threats. Trees on private four core standards of sound urban forestry properties are especially at risk to these management: maintaining a tree board or threats, as few local regulations exist to department, having a community tree protect trees from development and property ordinance, spending at least $2 per capita on owners may lack the knowledge and funds to urban forestry and celebrating Arbor Day. support tree health. PUBLIC TREES TOWN-WIDE TREE INVENTORY Public trees, including street trees, park trees The Town of Natick does not currently track or and trees on other Town land, are the monitor trees located on private property. responsibility of the Town of Natick’s Land However, a 2001 aerial survey of the town Facilities and Natural Resources Division. The identified more than 33,000 trees. Division maintains a Public Tree Inventory with information on each tree's species, age PROJECTS UNDERWAY class and monetary value. This is a working inventory and trees are added to the inventory Natick is in the process of updating local land in bulk on an annual basis. The database use regulations, including its general and currently has more than 500 trees recorded, zoning bylaws, to support low impact which are estimated to have a cumulative development and tree preservation. Proposed value of more than $7 million. changes are subject to approval by the community's local legislative body, a Once inventoried, trees are tagged with a representative Town Meeting, and are bronze or silver tag that can be used to expected to be presented for debate in stages inquire about specific attributes of a tree through 2020. online at: natickma.gov/treeplan The Town of Natick's Engineering Division is Current Public Planting Priorities also reviewing opportunities to better incorporate green infrastructure and tree Natick seeks to maximize the social and planting into its Complete Streets Plan. It has environmental benefit of every new public applied for funds to develop a design for a tree. Locations for future public trees are model Complete, Green Street, and, if awarded prioritized based on tree canopy per capita the grant, will seek to apply recommended ratios. Special attention is also paid to the guidelines to future roadway improvement town's low income and environmental justice projects. communities. WORKING TREE INVENTORY Add Rich's Impervious surface map LEGEND 2001 Ortho Tree Inventory Public Tree Inventory Natick Town Line Page 6 Page 7 TREE PLANTING PLAN Across these corridors, public property and streets were assessed, including: In collaboration with Professional Public tree planting areas such as Environmental Services, LLC, the Town of sidewalks, municipal buildings, municipal Natick identified 811 potential tree planting parking lots, public housing complexes, sites focused on reducing heat islands and roadways, parks, and other open spaces; associated stormwater runoff. Environmental Justice Protocol and Low Potential tree planting sites are located across Income areas, where populations are eight corridors with high recorded surface especially vulnerable to the impacts that temperatures, including: climate change has on their health and energy costs; and Golden Triangle (Speen St/Rte 9/Rte 30) Rte 9/Rte 27 Other private property, particularly parking Speen St/Rte 135 (shown as two maps) lots and hardscaped areas, where planting Natick Center could be targeted through public-private Housing Authority partnerships and future regulations. Northeast Natick Natick Army Labs Maps of each corridor and recommended West Natick planting locations are provided on the following pages. FIELD SURVEY & SITE ASSESSMENT Potential tree planting sites were identified using Google Earth maps and validated by an on-the- ground field survey. Each site was assessed for the following: Tree Category (Utility Corridor/Small Place; Non-Utility Corridor; Parks/Open Space) Growth Restrictions (Overhead Utilities; Underground
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