Keeping Weymouth Cool

KEEPING WEYMOUTH COOL

A HEAT ISLAND MITIGATION PLAN FOR A COASTAL TOWN

Prepared for the Weymouth Department of Planning and Community Development by

Ben Silverstone, Lion Waxman and Isabella Yeager The Conway School — Winter 2024

ACKNOWLEDGEMENTS

Our sincerest thanks to Andrew Hultin, the Conservation Administrator in Weymouth’s Department of Planning and Community Development, for being a core contact throughout the process of building this document and providing guidance on how to approach this project; along with Bob Luongo, director of the Department of Planning and Community Development; Harrison Carter, the Associate Grant Manager for the Mayor’s Office; and Frank Singleton, Vice Chair of the Conservation Commission. Thank you as well to Garrett Walsh, the GIS Administrator for Weymouth who provided the Conway team with mapping data and advice; Jay Donovan, the Town Engineer at Weymouth DPW; Teryn Hermenau, the Weymouth Public Health and Wellness Coordinator; and Stephen Reilly, the Parks and Recreation Director. Thank you to the community members of Weymouth who supported this process by showing up to the public engagement meeting, and to those who continued correspondence over email. This project could not have been completed thoroughly without your insight.

EXECUTIVE SUMMARY

Weymouth, Massachusetts, is a coastal town situated roughly 12 miles southeast of Boston, with a population of approximately 58,000 people. The town is experiencing the growing pains of being a village-oriented town in close proximity to a sprawling metropolis, with development pressure to boost their status as a bedroom community of Boston being a main conflict in town. Many municipal departments and town residents have expressed the feeling that development in town has not materialized in the ways that they hoped. Major renovations to village centers, state roads, and parks, along with multiple large housing, commercial, and industrial developments, have made some community members uncomfortable with the level of change being imposed on the town’s historic character and the town’s environment. Development pressure has brought to light concerns about declining water and air quality and the formation of urban heat islands, which pose significant public health hazards in the face of climate change. The town has made some progress in addressing tidal and inland flooding associated with more frequent storms, but has yet to study closely the effects of extreme heat on its infrastructure and ecology.

A close analysis of Weymouth’s existing conditions reveals that urban heat islands, inland stormwater flooding, and water quality decline are not separate issues to be studied and addressed separately; rather, they have shared roots in the composition of Weymouth’s land cover and urban form. Impervious surfaces in the urban landscape simultaneously absorb solar energy and radiate heat, generating the local heat island effect while also failing to infiltrate stormwater water, resulting in immense pressure on aging municipal infrastructure and severe degradation and pollution of urban wetlands. The loss of intact natural ecosystems and permeable soils supporting dense native vegetation results in a decreased capacity for ecosystem services to intercept pollution and cool the water, the ground, and the air through evapotranspiration and shading. Local zoning laws and design guidelines may have allowed urban form to progress in this direction, and may need to be updated in light of these findings. The analysis concludes with four major spatial patterns in Weymouth:

• Grey Streets: The overuse of impervious surfaces in the streetscape, leading to islands of contiguous asphalt between roads, sidewalks, parking lots and buildings;

• Big Roofs, Big Lots: The creation of large flat expanses of roof space and parking without integrated techniques to provide shading, cooling and stormwater infiltration, forming “asphalt archipelagos” which perforate ecological systems;

• Hot Neighborhoods: Residential areas in close proximity to heat islands without adequate shade, and a culture of extensive lawns and ornamental landscaping that are not equipped to meet Weymouth’s environmental challenges;

• Constrained Water Systems: Waterways and wetlands that are constrained too heavily by the built environment, inadvertently causing Weymouth to lose its most critical asset in terms of cooling the landscape and mitigating pollution.

In addition to intertwined causes, urban heat islands, stormwater flooding and pollution also have intertwined solutions. Tackling these issues simultaneously with integrated, nature-based solutions may be the most costeffective way to address looming environmental challenges. Ideally, these strategies could empower the municipality by helping them recognize their ability to influence land cover to great effect in the mitigation of climate change locally. Four strategies emerge from the spatial patterns identified in the analysis:

• Green and Complete Streets by building green infrastructure into Weymouth’s complete streets policy and better preserving existing tree canopy;

• Cool Roofs and Lots using updated design and materials guidelines, low-impact development, green stormwater infrastructure, and shading structures such as solar panels to ensure that the largest expanses of impervious surface in Weymouth are cloaked in vegetation;

• Green Neighborhoods which harness grassroots energy of homeowners to transform the aesthetic of neighborhoods, equipped with flourishing native plant communities, rain gardens, and permeable alternatives to impervious surfaces;

• Sponge Watersheds which turn Weymouth’s largest vulnerability into its greatest strength. The major tidal rivers and coves of Weymouth, their tributaries, headwaters and most importantly, their floodplains, could be restored to their maximum ecological function, radically increasing the cooling capacity of Weymouth’s natural spaces, connecting the city through water-rich greenways, and providing ample opportunities for outdoor recreation for residents and visitors.

These strategies combine and build on one another to in an attempt inspire a creative transformation in Weymouth’s approach to economic growth, development, and urban design.

INTRODUCTION

AN OVERVIEW OF WEYMOUTH

Weymouth, Massachusetts, is a coastal town situated roughly 12 miles southeast of Boston, with a population of around 58,000 people. Several major roads cross through the town, which has long been a bedroom community of Boston, while also supporting industry of its own along its major ports and rivers. The town can be split up into four distinct neighborhoods: coastal North Weymouth, a beach-dotted peninsula between the two major estuaries of the Fore and Back Rivers with its village center in Bicknell Square; Weymouth Landing, with its village center, The Landing, a historic gateway to the town at the mouth of the Fore River; East Weymouth, with its village center Jackson Square at the mouth of the Back River; and South Weymouth, a large mostly suburban area two the south of Weymouth which includes Great Pond and its watershed, Weymouth’s main source of water and largest forested area, with the village center, Columbian Square, located along the more developed strip of Route 18.

Weymouth proximity along the MA coastline. The town is just outside of the Boston’s metropolitan area, whose urbanized land alterations compared to forest are visible from space.

ECOREGIONS INFORM MUNICIPAL CHALLENGES

Ecologically speaking, the town straddles two major ecoregions: the Boston Basin, a highly urbanized region built on top of lowland forests and marshes in several major estuaries surrounding Boston Harbor; and the Coastal Plain, includes the coastal forests, wetlands, and ponds within a region of rolling hills surrounding the Boston Basin, including the slightly more rural south shore of Massachusetts. Both the ecological setting and the town character of Weymouth reflect this tension, which has relatively recently switched from a town meeting style of government to a city council representative style, and is experiencing the growing pains associated with being in close proximity to a rapidly growing and sprawling urbanized metropolitan area. The Boston metro area and the South Shore also have slightly different experiences of climate change, with Boston looking to armor itself from extreme heat, flooding, and pollution associated with urban conditions, while the South Shore is dealing largely with depleted aquifers, water quality issues, and major restructuring of remaining intact coastal ecosystems.

Weymouth

A map of the major ecoregions of Eastern Massachusetts.

THE NEED FOR CLIMATE RESILIENCE AND ADAPTATION

In 2018, Weymouth conducted a Municipal Vulnerability Plan (MVP) in order to study more closely its vulnerability to climate change and to access funds at the state level in order to tackle major environmental issues. The MVP found that Weymouth is dealing with the major challenges associated with both Boston and the Coastal Plains: Weymouth experiences extreme heat, flooding and pollution at a similar scale to highly urbanized areas, struggles to maintain an adequate water supply, and its intact coastal ecosystems are dwindling in the face of climate change and increased development pressure, unable to perform crucial ecosystem functions and services.

Weymouth immediately began the initial processes of tackling these challenges, with a 2021 Hazard Mitigation Plan describing in more detail the nature of Weymouth’s environmental hazards and steps to be taken to address them. These plans have materialized in the form of several projects to protect Weymouth’s coastline, map and renovate the town’s Municipal Stormwater System in order to comply with the newest MS4 permitting process, and efforts to restore ecological function to some of the town’s herring runs and urban tree canopy. The purpose of this plan is to delve in depth into the issue highlighted in the 2021 Hazard Mitigation Plan of extreme heat and the way it manifests in Weymouth as the urban heat island effect, without losing sight of Weymouth’s acute vulnerability to flooding as a coastal town, and its urgent need to address its stormwater system and water quality issues.

A summary of Weymouth’s major climate challenges. (Source: Town of Weymouth MVP)

WHAT IS THE URBAN HEAT ISLAND EFFECT?

The Urban Heat Island effect is the observed phenomenon of urbanized metropolitan areas being considerably warmer than surrounding rural landscapes. This occurs due to the combined effect of several properties of urban environments (source: EPA.gov):

Thermal Properties of Urban Building Materials:

Conventional building materials for urban roads, buildings, and roofs tend to be darkly-colored and impervious, causing them to behave like thermal batteries. This is especially true of asphalt, one of the most common materials in roads and roofs, but it is also true of concrete, bricks, and dark colored metals. Rather than reflect solar energy, these materials absorb it and begin to heat up. These materials often have a low specific heat capacity meaning that it takes less energy input for them to heat up, and also have high thermal conductivity, meaning that as air temperatures begin to cool off in the evening, these materials release their heat over time, causing consistently higher temperatures above and around them.

Waste Heat:

Metropolitan areas are densely populated with people. People’s bodies emit heat, and dense populations of people in a small space are sure to generate a lot of excess heat. Air conditioning units, a go-to technology for people which has become a necessity to remain cool during hot summers, release a considerable amount of waste heat into the air, as do cars, trucks, and industrial factories with a lot of machinery or generators.

Urban Design and Form:

Urbanized areas are often built up densely to maximize space. While this is an efficient use of valuable space,when buildings are situated close together or planes of impervious surface are completely contiguous with one another, large thermal masses are generated, where surface temperatures are consistently high without interruption. In areas where buildings are densely clustered, buildings behave like walls of a canyon, insulating the area and making it difficult for heat to escape and disperse. This is especially true when urban areas are built without considering wind direction, where tall buildings alter wind patterns and block breezes from flowing through and cooling the streets.

Reduced Natural Landscapes and Vegetative Cover:

In addition to generating thermal mass, as urban development expands, it can pave over, pollute, or severely confine vegetated or plantable spaces. Municipal agencies, especially when they are underfunded, may not be able to adequately care for and plan for the creation of more parks and green space in the face of development pressure. In addition, developed areas with dense clusters of buildings around roads may not leave adequate space for healthy street trees and roadside vegetation. Unlike impervious surfaces, the surfaces of leaves, wetlands, water bodies, and living soils actively cool areas around them through evaporation. Proper distribution of natural open space, in the form of street-side vegetation, green spaces, forests, wetlands and water bodies, is absolutely critical in preventing urban heat islands from forming (Ma et al. 2021)

Throughout this report, areas in Weymouth which have a high density of impervious surfaces and a low density of vegetation are referred to as urban heat islands (UHIs) or just heat islands, and are the main drivers of the urban heat island effect. In addition to generating dangerously high temperatures for people, heat islands are also closely associated with more severe pollution, as vehicle and factory emissions linger in the warm air above roads and in between buildings. Severe heat can also cause materials like asphalt to break down and release even more harmful chemicals. The next section explores how water which running off of these impervious surfaces can carry pollution and excess heat into local water bodies via the municipal stormwater system, exacerbating the public health hazards and environmental degradation associated with urban heat islands.

WHAT IS STORMWATER RUNOFF?

When precipitation falls in rural areas or in natural spaces, water is absorbed by soils and slowly infiltrates deeper into subsurface aquifers, or it is sucked up by plant roots and evaporated from their leaves in a process called evapotranspiration. If the soil is completely saturated with water, this water runs off the surface of the ground and collects in streams leading to larger bodies of water or to isolated wetlands, where it either infiltrates or evaporates. This process of precipitation, absorption/infiltration, and evaporation/evapotranspiration is part of the natural hydrological cycle.

However, when precipitation falls in urban areas, there is often not enough permeable surface to absorb the water, and a bulk of the water lands on impervious surfaces such as roofs or roads. Since these impervious surfaces cannot infiltrate water, large volumes of flowing water can quickly accumulate from rainfall on these surfaces, which is often referred to in urban design as stormwater runoff. In order to prevent flooding, roofs and roads are often graded so that water collects alongside curbs or in gutters and is conveyed to a storm drain, which leads to a municipal stormwater system, a system of pipes which conveys excess water into local natural areas and waterways. Stormwater systems are critical elements of urban infrastructure which provide crucial flood prevention by draining large areas of impervious surface, but many of them lack additional infrastructure needed to filter pollutants and sediments. Because of this, stormwater systems are a major source of pollution in urban and suburban waterways.

When water lands on impervious surfaces such as roads and parking lots, it picks up chemicals associated with automobiles such as motor oils, brake fluids, settled patinas of car exhaust and heavy metals. These pollutants can become major hazards in water bodies.

Large pieces of trash swept off the road by stormwatrer can clog up the storm sewer and cause it to fail, and smaller pieces can end up in waterways

Rooftops and other impervious surfaces collect large volumes of precipitation. This water does not infiltrate into the soil, but rather “runs off” in large volumes.

When water rushes through lawns, especially from heavy storm events or torrents of water coming out of a gutter, it does not infiltrate very efficiently. This water picks up excess fertilizer and pet waste and carries it into the storm drain. Excess Nitrogen and phosphorus, along with fecal coliform bacteria, are among the most common and most damaging pollutants in coastal waterways.

The bulk of stormwater coming off of impervious surfaces and lawns is collected by the Municipal Stormwater System, which drains the water, along with all of the pollutants it as picked up off of the streets. Often this water is conveyed directly to local waterways with minimal treatment.

Waterways cannot handle the loads of pollutants, nutrients, and sediment from urban stormwater systems, and water quality and structure often change dramatically in response to these new inputs, causing fish die-offs, eutrophication, erosion, and loss of native vegetation.

ADDRESSING CLIMATE RESILIENCE CHALLENGES IN TOWN

Weymouth’s 2021 Hazard Mitigation Plan stresses that flooding associated with more extreme precipitation events and tidal surge are a major concern for Weymouth, not just in the future, but currently. The report identifies the municipal stormwater system, which is aging and prone to failure, as a major risk to the town which must be updated in order to adequately deal with inland flooding and to prevent pollution and eutrophication of local waterways. However, there are significant costs associated with doing so, and it has taken decades for the state to update its own stormwater standards and best management practices, let alone fund the steps towards municipal compliance. Weymouth will need a major political and financial mobilization, with help from any source of funding available, in order to address the major hazards associated with its stormwater system.

When it comes to urban heat islands, however, the pathway towards mitigation has not yet been clearly delineated for the town. The Hazard Mitigation plan recognizes extreme heat waves to be a major hazard to the town and discusses how they are exacerbated by the urban heat island effect, creating conditions where temperature and air pollution can become hazardous, especially to people who work outdoors or vulnerable populations with chronic conditions. However, although extreme heat events are increasing in Weymouth, the 4 major heat events Weymouth has experienced (between 2011-2021) listed in the Hazard Mitigation Plan record 0 injuries, 0 deaths, and 0$ in property damage. This is likely inaccurate, as New England does not record heatrelated deaths, and the “slow-burn” nature of damage that heat can do to infrastructure makes the damage difficult to trace and quantify, though major damages such as heat-related blackouts are certainly possible in the future. However, due to data limitations, it’s possible that this major hazard is being overshadowed in Weymouth by the more visible challenges of sea-level rise and inland flooding. The next section illuminates the close relationship between heat islands and these more pressing issues for Weymouth.

A close up of the Heat Island Map for Weymouth can be found in the analysis section.

Data Source: Heat Island Severity in U.S. Cities, ArcMaps

Observed increase in annual mean air temperatures in the Boston region, measured from the Blue Hill Observatory, shows an increase of 3 degrees (F) since record keeping began in 1831.

(Source: 2021 Hazard Mitigation Plan)

The Northeast Climate Adaptation Science Center (NECASC) uses annual records of extreme heat events to project who future climate change scenarios will impact number of high heat days in the region. A Heat wave in Massachusetts is defined as three or more consecutive days above 90 degrees (F).

(Source: 2021 Hazard Mitigation Plan)

Heat index is the measure of heat based on how it feels to humans when humidity is factored in. The National Weather Service (NWS) issues a heat advisory when the heat index is forecast to exceed 100 degrees (F) for two or more hours, though hyperlocal conditions may create areas of exposure to dangerous levels of heat even if it is not forecast generally for the region.

(Source: 2021 Hazard Mitigation Plan)

HEAT ISLANDS AND STORMWATER ISSUES ARE NOT SEPARATE PROBLEMS

Urban heat islands and stormwater hazards are mutually constitutive problems, meaning that they have interconnected influence on one another, both in the conditions that underlie them and in their outcomes. In terms of cause, they are both linked to anthropogenic (human-caused) alterations to land cover and approaches to urban design and development, particularly the proliferation of impervious surfaces and the decline of vegetation. Conventional approaches to development can impose designs for buildings, parking lots, and other infrastructure onto the landscape, rather than integrating them within the context and function of broader ecological systems. In addition to harming ecosystems, this can cause issues such as flooding and create unpleasant environments for people. Heat islands can make stormwater issues worse by increasing the temperature and pollutant load of stormwater causing greater stress to the stormwater system and to receiving water bodies. Stormwater runoff can make heat islands worse by causing natural areas, particularly wetlands and waterways, to decline considerably in quality, affecting their ability to cool the air and to provide safe places to cool off for residents.

Both of these issues are not only exacerbated by climate change, they also contribute locally to air and water temperatures and to residents’ felt experience of their environment. While climate change is often considered a threat that is global in scope, materializing in the upper strata of the atmosphere and affecting municipalities in a way that is distant and impossible to control locally, local patterns in development and the material composition of landscapes already affect human and environmental health, and contribute to the effects of climate change that residents will feel on the ground, such as local air and ground temperatures, wind patterns, air quality, water quality and flooding.

This report analyzes the shared roots of these issues in the composition of land cover and the laws that affect land alteration in town, in order to tackle these issues jointly, and with more coordination among affected parties and stakeholders. Hopefully, the idea that Weymouth’s local land cover conditions will either exacerbate or mitigate looming climate change hazards will galvanize a more focused and determined will to tackle these issues concretely at the municipal scale.

On Bridge Street in North Weymouth, sparse vegetation, wide roads, sprawling parking lots, and narrow sidewalks are products of bygone days of urban design and maintenance, resulting in spaces that are uncomfortable for pedestrians and produce high volumes of polluted stormwater.

Photo by Ben Feldman.

CLIMATE CHANGE MITIGATION VS. ADAPTATION

In his 2009 article on Urban Climate Planning, expert climate analyst and clean energy planner Jeff Howard points to a concerning tension between climate change “mitigation” and climate change “adaptation” in climate resilience planning at the municipal level. Climate change mitigation, meaning actively stabilizing the climate and reducing greenhouse gas emissions, is often seen exclusively as a global or federal-scale issue involving broad economic and ecological policy overhauls. “Adaptation,” or actively adjusting to the climate change that is already occurring, and alleviating the symptoms of environmental disaster, often falls into the hands of local governments. This often leads to stalling of urban planning agendas and conflict between different scales of governance, and a failure to address the root cause of environmental issues. For example, adapting to extreme temperatures in cities by increasing access to air conditioning in housing is a critical public health issue for urban planners to address. However, pursuing this agenda alone actively hinders mitigation of climate change globally and of urban heat islands locally, as air conditioners release heat into the environment and potent greenhouse gasses into the atmosphere, alleviating the symptoms of heat while making the problem worse.

Strategies for mitigation can also be counterproductive with regard to adaptation. For example, the statefunded project in Weymouth to improve coastal resilience by raising seawalls, roads, and parking lots in North Weymouth is seen as a critical way to mitigate the effects of sea level rise. However, these projects, which rely heavily on impervious surface and grey infrastructure, may simply shift the problem elsewhere. In the long-term, the ocean cannot be held back by a wall, and filling a tidal floodplain with an additional volume of impervious surface may prevent flooding on that road, but it will inevitably cause tidal surges to fill an equal volume elsewhere, destroying property or overwhelming estuarine wetlands which are critical to climate change mitigation. These kinds of strategies can lead to a high-stakes and incredibly costly “whack-a-mole” game of infrastructure repair. At the global level, these may not even be considered “mitigation” projects, as they are really more of an immediate-term adaptation which do not alter the course or consequences of climate change. Municipal planners have the difficult job of navigating an impossible maze of political and financial barriers to solving immediate problems, which may explain why conventional short-term measures are often favored. This is why planning is critical to highlight strategies which are both adaptive and mitigate climate change, so that municipalities do not waste their money and time chasing problems down the road, which are impossible to solve without broad regional and federal collaboration.

PROJECT SCOPE

This project has been described by the core team in Weymouth’s Department of Planning and Community Development as a mitigation plan, meaning that it is critical that the plan explores solutions which mitigate the root issues of the problem while being simultaneously adaptive, alleviating immediate hazard of heat and flooding in the near and future terms. While strategies for heat adaptation like air conditioning and strategies for inland flooding like grey stormwater system repairs are a critical component of any municipal climate resilience strategy, this plan focuses on strategies that address the root of the problem, actively deconstructing urban heat islands in Weymouth and providing opportunities to treat and infiltrate stormwater which mitigate pollution, rather than exacerbate it. The project identifies strategies that simultaneously address stormwater pollution and extreme heat, in order to maximize the value of interventions which may take time to come to fruition. A thorough analysis of existing conditions informs these strategies by integrating them with spatial and ecological patterns in Weymouth, and provides insight into the town’s particular issues and assets.

Fast-growing Eastern Red Cedar, Goldenrod, and Little Bluestem thrive in the Union Point Grasslands, a disturbance-dependant ecosystem recognized for its value to numerous endangered species, directly within the harsh conditions created by sprawling asphalt and abandoned runways of the old naval base, exemplifying ecological adaptation and resilience.

The Blue Hills Reservation, a lush pocket of intact coastal forest within Boston’s highly urbanized metropolitan area.

Sprawling unused parking lot, Union Point

Photo By Ben Feldman

WHERE AND WHY IS WEYMOUTH HEATING UP? ANALYSIS

Analysis of Weymouth’s existing conditions reveals the extent and distribution of Weymouth’s heat islands. There are many ways municipalities can manage stormwater and tackle urban heat islands, but determining which areas are most suitable for intervention will allow the municipality to weigh the cost and benefits of interventions for Weymouth’s specific set of conditions.

As land cover and urban form are the primary drivers of both the urban heat island effect and stormwater runoff, each aspect of land cover in Weymouth is examined in this section, with a close eye towards its contribution towards or mitigation of these issues. Socioeconomic conditions and policy drivers which dictate the extent and forms of urban and suburban development are also analyzed. These analyses lead to the identification of dominant spatial patterns, and these patterns inform which adaptive strategies and avenues for improvement are the best fit for Weymouth’s environmental challenges.

CITGO Station Broad Street, Jackson Square. One of many places in Weymouth with contiguous asphalt across multiple parcels.

Photo by Ben Feldman

URBAN HEAT AND DEVELOPMENT PATTERNS:

COMPARING SURFACE TEMPERATURES USING SATELLITE IMAGERY

Landsat data which has been processed to show land surface temperature is capable of displaying the extent of urban heat islands. The dense clusters of man-made impervious surfaces frequently appear in dark red as the hottest surfaces on the map. While Weymouth’s Municipal Vulnerability Plan was working from a Landsat image taken on a hot summer day in 2010 (August 30), new Landsat 9 imagery allowed the Conway team to create an updated map using an image from exactly 12 years later: August 31, 2022.

Although exact temperatures vary depending on the daily weather and some glitches with the Landsat data prevent the map from displaying accurate temperature units, a clear pattern in temperature difference between developed and undeveloped areas is still visible. The new map displays an expansion in Weymouth’s heat islands since 2010. This is especially clear in dense commercial developments along major state roads and in neighborhoods between Jackson Square and Bridge Street. Forested areas, utility easements, and natural areas around open water show considerably cooler surface temperatures than built areas.

Bridge street Jackson Square

Bridge street Jackson Square

Data Source: Landsat Imagery USGS

Data Source: Landsat Imagery USGS

HOT SPOTS CORRELATE TO DEVELOPMENT PATTERNS

The Weymouth Heat Islands map uses a collection of 2019-2022 Landsat surface temperature data to show where particular areas significantly deviate in temperatures from the average town-wide temperature on the same day. For Weymouth, this layer shows that there are urban heat islands in every village in Weymouth, and a simplified Weymouth ‘Hot Spots’ map shows that heat islands appear to be forming around clusters of commercial and residential development, particularly surrounding major roads and village centers such as Jackson Square, Bicknell Square, Columbian Square, and the Landing.

Pavements and dark-colored roofs dominate the urban landscape and are the main contributor to the urban heat island effect due to their heat absorption and radiation properties (Mohajerani et al, 2017). But diffuse heat islands can also form in suburban areas due to the cumulative effect of sprawling largelyturfed lots (Cox 2014). A loose map of concentrated thermal mass (the Weymouth Thermal Mass map at right) was created by using soft pencils to trace over pavements and roofs in a satellite image, using darker colors to indicate concentrations of impervious surface and lighter colors to indicate dispersed or shaded impervious surfaces. Arterial roads and especially major intersections appear clearly on this map, as do commercial plazas, dense clusters of development, office buildings, and schools, which correlate directly to the heat island map.

The following sections explores how land cover and use in Weymouth contributes to the urban heat island effect, and to what extent certain land covers may be mitigating heat islands by breaking up impervious thermal mass and/or providing shading, evaporative cooling, or air convection.

Broad Street, Jackson square. Minimal shading along a wide street with narrow sidewalks. Photo by Ben Feldman.

Whitman’s Pond

Jackson sq.

Weymouth Landing

Union Point

Great Pond Route 18

Bridge St. (3a)

Data Source: ArcMaps ‘Heat

Whitman’s Pond Jackson sq.

Weymouth Landing

Vacant buildings, Union Point. Photo by Ben Feldman.

LAND COVER ANALYSIS

WEYMOUTH’S DOMINANT TYPES OF LAND COVER

The composition of surface materials in Weymouth directly influences the urban heat island effect. A 2016 map of land cover in Weymouth shows the extent and distribution of these surface types.

While the natural landscape of Weymouth between the Boston Basin and the Coastal Plain is a mosaic of winding streams, floodplains, wetlands, forests, shrublands, maritime grasslands, and large estuaries at the mouth of major tidal rivers, Weymouth is largely a densely populated urban and suburban landscape. Natural areas are fragmented by networks of roads, large commercial corridors, nodes of residential neighborhoods, turf lawns, and parks. The convergence and dispersal of these different land covers and their density is crucial for understanding what contributes to the heat island effect in town. The following sections investigate the dominant groups of land cover in Weymouth: forest and forested wetlands, impervious surfaces, maintained turf or lawn, and waters and wetlands (non-forested), along with their thermal and hydrological properties.

Forest, impervious surfaces, turf/lawn, and forested wetland are the four most prevalent land cover types in Weymouth.

LAND COVER BY TYPE

Bridge St. (3a)

Data Source: MassGIS

Route53 Route 18

Route3

Legend

Impervious Surfaces

Turf/Lawn

Shrub/Grassland

Water

Wetlands

Forested Wetlands

Froest

Whitman’s Pond Jackson sq.

Weymouth Landing

Union Point

Great Pond

TREE CANOPY

According to the 2016 land cover map, the town has a total tree canopy of around 47%, nearly half the town’s area. This map compiles areas designated as forest (but includes street and park trees) along with forested wetlands. However, clarifying where that tree cover actually is and where it is not helps explain why heat islands form where they do.

Trees cool areas by evaporating water from their leaves (evapotranspiration) and by providing shade, with particular benefits for surface cooling when they shade impervious surfaces (Rahman et al. 2020). However, at a larger scale, air temperatures are more significantly affected by larger aggregations of tree canopy with more of a forested form than dispersed street trees (Greene and Kedron 2018). This is why botanical gardens have been considered the “most effective” urban place to go for cooling during a heat wave when compared with wetlands and rain gardens (closely behind them), street trees, and parks. (Gayle 2024).

Tree canopy offers cooling, captures rainfall, and makes a comfortable environment for pedestrians in South Weymouth’s Gifford Playground.

Photo by Ben Feldman.

Data Source: MassGIS

Whitman’s Pond Jackson sq.

Weymouth Landing

In North Weymouth, tree canopy is largely concentrated in outlying park areas such as Great Hill Park, Esker Park, Pratt’s Meadow, and the Wessagussett Woodland. These natural areas are critical green spaces, but along the streetscape of Bridge Street (Route 3A) and adjacent neighborhoods, tree canopy is largely absent. While much of this has to do with residential and commercial development, it’s possible that the natural conditions in some areas of North Weymouth are less supportive of tree growth and more supportive of maritime grasslands and shrublands, which contain species that are even more adapted to salt and thin soils than many commonly planted street trees. The fact that the municipality lacks jurisdiction over the state roads right-of-way makes it even more difficult for the town to have an influence over tree canopy in this area

State Park (left) is an intact patch of maritime scrubland, composed of shrubs and warm-season grasses which are highly resistant to salt and wind disturbance. Despite having very little tree canopy, this ecosystem boasts some of the coolest surface temperatures in Weymouth due to its dense native cover and breezy location near open water.

Bridge St.

Great Esker Park

Webb State Park

Pratt’s Meadow

Great Hill Park

Wessagussett Woodland

Tree Canopy Cover, North Weymouth.

Webb

Bridge Street in North Weymouth is a wide road with narrow sidewalks, and parking lots up to the edge of the right of way. Little space is allocated for vegetation.

In Central Weymouth south of Whitman’s Pond, tree canopy is severely perforated by large expanses of impervious surfaces along Washington Street (Route 53), Route 3, and Main Street (Route 18), especially in commercial plazas and major intersections at the confluence of Route 53 and Route 18. Much of the perforation in tree canopy seems to correspond to areas of commercial development, while tree canopy is limited to patches of non-buildable space, such as narrow rights-of-way and water resource protection areas.

Rt 3

Whitman’s Pond

Tree Canopy Cover, Central Weymouth.

A commercial plaza at the crossroads of Main Street (Rt. 18) and Washington St. (Route 53) lacks tree canopy to shade the asphalt. Photo by Ben Feldman.

Photo by Ben Feldman.

In South Weymouth, tree canopy coverage is dense in the west within the watershed of the Great Pond Reservoir and in large patches around the old naval army base at Union Point. Tree canopy is lacking in Union Point largely due to NHESP-protected native grasslands, but adjacent cluster developments, while sparing the grasslands, appear not to have integrated much forest canopy into the dense housing clusters. North of Union Point, commercial districts appear to sprawl into residential neighborhoods, and tree canopy in these areas is sparser than the single-family neighborhoods adjacent to protected forested areas.

Union Point

Columbian sq.

Great Pond Rt 18

Tree Canopy Cover, South Weymouth.

A remnant open-grown white oak stands in a neglected area of old pavement in Union Point. Photo by Ben Feldman.

iTree Estimates The Benefits of Tree Canopy in Town

Beyond directly mitigating urban heat and providing shade, trees simultaneously provide other ecosystem services such as purifying the air and mitigating large flows of stormwater runoff by intercepting, filtering, and uptaking water.

According to iTree, an ecosystem services calculator for urban tree canopy, the trees of Weymouth, simply by existing, save the town upwards of $2 million per year in costs associated with air pollution removal and stormwater runoff management.

According to iTree, a 10% increase in tree canopy would add an additional $195k in integrated benefits, including 6.6 million gallons of avoided stormwater runoff. To get the most value out of these trees, a planting focus may be needed in areas where tree canopy is most lacking such as in streets and parking lots, and where large expanses of lawn or park turf could allow space for a more densely forested landscape.

Source: www.itreetools.org

Forest canopy protects the watershed of Great Pond, a critical source of drinking water in the town. Photo by Ben Feldman.

Photo by Ben Feldman

IMPERVIOUS SURFACES

While tree canopy is a crucial element of comfortable, liveable cities, studies indicate that the most important element of urban heat island mitigation is not simply the planting of trees in already plantable space, but the removal of unnecessary impervious surfaces (Ziter et al. 2019, Yuan and Bauer 2007). Impervious surfaces cover around 30% of the town, and are concentrated within streetscapes and commercial corridors. Especially on impervious surfaces where cars travel frequently, stormwater runoff is not only likely to be flowing in large volumes, but also to have high concentrations of pollutants (Petrucci et al. 2014). By zooming in on the map of impervious surfaces, several patterns of impervious surface distribution in Weymouth can be distinguished.

MassGIS, the source of the landcover data, defines “impervious surfaces” as:

• All constructed surfaces that do not infiltrate stormwater such as roofs, walls, roads, parking lots, brick, asphalt, and concrete.

• Also included are areas of artificially compacted soil such as mining pits or unpaved parking lots where there is no vegetation present.

Artificially compacted and bare soil function much like fully impervious asphalt or cement.

Photo by Ben Feldman.

Medium-capacity asphalt road in a residential part of Weymouth. Photo by Ben Feldman.

Data Source: MassGIS

Whitman’s Pond Jackson sq.

Weymouth Landing

Pond

In some cases in Weymouth, such as along Bridge Street, impervious surface is completely contiguous from the road to front parking lots to buildings to rear parking lots with no interruption, an urban form which may be the root cause of Weymouth’s challenges regarding heat islands and urban flooding. These heavily paved areas closely abut densely packed residential neighborhoods.

In Central Weymouth, major road intersections and large parcels of land around them are zoned for commercial or industrial uses and planned office parks. This zoning has led to areas with large flat roofs and expansive parking lots that form something like an asphalt archipelago, with seemingly little incentive to find opportunities for alternative materials or cover using these building forms.

These areas are also very close to Whitman’s Pond, and are likely to cause water quality issues with unmitigated stormwater runoff. Much of Weymouth’s low-income and minority populations live in and around this asphalt archipelago, and they bear the brunt of the environmental impact caused by development they do not control.

Bridge St. (Rt. 3a)

Impervious surface cover, North Weymouth.

Impervious surfaces, Central Weymouth.

Contiguous pavement, Bridge street, North Weymouth.

Big-box commercial plaza Rt. 18, Central Weymouth.

Rt 3

Whitman’s Pond

In village centers, such as The Landing and Jackson Square, a combination of mixed-use developments, parking lots, smaller commercial corridors, parks, and schools result in densely packed impervious or turf lots with little room for other vegetation.

Important herring runs cross through these both the Landing and Jackson Square, and high impervious cover around herring runs has been closely linked to decline in spawning habitat quality and subsequent population declines (Hare et al, 2021).

These villages also appear to be surrounded by dense residential lots and housing in a suburban form, which are both impacted by and extending the urban heat island effect.

Impervious surface cover, East Weymouth.

Concrete-confined Herring Run Brook, Jackson Square.

New mixed-use development, Weymouth Landing.

Impervious surface cover, Weymouth Landing & Rt. 53/18.

The Landing Rt53/18

Jackson Square

Weymouth Middle School Lovell Park

TURF AND LAWN COVER

The third most-prevalent land cover element in the public and private realm is turfgrass, which covers 15% of the town. While turf is a critical component of public gathering spaces, there are numerous environmental and human health impacts linked to its overuse. Monocultures of turfgrass tend to have high chemical, labor and water inputs, and result in green spaces that have limited diversity of vegetated cover and limited layers of habitat for wildlife (Robbins and Birkenholtz, 2003). This extent of this land cover type far exceeds that of remaining native grassland in town, which only amounts to 2% of all land cover.

Monocultures of turfgrass tend to have high chemical, labor, and water inputs and contribute very little to habitat or cooling of the air.

Artificial turf covers some of Weymouth’s sports fields and gets even hotter than turf grass does. Photo by Ben Feldman.

Stretches of residential lawn do little to absorb water or lower ambient temperatures, while contributing fertilizer and waste into stormwater systems. Photo by Ben Feldman.

Native grasslands, like these in Weymouth’s Union Point neighborhood, have a much higher capacity for cooling and water absorption than turf grass.

Data Source: MassGIS

Whitman’s Pond Jackson sq.

Weymouth Landing

Point

Turf and lawns are often referred to in land cover maps as “Developed Open Space,” which includes residential yards, school yards, sports fields, cemeteries, and turfed road medians. While they are covered by grasses, these spaces function much more like impervious surfaces than Weymouth’s natural grasslands. Some of these grasslands exist around Union Point.

Unlike natural grasslands, turf lawns are frequently mowed, resulting in soil compaction and shallow root systems, meaning they neither infiltrate nor filter stormwater at the same rates as natural vegetative cover. Stormwater runoff from residential lawns is likely to be high in nitrogen from fertilizers, clippings, and pet waste, which can damage ponds and coastal water bodies (Lusk et al., 2020).

When it comes to urban heat, lawns do not perform very well compared to other covers. Lawns barely shade the ground, let alone people, and can result in surface temperatures that are up to 47 degrees hotter than a meadow of medium-height grasses or a hedgerow (Francoeur et al. 2021). Unlike asphalt, however, areas that are covered in turf are much easier to remove and revegetate with more layered native vegetation. Thus, sprawling acres of turfgrass represent untapped potential for conversion into a cooling, stormwater-intercepting, biologically rich landscape.

Root Systems of Native Grasses

Conservation Research Institute

Heidi Natura,1997

Kentucky Bluegrass Poa pratensis

Indian Grass

Sorghastrum nutans

Blig Blue Stem

Andropogon geradii

Switch Grass

Punicam virgatum

Little Blue Stem

Andropogon Scoparius

Tough native grasses like little bluestem colonize even the harshest environments, like this old asphlat landing pad at Union Point.

In the public realm, turf in Weymouth covers large portions of public space. Sometimes, these areas are artificial turf, which can get up to 37 degrees hotter than asphalt on a hot day, enough to cause burns to people who touch it (NRPA, 2019). Stephen Reilly, the Director of Weymouth’s Parks and Recreation Department, reports that these artificial turf fields were put in because regular turf was being damaged by overuse, but that now, the artificial turf fields frequently get so hot that sporting events planned for those areas have to be canceled on hot summer days. Artificial turf areas may benefit from shade structures nearby. Alternative management regimens may need to be implemented for natural turf to prevent overuse without resorting to more artificial surfaces that make the urban heat island effect even worse. In outlying areas of these parks, where turf is not needed for sports games, picnics or other public uses, parks may consider replacing it with alternative forms of vegetation, such meadows, wetlands or both.

In private residential areas, expanses of lawn fragment tree cover, natural drainage basins and habitat, while taking up space that could otherwise be used in much more water-efficient and heatmitigating ways. Some residents noted in the public meeting held by the Conway team that the lawncentric paradigm of suburban landscaping may be an unsuitable one going forward, given the region’s increasingly hot and dry summers, as lawns are “barely even green anymore,” and exotic ornamental perennials can’t thrive in the heat without pampering. Finding ways to encourage residents to shrink or completely transform their lawn into other kinds of attractive, site-adapted native vegetation may represent a unique opportunity to significantly mitigate urban heat and stormwater.

The lawn-centric paradigm of suburban landscaping may not be feasible going forward in light of increasingly hot and dry summers.

Turf/lawn cover East Weymouth.

Turf/lawn cover, South Weymouth.

Lovell Park

Weymouth Middle School

Weymouth Public Housing

Columbian Square

Stella Tirrell Park

Legion Field Libby Field

COMBINED IMPERVIOUS AND TURF COVER

Since turf/lawn and impervious surfaces both contribute to heat islands and stormwater runoff much more so than other land covers, mapping them together displays a more accurate depiction of the land cover types that are most responsible for the issues at hand. Collectively these two land cover types make up 43% of the total land cover in town, and together correlate closely with Weymouth’s heat islands. The Strategies section of this report explores ways to mitigate the impacts of these surfaces and replace them with more permeable, more densely vegetated land covers.

Turf and sidewalk with little room for perennials, Gifford Playground. Photo by Ben Feldman.

Artificial turf, Lovell Park.

Photo by Ben Feldman.

Impervious surfaces and turf/lawn make up 43% of Weymouth’s total land cover.

Data Source: MassGIS

Places with more impervious surfaces and turf/lawn correlate with Weymouth’s most prominent heat islands.

Data Source: MassGIS & Landsat Imagery

Whitman’s Pond

Jackson sq.

Weymouth Landing

Parking lot graded directly into tighly-cropped turf, Union Point Sports Complex. Photo by Ben Feldman.

IMPERVIOUS SURFACES AND TURF/LAWN BY OWNERSHIP

The combined area taken up by impervious and turf surface can be mapped according to public and private ownership. Public areas on this map consist mostly of roads, parks, public schools, public housing, and public parking, which account for 28% of the combined land cover in town. The private areas include residential properties and commercial buildings and parking lots. The private areas account for 72% of the combined impervious and turfed area in town. While public areas have a critical role to play in modeling best management practices for land and providing public access to cool spaces, it is clear that interventions on private property when implemented across town would have the greatest impact on Weymouth’s urban heat island and stormwater issues.

Municipal policy interventions and depaving programs could significantly alter the land cover and structural forms of private development, particularly the sprawling commercial plazas which create condensed urban heat islands. The municipality could also find ways to educate, encourage, and incentivize homeowners to take matters into their own hands with their roofs, driveways, and lawns.

It is clear that interventions on private property, when implemented across town, would have the greatest impact on Weymouth’s urban heat island and stormwater issues.

Data Source: MassGIS

Whitman’s Pond Jackson sq.

Weymouth Landing

WEYMOUTH’S WATERS

WETLANDS AND WATERWAYS

Wetlands account for 16% of Weymouth’s total land cover and open water for another 5%, totaling 21% of the total land cover, a considerably large proportion of the town. This does not include water bodies immediately outside municipal boundaries, such as Hingham Bay and the Fore and Back Rivers.

Despite wetlands constituting a much lower percentage of Weymouth’s land cover than upland tree canopy, which occupies 34%, does, it is likely that the town’s urban wetlands mitigate heat in Weymouth at a disproportionately higher rate than tree canopy can: studies that have attempted to quantify the cooling capacity of specific land covers in urban landscapes into a “normalized cooling capability index” have found urban wetlands to have a cooling value forty-two times higher than parks with tree cover (Xue et al. 2020). This may not be surprising to any Weymouth resident who sees people flocking to the beaches on a hot summer afternoon: although forests, and the shaded relief they provide, can’t be found at the beach, looking out over a large, flat expanse of water offers cooling breezes. While green spaces remain crucial assets in the urban landscape, these critical “blue spaces” function like giant air conditioners that cool the surrounding landscape through water evaporation (Ampatizdis and Kershaw, 2020), especially during the hottest parts of the day.

“Blue spaces” — wetlands, ponds, beaches and other expanses of water — are an often-overlooked source of heat island mitigation in an urban environment. Air temperature lowers over the water through evaporation and provides residents with cooling breezes on hot summer days.

Data Source: MassGIS

Whitman’s Pond

Fore River

Great Pond

Back River Mill River

HerringRunBrook Old RiverSwamp

Hingham Bay

Legend

Open Water

Wetlands

High Yield Aquifer

Low Yield Aquifer

Creeks & rivers

Water has a high specific heat capacity and low thermal conductivity compared to impervious surfaces, meaning that water heats up much more slowly than dry landscapes and asphalt. For this same reason, however, water has the ability to store heat, meaning that it can create a warming effect at night or during fall and early winter (Ampatizdis and Kershaw, 2020). It is critical, then, to shade and keep waters cool with vegetation (e.g., wetland ecosystems) in order to create critical cooling resources that harness the temperaturelowering powers of shade, evaporative cooling, evapotranspiration from plants, and airflow regulation. (Jain and Carpay, 2020). While tree canopy is a key engine of cooling with strong correlations to the Landsat surface temperature map, there is a much clearer correlation between wetlands and waterways and lower surface temperatures in Weymouth, and as discussed above, its likely perceived air temperatures around bodies of water also reflect this pattern.

In addition to providing cooling, Weymouth’s wetlands are also a critical resource for breaking down pollutants and providing Weymouth’s residents with clean, fresh water. Unlike Boston and many other towns in the Boston Metro Area that get their water from the Quabbin Reservoir, Weymouth draws its drinking water locally from Great Pond and the Basin of the Mill River Watershed (Weymouth DPW). Wetlands play a crucial role in ensuring water quality supplies remain intact: shallow vegetated wetlands hold back contaminants and excess nutrients, breaking them into base elements as water flows from the carbon-rich, anoxic conditions of wetland soils back into cooler, oxygenated river systems, a physicochemical process analogous to the carbon filtration system in water treatment plants (Wingham et al. 1988).

Wetlands also play a critical role in regulating the hydrological cycle, absorbing high flows to prevent downstream flooding and recharging groundwater to prevent intensified drought conditions (Bullock and Acreman, 2003). Decreasing the extent of wetlands via development, over-extraction of groundwater, or undersized culverts through roads would have dire consequences on many fronts.

Whitman’s Pond

Fore River

Great Pond Back River

Data Source: Landsat Imagery USGS

The Mill River flowing into the south branch of Whitman’s Pond, which may have once had a much more extensive floodplain prior to damming and development. Photo by Ben Feldman.

Weymouth has instituted a number of bylaws that aim to protect water resources, such as wateruse restrictions and zoning overlays which restrict development in the Great Pond and Mill River watersheds and critical groundwater resource zones. However, many of Weymouth’s urban waterways, including the prized herring run in Jackson Square, remain confined in culverts or narrow concrete channels, which are encroached upon by roads and parking lots. These structures prevent these waterways from taking on a naturalistic form, thus preventing them from performing at their maximum potential for ecological services (Zang et al. 2010).

As Weymouth continues to urbanize, demand for water grows, and climate change creates a less dependable hydrological cycle, additional protections and restoration may be necessary to ensure the long-term health of Weymouth’s watersheds.

Data Source: MassGIS

The channelized Herring Run, confined by steep concrete walls. Photo by Ben Feldman.

IMPERVIOUS SURFACES THREATEN THE INTEGRITY

OF WEYMOUTH’S

WATERS

Most of the water that lands in Weymouth flows into Hingham Bay and Boston Harbor via the Fore River and the Back River Watershed. While the majority of the tributaries to the Fore River lie outside of Weymouth apart from a few tidal creeks, the water flowing into the Back River comes from tributaries that lie mostly within Weymouth: The Old Swamp River and the many fragments of the Mill River Basin. In Weymouth, the Mill River flows from the Great Pond reservoir and several forested wetlands around it, joining with the Old Swamp river in Whitman’s Pond. The Mill River continues, flowing over a dam and entering a concrete-channelized run known as Herring Run Brook. After crossing through Jackson Square, Herring Run Brook flows into the tidal Back River.

The Subbasins by Impervious Cover map shows the Weymouth Watershed and its subbasins, colored by the percentage of their surface area now covered by impervious surfaces. As discussed in the Introduction, the urban impervious surfaces that cause the urban heat island effect are the same materials that allow pollutants to run off into waterways and enter groundwater; polluted watersheds themselves can further exacerbate the urban heat island effect. By showing which watersheds are most impacted by impervious surfaces, it may be possible to develop a plan of prioritization in order to find ways to reduce impervious cover in certain areas and commit to further wetland restoration throughout particular watersheds.

In this section, maps of Weymouth’s stormwater system will show how runoff from these impervious surfaces carries pollutants into Weymouth’s wetlands and waterways, further compromising their ability to perform critical functions with regard to heat island mitigation, water purification, fish habitat, and flood control.

The broader watershed around Weymouth’s Fore and Back Rivers.

Data Source: MassGIS

Whitman’s Pond

Fore River

Great Pond

Back River Mill River

Herring Run

Mill River & Great Pond WatershedBorder

WEYMOUTH’S STORMWATER SYSTEM

Weymouth uses a Municipal Separate Storm Sewer System (MS4) to collect runoff from impervious surfaces. According to the Town Engineer, the system has serious capacity issues and is in need of significant upgrades and renovations in order to safely accommodate current and predicted stormwater capacities. As the town continues to grow in size, demand on the stormwater system increases, and both point- and non-point sources of water pollution proliferate.

Due to the size of Weymouth’s population, the Town must maintain a National Pollution Discharge Elimination System (NPDES) permit. In order to be granted this permit, the EPA required that Weymouth “develop and implement a Storm Water Management Program to minimize the discharge of contaminates [sic] into surface waters”. The Town of Weymouth files an annual report with the EPA and the Massachusetts Department of Environmental Protection (DEP) to demonstrate compliance with the NPDES permit.

In many cases in Weymouth, the storm system outfalls directly into its own waterways. Buildup over time of pollutants and nutrients from untreated stormwater in Weymouth’s rivers, ponds, and tributaries will continually worsen water quality until stormwater runoff is addressed. When the water bodies that receive stormwater pollution reach a certain threshold of pollutants like coliform bacteria, heavy metals, hydrocarbons, nitrates, phosphates, and/or sulfates, these water bodies are designated by regulators (DCR) as impaired water bodies, and are deemed unsafe for particular recreational uses such as swimming or fishing. Almost all of Weymouth’s major rivers are now impaired, as is Hingham Bay and Whitman’s Pond. While wetlands and smaller bodies of water are not included in the DCR’s list, it is likely they are also impaired as they are hydrologically connected to impaired rivers and streams

WHAT IS “RIGHT TO FISH AND SWIM”?

A colloquial name for the Massachusetts Public Waterfront Act, known also as Chapter 91, this law seeks to protect citizens’ rights to safe and enjoyable use of public waterways by protecting water quality and access, and applies to flowed and/or filled tidelands, Great Ponds, and non-tidal rivers and streams. Weymouth’s Great Pond and Whitman’s Pond are both protected bodies under Chapter 91, as are its tidelands, the Back River, the Fore River, and the Mill River. Authorization is required for construction or demolition, filling, dredging, or change in authorized uses within a set buffer zone of these water bodies.

Source: www.mass.gov

WHAT ARE POINT-SOURCES AND NON-POINT-SOURCES OF POLLUTION?

Point-Source pollution enters a waterway from a clear, single source (a factory, a wastewater treatment plant), while NonPoint Source pollution does so from many sources (runoff from a city’s streets).

Almost all of Weymouth’s major rivers are now impaired, largely due to non-point source pollutants conveyed into them by the stormwater system.

Infall where street runoff enters directly into Back River near Jackson Square. Photo by Ben Feldman.

Impaired

Impaired Open WaterTMDL Completed

Impaired Creek/river TMDL Required

Impaired Creek/River TMDL Completed

MassDot Stormwater Outfall

Weymouth Stormwater Outfall

Data Source: Stormwater Management Plan, Town of Weymouth, Tighe & Bond 2019

THERMAL SHOCKS AND POLLUTION IN WEYMOUTH’S WATERWAYS

Another “hotspot” of pollution can be identified by combining the stormwater inlets data layer with the Landsat surface temperature map, and point-sample the displayed surface temperature at the point of stormwater entry into the system. At that entry point, in warm weather, the water might be heated by the asphalt before being swiftly carried to the outfall (Buren et al. 2000), often a wetland or directly into open water. Treating stormwater before it reaches these inlets, rather than dealing with the consequences in receiving water bodies, is likely to have an major impact on water quality.

This map may be useful for many reasons: first, the temperature of stormwater can be a pollutant in water bodies, causing “thermal shocks” that can stress and even kill aquatic life, causing lasting long-term damage to the biology of an aquatic system over time (Wiley et al. 2008). Second, urban heat islands are directly correlated to urban pollution both in cause and effect (Ulpiani 2020), thus a map displaying stormwater inlets intersecting high concentrations of super-heated impervious surface could be a potential surrogate for points where the most particulate pollution is being picked up by warm stormwater. Third, thermal expansion is a main concern in the deterioration of stormwater pipes (Tran & Perera, 2008). Since warm water takes up more volume than cool water and heat wave conditions may stress the pipes further, the hottest portions of the stormwater system might be the most vulnerable to failure.

In the image of Whitman’s Pond, superheated stormwater from Lake Street and from the commercial plazas on Washington Street are conveyed directly to the pond. Green pond scum and plants provide visual cues to eutrophication in plumes which appear to stem directly from stormwater outfalls. Warm, polluted stormwater discharge is directly linked to increases in E. Coli infestation (Armour, 1991), decreases in dissolved oxygen, and increases in temperature and nutrient loads (Kolath and Edgmose, 2023), causing the native ecosystem to collapse and opening new niches for invasive species to thrive (Alexander et al. 2017). All of these pressures create conditions that are toxic to pets and hazardous to people, and thus are the main causes of impairment in Weymouth’s waterways, including Whitman’s Pond, a water body where swimming was historically allowed but has since been designated as unsafe for people and pets (DCR Integrated List of Waters 2021).

A report on management of Whitman’s Pond invasive species mentions stormwater management as a crucial root cause of water quality decline and ecosystem collapse (ESS group 2013), but efforts to restore Whitman’s Pond since that report have mostly been focused on mechanical and chemical removal of invasive species (ESS group 2020).

While removal of invasive species biomass may ameliorate eutrophication, it does not address the root cause, and some native aquatic vegetation and vegetated buffers may actually be necessary to prevent algal blooms and manage nutrients in this shallow urban pond (Peretyakto et al. 2007).

Stormwater inlets intersecting high concentrations of super-heated impervious surface could potentially be points with the highest concentrations of pollutants.

The map to the right shows the stormwater inlets/ catch basins colored according to the surface temperature at those points. As most of these inlets are on asphalt roads, even the least warm inlets (yellow) are still likely to be considerably warmer than areas not mapped. Note clusters of superheated stormwater inlets in village centers, and along major roads and commercial corridors.

Warm puddles dot the expansive parking lot at George Lane Beach, a public recreation resource deeply in need of greener stormwater infrastructure.

Stormwater pipe outfalls directly into the Herring Run’s channel.

Photo by Ben Feldman.

Data Source: Landsat Imagery, USGS & Stormwater Management Plan, Town of Weymouth, TIghe & Bond

STORMWATER AND FLOOD RISK ANALYSIS

In addition to polluting waterways, proliferation of impervious surfaces too close to floodplains and tidal surge areas exacerbates flood risk (Li and Bortolot, 2022, Andreadis et al, 2022). This increases the need for costly infrastructure to prevent flooding in those locations, a maladaptive pattern which may exacerbate flooding in other locations or provide a false sense of security (Logan et al. 2018). Another concerning pattern is that these densely populated areas all appear to drain to a limited set of outfalls on Weymouth’s tidal rivers. This means that during severe storm surges, or even during high tides, these outfalls may not be functioning at maximum efficiency and could fail entirely, potentially causing runoff to back up through the system, destroying pipes and flooding streets and buildings. Comparing this data to the maps of properties with a history of flooding (RiskFactor.com) reveals a spatial pattern strikingly similar to the dispersal of street storm drain inlets connected to outfalls along tidal rivers and marshes, suggesting that some of these properties may not be at risk simply because of topography, but also due to pressure points in town stormwater infrastructure.

In these images of Bridge Street and of Commercial Street by Weymouth Landing, areas established as major heat islands in the heat island analysis, stormwater runoff is especially hot, causing pollution, and have a high concentrations of flood incidents corresponding to areas with capacity issues and limited outfalls.

Proliferation of impervious surfaces in and near floodplains exacerbates flood risk, which costly grey infrastructure can only mitigate temporarily. High tides and storms could cause the stormwater system to fail as pipes are overwhelmed and buildings and streets become inundated.

Spatial distribution of stormwater inlets (squares) corresponds to flood risk parcels, Weymouth Landing. Outfalls are triangles, and pipes are blue arrows.

Distribution of stormwater inlets (squares) corresponds to flood risk parcels, Bridge Street.

Weymouth Landing

Weymouth Landing

The stormwater outfall on Neck Street may be backed up by tidal surges.

100 year fema Flood Plain

500 year Fema flood plain

Floodgate-Controlled Waterway

Union Point Exclusion zone

Flood Risk Parcel*

Data Source: FEMA Flood layes, Mass GIS & *RiskFactor.com

Weymouth Landing

Whitman’s Pond

A neighborhood in North Weymouth situated directly adjacent to the natural gas compressor station.

Photo by Ben Feldman.

VULNERABLE

POPULATIONS AND ENVIRONMENTAL JUSTICE

VULNERABLE POPULATIONS AND ENVIRONMENTAL JUSTICE

MassMapper’s data on Massachusetts towns’ environmental hazard-vulnerable populations, which are referred to as Environmental Justice Populations by the Massachusetts Executive Office of Energy and Environmental Affairs, are organized to show the areas in which minorities, non-native English speakers, and those with low income reside in comparatively high concentrations. The State acknowledges that these populations may be more subject to environmental hazards, from dangerous and expensive disasters caused by extreme weather incidents to daily exposure to heat and smog, as they are “least able to prepare for, and recover from, heat waves, poor air quality, flooding, and other impacts.” They are also less able to participate in environmental and climate change-related decision-making processes.

In Weymouth, minority populations exist in high concentration directly north and south of the Route 3 corridor where residential, business and industrial zoning occur frequently near or adjacent to one another. In this area, tree canopy is sparse amid large expanses of impervious surface, and pockets of heat speckle the map on both sides of the highway. Minority populations also reside with almost no tree cover whatsoever in the northwest peninsula of Weymouth, near the Compressor Station, and in the southern part of the town near the South Shore Hospital, in an area of which the demographic boundaries are nearly contiguous with those of a prominent heat island. On the tree canopy map, there is a visible gap in tree cover that correlates to this heat island as well.

Weymouth’s combined numbers of Black, Asian, Latino, and other minority groups came to around 2,400 individuals in 2018, all likely, per the EPA, to reside in areas with conditions that could exacerbate the effects of climate change. The parts of Weymouth with the highest density of minority communities do correspond to those with the most impervious surface cover, making them likely to experience smog, severe heat, and flooding crises. Latinos specifically, and lower-income individuals generally, are also more likely to perform professional outdoor work, putting them at risk for heat stroke and other potentially deadly outcomes of prolonged extreme heat exposure. Few regulations exist to protect these workers from heat.

Data Source: MassGIS, ArcMaps Heat Severity US Cities 2022

Rt.3Corridor

Rt.3Corridor

Compressor Station

Data Source: MassGIS

Bridge St. (3a)

Minority & English Isolation

SouthShore Hospital

Whitman’s Pond

Jackson sq.

Weymouth Landing

Weymouth’s citizens face risks from smog, heat, and flooding due to combined factors of age, health conditions, income, and racial inequalities.

Beyond what research tells us about the ways in which hazards of climate change disproportionately affect minorities, there is also strong evidence to suggest that a variety of other factors, from age to health conditions to income, make residents vulnerable to climate-related risks. As of 2018, per the census and as mentioned in the Municipal Vulnerability Report (MVP), Weymouth’s population of individuals over 65 years of age was at 18%, expected to increase to 20% by 2023. Older adults are already less able to adjust to heat than younger people*; when living with at least four chronic health conditions, which in Weymouth is the case for 63.7% of individuals 65 or older as of 2016*, this risk factor increases, in part due to the accompanying side effects of prescribed medications. Obesity creates added risk for heatrelated illness; among Weymouth’s older population, 39.2% are either self-described or clinically diagnosed as obese.* For the combined 75% of those over 65 years of age living with heart problems, heat is of particular concern as high temperatures put strain on the heart;* this could be even more worrisome for aging Weymouth citizens living in Environmental Justice Communities due to their frequent proximity to highway and industrial noise pollution, which have also been shown to exacerbate heart problems.*

According to the 2018 Massachusetts Healthy Aging Community Profile, 34% of those 65 or older in Weymouth live alone, having never married, having divorced, or having been widowed. Access to Weymouth’s supermarkets was described as poor for almost 40% of those over 65*, compounding health complications in a heat wave. A 2016 study, Healthy Aging Data to Promote Community Action*, deemed Weymouth a car-dependent community with a low walkability score and “fragmented local MBTA services,” indicating that it could be challenging for the elderly, particularly those who no longer drive, to get around safely or at all. Without support networks, older people, especially those living alone, could have very limited ability to access food, health support, or other essential services, a state made worse during heat waves when Weymouth’s already poor walkability declines dramatically. While Weymouth has opened several cooling centers in recent years at the senior center, libraries and Town

Hall, residents must provide their own means of transportation,* rendering these sites unreachable for those who do not live on a bus route and cannot easily walk, drive, or find other means of transport.

Low-income, housing-cost-burdened, and renting populations face particular challenges related to heat and flooding. In Weymouth, 3,300 individuals were categorized as below the poverty line in 2018,* while 47% of renters reported spending more than 30% of their income on rent alone. 33% of Weymouth’s total population were renters as of 2019.* These groups could experience hardship during heat waves due to the high cost of cooling their homes, which, due in part to a historic lack of need for home cooling in the Northeast and other parts of the country, is almost never among the centralized utilities maintained by landlords, and thus often falls upon tenants to pay for and maintain out-of-pocket.* Weymouth displays statistics on its website about its electric, oil, and gas-heated rental units, but does not have public information about its rental units’ cooling capacity. In many older buildings*, which lowerincome populations could be more likely to occupy, the electrical system may not be robust enough to support the draw of an air conditioning unit, leaving residents unable to sufficiently cool their homes without risking a power outage. Even the outlets themselves, which in older buildings frequently do not accommodate three-prong plugs, can prevent the use of an air conditioner. Older houses can be poorly insulated due to corroded window casements and other aging temperature-regulating features, making efficient heating and cooling more difficult. More than half of Weymouth’s housing units were built before 1959.* When it comes to aid available to those struggling to maintain a safe and habitable temperature inside their homes year-round, programs that provide heating support to low-income families and individuals, such as the Quincy Community Action Programs, are more common than those that address cooling deficits.

A densely populated housing unit near Columbian Square, adjacent to several busy commercial plazas, appears not to offer much greenery or roof space to residents. Photo by Ben Feldman.

Pregnant women* are also at high risk for heatrelated health concerns, as are the very young*. If Weymouth hopes to be an attractive community for young parents and families, it needs to be a safe one. In the words of the International City/County Management Association, “Families are worth prioritizing because they are particularly invested in the success of their community as the place in which they live, work, play, and raise their children. This generational commitment to the city is indispensable because it builds a form of social capital that is nearly impossible to replicate otherwise. Perhaps the best indication of a thriving city is the desire of parents to raise their children within it.”*

Weymouth’s citizens face risks from smog, heat, and flooding due to combined factors of age, health conditions, income, and racial inequalities. As Weymouth moves forward with plans to mitigate its urban heat island effects, it could follow in the footsteps of the recent federal Justice40 Initiative* to ensure that a large portion of heat mitigation funding and efforts go toward making life safer and more bearable for its most vulnerable.

“Families are worth prioritizing because they are particularly invested in the success of their community as the place in which they live, work, play, and raise their children. This generational commitment to the city is indespensable because it builds a form of social capital that is nearly impossible to replicate otherwise. Perhaps the best indication of a thriving city is the desire of parents to raise their children within it.”

-International City/ County Management Association

The compressor station in Northwest Weymouth poses health and safety risks to residents and wildlife. Photo by Ben Feldman.

A juxtaposition of industrial and residential uses. Photo by Ben Feldman.

ZONING ANALYSIS

ZONING ANALYSIS

A town’s zoning is the mechanism that governs relationships between built structures, types of use, and natural resources, ultimately shaping a town’s character by guiding spatial patterns in the landscape and dictating how features look. Zoning can allow for or restrict sprawl, keep some uses separate or combine them, and, ideally, preserve habitat for people and wildlife. Through base zoning and overlay districts, Weymouth has made efforts to encourage development that is sensitive to natural resources and town character while serving its growing population. Zoning language across its four base residential districts reflects an understanding of shifting housing needs, ranging from districts that allow only detached one-family dwellings and municipal uses (R-1) to those that allow for mixed-use development and increased housing density while expressly seeking to preserve residential character. Three of the four residential districts allow for modifications to existing properties to enable densification, including the addition of multi-family units and high rises (R-2, R-3, R-4). The increase in demand for infill in residential districts represents an opportunity for the Town to revise development standards, integrating green design guidelines that require tree planting, stormwater detention, and other measures that reduce Urban Heat Island effects.

Weymouth’s zoning provides valuable insights into a major source of its heat island and flooding problems: urban form. Zoning bylaws help inform which tools might help to solve these problems across each of the town’s zoning districts.

The most detailed version of the town of Weymouth’s zoning map is granular and complex, and therefore difficult to analyze for broad patterns. A more simplified version of the zoning map is displayed on the facing page.

Data Source: Weymouth Town Website, Planning and Community Development: Zoning

Legend

General Zones

Residential

Neigborhood Center District

Business

Industrial

Medical services

Highway Transportation District

Public, Semi-Public & Open Space

Overlay Districts

Commercial Corridor

Village Center

Upper Jackson Sq.

Lower Jackson Sq.

Upper Commercial Street

Water Protection Districts

Watershed Protection District

Groundwater protection district

Whitman’s Pond Jackson sq.

ZONING OVERLAY DISTRICTS

Many of Weymouth’s zoning overlay districts express intent to encourage the use of low-impact design (LID) standards and green infrastructure. The Commercial Corridor zoning overlay, for example, states an intent to support mixed-use development and redevelopment with a particular eye toward identifying and putting to use obsolete or underutilized commercial properties, with any new or redevelopment projects subject to LID standards.

LID standards include such requirements as the detention of stormwater onsite, detailed landscaping plans subject to review, reduction of impervious surfaces, or “enforced setbacks” to prevent corridors from being “visually dominated by large expanses of paved areas.” This being said, the meaning of “setbacks” and the mechanism of their enforcement are unclear and these measures are not required for sites not undergoing redevelopment, thus they do little to decrease impervious surface cover on existing properties.

The zoning overlays do not give the Town the power to protect vegetative cover or reduce impervious surface on properties that are not undergoing renovation or new development.

Town Center Overlays

Zoning overlays like Historic Mill District, Jackson Square and Village Centers aim to protect the distinctive character of mixed-use areas, but they also explicitly seek to mitigate sprawl by encouraging dense new development. They include measures intended to prevent urban stressors associated with increased density, like traffic congestion, and prioritize walkability and bike-friendly features. In these overlay districts as well, much of Weymouth’s ability to enforce LID standards is reliant on new and redevelopment, through which the Town is able to hinge permitting on compliance. Thus, landowner and developer buy-in is important to the cooling and greening of Weymouth across residential and business zoning districts.

Water Protection Districts

Weymouth has two overlays dedicated to protecting its hydrologic resources. Its Watershed Protection District and Groundwater Protection District encompass the Great Pond, Whitman’s Pond, and the Mill River Basin. The base zoning within these overlays (Residential, Business, and Industrial) has ultimately allowed, whether through site plan review or special permit, development projects with large expanses of roof and parking lot to proliferate within both the Watershed Protection District and the Groundwater Protection District, in particular around the junction of Route 3 and Route 18, where a massive intersection bisects the Mill River Basin. Weymouth’s zoning ordinance does not protect the contiguity of waterways in town, allowing for blockages to interrupt their flow in the case of the Mill, the Fore, and the Back Rivers.

The Commercial Corridor Zoning Overlay, East Bridge Street.

Within the Residential districts inside the Watershed and Groundwater Protection Districts, wide expanses of asphalt parking lots and rooftops are visible from the air; one asphalt parking lot alone southeast of the Route 3 and Route 18 intersection has an area of almost 37,000 square meters. Its footprint can be seen prominently on the heat island map. Also within these protective districts, areas zoned for Business have large expanses of roofs and parking lots that abut Residential zones, threatening the health of the groundwater and exacerbating heat island conditions for homeowners and renters nearby.

Elsewhere in the Residential section of northwest Weymouth, massive lawns do little to minimize UHI or capture stormwater. The zoning code has no language to cap acceptable square footage of compacted, hot turf, which requires constant maintenance that in turn creates vast emissions output. The cumulative effect of private residential lawns contribute to this phenomenon as well.

A small specialized village center district for The Landing appears to have allowed a wedge of near-total impervious surface coverage in an area where stormwater best management practices and infiltration could not be more important for preventing flooding and water contamination. With different design standards for mixed-use construction and renovation within village centers, Weymouth could encourage this landscape to include stormwater bio-infiltration and green roofs, breezy roof decks, and other low-impact features to reduce UHI, mitigate flooding hazards, and attract visitors.

Areas of expansive lawn is, like this one in northwest Weymouth, are allowed in the Residential Districts.

Parking lot sand large flat roofs forming an “asphalt archipelago” within Residential, Watershed Protection, and Groundwater Protection Districts.

Near-complete impervious surface strip in the Landing abutting the Fore River and Residential areas.

Middle Street Boat Launch at Whitman’s Pond features impervious surface, turf, and wonderful views of open water, but minimal shoreline buffer. Photo by Ben Feldman.

SUMMARY OF ANALYSES

SUMMARY OF ANALYSES: DOMINANT SPATIAL PATTERNS

These analyses reveal four spatial patterns in Weymouth with critical implications for stormwater and urban heat islands.

1) Grey Streets

Public infrastructure and transportation corridors have very little tree cover, and are dependent on an overworked and aging grey stormwater system, which may be altering or inhibiting the natural function of Weymouth’s wetlands. Many of these roads are state-controlled and would require collaboration with state bodies such as MDOT or MBTA, but many areas contain public sidewalk or turf strips that are municipally controlled and drained by the municipal stormwater system. These areas have a high level of public visibility and use, especially in village centers, and due to vehicle traffic are likely to hold high concentrations of the pollutants that are entering Weymouth’s waterways.

Weymouth also contains several large dangerous intersections with sprawling impervious surfaces. Alterations to roads for safety purposes and for pedestrian comfort, such as Weymouth’s Complete Streets Program funded in part by MDOT, may also provide opportunities and funding for more functional roadside vegetation and green infrastructure installations.

A grey streetscape of Bridge Street, featuring pavement which sprawls across public and private parcels, and little room for trees within the right-of-way.

Photo by Ben Feldman.

Perspective of Bridge Street, North Weymouth.

Whitman’s Pond Jackson sq.

Weymouth Landing Union Point

Contiguous asphalt on a treeless section of Bridge Street. Unnecessarily

2) Big Roofs, Big Lots

There are many commercial corridors in Weymouth for large retail stores, mixed-use and cluster housing, and office parks and industrial spaces which have been encouraged by existing zoning. While these kinds of development have certain economic benefits, the town has not been able to sufficiently control the form of these developments in a way that mitigates their environmental drawbacks. Urban heat islands and stormwater pollution appear to emanate from these large, privately-owned plazas, which represent the vast bulk of uninterrupted impervious surface in Weymouth.

Interventions which alter the vegetative cover and drainage patterns in horizontally sprawling parking lots and large, flat roofs are likely to have a considerable impact on Weymouth’s heat islands.

An axonometric drawing of the shopping center, displaying the large, blank roofs and expanses of unshaded asphalt.

A shopping center on Main Street (Rt. 18) commercial corridor.

Photo by Ben Feldman.

Whitman’s Pond Jackson sq.

Weymouth Landing

(3a)

Sprawling shopping centers near Mill River Basin public water supply.

Expansive parking lots generating heat islands on Rt. 18. commmercial corridor, adjacent to residential neighborhoods.

3) Hot Neighborhoods

Many of the residential neighborhoods in Weymouth contain large areas of pavement and lawn that break up the contiguity of tree cover and provide no shade along with minimal hydrological benefits. Waterfront properties on the coast and along inland ponds with lawns close to the shoreline can create conditions for nutrient-enriched stormwater runoff to enter ecologically sensitive waterways, which should be buffered by riparian and shallow marsh habitats. Lawns and other kinds of traditional ornamental landscaping provide very little ecological benefit to the town, and these spaces represent untapped potential for mitigating heat islands and relieving the pressure on the municipal stormwater system.

With incentives and encouragement, Weymouth could harness the grassroots energy of homeowners. Ecologically improved residential landscapes could not only be a source of pride in the community, but also a crucial element for addressing environmental issues which affect everyone in town.

Standish Road in North Weymouth, a wide residential road which connects without interruption to closely-cropped residential lawns.

Photo by Ben Feldman.

High-density residential development

Whitman’s Pond Jackson sq.

Weymouth Landing

Low-density residential development featuring scattered trees and a lot of lawn near Mill Cove.

4) Constrained Water Systems

Urbanization and impervious surfaces cause hydrological and ecological degradation of wetlands and riparian areas leading to habitat loss, flooding, and heat. Weymouth is a town on the coastal plain, where water and wetlands are an undeniable feature of the landscape. In a densely populated landscape, water is both a critical resource and a potential liability, and municipalities have always sought to control it to protect property and infrastructure. However, conventional approaches to stormwater and flood management often seek to drain the landscape quickly and wall off flooding. These methods do not adequately take into account existing conditions of the rivers’ ever-changing shapes, their rates of their flow, and their connection to their historic floodplains. They also often do not properly account for the benefits of existing wetlands and the impediments to infiltration and flow caused by impervious structures. These decisions often involve grey infrastructure which degrades over time, and such methods, while theoretically straightforward, are incredibly costly and laborintensive in the long-term, prone to failure, and damaging to local ecology.

Existing zoning regulations help determine where development goes and where it does not, but they do not adequately encourage adaptive measures to integrate buildings and lots more conscientiously within their ecological conditions. Sea levels rise, marshes move, rivers wind and change, and floodplains flood: attempting to prevent these processes (for example, channelizing a stream into a straight line, filling a wetland, or walling off the tides) may cause more costly problems to pop up elsewhere. And yet, these processes can be adapted to, and even taken advantage of strategically for cooling, flood control, or recreation. Wetland and floodplain restoration could have a significantly positive effect on heat island mitigation.

Urban Stream Syndrome: Channelized Waters, Polluted Runoff, Ecological Degradation.

Stormwater outlet into concrete-confined Smelt Run, Weymouth Landing.

Photo by Ben Feldman

Channelized Herring Run Brook does not perform at its maximum potential for ecological services, and is highly vulnerable to pollution from adjacent lots.

Whitman’s Pond Jackson sq.

Weymouth Landing

Eutrophication in Whitman’s Pond due to warm, nutrient rich water brought in by the stormwater system.

Herring Run Park

Broad St.

Whitman’s Pond

STRATEGIES FOR COOLING

1: Grey Streets → Green & Complete Streets

2: Big, Hot Roofs and Lots → Cool Roofs & Lots

3: Hot Neighborhoods → Green Neighborhoods

4: Constrained Waterways → Sponge Watersheds

The Analysis identified four spatial patterns that contribute to Urban Heat Island Effect in Weymouth, and from those patterns, four possible mitigation strategies emerge. The first strategy focuses on municipal interventions within rights-of-way that can provide shading on municipal streets and more vegetation to treat and intercept stormwater runoff. The second strategy focuses on mitigation strategies within commercial corridors and other areas that contain large flat-roofed buildings and wide parking lots. The third strategy focuses on grassroots initiatives at the neighborhood level that may enable Weymouth residents to mitigate heat and stormwater runoff on their own properties. The fourth and final strategy proposes a watershed-scale, rivers-and-wetlands-focused mitigation strategy that uses nature-based solutions to address heat, pollution, and flooding in town. All strategies aim to provide better long-term climate resiliency.

STRATEGY 1: GREEN AND COMPLETE STREETS

Goal: A “Green and Complete Streets” policy, backed by a robust urban forestry initiative, that enables Weymouth to keep its streets cool and comfortable, intercept harmful pollutants before runoff enters waterways, and encourage vehicular safety along with alternative modes of transportation. The integrated approach to green streets involves informed collaboration between multiple municipal departments, state agencies such as MassDOT, and private property owners abutting rights-of-way.

Bridge Street/Route 3A with conceptual green street features.

Curb Cuts to infiltration Basin

Native Grass Median Bioswale

Bike path

Shade Trees in ROW

In 2015, Weymouth adopted its first Complete Streets Policy, with the goal of incorporating the principles of Complete Streets into all subsequent municipal transportation projects. Weymouth’s policy was ranked one of the nation’s best by Smart Growth America’s National Complete Streets Coalition. The town website describes a Complete Street as “one that provides safe, accessible options for people of all ages and abilities and all modes of travel,” and states that “designing streets with these principles contributes to the health, safety, and quality of life in a community by improving the pedestrian and vehicular environments and providing safer, more convenient travel options between the places people live, learn, work, and play” (Town of Weymouth, 2016).

Unfortunately, many of Weymouth’s streets are too hot in the summer for much walking and biking, meaning that Complete Streets projects designed to reduce car use by encouraging pedestrian and bicycle traffic could be rendered ineffective by the negative effects of heat conditions. Poor drainage due to a high percentage of impervious surface leads to flooding that also prevents safe walking and riding conditions, while endangering residential and commercial properties.

Sidewalks, lower-capacity municipal streets, and arterial main roads in Weymouth suffer from and are major contributors to its heat problem. Few are shaded by trees and almost none have sufficient

infiltration capacity. Sizeable heat pockets bloom outward along roads, creating unpleasant, and even dangerous, day-to-day conditions for residents and businesses, possibly preventing the pedestrian and bicycle traffic that Complete Streets projects are attempting to encourage. During rainstorms, the water falling on vast expanses of impervious streets, sidewalks, and medians has nowhere to infiltrate, instead collecting on hot asphalt, heating up, and carrying toxic chemicals into the town’s overworked grey infrastructure system and its sensitive water bodies.

Dangerous heat and flooding are both existential threats to Weymouth’s future, but at the very least they are obstacles to the successful implementation of a Complete Streets policy, as they obstruct its explicit aims of creating a more enjoyable, walkable, and sustainable urban environment. Green infrastructure and other cooling measures are absent from the Weymouth Complete Streets Policy; these tools would further its goals and help to shield the town from the massive financial, environmental, and community consequences of extreme weather events.

Importantly, some of the greyest streets in Weymouth, such as Bridge street (Route 3A), Route 53, and Route 18, are state rights of way which are controlled by MassDOT and are tightly flanked by sprawling commercial development. In these areas, the

The many functions of urban tree canopy.

municipality has had trouble intervening and encouraging the swift replacement of declining street trees. The Weymouth town website highlights a reduced carbon footprint as a benefit of Complete Streets, citing a number of case studies that show the effectiveness of Complete Streets at reducing carbon emissions. The Town’s Complete Streets program gets most of its funding from state agencies, and the State of Massachusetts has also signaled its commitment to Complete Streets, climate-resilient urban centers, and ecologically responsible stormwater management.

This strategy set uses street trees, median plantings, green stormwater infrastructure, and permeable pavements to bolster Weymouth’s Complete Streets Policy, and proposes updates to Weymouth’s tree

preservation policies. These are presented along with potential ideas to bring to state agencies, which control some of the major sources of urban heat in Weymouth, and to remind the State of its commitment to assisting towns with climate resiliency and stormwater management. This strategy aims to tackle the urban streetscape with an integrated, multi-pronged approach that facilitates the engagement of all stakeholders in creating a greener, more comfortable, more accessible municipal streetscape in Weymouth: a crucial step towards achieving town-wide resilience to climate change.

A roadside bioswale is a form of GSI that allows road runoff to enter into a rightof-way bioretention basin via a curbcut. The runoff is filtered by the plants and soil before infiltrating onsite or returning to the stormdrain system.

WHAT IS GREEN STORMWATER INFRASTRUCTURE (GSI)?

As a city’s grey infrastructure ages, its ability to successfully manage large volumes of water declines. The concept behind GSI is to slow, spread, and sink stormwater where it falls, using a suite of environmentally low-impact strategies for preventing large volumes of hot, contaminated water from immediately entering a municipal grey stormwater infrastructure system all at once during a rain event. These strategies include but are not limited to:

• Bioswales

• Planted bump-outs around crosswalks and street parking

• Stormwater wetlands

• Infiltration basins

• Rain gardens

• Replacement of hardscapes with vegetated filter strips or permeable paving materials

• Restoration of riparian buffers and grasslands

• Greenways and wildlife corridors

• Street trees

• Native landscaping

A wide municipal street in need of better drainage options, Fridley Street, Minneapolis.

Bump-out bioswale installation filters stormwater and calms traffic, Fridley Street, Minneapolis

A residential rain garden captures water running off a suburban lawn before it can enter the municipal stormwater system. Photo by Alex Kim.

A rain garden in a public park provides pollinator habitat while detaining stormwater. Photo by Kate Cholakis.

INTERVENTIONS

1. Add Green Stormwater Infrastructure (GSI) to Weymouth’s Complete Streets Policy

• Add requirements for GSI and streetside planting bays to Weymouth’s existing Complete Streets Policy.

• Work with MassDOT to allocate funding for street greening projects, using funds already designated for Complete Streets Policy implementation.

• Consider allocating Community Preservation Act funds to implement features of Green and Complete Streets.

• Explore the potential for municipal green jobs programs and upskilling programs, working with DPW, experts in ecological horticulture and design, volunteer committees, and in-house parks maintenance crews to manage installations of GSI and other kinds of perennial gardens.

• Update municipal Stormwater Management Plan to include GSI strategies.

• Analyze long-term GSI costs alongside long-term costs of grey stormwater infrastructure maintenance, rather than up-front installation costs alone.

• Analyze failure rates of properly installed GSI alongside failure rates of properly installed grey stormwater infrastructure.

• Put in place a Stormwater Utility, either flat-fee or based on percent cover of impervious surface, to help encourage adoption of these practices in the private sector while generating funds for municipal stormwater infrastructure repairs and GSI.

Rain Garden Project led by Southeast Como Improvement Association

Together with the Mississippi Watershed Management Organization and other local partner organizations, workers and volunteers transformed a defunct, overgrown traffic diverter into a raingarden, filtering stormwater, creating wildlife habitat and beautifying the Southeast Como Neighborhood of Minneapolis.

CASE STUDY: A HOLISTIC APPROACH TO STRENGTHENING URBAN TREE CANOPY IN BROOKLINE

The town of Brookline sits within the Greater Boston area, directly adjacent to Boston’s more urbanized communities. With a population of around 60,000, Brookline is a bedroom community of Boston with a mixture of urbanized and suburban neighborhoods. Residents of Brookline have long valued their trees, their park landscapes, streetscapes, and residential gardens. In an 1841 book, A Treatise on the Theory and Practice of Landscape Gardening, author and prominent horticulturalist Andrew Jackson Downing states, “The whole of this neighborhood of Brookline is a kind of landscape garden, and there is nothing in America of the sort…these lanes are clothed with a profusion of trees and shrubbery, often almost to the carriage tracks, that curve and wind about; there are more hints here for the lover of the picturesque in lanes than we ever saw assembled together in so small a compass.”

Brookline has sought to preserve this landscape character in the community today by instituting a variety of programs such as a Front Yard Tree Program, where the town plants and cares for trees on residential properties for two years before passing responsibility to the landowner, and regulations that protect larger trees from being damaged in construction activities. These efforts culminated in a 2021 Urban Forest and Climate Resiliency Master Plan, which analyzes the characteristics of Brookline’s urban forests and provides a variety of recommendations for tree protection and expansion efforts in certain areas. This study was a key step in retaining the crucial services trees offer, which make Brookline resilient to urban heat, pollution, flooding, and noise despite its close proximity to some of the most built-up areas in Boston. Individually, these singular plans may not have made a significant impact, but when woven together, they built public and municipal support for their urban forestry program that continues to this day.

However, this process was not all harmonious and easy, and there were several roadblocks they faced throughout the process. Brookline first attempted to incorporate tree preservation into their bylaws in a Town Meeting in 2001, when a committee was formed to explore regulating the removal of trees above a certain size on private land. The committee found that, although these regulations were reasonable and would have a strong impact on urban canopy, more staff would be required to enforce the policy, which the town could not afford at the time. A draft bylaw was written for future consideration, and when the Select Board’s committee revisited the bylaw, they decided to take on a two-phased approach: the first phase was to include tree protections in an amendment to the stormwater bylaw, followed by a second phase which would involve working with the Building and Planning department to consider a Site Plan Review model. After an arduous political process, The Stormwater Management Bylaw was amended in 2018, which provided protection for trees when certain disturbance thresholds were exceeded on construction sites.

While the Stormwater Bylaw was mostly about erosion and sediment control and may not have adequately addressed tree canopy loss on its own, regulators considered it an important first step in ensuring proper oversight and protection of the root zones of larger trees on private lands. In 2021, the more comprehensive urban forestry plan was released, providing detailed analysis of Brookline’s urban forest coupled with concrete action steps to improve funding their tree planting program and more specific additions to their protection bylaws. Brookline’s patient and holistic approach towards urban forestry resulted in a guided push through multiple town regulatory bodies and departments who all recognized, in different ways, the value of tree canopy in town. These policies work in concert in order to generate a built environment in Brookline that is integrated with its natural conditions, providing opportunities for preservation and enhancement of urban forests which make the town more resilient to the effects of climate change and urban pollution.

2. Preserve and Enhance Existing Urban Tree Canopy

• Update existing tree preservation measures.

• Consider a Payment-in-Lieu program for tree replacement in areas where 1:1 or 2:1 tree replacement is infeasible to create a tree planting fund for projects elsewhere in town.

• Along with Payment-in-Lieu, consider additional alternatives to tree replacement such as ecological restoration and GSI plantings that utilize shrubs and grasses.

• Consider site review by certified arborists for construction activities on private sites that may damage trees.

• Consider updates to Land Clearing Bylaws or Stormwater Bylaws which recognize the many costeffective benefits of street trees for stormwater interception in order to encourage additional tree protection and planting (see Brookline’s Erosion and Sediment Control Bylaw Case Study).

3. Create a Comprehensive Urban Forestry Plan

• Update street tree inventory, identifying the location, size/age, and health of each municipally managed tree in Weymouth, and determining specific sectors of the town in need of more tree canopy.

• Rather than a town-wide goal, pursue canopy cover increases with yearly benchmarks within each census block, neighborhood, or particular streetscapes.

• Update the Street Tree List to contain a wider variety of northeast native, site-adapted tree and roadside vegetation options (see Appendix).

• Consider including other types of vegetation, such as shrublands and constructed wetlands where street tree planting is not appropriate.

• Engage relevant multiple-member bodies including the Tree Board, the Weymouth Redevelopment Authority, Weymouth Youth Coalition, Community Events Committee, and Community Preservation Committee in street tree planting and street greening discussions and project planning.

Staghorn Sumac, a northeastnative shrubby tree with beautiful red fall foliage and fruit, is an alternative option for right-of-way vegetation where large trees are not feasible.

4. Update Tree Planting and Maintenance Program for Land within Town Rights-of-Way

• Create a steering committee to organize and implement a tree planting and maintenance program, working closely with DPW, the Tree Board, the Tree Warden, and the Town Arborist.

• Engage community volunteers in tree planting and care.

• Update tree care best management practices, including planting, mulching, watering and pruning, to reflect ecologically sound practices

• Keep MassDOT, MBTA, and Public Utilities informed about the town’s street tree policies and standards.

• Consider removal of unused impervious surface in municipial right of way to create additional space for planting as part of this program.

• Offer free tree plantings for privately owned setbacks

Northampton Free Setback Tree Planting Program

Since 2013, Tree Northampton, Inc. has planted over one thousand setback trees, tending to them over several years to ensure their establishment and ongoing health, with the help of the municipality and volunteer groups. Residents gain all the benefits of the tree such as privacy, shade, and beauty, while the community benefits from an additional shade tree, increasing the city’s canopy. This is an example of a private group partnering with citizens and a municipal shade tree initiative to make a signficant difference in tree cover.

Source: www.treenorthampton.org

Tree planted with “mulch volcano,” which can suffocate the tree and shorten its life span.

Tree planted in wide mulched basin, protecting soil and roots from compaction, enhancing long-term tree health.

5. Explore Alternative Modes of Greening where Municipal Street Trees Are Not Feasible

a) Develop a plan for regreening state roads with MassDOT, which utilizes their restoration seed mixes for roadside and coastal grasslands and provides a list of best management practices for roadside vegetation and pollinator landscapes.

• Create planting strips in medians and along rights of way which mimic the form of maritime scrublands.

• In addition to MassDOTs seed mixes, consider smaller trees or taller shading shrubs such as Sumacs (Rhus spp.), Bayberry (Morella pensylvanica), Eastern Baccharis (Baccharis halimifolia), and native Junipers (Juniperus spp.). (See appendix)

b) Implement coastal meadow, shrubland, and dune planting features along municipal coastal roads, medians, and beach parking lots.

• Utilize established MassDOT seed mixes, or work with local native nurseries to supply appropriate plants, for municipal roadside landscapes.

• Put out a call for citizen scientists, or conduct a municipal study on the roadside ecology of Weymouth, to highlight local-ecotype native plants that thrive in marginal roadsides and disturbed lots, and consider using them as seed sources.

• Consider developing stewardship plans or protections for existing roadside native plant communities, as they currently offer plentiful cooling and stormwater collecting capacity without any added expense to the Town.

MassDOT Landscape Guidelines for Maritime Shrublands & Grasslands

Conditions on Weymouth’s busy state roads tend to mimic the harsh conditions of the coast, where salt and wind can cause many inland species to struggle. However, plantings modeled after maritime shrublands and grasslands along medians and rights-of-way in these areas may represent a scalable opportunity to repopulate these degraded soils with dense vegetation. These tough plants are capable of growing quickly in disturbed conditions, and may also be able to rapidly thrive in sites where unnecessary pavement in the right-of-way is removed. This list also features shorter plantings that are less likely to interfere with utilities and roadside visibility, while still providing benefits of shading the ground, cooling the air, providing roadside snow storage, and taking up stormwater. Weymouth should follow MassDOT landscape guidelines and seed mixes .

c) Install awnings, shade structures, or container plantings in narrow sidewalk strips or alleys where trees are not suitable. Allow cafés and bars to use parking spaces for outdoor seating if they include cooling elements such as shade structures and container plantings.

• Consider design guidelines for village shopping strips and municipal Third Spaces that include shade structures and large planting containers.

Native grasses thriving next to pavement in harsh conditions, Union Point, Weymouth.

THE CO-BENEFITS OF PERMEABLE PAVEMENT

By leaving the finer particles out of pavement aggregate mixes, it is possible to create paving material that allows for infiltration into the ground and cools the air on hotter days when moisture evaporates up and out of the permeable pavement into the surrounding air, mimicking the natural cooling effect of watersaturated soils. In addition, the majority of permeable pavement is lighter in color than traditional dense asphalt pavement, making it more reflective, and therefore cooler. It can be poured into place or sold as pavers. When properly maintained, permeable pavement can absorb up to 100 inches of rain in an hour. Given that even intense rainfalls generate only a few inches of rain per hour, permeable pavement performs well even if its porosity is periodically reduced between maintenance periods. According to NPDES best management practices, permeable pavement responds well to the pressures of low- to medium-speed roads, making it an ideal choice for road shoulders as well as “local roadway, pedestrian walkway, sidewalk, driveway, parking lot and bike path applications” (EPA 2021). It is ideally suited for lowslope roads where water can infiltrate directly through the substrate below rather than flowing downhill.

PERMEABLE PAVEMENT IS SAFER

With its slightly rougher texture and by reducing standing water and ice on the surface of roads, permeable pavement has been shown to reduce hydroplaning and reduce braking distance, thus making roads and intersections safer. *

Despite its rougher texture, the porosity of permeable pavement decreases overall road noise (Sha et al, 2021), reducing stress in the urban environment and the effects of physiological damage that have been linked to urban noise pollution (Hansen 2021), including heart attacks and strokes.

After much study, permeable pavement has been shown to effectively capture and filter chemical contaminants as they make their way through the substrate layers of the aggregate and the soil below.

PERMEABLE PAVEMENT REDUCES LIGHTING NEEDS AND ELECTRICITY COSTS

The reflective capacity of permeable pavement has been shown to significantly reduce nightime lighting needs as its lighter color does not absorb street lighting the way black pavement does. The number of new lamps can be reduced in street renovations, and night-time lighting wattage can be reduced, potentially generating savings for the Town and reduced demand on the electrical grid.

Pemeable asphalt walkway.

Lattice-style permeable pavers. Photo by Kate Cholakis.

6. Incrementally Replace Asphalt and Concrete

a) Consider redesigns of some of Weymouth’s most dangerous intersections with an eye towards opportunities for impervious surface removal or regreening.

• Turning standard intersections into roundabouts with large bio-infiltration basins and/or native plantings at their centers could increase the Town’s opportunities to depave. According to a 2012 Patch article, Weymouth has nine of the most dangerous intersections in the state of Massachusetts. One of Weymouth’s most dangerous intersections, at Middle Street and Washington Street, is located in the sensitive Groundwater Protection District and could be an optimal location for a new roundabout, which are known to dramatically decrease vehicular accidents.

• Review upcoming road and sidewalk repair plans for opportunities to depave and open up areas for permeable pavement and/or GSI.

• Incrementally replace asphalt parking spaces with permeable materials (e.g. porous asphalt, porous pavers).

• Remove parking spaces abutting crosswalks and install GSI or planting bays for street trees.

• Incrementally replace sidewalks and crosswalks with permeable pavement or pavers.

• Connect street tree bays on the edges of sidewalk with permeable pavers, bricks, or metal grates to allow for more infiltration and root space while allowing foot traffic

c) Protect strips of vegetated and/or plantable space, no matter how small.

• Update existing zoning laws to require that a proposed conversion of vegetated or permeable soils into pavement pass through a stringent review process, requiring planting replacement or Payment-in-Lieu.

• Consider a tiered system (see right) for reviewing the heat and stormwater mitigation capacity of various land cover alterations, with impervious surface at the bottom, followed by turf, followed by various forms of ecological landscaping, with protected natural lands at the top. This tiered evaluation system could be used to enforce the use of better materials in Town projects, and encourage it in the private sector.

Washington St.

Middle St.

Intersection of Middle & Washington Streets, Central Weymouth.

STRATEGY 2: COOL ROOFS AND LOTS

Goal: Reduction of the extent of dark-colored, impervious roofs and parking lots, and their contribution of runoff to the municipal stormwater system across municipal and private properties by adding cool retrofits, increasing vegetation, and infiltrating stormwater onsite.

Green Roof

White Roof

Shaded ParkingSolar panels and Trees

On-site Stormwater Infiltration Basins

Central Weymouth shopping center, with conceptual rendering of added cooling GSI techniques and shading solar panel systems.

In Weymouth’s business districts, zoned B-1 and B-2, and its industrial districts, zoned I-1 and I-2, large expanses of asphalt parking lots and roofs characterize the landscape of “big box” stores, office complexes, and industrial facilities and create one of the hottest elements of the urban landscape. Municipal sites such as schools also have large rooftops and expansive parking lots. Dark-colored roofing is the single hottest feature of a city, with street-level asphalt coming in second, due only to its tendency to be more shaded by tree cover. Asphalt generates heat, but in doing so it also absorbs it, and is worse for the wear: exposure to sun breaks asphalt down into particulate matter, which rain washes into waterways. It is a never-ending burden upon the town and private property owners, who are locked into a cycle of repairing streets, parking lots, rooftops, and stormwater pipes damaged by thermal expansion and the strain of managing high volumes of runoff.

Distinguishing between municipally owned and private properties helps to identify where the municipality can intervene directly and where it may be necessary to make use of incentives, permitting requirements, and other mechanisms to motivate private property owners to make cooling and greening retrofits to their new and redevelopment projects.

The sections of Weymouth that are primarily defined by big roofs and big parking lots are some of the most significant contributors to its urban heat islands.

In many cases, these are adjacent to lower-income and minority neighborhoods, known as Environmental Justice Communities for their vulnerability to the effects of heat, flooding, and other dangerous climate-related conditions. Frequently Environmental Justice Communities live in places where urban deforestation has been most extreme. This phenomenon is deserving of a deeper examination and should be considered when locations for green infrastructure projects are being prioritized.

While the scope of this problem might feel discouraging, it is potentially one of the most straightforward aspects of the urban landscape to impact in a meaningful way due to the wide availability of cool materials that can replace asphalt pavement and roofing. This section first presents ideas for physical interventions in the landscape to mitigate urban heat island (UHI) effects, including stormwater pollution, then suggests ways in which Weymouth might require or incentivize implementation of these interventions. Should Weymouth decide to leverage its power to impact developers’ and business owners’ choice of materials for new development and property repairs through a Stormwater Utility or a Green Design Guidelines package it could make sweeping changes to the large roofs and parking lots that are contributing to its heat island and flooding problems in the business and industrial sectors.

Weymouth could set an example for other towns by showcasing the multifaceted benefits and beauty of cool, green roofs and permeable pavement.

Construction detail of green roof layers.”Gardening in Unconventional Spaces”.

Source: www,mwmo.org

COOLER ROOFING OPTIONS FOR LOW-SLOPE ROOFS

GREEN ROOFS

A green roof is a flat or pitched roof covered by a waterproof membrane and a growing medium, and planted with vegetation to provide benefits of water capture, cooling, and management of rainfall that would otherwise require grey stormwater infrastructure. Intercepting and detaining rainfall before it reaches the ground results in cleaner water of less volume entering the municipal system at peak flow times. [Green roofs can maintain 70-90% of rainfall in summer when plants are at peak foliation and evapotranspirative capacity, and 25-40% in winter. Through the process of evapotranspiration and the reduction in impervious surfaces, particularly of asphalt roofing, green roofs cool urban environments during hot summer months, while lowering the interior temperature of the buildings below.

Green roofs have many social and economic benefits in addition to their ecological ones. They have the ability to improve urban quality of life, transforming unused rooftops into spaces for gathering, dining, and gardening, which can add appeal to new residential and business development projects while increasing seating space, and revenue, for restaurants and bars. Green roofs have the potential to create employment opportunities in a growing town.

Intensive green roof An intensive green roof is a more robust planting scheme that can support larger plants including shrubs and trees with soil often two feet or more in depth. These are well suited to low-slope roofs, and can create a beautiful gathering space on a rooftop bar or cafe.

Extensive green roof An extensive green roof has shallow root depth and less planting medium; often between four and eight inches; well suited for low- as well as steep-slope roofs. Sedums, perennial herbs and other low-profile plants are common, but there are countless native species that would bring increased ecological functionality to an extensive green roof.

The Mississippi Watershed Management Organization offices’ green roof in Minneapolis, MN, seen here in September, 2016, captures stormwater and slows the flow of runoff from the building.

BLUE ROOF

Using a simple water detention system, a blue roof acts like a sponge in a rainstorm, capturing stormwater temporarily and releasing it at a slow and manageable rate after the peak flow time has passed. This water capture system keeps roofs cool, lessening the UHI effect, and by intercepting water before it comes into contact with street-level pavement, has the power to minimize the amount of dangerously hot, contaminated water running off into streams, rivers and ponds. Blue roofs tend to be less expensive to install than green roofs, and can be worked into a DIY irrigation system at the residential scale, or provide an integrated stormwater management solution for commercial businesses with flat rooftops.

COOL ROOF

Light-colored roofs are one of the simplest cool roofing options. By covering an asphalt-based roof with a lighter reflective coating or material, it is possible to keep a roof significantly cooler, and reduce internal temperature by up to 30%, which in turn reduces strain on the power grid as less electricity is required for cooling. This has the added benefit of extending the life of a building’s roofing and HVAC systems. By reducing heat, cool roofs reduce smog, improving the urban air quality for residents and wildlife. Cool roofs are available in a variety of forms, for low-slope and steep-slope roofs. For low-slope roofs, effective options include light-colored liquid (“elastomeric”) coatings or sheeting and light-colored aggregate. Options for steep-slope roofs are more limited by aesthetics and are typically more costly, but hold up well compared to traditional black asphalt shingles. Materials include asphalt shingles surfaced with light-colored granules; terra cotta, metal and other cool-colored or reflective tiles; directionally reflective materials, and wood shingles or shakes.

Hybrid green and blue roof by the Urban Greening Company.

Map data from Google.

INTERVENTIONS

1. Make Hot, Impervious Roofs Cooler and Greener

• Replace fragile, hot asphalt roofing on municipal, commercial, and industrial rooftops with one or a combination of several cooler, more resilient roofing types. Light-colored, blue, or extensive green roofs may be most appropriate for large low-slope roofs on commercial buildings, office parks, and municipal buildings.

• Identify ideal locations for rooftop decks featuring semi-intensive or intensive green roofs: possibly mixed-use buildings and residential developments.

• Add native vines such as Virginia creeper to the walls of municipal, commercial, and industrial buildings.

2. Mitigate the Impacts of Sprawling Parking Lots

• Convert black asphalt to light-colored paving by white-topping or adding light-colored aggregate to increase reflectivity.

• Increase permeability of pavement in parking lots and walkways of municipal, commercial, business, and office buildings incrementally where repairs are needed. Permeable pavers or block pavers may be appropriate for walkways, while open-graded asphalt or porous concrete may work best for parking lots.

• Incorporate tree cover, dense plantings and/or GSI into parking lot medians.

• Explore options for incorporating solar panels over large parking lots to create shade cover and generate usable energy, while reducing draw on municipal grid and directing stormwater flows.

• Conduct a parking study to identify places where parking can be condensed and/or shared, and designate test zones for eliminating parking minimums where possible.

River Valley Co-Op Solar Panel-Shaded Parking and Stormwater Meadow, Easthampton, MA

Shaded parking areas can protect cars from reaching an average interior temperature of 140 degrees on a 95-degree summer day. In combination with other green infrastructure techniques, River Valley Co-op in Easthampton, MA, utilizes solar panel shaded parking. Water is directed from the solar panels into drainage swales diverting stormwater to onsite infiltration basins and wetlands all while producing energy for the building’s needs.

Conceptual rooftop cafe and intensive green roof

gardens. Features like this could be a popular draw in mixed used development areas in town.

River Valley Co-op, Easthampton, MA.

Solar panels shade parking lot.

3. Require or Incentivize Implementation by Commercial and Industrial Property Owners

• Allow green roofs and blue roofs to satisfy a portion of the stormwater management plan requirements for new and redevelopment projects.

• Engage with local roofing and paving contractors to understand market and training obstacles to their businesses using cool and/or green roofing and light-colored and/or permeable materials.

• Consider financial incentives for use of cool and/or green roofing materials and light-colored and/ or permeable pavement.

• Host a conference of green building professionals to connect developers with supportive education, technological expertise, and potential customers

• Create a Stormwater Utility to expand adoption of these practices in the private sector by implementing a percent-impervious-surface fee which can in turn generate revenue for the Town to put toward greening efforts

• Create Green Design Guidelines Package and add to the zoning ordinance

Image source: www.depave.org

Green Design Guidelines Package

Working with a consulting or design firm specializing in low-impact design, Weymouth could develop a thorough set of green design guidelines to replace and supplement existing standards for sustainable development within the zoning ordinance (see p. 105) in order to promote the adoption of cooling strategies. These design guidelines could encourage new developments to include plans for shade trees, GSI, permeable concrete, block pavers, and open-graded asphalt, and set required minimum roof material reflectivity for new roof development, repairs and/or retrofits.

Median bio-infiltration basin collects and filters runoff from surrounding parking lot, growing cooling vegetation.

STORMWATER UTILITY

A Stormwater Utility can be a flexible tool for encouraging the reduction of impervious surface cover across zoning districts, while raising funds to help cover the costs of municipal infrastructure upkeep and upgrades. A Stormwater Utility creates a dedicated source of funding to be used to maintain a municipality’s stormwater infrastructure system and, if applicable, to meet NPDES permit requirements, either through a flat annual fee or a fee based on percent impervious surface cover on private properties.

While many municipalities use the Stormwater Utility to disincentivize impervious surface cover by charging a fee based on the square footage of impervious surface on a given property; others, such as Chicopee, charge a flat annual fee [PER PERSON/PER BUSINESS?], which can result in less community pushback while still generating significant revenue for the Town. Both approaches have their advantages, and a phased implementation method could be a strategy for harnessing the advantages of both. The flat-fee Stormwater Utility model allows a Town to generate revenue quickly and efficiently without penalizing residents and businesses based on their impervious surface cover before they are given a fair chance to make alterations to their properties. Phasing in a fee proportional to impervious surface after a grace period of a lower flat fee, while providing residents and businesses with resources to reduce their impervious surface cover in anticipation of the next phase, could work toward the ultimate goal of reducing overall impervious surface over time. Launching the Stormwater Utility with a flat “EPA stormwater management fee” could generate immediate revenue for the Town to put towards green infrastructure, which the EPA “strongly encourages” as a method of meeting NPDES permit requirements.

In its 2011 memorandum entitled “Achieving Water Quality Through Integrated Stormwater and Wastewater Plans,” the EPA’s Office of Water (OW) and Office of Enforcement and Compliance Assurance (OECA) “[identify] green infrastructure as one comprehensive solution that can improve water quality and provide other benefits that enhance the vitality of communities.” That same year, an earlier memo, “Protecting Water Quality with Green Infrastructure in Water EPA Permitting and Enforcement Programs,” was issued, supporting the use of green infrastructure to satisfy the NPDES permit requirements with the statement, “The offices reaffirm their commitment to working with interested communities to incorporate green infrastructure into stormwater permits and remedies for noncompliance with the CWA.”

Precedent: City of Chicopee, MA

The city of Chicopee, MA raised $400,000 in the stormwater utility’s first year of implementation (1998)and $550,000 in the third year. “To date, the money has been used for activities such as stepping up cleaning of catch basins, purchasing a catch basin cleaning truck, grouting joints in the sewer system to stop leakage and inflow, stenciling storm drains, and cleaning sewer lines. Chicopee has also used the funds to leverage additional state loan funding for a $5 million sewer separation project.

Strategy 3: Green Neighborhoods

Ecological Landscaping create habitat and provide food for residents

Goal: A network of green corridors weaving across Weymouth made up of shady residential properties cooled by trees, meadows, and other native plant landscaping. Stormwater is slowed, captured and infiltrated in rain gardens and bioswales, and a sense of pride and purpose spreads throughout Weymouth’s neighborhoods via grassroots action and tangible change.

Weymouth Housing Development, with conceptual rendering of added ecological landscaping, shade trees and rain gardens.

Rain Garden collects stormwater from roof

Shade Trees mitigate heat

12% of Weymouth’s land cover is residential lawn. While not fully impervious, lawns have very limited cooling capacity, frequently heating up in the sun to temperatures only marginally lower than that of concrete. These expanses of lawn cannot stand up to summer heat and drought, require huge inputs of water to stay alive, and never grow tall enough to provide substantial shading or evaporative cooling. Furthermore, lawns cannot absorb large quantities of water at once, leading water to pool on lawns or send fertilizer-rich runoff into the municipal stormwater system.

Of the 48% of Weymouth’s land cover taken up by residential impervious surfaces, the portion not dedicated to roofing corresponds to residential driveways, parking areas, walkways, and hardscaping typically composed of asphalt, concrete or other non-porous materials. While the dispersed nature of these impervious surfaces make their contribution to the urban heat island effect less obvious than commercial areas that are almost entirely devoid of vegetation, unshaded roofs still heat up and contribute to elevated temperatures locally, as steep-slope residential roofs are often also made of asphalt, and are often the hottest feature of the urban landscape. Large urban areas like Boston have dealt with rolling summer electrical blackouts when air conditioning units city-wide overtaxed the City’s electrical capacity. In addition, residential impervious surfaces often channel contaminated stormwater directly into the municipal stormwater system, putting strain on expensive grey infrastructure networks and polluting waterbodies.

Because the majority of impervious surface cover and lawn are situated in residential parts of Weymouth, it is clear that creating and supporting grassroots greening efforts at the individual residential, block-wide, and neighborhood scales is an important part of mitigating Weymouth’s heat island crisis, while also significantly reducing pressure on public utilities such as public water, energy, and the municipal stormwater system. Native plant landscaping, lawn-reduction, and impervious surface replacement movements have become incredibly popular throughout the country in the last few years, and there are numerous resources available to educate residents about making the switch.

Many residents already desire more environmentally responsible landscapes, but the up-front technical or financial challenges of installing these complexto-design yet low-maintenance landscapes often prove too much for folks who are not already hobby gardeners. This section offers strategies for educating residents about residential-scale greening techniques, promoting cooperation among neighbors to put these strategies into practice, and providing financial incentives to residents who wish to take Weymouth’s environmental challenges into their own hands.

Residential rain garden, with pollinator-friendly plants, filters stormwater onsite and cools the environment via evapotranspiration.

Unmowed vegetated buffer strip along a residential shoreline property protects water quality and mitigates erosion.

INTERVENTIONS

1. Convert Municipal Lawn to Meadows and Rain Gardens, and Encourage Homeowners to Follow Suit

• Create public projects that demonstrate the replacement of lawn with meadow gardens, rain gardens, and native trees on high-visibility municipal sites (e.g., schools, municipal buildings, and public housing).

• Partner with ecological designers and native plant nurseries to host information sessions and distribute educational materials to homeowners about the aesthetic and functional benefits of replacing lawn with meadows, rain gardens, and other native plantings. Public schools could host these events.

• Conduct comprehensive zoning review.

• In addition to Payment-in-Lieu options for areas where tree replacement is not feasible, consider allowing homeowners who are removing trees to replace them with lawn-to-meadow conversions, rain gardens, vegetated bioswales or berms, and shoreline buffer enhancements in areas where development is triggering review by the Conservation Commission review.

• Promote shoreline buffers and reduction of lawns on waterfront properties over the addition of hard and/ or grey infrastructure, and request shoreline buffer plantings and dune plantings when waterfront property owners appear before the Conservation Commission for project approval.

• Survey residents to gauge interest in and site community gardens and pocket parks on underutilized parcels, particularly in low-income neighborhoods and areas where the Town wishes to increase foot traffic and village feel.

• Initiate a Free Yard/Setback Tree Planting Program, described in “Green Streets” Section.

Representative from “Recharge the Rain,” a joint effort of Tucson, AZ’s Watershed Management Group and Arizona Project WET, explains stormwater best management practices at a public high school.

Comprehensive Zoning Review

In order for the town to implement these strategies, it could be helpful to conduct a comprehensive review of Weymouth’s zoning ordinance and investigate current zoning codes that may prevent homeowners and private landowners from using green stormwater management strategies, like GSI and disconnected downspouts, to manage stormwater on their property, or from replacing lawn with dense native plant gardens. A comprehensive zoning review could allow Weymouth to take inventory of where in its zoning code LID standards are not mentioned, where they are encouraged, and how they could be improved and made more consistent throughout the ordinance. A Green Design Guidelines Package (p.100) could be included in the zoning ordinance to replace outdated and insufficient language.

2. Offer Financial Incentives to Residents for Rain Gardens, Green Roofs and Other Impervious Removal

• Collaborate with local/regional ecological landscape designers and watershed groups to develop a municipal rebate program, akin to the rain garden rebate programs in the Washington D.C.-metropolitan area, which assists residents with the design and implementation costs of rain gardens and bioswales, roof retrofits, permeable pavement retrofits, and impervious surface removal.

• Ensure that the program is marketed directly to residents in all neighborhoods, has an accessible online interface, and has a relatively straightforward application process

• Look to MS4 Assistance Grants, watershed group fundraising, a commercially focused Stormwater Utility fee, and Payment-in-Lieu fees for tree removal as possible sources of funding for the program.

• Offer direct financial assistance to low-income neighborhoods who need it most, and/or properties adjacent to critical water resources or conservation areas.

• Publish a database of ongoing and completed projects so that the program’s progress can be tracked and inspirational content can be accessed and shared.

Source: goodearthgardens1.com

Residential lawn conversion to raingarden project partially funded by stormwater management rebate program in cooperation with Jackson County Soil and Water Conservation District, Jackson County, OR.

Source: goodearthgardens1.com

CASE STUDY: WASHINGTON D.C.’S WILDLY POPULAR RAIN GARDEN REBATE PROGRAMS

Many cities on the East Coast are surrounded by sprawling single-family suburbs whose lots collectively put an immense amount of pressure on municipal stormwater systems, and contribute significantly to stormwater pollution in major rivers and estuaries on the eastern seaboard. Because of this, many municipalities have tried to imagine ways to encourage residential homeowners to divert runoff from their houses and driveways, in hopes that their collective effort will add up in the management of stormwater, while also contributing to the comfort and beautification of neighborhoods. In addition, these programs appeal to residents who wish to attract pollinators and birds to their property, or residents who wish to address flooding or drought conditions in sections of their lawn. In metropolitan DC, a city built on a giant marsh in the Chesapeake Watershed, these programs have become wildly popular both within the city and in adjacent counties. While many of these programs have their nuances and merits, this case study focuses on the RainScapes Program of Montgomery County, MD.

The program, managed by the Montgomery DEP’s Watershed Restoration Division, was a response to the county’s MS4 permit goals, which tasked the program with controlling stormwater runoff from at least 50 impervious acres in the county, and hoped that it could also build capacity for green infrastructure among industry professionals by providing training opportunities and technical resources for designers and construction managers. The program has several elements, including these training programs, outreach and event speaking, school programs, and the main residential rebate program, which assists homeowners in design and installation of features such as rain gardens, water harvesting mechanisms, green roof retrofits, permeable pavement retrofits, conservation landscapes, and removal of impervious surfaces. The program began with rebates of up to $2,500 for residential projects and $10,000 for commercial projects, and has since increased these funds to $7,500 and $20,000 respectively, as of 2018. Since its grant-funded initiation in 2007 with the help of local watershed groups, the program has treated over 55 impervious acres at the cost of around $20,000 per acre and distributed over 988 completed projects. The program has made a point out of being relatively easy and straightforward to apply on the program website, and they continuously sell out every year. The ability of the program to engage the community while cost-effectively siting and dispersing stormwater management projects has allowed it to grow and attract more funding while simultaneously educating homeowners and changing the culture of prolific, sprawling lawns within critical watersheds.

While many residents of urban metro-areas wish to do the right thing for the environment and have dreams of landscaping their property, these processes often require complex technical assistance and a large upfront cost. By offering financial incentives to homeowners and design /construction guidance from experts to municipal crews, the RainScapes rebate program has created and implemented a formula for grassroots stormwater management which has been wildly successful and replicated in many communities throughout Maryland and the rest of the country.

3. Harness Grassroots Volunteer Energy for Environmental Stewardship and Education

Consider assembling a “Green Blocks Task Force” that could fill the need for a neighborhood-level support system for the Town in its multi-pronged approach to greening Weymouth. This group could help to provide an outlet for citizens with a deep desire to make a difference in their community but who may lack an organized way to do so. The duties of the task force might include:

• Conducting an informal Sustainability Audit and/or “Cooling Our Neighborhood”-themed charrette to deepen understanding of what assets and challenges to community-led greening efforts exist on the neighborhood level. This process could involve discussions about zoning/regulations for land use and tree planting, stormwater and right-of-way management; surveying community members about their knowledge of green infrastructure and native plants; documenting community concerns and recommendations.

• Compiling a Green Idea Bank to validate and record community input.

• Compiling educational materials about the value of mature trees and GSI, along with precedent and case study materials to generate enthusiasm for neighborhood cooperative greening projects, for wide distribution.

• Creating phone trees or buddy networks to foster community and encourage sharing of cooling resources among neighbors during dangerous heat events.

• Organizing street planting campaigns, targeting parts of town with vulnerable populations and large amounts of impervious surface.

• Networking to generate funding/partnerships with corporate sponsors as well as local, statewide and regional nonprofits, cultural institutions, government agencies, and foundations.

• Organizing “Green Block Challenges” with funding awards from participating local partners to promote cooperative green innovation.

• Forming relationships with local schools, businesses as well as native plant nurseries and green contractors to site and implement GSI demonstration projects.

• Organizing and/or leading workshops on rain gardens, residential-scale rainwater-harvesting, DIY green-roofing, and ecological landscaping.

• Setting tiered percentage goals for block- or neighborhood-wide implementation of green infrastructure, tree planting, etc., to motivate and reward residents for their work towards greening their environs.

Opposite page: Community volunteers planting a raised bed demonstration garden, Nicollete Island, Mississippi.

Photo credit Kate Cholakis.

Strategy 4: Sponge Watersheds

Goal: A network of multifunctional, lush urban greenways extends across the town, simultaneously providing cooling, stormwater filtration, and flood mitigation through corridors of intensive stream and wetland restoration.

According to riskfactor.com, Weymouth is facing major flooding risk in the next 30 years, with flooding predicted to affect over 15% of properties, a high risk of impacting day-to-day life of residents and access to crucial services. As discussed in the analysis section there is potential for overlap between strategies that mitigate Weymouth’s urban heat island effect and strategies that mitigate flooding. Strategies that reduce impervious surface and add green stormwater infrastructure to commercial and public property have the potential to tackle multiple environmental issues simultaneously and costeffectively.

One of the major issues that came up in the analysis was constrained water systems. In other words, in a city of drains, culverts, concrete walls and flood control gates, where is water allowed to go? How can flooding be guided strategically, and how can the natural behavior of rivers and their floodplains be harnessed in Weymouth’s heat island mitigation strategy? Simply raising impervious surfaces higher and higher above flood prone areas while relying exclusively on grey stormwater infrastructure to drain streets is not only economically and ecologically costly, but it may not even be enough to address the challenges at hand. Furthermore, just as Weymouth is now facing the major costs of repairing seawalls, culverts, flood gates, and stormwater pipes that were built over 40 years ago, what will Weymouth do 40 years from now, when the repaired infrastructure is degraded again, the flood risk is even higher, and

development potentially even more dense? Perhaps Weymouth doesn’t only need more elaborate grey infrastructure, Weymouth simply needs wider floodplains.

As discussed in the Wetlands and Waterways section of the Analysis, wetland and floodplain restoration, while much more complex than tree planting, could have a disproportionately significant effect on heat mitigation. But Weymouth is developing, and is desperately in need of better opportunities for public recreation, more ways to access and use transportation corridors, and more ways to spur vibrant economies in its village centers, all while protecting its limited freshwater resources, retaining its character, and providing clean air, shade, and cooling for its residents. This Strategies section explores ways of combining floodplain restoration and green stormwater infrastructure with renovation of urban parks and recreational spaces, turning channelized streams, ditches, stormwater pipes, and underutilized parks into a lush network of streams and urban greenways. Strategies like this, collectively grouped under the concept of a “sponge city,” are capable of accomplishing numerous development and climate-related goals at once, by stacking multiple functions of stormwater treatment, heat island mitigation, flood capacity, wildlife habitat, recreation, and pedestrian connectivity.

Heritage Park stormwater wetland project, Minneapolis, MN.

INTERVENTIONS

1. Widen Urban Watercourses and Restore River-to-Floodplain Connectivity

Rivers and streams naturally sprawl out over large flat areas, creating a winding patchwork of riparian habitats which support a wide variety of vegetation. These banks and floodplains not only provide habitat for wildlife and beautiful vistas for people, they also play crucial roles in upstream flood retention, removal of pollutants from stormwater, and mitigation of the urban heat island effect. Multiple studies have found that urban river corridors not only have significantly lower air and surface temperatures than surrounding areas, but they cool the surrounding urban landscape through evaporation and ventilation and the effective distance of this cooling effect on the surrounding areas was directly correlated to the width of the natural watercourse (Lin et al. 2022, Hathway and Sharples, 2012). When encroaching urban development disconnects rivers from their floodplain, by sending the stream underground in a culvert or by filling in the bank and walling the steam in concrete, the ability of the river system to perform all of these crucial ecological services is severely diminished. Weymouth has already begun to recognize the environmental importance of its streams, and several culverted streams have been daylighted or have had obstructions removed. However, these restoration efforts have been mostly focused on river continuity for fish passage up and down the stream, but not on lateral connectivity to the stream banks and floodplain, so many daylighted streams remain confined in narrow concrete passages through highly paved and polluted areas. By continuing to daylight streams but with more emphasis on widening the stream channel, preserving and naturalizing adjacent parcels of land, and moving walls further back or replacing them to provide room for gently-sloping vegetated streambanks, Weymouth could turn its waterways into powerful ecological engines of cooling. More naturalistic waterways with wider buffers of protection would not only mitigate urban heat island effect, but would create potential for spacious linear parks which could increase connectivity and opportunities for recreation, increase opportunities for healthy tree canopies and diverse plant communities, create more opportunities to store and filter flood water, and provide significantly better quality spawning and feeding habitat for herring. Due to the presence of herring, there is already considerable support for stream restoration efforts in town, but bolstering the conservation argument with evidence that wider natural floodplains and restored streambank profiles would decrease urban heat island, treat stormwater, prevent downstream flooding, and provide better quality of life for residents might generate even more political support and more opportunities for grant funding.

• Conduct a “Sponge City” visioning/feasibility study which combines surveys of the towns existing and past hydrology, siting of specific GSI projects, and coordination of climate change mitigation projects (heat island, flooding, drought, sea level, loss of biodiversity). Include these socio-ecological considerations in an updated master plan with a cohesive long-term vision for Weymouth’s economic development, infrastructure, and wetlands. A study like this could be an excellent complement to an Urban Forestry study mentioned in the Green & Complete Streets Section.

• Increase size and/or enhanced quality of stream buffers and wetland buffers Increasing buffers to wetlands, especially rivers, in order to reflect their need to widen and change over time. Rather than simply “no touch” buffers, add language about enhancement and expansion of vegetated buffers within a certain distance using site-appropriate native plants.

• Install larger culverts and advocate for flatter stream banks to allow lateral river-to-floodplain connectivity in stream daylighting and dam removal projects, allowing for wider corridors of riparian habitat and more dynamic urban wetlands.

Partial removal of concrete confinement of an urban stream resulting in protected shoreline vegetation, stormwater runoff treatment, healthy aquatic habitat, improved quality of life.

People enjoying the fully restored floodplain of the Coonamasset River Greenway, Falmouth, MA.

2. Create Stormwater Wetland Parks

Due to the hydrological benefits of wetlands and the ability of wetland plants to sequester urban pollutants, many cities have been constructing wetlands as features in public parks which help to treat stormwater runoff and retain floodwater while providing passive recreation opportunities to visitors. These urban wetland features also have the benefit of mitigating the urban heat island effect, even more so than street trees.

Stormwater wetlands typically consist of a sediment forebay which catches heavier sediments at the inlet pipes that release water into the wetland system. The water than flows through a varied patchwork of deep pools and shallow marsh systems with wetland plants that help to filter out pollutants, followed by an outfall structure at the end which helps to control the movement and quantity of water that is stored within the wetland at any given time. The result is often a beautiful naturalistic feature that provides many opportunities for public education, wildlife viewing, and catching a cool breeze off the marshes.

In Weymouth, many urban parks and school yards feature large expanses of turf or marginal areas where existing wetlands are cut off from streams, partially filled in, or heavily degraded by polluted runoff and sediments, leading them to become overgrown with invasive species. Places like this may provide good opportunities for stormwater wetland projects, which could be simultaneously framed as stormwater infrastructure improvements, park renovations, and educational opportunities both for visitors and volunteer stewards. When located near large buildings such as public schools or in parks that are surrounded by densely populated urban development, such as Lovell park in Jackson Square or Weston park in Weymouth Landing, these stormwater wetland features would provide cooling services.

• Assemble a Council on Green Infrastructure which combines voices from Health, Planning, Conservation, Parks and Rec, Executive, and DPW, including ideally at least two new positions, one which coordinates between departments and advocates for the development of a network of GSI throughout the town, and an architect or engineer who can assist DPW with the design and management of ecological landscape installations and GSI. This position will help to spark an evolution in design and maintenance of vegetation on public lands, in order to advance stormwater goals and comply with MA stormwater handbook (ecological management of plant communities and maintenance of GSI features).

• Capitalize on the potential for green jobs and volunteer programs in the installation and ongoing maintenance of green infrastructure features.

• Consider a Stormwater Utility to relieve funding pressure that prevents the DPW from undertaking larger stormwater management projects. Addressing the funding gap in public works which happers their capacity to take on green infrastructure projects is a crucial hurdle in enabling Weymouth to meet its environmental challenges.

CASE STUDY: CAN STORMWATER BE FEATURED IN PUBLIC PARKS? ALEWIFE STORMWATER WETLAND

Sparked by the federally mandated Boston Harbor Cleanup, the Alewife Stormwater Wetland was the product of collaboration between the City of Cambridge, State Government, and multiple design and engineering firms. The project area was in the CAM 004 catchment, a 420 acre, densely populated urban residential and commercial area which frequently experienced severe flooding and combined sewer overflows. These overflows severely degraded the water quality of Alewife Brook and its receiving water bodies, and caused flooding of sewage into residential basements and public rights of way even in small 2-year storms. The City was tasked with the immense goal of full sewer separation for the CAM004 stormwater catchment area while ensuring that peak stormwater flows into the brook would still not flood the town.

The answer lay in the existing but severely-degraded floodplain of the Alewife Brook, a natural ecosystem which evolved to receive incoming flood pulses. The 3.5 acre reconstructed wetland, one of the largest in New England, treats urban stormwater runoff from over 400 acres of dense urban residential and commercial land, and eliminates 10-year storm nuisance flooding in the surrounding areas while significantly mitigating the flood damage from larger storms. The wetland and its surroundings also provide an exemplary space for passive recreation and habitat for a variety of fish and wildlife. The value of the ecosystem services provided by this wetland restoration is felt by Cambridge and Medford citizens, who report a significant increase in quality of life and recreational opportunities, while also recognizing the significant public health benefits of decreased flooding and access to cooling green space in the midst of a densely developed urban landscape. The wetland park features educational signage, a bike path, half-mile long boardwalk featuring panoramic views of the floodplain, and a raised platform overlooking one of the man-made oxbows in which herring occasionally spawn.

Due to the high complexity of the project as a CSO-retrofit and the fact that it is one of the largest stormwater wetlands ever built in New England, the project bore a hefty $117 million cost. The project succeeded in reducing CSO overflow in the area by 84%. Analyses of the value of the ecosystem services of constructed wetland features in the Boston Harbor’s watershed (such as the Alewife Stormwater Project) approximate their asset value to be roughly 15 times the cost of implementation, and researchers admit that these are extremely conservative estimates (Jin et al, 2018). While a project as large as this may seem daunting to a town like Weymouth, the numerous stakeholders involved in such a critical natural area is reminiscent of Weymouth’s major estuaries which are shared with adjacent towns, and they harbor resources of critical regional importance. Weymouth also has the advantage of not having any CSO’s to complicate and extend the engineering costs of this process. If Weymouth found a suitable site for a stormwater wetland that is even a third of this size, it could have significant impact, and it may be able to receive funding and support from a range of public and private grants and organizations with interests in parks & recreation, cultural resources, flood mitigation, heat island mitigation, safegaurding water quality, and fisheries conservation.

Images of Alewife Stormwater Wetland, Cambridge MA. Images by Stantec.

3. Guide Park Landscaping Towards Plant Community-Based Designs

Landscaping in all areas of town, from public parks to road medians, could be amended or replanted in order to increase cooling and stormwater filtration. While conventionally landscaped medians in town often contain a collection of ornamental perennial cultivars widely spaced within dark-colored mulch, amended plantings could be modeled after local native plant communities, completely covering the ground with multiple layers of site-adapted grasses/creeping groundcovers, flowers, and shrubs. Consider the approach laid out in “grounded design” a blog by landscape designer Thomas Rainier who, along with Claudia West, wrote the landmark landscape design book, Planting in A Post-Wild World.

• Protect more open space even if that space is degraded and hemmed-in by urban lots. Even small or narrow parcels may provide a good location for combining ecological restoration with green stormwater infrastructure into a project with high public visibility and access.

• Enhance existing strips of turf or conventional landscaping in municipal parks and roadways using denser growth patterns typical of native vegetation.

Comparison of green infrastructure planting approaches. Designs and images by Thomas Rainer.

4. Incorporate Salt Marsh and Dune Reconstruction into Shoreline Stabilization

In a coastal town facing significant sea level rise and increased frequency of coastal storms, construction of living shorelines and reconstructing salt marshes to insulate the coast from tidal surges should be a prime concern of the town. Consider incorporating these projects into existing repairs of infrastructure along coastal corridors, as these strategies have significant potential to complement grey approaches to coastal stabilization by insulating them from wave action, providing crucial habitat for endangered coastal wildlife, and providing more attractive views for property owners and visitors. By revegating areas that are dominated by impervious surfaces, these strategies will also contribute significantly to heat island and stormwater mitigation.

5. Use Best Management Practices for Healthy, Resilient Lawns

Appropriately sized areas of turf will always remain a crucial element of parks and gathering spaces. Organic turf best management practices can help provide resilient cover with healthier and deeper root systems, good soil aeration, and infiltration of stormwater. Interventions include mowing at higher heights, overseeding in the fall, regular aeration and compost applications, using better adapted turf species for Weymouth such as fescues, and allowing for harmless (even beneficial!) mixed species “weedy” groundcovers to become part of a longer, more textured lawn. These species include clover, self-heal, wild strawberry, barren strawberry, 5-fingered cinquefoil, dandelions, Plantago species, canadian lousewort, azure bluets, native woodland sedges, and violets. The Town could consider following the University of Massachusetts, Amherst’s guidelines for Turf Best Management Practices and Integrated Pest Management (see Bibliography).

Webb State Park, Little Cove.

5. Putting It All Together: A Greenway/Blueway Circuit

Weymouth’s could create a “Green-Infrastructure Necklace,” a circuit of urban greenways which utilize riverbank restoration, green stormwater infrastructure, and spaces for passive recreation as a critical strategy for keeping Weymouth comfortable and cool. In addition, Weymouth will define its town character by celebrating the ecological wealth of wetlands and waterways which are defining elements of Weymouth’s landscape and economic history. By daylighting streams; excavating and restoring natural floodplains and wide, winding river channels; constructing stormwater wetlands and rain gardens; and enhancing living shorelines, Weymouth will increase the water storage and infiltration capacity of its parks and waterways. In doing so, Weymouth will increase evaporative cooling and shade in its public parks and urbanized spaces, and simultaneously increase insulation from coastal and inland flooding, increase the quality and quantity of fresh water, protect fisheries and wildlife habitat, and altogether provide increased quality of life for Weymouth’s residents.

• Consider requesting to expand state ACEC to include Herring Run and Whitman’s Pond, enabling greater funding and oversight into management of lands surrounding those bodies of water, and potentially allowing for more public acquisition of lands surrounding them, and funding for their restoration.

• Conduct a feasibility study for a greenway through Jackson Square which connects the string of public parks from Whitman’s Pond to the Back River along the Herring Run. Such a plan may involve a restoration of natural streambanks in Herring Run Pool Park, and municipal acquisition of land or drainage rights from abutting properties, particularly parking lots, industrial or roadside service sites which would have a high likelihood of contaminating the herring run.

• Update OSRP and PPP to align with the goal of more blue spaces and greenways along rivers and wetland corridors. Ensure that public recreation infrastructure does not encroach on already confined wetland spaces, but rather expands these places into the more paved-and-turfed public sphere.

• Consult with ecological design professionals who have experience in living shorelines projects, dune reconstructions and saltmarsh restoration when renovating seawalls, boat ramps, and coastal roads, rather than exclusively leaving these tasks to civil engineers.

• Develop a stewardship plan with public utilities that involves potential land uses within utility easements which could assist in heat and stormwater mitigation without conflicting with overhead or underground utilities, such as constructed stormwater wetlands, shrub-thicket restoration, stream profile enhancements, and public trails.

Greenway #3

The Neck/Wessagusset Living Shoreline

Whitman’s Pond To Fore River & Salt Marsh Walk To Pratt’s Meadow

Whitman’s Pond to Back River: Renovating the Herring Run

Greenway #1

Greenway #2

APPENDIX A

RESOURCES

Climate Resilience and Urban Forestry Planning Documents

• Seeing the Forest, and the Trees: A Tree Preservation Study for Dover, MA*

• Waterwise Whately, A Watershed-Scale Climate Resilience Plan*

• Inland Interventions for Coastal Resilience in Mystic, Connecticut*

• Brookline’s 2021 Urban Forest Climate Resiliency Master Plan

• A Living Shoreline: Charles River (Charles River Conservancy)

• Green Infrastructure in Parks: A Guide to Collaboration, Funding, and Community Engagement (EPA)

• Coastal Stormwater Management Through Green Infrastructure: A Handbook for Municipalities (EPA)

Low-Impact Design Guidelines/Stormwater Best Management Practices

• MAPC Low Impact Development Toolkit

• Massachusetts Stormwater Management Handbook Vol. 2, THIRD EDITION

• Minnesota Stormwater Manual - Stormwater Control Practices

• NPDES Stormwater Best Management Practices - Stormwater Wetlands (NPDES BMPs for Stormwater Topics, category: Post-Construction, sub-category: Retention/Detention)

• City of Raleigh 2016 GI-LID Fact Sheets

• Montgomery County DEP, Rainscapes: Rain Garden Planting Design Templates Zoning Tools

• Model Open Space Design / Natural Resource Protection Zoning Bylaw (MA’s Smart Growth / Smart Energy Toolkit)

• NPDES Stormwater Best Management Practices - Zoning (NPDES BMPs for Stormwater Topics, category: Post-Construction, sub-category: Municipal Program Elements) Toolkits For Neighborhoods

• City of St. Louis Sustainable Neighborhood Toolkit

• NYC Be A Buddy

• Oswego, NY Rennasaince Block Contest

• MA CZM, Stormwater Solutions for Homeowners Fact Sheet: Reducing Impervious Surfaces

*Conway School student projects available on The Conway School website: http://www.csld.edu

20 communities in MA have implemented a Stormwater Utility as of 2022:

• Ashland

• Belchertown

• Bellingham

• Braintree

• Brockton

• Chelmsford

• Chicopee

• Dracut

• East Longmeadow

• Fall River

Stormwater Utility Comparison

• Longmeadow

• Millis

• Milton

• Newton

• Northampton

• Pepperell

• Readings

• Shrewsbury

• Westfield

• Westford

TOWNS THAT HAVE IMPLEMENTED TREE PRESERVATION BYLAWS

Tree Protection Bylaws, Private Property

• Cambridge - Cambridge Tree Protection Bylaw

• Concord - Concord Tree Preservation Bylaw 2021

• Granby - Sec 8.09 Trees and Plantings

• Lawrence - Zoning Landscape Regulations

• Lexington - Town of Lexington Tree Bylaw

• Lynnfield - Lynnfield Tree Preservation Bylaw

• Newton - Ch. 20 Article 5, Tree Preservation

• Northampton - Northampton Tree Ordinance

• Springfield - Significant Tree Policy

• Wellesley - Wellesley Tree Bylaw

• Weston - Proposed Suitable Tree Initiative

Land Clearing Regulations

• Ayer - Ayer Bylaws Section 9.2 and 9.6

• Brookline - Erosion and Sediment Control (Stormwater Bylaw)

• Northborough - Chapter 7-09 Development Regulations

Public Shade Tree Bylaws

• Amesbury - Tree Ordinance

• Barnstable - Ch. 221 Trees

• Belmont - Regulations for Protection and Preservation of Public Shade Trees During Construction

• Chelmsford - Ch. 161 Trees

• Chicopee - Ch. 257 Trees

• Fall River - Fall River Tree Ordinance

• Grafton - Article 33 Shade Tree

Source: Seeing the Forest, and the Trees: A Tree Preservation Study for Dover, MA by Kaitlynn Campbell, Audrey Logan, and Brett Towle. Conway 2022

Plant Lists

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Weymouth, Massachusetts, is a coastal town twelve miles southeast of Boston, with a population of 58,000. The town is experiencing the growing pains of a village-oriented community within commuting distance of a sprawling metropolis. Several municipal departments, along with many town residents have raised concerns that development may be leading to declining water and air quality and the formation of urban heat islands, which pose significant public health hazards in the face of climate change. This report analyzes how urban land cover contributes to the formation of urban heat islands in Weymouth and explores opportunities to reduce such effects, improving quality of life for residents while also helping to mitigate climate change.