Periferia
Internet Resources for Architecture and Urban Design in the Caribbean
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Periferia:
Urban: Resources: Preservation,
Mixed Use and Urban Vitality
Preservation, Mixed Use and Urban Vitality
by Jonathan Cohen, AIA
Synopsis
This project will examine the roles of preservation and mixed use as two among several
interconnected factors contributing to urban vitality. Jane Jacobs' book, The Death and
Life of Great American Cities
(1961), warned that land use segregation and low density dispersal were killing off
the diversity that is the basis of urban life. For Jacobs, the essential phenomenon
of cities is the mixture of activities they support and encourage. She identified
four conditions which must be present for vital cities:
All districts in a city must serve more than one primary function, and preferably
at least three, so that there will be people on different schedules using facilities
in common.
Short blocks and distances scaled to pedestrians.
A mixture of buildings of varying age and condition, so that there are cheap rents
for enterprises just starting out as well as high quality space to keep successful
enterprises from leaving the area.
Dense concentrations of people to support diverse activities within a compact area.
Seen this way, preservation is part of a broad strategy to reinvigorate central cities.
Heretofore, urban renewal has been a process of replacing "blighted" areas with
new development, analogous to a farmer clearing a field and preparing it for a new
crop. But Jacobs' observations point to a different paradigm: that of a living forest,
a complex ecosystem in which old growth coexists with new, indeed they are dependent
on each other for sustenance.
In order to illustrate this concept, it is necessary to examine the influences that
have historically shaped city form. These include government and military organization,
forms of taxation, social, artistic and political movements, transportation and communications,
and the influence of nature. The intention is to promote this "organic"
vision of cities as incubators of diverse activities in a way that is stimulating
both economically and culturally. I will examine how misapplied planning practices
have thwarted healthy urban growth and contributed to destruction of the natural synergism
of cities, resulting in sprawl, the abandonment of city centers, segregation by race,
class and age, wasteful overconsumption of resources, and the loss of environments worth
preserving.
The product of this research will be a kind of matrix which approaches the idea from
several simultaneous directions and over time. Although not intended as a picture
book, it will be a well illustrated treatise on the physical design of cities and
its effect on human activity (and vice versa). It will focus specifically on preservation
and mixed use as parts of a strategy for urban vitalization. Eventually, the material
will be assembled into an interactive hypermedia project, employing text, graphics,
sound, and video, to be published as a book and CD-ROM.
The short segments that follow show the approach I intend to take to this subject.
In the book, each segment will be expanded to chapter length and many more will
be added. There is no linear order to these segments, instead "hyperlinks" will connect
them interactively.
Rigid land use control has historically existed only in the presence of a strong central
authority. The transition from medieval to baroque urban form, for example, reflected
the emergent power of the state in the 16th to 18th centuries. The radial symmetry of Versailles is a diagram of the throne's preeminence over its realm: all things
are focused to the center.
This shift from the fine-grained complexity of medieval cities to the grand gestures
of the baroque was not merely symbolic. It had economic and military value as well.
The most active town planning in the period following the Middle Ages was in the design
of military outposts. Their form derived largely from the new Italian theories of
military encampment published in Machiavelli's Arte della Guerra
in 1521. Meandering fortifications formed a star-shaped edge linked by streets radiating
from the town "square", itself originally a mustering place for troops. All points
on the perimeter had a direct connection to the center.
The baroque radial plan established a hierarchy of place which the medieval urban
form of randomly connected streets didn't have. Major and minor axes, rond-ponts
and relative distance from the center are all attributes which make some locations
clearly more important than others. This aspect of relative importance is a key to the development
of land separation, especially with regard to public and government functions versus
private uses.
When Pierre L'Enfant planned the new city of Washington, his model was Versailles,
with its axial views and formal gardens of clipped hedges. Washington, the seat
of power, remains the only city in America planned on baroque principles. It also
has perhaps the most extreme form of land use separation. Georgetown, which predated the new
city, provides an interesting contrast. With its finer grain, small scale, and non-radial
pattern of streets, it remains the most vibrant and walkable part of modern Washington.
The grid system of city planning, which had originated with the Romans, became the
predominant urban form of 19th Century America. Its' efficiency and ease of surveying
made it attractive to speculators and it proved well suited to merchant house builders from Baltimore to San Francisco.
The grid provided a framework which was infinitely expandable but which allowed small
increments of growth within a well understood pattern. A builder of two or three
rowhouses or one of two hundred could build in the same tract simultaneously. At
the same time, the system allowed a considerable variety of detail within standardized design
and materials.
But the grid system had drawbacks, too, especially where the blocks were to long or
too large. Compare Manhattan's Upper West Side with Greenwich Village. On the West
Side, the long cross-town blocks create traffic problems and tend to channel all
pedestrian movement to the few north-south streets. The result is a form of strip commercial
development which is neither lively nor varied. Greenwich Village, with its fine
grain of streets predating the 1811 grid plan for Manhattan, has a bustling street
life and a much greater variety of shops and restaurants.
The same phenomenon can be seen in San Francisco, where two gridiron plans meet at
Market Street, at 45 to each other. The grid north of Market, with its short blocks
and numerous mid-block alleys, has always been the compact commercial heart of the
city. The South of Market, it' grid composed of large, long blocks, is a poor neighbor.
Originally a residential and warehousing district, it has comparitively little pedestrian
activity, moribund commercial development and until very recently, a long history of decay.
The Utopian reform movements of the 19th Century were a moral reaction to the overcrowding
and filth of the industrial age. Proposals by Robert Owen, Charles Fourier, Etienne
Cabet and others led to experiments in community living with various degrees of success. They all had in common an impulse to treat social ills with large doses
of light, air and greenery.
By far the most influential of these proposals was Ebenezer Howard's Garden Cities of Tomorrow
, published in 1898. Howard combined Victorian rationalism and Christian benevolence
with a theory of urban growth based on biology. His ideal town had a population
limited to about 30,000 and grew not by expansion but by "reproduction". Ten or
more such cities, although physically separated by open space, would form federations for
the purpose of sharing cultural facilities. Comprehensive planning would be achieved
through public ownership of all land.
Each Garden City was conceived as a self-supporting unit, but land uses were separated
by zoning. Housing was in the form of detached dwellings with individual gardens
for food production.
The ideas of "reproductive" growth and planned self-sufficiency provided the model
fifty years later for the English New Towns, which were established to stem the sprawl
of London.
Unfortunately, it was the anti-urban, dispersed forms of Howard's proposal which proved
most influential and not the notions of self-sufficiency and planned growth. The
reform movement associated the country with health and the city with disease, both
moral and physical. This notion has encouraged the gradual disurbanization of housing
prototypes throughout this century.
Clarence Stein's Radburn plan of 1926 was the first application to suburban housing
of Romantic planning ideas descended from Frederick Law Olmstead's parks and cemeteries.
It was also the first to acknowledge the arrival of the auto age.
Several elements have been influential:
The curving streets culs-de-sac which Olmstead used so picturesquely in Central Park
were here also employed to isolate through traffic from neighborhood access roads.
For the first time, streets were used to separate, not connect.
Neighborhood units were formed in "superblocks" with interior greenbelts to be used
as common open spaces by residents.
Community facilities were grouped into a park-like "civic center" of elementary school,
swimming pool, etc.
The effect on urban form of a shift in transportation modes can be seen in the gridiron
plan of New York City. The numerous east-west river to river cross streets provided
in the 1811 plan were made less important when shipping and other waterfront activities became but a minor part of the city's commercial activities. The few north-south
avenues, however, quickly became choked with traffic.
The environmental movement which began in the 1970's and became mainstream in the
1980's has had great significance for cities. Three important effects of this movementt
are now being felt.
First, the notion of ecology applied to human settlements provided a way to study
the tangle of activities which make up a city. The component uses of cities do not
simply coexist, but interact with each other in complex ways. The separation by
zoning of home, work and cultural activities into isolated enclaves tended to frustrate this
process. Cities are now seen as habitats, their form the product of something like
natural evolution.
Second, the need for preserving open space and agricultural land from the ravages
of sprawl took on a new urgency. For the first time, there was a process for assessing
the indirect and environmental costs of development; the "real" costs. Continued
expansion of the urban fringe was made more difficult and costly, creating pressure to
increase density in existing communities. Many suburban areas promoted "no growth"
policies, usually in the form of onerous or arbitrary zoning restrictions, creating
artificial housing shortages and inflation of land values. Mixed use may be a way to create
"new" land without losing open space or straining community services.
Finally, the idea of "recycling" was expanded from aluminum cans and newsprint to
reusing old buildings and adapting them to new uses. Ghirardelli Square first showed
the commercial potential of adaptive reuse and was widely imitated. Developers saw
a vast "nostalgia" market, and an alternative to the standardized shopping malls. Recycling
was successfully applied to other uses, from artists' lofts in SoHo to renovation
of Art Deco movie palaces and railroad stations turned into cultural centers.
The form of housing in America was changed drastically during the 1970's by two new
legal devices: Planned unit development and condominium ownership.
Planned unit development replaced zoning in the form of prescriptive formulas with
"contract zoning" based on the merits of specific proposals. The site plan defines
the agreement between developer and city which takes the place of a subdivision
map. Rather than placing each house on its individual lot, with standard setbacks, lot size
and coverage, etc., PUD zoning allows housing units to be clustered at high density
over portions of the development, leaving large areas of open space to share. The
housing user gives up a measure of private "back yard" for the greater amenity of aggregated
open space and community facilities. The result is usually more land- and energy
efficient than conventional development, achieving higher density with more variety.
Suburban housing has recently become denser and more "urban", borrowing elements
from old city housing prototypes such as townhouses and attached dwellings.
The success of planned unit development has spawned new zoning "tools" to accomplish
specific urban design objectives, including preservation. "Incentive zoning" is highly
evolved in New York, where special purpose zoning districts have been created to
serve a variety of public goals. Bonuses of extra density and height are granted to
developers in return for the preservation of desirable existing uses or promotion
of new ones. Creation of such special districts has helped preserve the theater
district, for example, encouraged mixed uses along Fifth Avenue and protected historic landmarks
through air-rights transfer.
The economics of mixed use derive from the notion that mutually supporting activities
will have a synergistic effect on each other; that is, the total revenue generated
will be greater than the sum of the parts. If housing and office uses are combined,
for example, a market is created for shops and services which could not be supported
by either alone. This does not have to occur in one building, but the uses must
be physically integrated in a way that permits pedestrian circulation between them.
For developers, the great front end risk, more complex management and planning and
the problem of penetrating different markets simultaneously has created a higher
"price of admission". As a result, most mixed use developments have been at large
scale. In addition, developers have sought greater public sector participation in several
ways. Publicly owned facilities such as convention centers and parking structures
have been integrated in privately developed projects. More often, however, public
involvement has been in the form of land assembly through eminent domain, tax abatement, incentive
zoning, modification of development standards and below market rate financing.
Unfortunately, the large scale of most mixed use projects of the 1970's created problems.
Popular political attitudes towards urban renewal have changed, especially when
families are displaced or useable existing buildings demolished. In addition, the
coarse grain of such projects tends to isolate them from the existing fabric of the
city, as in the Golden Gateway Center in San Francisco.
Mixed use at a smaller scale can provide a way to introduce commercial and office
use into residential area, as in suburban downtowns. It should also be tried as
infill in existing mixed use areas as magnet projects to stimulate neighborhood development.
At the same time that suburban zoning was isolating commercial activities into shopping
centers, the economic trend was toward large, standardized retail enterprises of
national scale. The ultimate manifestation of this trend has been the "big box"
retail that is now prevalent all over the continent. With this isolation came a loss of
both diversity and local flavor, with retailers offering the same products from coast
to coast. The scale economies of large production have produced less variety, not
more.
It has been observed that in lively parts of cities, small enterprises tend to outnumber
large. The reverse is true in suburbs, where stores are large but standardized in
appearance and merchandise.
Despite the ascendancy of the automobile, retailers have learned that effective shopping
environments have to be pedestrian oriented, whether they are in city or suburb.
Shopping malls are artificial village centers - pedestrian streets that you have
to drive to.
The rise of postmodernism as a movement signaled a new preference for complexity over
simplicity and inclusiveness over exclusiveness, less, in other words, is no longer
more. Modernism had rejected the past for a clean slate from which to produce freestanding, sculptural forms. Architects now seek to relate buildings to their context,
borrowing from vernacular and historical sources, and showing new appreciation for
the messy complexities which make urban life interesting.
The new activity is propitious for mixed use in several ways. Mixed use is a return
to a historical form of urbanism and points to the revival of old building types
like the Agora and Galeria. Different functions in one building allow for a richer,
more complex formal expression. Mixed use frequently requires the integration of a new
project in already developed areas, sometimes with adaptive reuse of exiting buildings.
Universities have been fertile ground for experimentation in urban forms and mixtures
of uses. Many campuses are like remnants of the medieval city: Formal public spaces
and symbolic building types, long traditions, world-wide faculty associations and
an emphasis on community life. Students tend to be open to new kinds of living arrangements.
It is not surprising then that several of the most forward-looking mixed use projects
have been built in university settings. The first mixed use housing scheme was Sert's
Peabody Terrace at Harvard. Charles Moore's Kresge College at UC Santa Cruz is a
"medieval" mixed use street with housing, offices and classrooms. Donlyn Lyndon's
Pembroke dormitories used the urban vernacular of walk-up apartments over shops,
reinforcing the existing streets. Diamond and Myers; interior gallery of housing
and shops for the University of Alberta is an urban street space protected from the harsh prairie
climate.
The complete text is available at http://www.dnai.com/~kvetcher/MixedUse.html
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