The City - Paper 3 – My Site and Natural Processes

Early map of pre-filled Back Bay. Note the existing highway and railroads crossing the bay and restricting the flow of water.

A street sign emphasizes the narrow passageway through a street canyon (St Germain St).

Buildings in the site. There are street canyons between every residential block, and some cut through the middle of blocks.

A look down Clearway St. This street ends at the end of the block and is used primarily by residents of the apartments.

A diagram of air flow patterns in street canyons.

The effect of trees on air flow in my site.

Soot and grime catch on in this recessed corner along a street canyon, discoloring the red brickwork.

Wind and water erosion have worn this vulnerable brick surface smooth. This wall runs parallel to Mass Ave and prevailing winds.

Large trees provide much needed shelter from the sun, wind, and dust in the children's playground in block 1.

This tree, at the north end of the site, struggles to survive in harsh city conditions.

Trees further south have relief from the congestion and grow taller.

Supported by open soil, good ventilation and well-lit location, these trees on the east side of Mass Ave grow tallest.

A tree is carefully balanced by cables into growing vertically and symmetrically.

Trees along Clearway St reach out to the sun that shines unobstructed in the center of the canyon.

An unsuccessful ivy planter makes no use of the support mesh behind it.

A few feet over, a better-lit planter has grown ivy up the side of its mesh.

Pioneering plants sprout in the cracks of a canyon, but will not likely be around for long.

Paper 3 – My Site and Natural Processes

When asked to describe the origins of a city as historically rich as Boston, one would probably cite such historic events as the Boston Massacre before considering any natural events like the expansion of glaciers into the bay area many years before. Yet, natural processes have played a huge role in shaping Boston into the city it is today. Events happening on a geological time scale have repercussions on current decisions made in city planning, such as what kind of building materials are readily available for use and where to send sewage to ensure it is washed away from the city. My site is located in Back Bay, perhaps the most drastically altered portion of the Boston landscape in the last two centuries, and the processes by which my site evolved into its current topography are common with those by which the Back Bay was formed. The focus of this paper will be on the history of Back Bay as a whole and on features of the current topography of the site. I will also be concentrating on two natural processes visibly acting on the site in the present: air flow and vegetation.

History of the Back Bay

In my second paper, which concentrated on the history of human development in the area of my site, I discussed the process of land filling in the Back Bay. While this actual process was carried out with human technology and labor, the reasons for filling the submerged bay area and its subsequent topographical character as dry landfill are intertwined with natural processes. The topics of this discussion on history are three-fold: to trace the origins of the Back Bay as a body of water, to determine how pollution and stagnation led to its conversion to dry land, and to explore ways in which the process of filling has affected the current shape of the site.

Up to about three million years ago, the main forces acting on the Massachusetts Bay area were geological. Plate tectonics and volcanic intrusion formed the mountains and hills west of Boston, and the abundance of granite below and around the Greater Boston area can be traced back to these relatively violent processes. In the past three million years, however, the dominant force in shaping the landscape was glacier movement. Glaciers covered the entire area, advancing and retreating over the terrain and smoothing down mountains and hills in the process. The weight of glaciers forced down the terrain in areas to altitudes below sea-level, forming a rough coastline, and friction from glacial movement ground the earth below into clay, sand, and soil. These finer materials comprise layers of sediment that cover the granite bedrock, and the eventual retreat of the glaciers carved out of these layers the form of Massachusetts Bay, and subsequently, the Back Bay. Melting glaciers also formed temporary rivers which deposited channels of sand and gravel into eskers. One particular esker in Needham, a town nearby Boston, was mined extensively for materials to fill in the Back Bay in the 19th century. ¹

Why fill in the Back Bay? As in any coastal city, land in Boston carried a high premium, especially as congestion in the Shawmut Peninsula during the 1800’s forced development outward towards the sea. Already several hills in Boston, including Beacon Hill, had been cut down for material to use in filling new land around the peninsula. However, the desire for more development space was not the only reason behind initiating the largest and most important land-filling project in Boston’s history. Public concern over sanitary conditions in the Back Bay was decisive in forcing the city government to action.

The poor sanitary conditions in the Back Bay were, ironically, a result of the natural response to prior attempts to capitalize on the Back Bay. As a receiving basin for the Charles River, the Back Bay was well-suited for the construction of mills to harness the power of its flowing water. A long dam crossing from Boston to Roxbury was built to control the tides, and in the process it created a popular promenade connecting the suburb with the city. However, this early highway was perhaps the most useful result of the dam’s construction; few mills were built that actually took advantage of the dam. Instead, the Back Bay became a common dumping ground for trash, sewage, and other refuse, with a sewer emptying out directly into the water and rats plaguing the sea walls surrounding the bay. Already cut off from a constant circulating current by the dam, the dirty water remained dirty, which, when combined with warming during the summer, allowed bacteria to thrive. The resulting stagnant pond, made worse by two new railroads that crossed the water and further restricted flow, became a cesspool that looked and smelled noxious. Thus, this miscalculation of environmental planning resulted in a glaring public health problem, and the only way to correct it was to fill in the contained water basin and extend sewage lines further out past the bay. (Actually, the stagnating ponds and filthy marshes persisted until the Fens park system was created, but that is beyond the scope of this discussion.) ² ³

In filling the Back Bay, the commissioners (working for various private interests and the Commonwealth of Massachusetts) faced an enormous task: find an immense volume of material to transform into land, and transport it to the Back Bay site. Here, the aforementioned esker in nearby Needham played an important role, providing a plentiful supply of sand and gravel that could be easily transported by railroad to the site. Again, glacial action from millions of years before affected the development of the physical Back Bay site, by determining the types of materials that would be most convenient to use in altering the landscape. Of course, sand and gravel do not provide the most solid ground for city buildings; wood pilings are required underneath to help keep structures from sinking into the ground. These self-imposed restrictions help account for the current topography of the Back Bay area and my site in particular. They are not the only reason why the commissioners chose to build a wide, flat expanse of land from the former body of water, but they are an excellent example of natural processes affecting human decisions for city planning. ⁴

Topography

Back Bay land is flat; this is more a result of convenience, not natural process. Flat land is easier to build on and facilitates a more efficient use of space than the side of a hill or a bumpy plain. It also allows for the use of flat wood pilings underneath the foundations of buildings, a necessity for construction on relatively unstable filled land. Since the land in Back Bay exists because of a need for building space, a uniform geographical plane is the obvious goal for a filling project. The area of the site conforms to this standard, and thus the ground topography of the site is artificially flat.

The layout of buildings, in contrast, adds a layer of complexity to the otherwise uniform topography of the site. “Street canyons,” in the form of alleyways and streets running between high-storied buildings, are abundant in the site. These canyons form on Belvidere St, St. Germain St, Clearway St, Public Alley 903, and Edgerly Rd, as well as alleys in the middle of blocks 3 and 4. Each canyon differs in the height of its walls and width of its channel, but in general every canyon consists of a narrow asphalt pathway bounded on either side by buildings at least three stories high. Asphalt pathways are required as each canyon must accommodate vehicle traffic; marked streets are also lined with a sidewalk for pedestrian traffic. These sidewalks are made of granite or brick to withstand constant weathering from frequent snow and rain, and are raised from the street level so that water may drain away from the buildings and footpaths along the walls. For similar reasons the walls of the buildings are usually made of brick, ideal as a water-resistant and fire-retardant material in an area barely accessible by wide fire trucks. Note that both granite and brick (which is created from clay) are abundant resources in the areas surrounding Boston; it is no coincidence that they are used all over Boston as pavement and building material. We can trace the cause of these patterns back to glacial and volcanic processes millions of years ago. ⁵

Wind patterns, air pollutants

The orientation, width, and height of canyons affect the degree to which they are affected by the wind. Strong winds in the area of my site originate from the Charles River, where powerful gusts flow across the water unimpeded by structures or vegetation. Since the site is south of the Charles River, the prevailing wind direction is north-to-south. The streets that run roughly north-south in my site (Massachusetts Ave, Edgerly Rd, and Public Alley 903) experience the strongest winds; however, these winds are relatively weak due to the site’s distance from the Charles River, the density of buildings blocking a direct path to Edgerly Rd and Public Alley 903, and the wide cross-section of Massachusetts Ave. Street canyons running east-west through the site (Belvidere St, St. Germain St, Clearway St, and the alleys in between) face even weaker winds, but are subject to other effects that we do not immediately see in the north-south streets.

A common problem with street canyons perpendicular to the direction of prevailing wind patterns is the tendency to retain air pollutants within the canyon walls. This happens for two reasons. The air inside the canyon may warm up faster than the air above, creating a temperature inversion which traps the warmer air and pollutants from cars underneath. A lack of direct wind keeps this air from circulating, and the resulting accumulation of pollutants can reach hazardous levels. In addition, pollutants carried in the wind may get trapped within the canyon should the wind enter and swirl around within the walls. Street canyons running in the north-south direction do not face these problems as wind can easily sweep particulates and gases out of the area. The east-west canyons in my site also avoid these problems, but in a different way. ⁶

Streets like St Germain St and Clearway St use trees as ample shade cover and as an air filter to counteract both effects of street canyon air pollution. The shade provided by the large trees keeps the streets cooler in the summer, avoiding the “heat island” effect that leads to inversions. The leaves of the trees also help filter out pollutants in the wind that cycle into the canyon space. Since these streets are also low-traffic areas, there are fewer direct sources of pollution, and the overall effect is a minimization of dust and soot in a relatively narrow street canyon. This is very important for the quality of life in residencies along these streets, since many apartments depend on fresh air coming from windows facing these streets. We still see some signs of degradation from air particulates in the form of accumulating soot where the lower parts of buildings meet the sidewalk, and wind erosion contributes to the smoothing of brick in directions parallel to the wind, but overall it seems that the design of these street canyons was made with processes of air flow and pollution control in mind. ⁷

Vegetation

Trees comprise the majority of living plants in the area of the site. They are most visible in orderly rows mirroring the rows of apartment houses that line every street of the site. Because the site was built on filled land, there was no existing vegetation when building construction on the site began in the late 19th century. Thus, none of these trees can be more than a century old, and all of them were planted by human hands for specific purposes. As we have already seen, trees in the street canyons of St Germain St and Clearway St help shade the streets and minimize air pollution. Trees in the children’s playground in block 1 also provide comfortable shade, as well as mitigating the harsher effects of wind and rain. Perhaps less practical is the planting of trees for the beautification of areas of the site. On Massachusetts Ave we see several different ways of approaching this, with varying degrees of success.

The trees on the northern end of block 2, facing the street, are twisted, stringy, and provide little comfort in terms of shade or protection from wind. They mainly fail to grow because of close proximity to sun-blocking tall buildings, as well as a very exposed soil area in a high traffic zone. The ability of these trees to grow long, deep roots is hampered by the small planters and tough soil in which they are placed, and they will need a long period of growth before they can stand up to the wind and snow that are shaping their peculiar state. In contrast, the trees further south on Massachusetts Ave fare much better in larger planters. A large apartment building sometimes blocks sunlight to the trees on the west side, which cannot match the growth of full-bodied trees with little to obscure them on the east side. The east side trees have an added advantage of an extended lawn surrounding them providing soil cover. Still, the gray color of the apartment building offers some light reflectivity (more than the red brick of buildings north) that gives all the trees here an advantage over the struggling ones north of them. ⁸ ⁹

Also on Massachusetts Ave, nestled in with the clean, elegant courtyard of the Christian Science Publishing Society building, are smaller, more tightly-controlled trees. These trees are radially symmetric and stand straight up, thanks to the three sets of cables wrapped around the trunk to ensure proper orientation. They will probably not reach the size of the larger trees further down Massachusetts Ave, but they will achieve the desired look that the exterior designers wanted in that area. Like bonsai trees, these carefully engineered plants are an extreme example of the control man tries to exert over natural processes. Not all plants in the site, however, are so easily restricted. ¹⁰

Light is more essential to the life of a plant than cages and cables, and the growth patterns of trees in the street canyons reflect this nature-over-nurture principle. Trees in the street canyons tend to “face inwards”; they are thicker and extend further towards the center of the canyon than to the walls. The resulting shape is asymmetrical, with the impression that they are gravitating towards the center. This is because the further away their leaves are from the walls of buildings, the more hours per day they can spend in the sun. Branches with greater exposure to sunlight produce more energy and tissue, and growth is accelerated towards the center of the canyon and stunted at the edges. The effect of radiance is even more pronounced underneath the apartment building in block 2. Planters set against the walls are adjacent to mesh to support ivy growth, but only the planters not directly underneath the overhang contain ivy climbing up the mesh. An identical planter two meters away from one with ivy does not have any extending onto the mesh, because of its positioning relative to daylight patterns. Similarly, trees on the site located in open areas with access to sunlight are the largest on site. Despite our efforts to optimize the placement and growth of all trees, basic natural needs often take precedence in determining which ones will flourish.

There was a noticeable lack of spontaneous plant growth on my site. Every curb was mostly bare of anything other than granite and brick. I found this peculiar, because while granite is a very difficult medium to grow anything in, the frequent spacing between bricks should allow for some hardy plants to grow. Yet, for all of my searching I could find little sign of untouched plant life. In one alley, however, I finally discovered a few urban plants in a patch of dirt path. They grew in that particular spot because a vent just behind them allowed hot air to melt the snow around them, giving them a clear path to air and sunlight. It seems unlikely that these plants will grow into substantial trees; while they can certainly survive in rugged conditions, human hands will need to pluck them out to protect the vent and the wall. Uncultivated plant growth in the site as a whole probably suffered the same fate, a selective extermination based on human needs and tastes.

Conclusion

Humans desire to conquer their environment, shaping the landscape and ecosystem of their surroundings to satisfy their needs. Sometimes, this leads us to create something from nothing, to create a landmass from a body of water, to build granite and brick canyons from flat landfill. Sometimes this leads us to plant temporary forests to counteract our own air pollution, or to cultivate ivy to beautify the exteriors of our buildings. Nature, however, always has a way of surprising us and counteracting the ways we try to restrict her. Even when choosing to build buildings or fill land, we are at her mercy, as she decides what materials we may use and how we can apply them. Nature did not stop after millions of years of topographical change just for us to take over; thus, we should never lose sight of how natural processes will affect every subsequent decision we make in city planning.

References

1   Warner, Sam Bass. Greater Boston. University of Pennsylvania Press, 2001. p 6-10.
2   Whitehill, Walter Muir. Boston: A Topographical History. The Belknap Press of Harvard University, Cambridge, 1968. p. 90-94, 145.
3   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 18-23.
4   Whitehill, Walter Muir. Boston: A Topographical History. The Belknap Press of Harvard University, Cambridge, 1968. p. 150-154.
5   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 56-58.
6   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 56-57.
7   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 55-60.
8   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 190-191.
9   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 175-179.
10   Spirn, Anne Whiston. The Granite Garden. Basic Books Inc., Cambridge, 1984. p. 179-180.
Computerized maps created in Boston Atlas http://www.mapjunction.com.
Original site boundary map courtesy of Microsoft MapPoint service.
All other photographs and illustrations by David Lee.