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Urban Morphology (2009) 13 (2), 105-20 International Seminar on
Urban Form, 2009 ISSN 1027-4278
Aspects of urban form
Karl KropfUrban Morphology Research Group, University of
Birmingham and
Roger Evans Associates Ltd, 59-63 High Street, Kidlington, OX5
2DN, UK.E-mail: [email protected]
Revised version received 23 March 2009
Abstract. The diversity and complexity of human settlements is
reflected in therange of ways we try to understand them. The
richness of subject matterpresented by cities has given rise to an
equal richness in methods ofinvestigation. Even within a single
field such as urban morphology, there aredifferent approaches with
different terms of reference. The challenge raisedby the diversity
is not how to select between the different views but how tocombine
and co-ordinate them. The purpose of this paper is to undertake
aninitial critical analysis of different approaches to urban
morphology in aneffort to meet that challenge. The first aim is to
identify the range of differentphenomena taken as the object of
urban morphological enquiry. The secondis to identify an aspect
that is common to all the approaches and that can beused as a
reference key to co-ordinate different views in a rigorous way.
Theultimate goal is a composite view in which the different
approaches supporteach other to provide a better understanding of
human settlements.
Key Words: urban form, spatial analysis, space syntax, process
typology,historico-geographical approach
It might be said that the gamut of humancivilization is
condensed within the urban.Villages, towns and cities present a
density andrichness of subjects that is hard to find in anyother
human product. That richness is evidentnot only in the wide
diversity of settlementsand the depth of their complexity but also
interms of our capacity to identify and selectdifferent aspects to
explain.
Just as settlements are diverse and complex,so there are many
ways to describe andunderstand them. To only touch the
surface,approaches range across the broad categoriesof social,
economic and environmental andfocus variously on the statistical,
spatial/geographical, formal, historical,
psychological,informational and aesthetic dimensions. Evenwithin a
particular area of interest, there are
commonly a number of different approachesfocusing on the same
thing.
So, if we acknowledge that humansettlements are diverse and
multi-faceted, weshould not be seduced by the
superficialattractions of a single point of view. And toacknowledge
the wide range of methodsshould not put us on a tower of Babel,
deaf tothe voices of others. Rather it should place usat the
confluence of routes radiating out to thedifferent regions of the
world. This isparticularly true of the morphologicalapproach which,
as originally conceived byGoethe, should be an independent study
thatmakes use of the findings of all the othersciences,
co-ordinating them under theunifying aspect of form (Wilkinson,
1962, pp.177-8).
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106 Aspects of urban form
A similar, though slightly stronger, viewcomes from Kevin Lynch
(1981, p. 37) wholikens theories of city form to the branches ofa
tree, but states that,
unlike the branches of trees we know, theyshould not diverge.
They should interconnectand support each other at many points.
Acomprehensive theory of cities would be a matof vegetation, and
some day the branches willno longer exist in separate form.
Even in seeking the milder connections of co-ordination (as
opposed to a comprehensiveunification), the current state of our
under-standing would appear to acknowledge thereare a number of
unresolved splits or gaps tobridge along the way.
There is the disparity between the fact thatcities are the
result of deliberate and co-ordinated human effort on the one hand
andexhibit characteristics of self-organizationand emergent
behaviour on the other. Cancities be both planned and emergent? If
theyare both, what is the balance between the twoand can we
articulate the relationship andinteraction in more detail? What is
the relationbetween local processes and global structure?
There would also appear to be a parallel splitbetween on the one
hand our ability to identifyand describe coherent structures
andrelationships and on the other the seeminglyinescapable level of
ambiguity that emergesfrom close scrutiny. By what means shouldwe
seek to co-ordinate the different views andapproaches?
In a number of fields, evolutionary thinkingseems to be
providing a common frameworkwith the most promising potential to
bridgethese gaps. Yet again, it is not clear that thereis a common
idea of what exactly is evolvingor adapting. Nor is it clear which
(or whichcombination) of the related theories ofevolution,
developmental biology (morph-ogenesis) or ecology is most
appropriate toapply (Kropf, 2001; Steadman, 2008). Thisshould
perhaps not be surprising because in aprofound way we are
approaching the matterbackwards.
Theories of evolution developed out oflengthy, progressive
efforts of classification
and the perception of relationships between thespecies
classified. Those theories have beenelaborated and refined over a
similarly longperiod of time so that we now have the benefitof
ready-made theories that we can try to applyto a range of
phenomena. The elaboration ofthe theories has also fed back to
ideas aboutclassification, which have been refined in turn.In the
case of human settlements, if weacknowledge the complexity,
diversity andambiguity of the objects we are seeking tounderstand
and the range of different ways wecurrently use to describe them,
it is fair to saywe do not have the benefit of a clearly definedset
of objects to explain.
The wider state of affairs reflected in thesequestions is
represented as a kind of micro-cosm within the field of urban
morphology.There are several distinct approaches to thestudy of
human settlements that go under thebanner of urban morphology.
Close examin-ation of key texts suggests that urban form
isdescribed in a number of different ways in thedifferent
approaches. The gaps do notrepresent insuperable barriers. Already
thedifferent approaches are broadly comple-mentary. How could they
be made morerigorously and effectively so?
The purpose of this paper is to explore theseissues through a
critical analysis of a few coreconcepts used in the various
approaches tourban morphology. The aim is to find aspecific means
of co-ordinating the findings ofthe different approaches and help
them worktogether and realize the significant potential toestablish
a richer multiple description. With aricher and co-ordinated
description it mightthen be clearer how the various elements
fitinto or inform evolutionary thinking.
Methodology
The goal of the analysis is to identify acommon element, defined
in a consistent way,that can be used as a reference key
orregistration mark to co-ordinate differentdescriptions. The
analysis is not meant as adeconstruction but a sorting through
andcomparison of existing concepts and methods.
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Aspects of urban form 107
Because the analysis entails a comparison oftexts, it
necessarily entails a scrutiny oflanguage and the concepts and
phenomena towhich the language refers. That in turnfocuses
attention on the particular character-istics of the phenomena that
are pertinent tothe authors own objectives (Eco, 1979, pp.77-8,
245-61; Putnam, 1995, pp. 5-26). Theanalysis therefore involves a
sorting orclassification of pertinent characteristics intogeneral
categories.
This focused analysis is part of a moregeneral process of
enquiry that seeks todescribe and explain the phenomena inquestion.
Broadly, it is a free movement oriterative cycling through
hypothesis, deductionand induction (Peirce, 1958, p. 367).
Thestandards for the deductive component of theenquiry are those of
formal logic. Ofparticular importance is the distinction
madebetween class, relation and property andbetween a class and a
member of the class.
For effective comparison, it is necessary toestablish a
consistent method of analysis usingthe same set of terms for all
examples.Because the common view used in analysis isto see each in
terms of classes, relations andproperties, this then provides the
best basis forcomparing terms. The question to be asked is,are the
terms used in each method defined inthe same way? If not, which
offers a betterdefinition? The second question demands avalue
judgement. The primary criterion forevaluation is consistency: all
instances of agiven definition should be based on the samepertinent
characteristics. Secondary criteriainclude specificity definitions
should clearlyposit classes of identifiable phenomena insufficient
detail; generality definitionsshould be based on pertinent
characteristicsfound in as wide a variety of examples aspossible
while still allowing for theidentification of specific
differences;comprehension definitions should accountfor as wide a
range of objects as is appropriateto the task of explanation;
coherence definitions should be related to each other in
aconsistent way in order to form a clearstructure.
Urban morphology
The obvious and perhaps superficiallybelaboured starting point
for critical analysismust be the terms urban morphology andurban
form. It is the multitude of assumptionspacked into those terms
that is of particularinterest, not at a wider semantic level but
interms of the operative definitions manifest inthe works within
the field.
While urban by derivation and connotationrefers specifically to
cities, the work of urbanmorphologists clearly suggests that the
term istaken to refer more broadly to humansettlements. Examples
include the studies byConzen (1966) of small market towns andlinear
settlements, the works of Slater (1982)on market towns and rural
settlements, studiesof suburban development and fringe
belts(Stanilov and Scheer, 2004; Whitehand andCarr, 2001; Whitehand
and Morton, 2003) andexamination of modern peripheraldevelopment
(Levy, 1999) to cite only a few.
Morphology, as originally conceived byGoethe (1952) (see also
Wilkinson, 1962) isthe study of physical form, principally ofliving
things but also works of art. His majorinsight and contribution was
to relate theoutward form of an organism or artisticcreation to its
internal structure and to definethe internal parts making up that
structure interms of their position relative to each
other.Importantly, Goethe also saw outward andinternal form as the
product of a process offormation and transformation.
It is worth noting that comparative grossmorphology in plants
and animals is one formof evidence that led to theories of
evolution.For example, similarity or, more strictly,homology of
internal structure such as theskeletal structure of mammals,
suggested acommon descent.
While it may again seem laboured, to get atthe use of morphology
within the sphere ofhuman settlements, it is worth examining theuse
of urban morphology in non-specialistcontexts. Concepts, ideas and
theories arefundamentally social and reside, as it were,within a
population (Eco, 1979, p. 66; Peirce,
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108 Aspects of urban form
1958, p. 69). Simplified, outdated or partiallycorrect concepts,
if commonly held, canpresent an inertial weight or resistance
tochange (Dennett, 1995; Gould, 1991, 59-75).
School urban morphology: the persistenceof Burgess and Hoyt
In a number of documents and websitesintended for school level
geography (forexample, the General Certificate of
SecondaryEducation in the UK), urban morphology isdefined as the
pattern of land use within atown (an example in book form is Helm
andRobinson, 2002). The models cited are theconcentric zone
(Burgess, 1925) and sector(Hoyt, 1939). The material makes
reference tobid-rent theory, functional zones, centralbusiness
districts and residential zonesdistinguished by income groups.
Somesources also distinguish between cities withinMore Economically
Developed Countries andLess Economically Developed Countries
forpurposes of comparison.
To go beyond the superficial interpretationof land use in this
instance, it should beremembered that Burgess was a sociologistand
referred to his own work as an ecologicalapproach. With this in
mind it is fair to saythat his ideas discerned the
relationshipbetween human activities and their
urbanenvironment.
In the Dictionary of the social sciencespublished by Oxford
University Press(Calhoun, 2002), the focus on land use isshifted
and qualified, perhaps as a reflection ofa target audience further
through theeducational process. The definition states thaturban
morphology
refers to the shape of a city, including itsarchitecture, layout
of streets, and differentdensities of habitation. It is often
distinguishedin urban studies from functional zonation thepattern
of land use in a city.
The examples present two differentconceptions of urban form that
eachdistinguish two more or less distinct aspects:physical form and
land use or function.
The pragmatic insights of Kevin Lynch
Working within the fields of urban planningand urban design,
Kevin Lynch (1981)highlights the lack of clarity in
theconsideration of form with respect to use. Heexplicitly defines
settlement form as
the spatial arrangement of persons doingthings, the resulting
spatial flows of persons,goods and information, and the
physicalfeatures which modify space in some waysignificant to those
actions, includingenclosures, surfaces, channels, ambiences
andobjects. Further, the descriptions must includethe cyclical and
secular changes in thosespatial distributions, the control of
space, andthe perception of it (p. 48).
In Appendix B (p. 349) of the same book,however, he warns
that
while standard descriptions agree onemphasizing human activity
in its relation tophysical form, they are prone to confound thetwo
in a single ambiguous description, such assingle-family house or
church. Is it a typeof building that is being denoted, or
theactivities of worshipping or residing?
If interpreted broadly, his initial definition ofsettlement form
encompasses the wholesubject of urban morphology. Yet his
caveatalso points to the potential hazards implicit inour modes of
description. Lynch is clearlystating that the fluidity between form
and usein common names and descriptions, evenwithin specialist
spheres, can be a barrier tounderstanding.
The potential for conflating different aspectsis not limited to
form and use. Lynchsdefinition of form contains within it a
numberof distinct features that should be made moreexplicit if
descriptions, explanations andproposals are to be clear and
coherent. Just asLynch has distinguished between the class
ofphysical form and its relation to the classactivities, it is
possible to examine theremaining parts of his definition in terms
ofclasses, relations and properties.
Physical features which modify space insome way clearly refers
to the class of
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Aspects of urban form 109
physical objects and their spatial relations,which, in a number
of cases result in a patternof solid and void such as the interiors
ofbuildings or patterns of streets and blocks.Enclosures, surfaces,
channels andambiences (in the sense of surroundings)are different
types of object or space createdby the spatial relation or
arrangement ofobjects.
Persons doing things and flows ofpersons refer to the class of
humans and theproperty of being engaged in some activity,including
movement, and imply therelationship with the object or space
thataccommodates the activity. The flow ofgoods and information
refers to classes ofobject and the property of movement sharingthe
relation of being directed by humans forhuman purposes.
The control of space and the perception ofspace are two
different types of relationbetween a human (or group) and a space
(and,by implication, part or all of the objects thatdefine the
space). A space or object iscontrolled by someone or some group
and,equally, perceived by someone or some group.The concepts of
control and perception makeno sense without both sides of the
relation.
Cyclical and secular changes in spatialdistribution refers to
alterations in relationsbetween a class or object over time. The
twobroad temporal relations are continuity andchange. Both change
and continuity can onlybe described with reference to at least
twostates of the same thing. What becomesimportant in describing
the relations is theevidence we have for previous states in orderto
describe the relation one way or the other.
Compressed within Lynchs concisedefinition of urban form are six
distinctaspects:
physical form use/activities/movement control perception
continuity/change movement or flow of materials and
information
Looking back at the definitions examinedpreviously, the first
only explicitly includeduse, qualified by the relative position
ofoccupants within a social structure (socialstatus). The second
included both physicalform and use. The six aspects picked out
byLynch, as already noted, cover most of thoseincluded within the
discipline of urbanmorphology. For the purpose of determiningmore
explicitly which aspects are included,four broad approaches to
urban morphologycan be identified, each taking a slightlydifferent
view of form:
spatial analytical configurational process typological
historico-geographical
The spatial analytical approach
The spatial analytical approach is perhaps bestcharacterized by
the work of Michael Battyand the Centre for Advanced Spatial
Analysisat University College London. Using a rangeof methods and
models including GIS, cellularautomata, agent based models and
fractals,Batty seeks to understand the spatial structureand
dynamics of cities as complex, emergentphenomena, in which global
structure developsfrom local processes. Citing Jane Jacobs(1961, p.
349), Batty sees the city as a problemof organized complexity and
applies theconcepts of emergence and evolution inmoving toward
solving that problem.
The models employed and cited by Batty areopenly stated to have
a loose correlation withthe scale of the phenomenon modelled
(2007,pp. 35, 144-6). The models might representcity regions or
areas within a city. Cells in amodel most appropriately represent
plots orparcels or their simple aggregations but mightfall
somewhere between parcels and censustracts or other administrative
aggregationsdepending on the source of the data.
Similarly, the specific objects modelled areopenly left loose.
In many cases they can beinterpreted to represent generic
development
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110 Aspects of urban form
or built-up area and in some cases the modelsinclude routes. The
concept of the neighbour-hood is fundamental to the functioning of
thecellular automaton as a model but it is definedexplicitly in
terms of the structure of the modelrather than the phenomena
modelled.Importantly, there is ambiguity surroundingform and use in
what is represented. Muchof the work cited by Batty deals with
changes,growth and segregation of land uses as well asthe diffusion
or migration of residentpopulations based on a range of factors
(2007,pp. 142-3, 154) yet the morphologies thatemerge from the
models most clearly resemblethe spatial distribution of urbanized
areaswithin a sub-region (Figure 1). Indeed, Battystates that the
models are not intended to
provide accurate or predictive descriptions butto strip the
processes of city growth to theirbare essentials, and thus to
uncover the basicmechanisms at work (2007, p. 109).
There seems to be a deliberate blurring ofthe aspects of
physical form and use atdifferent spatial scales. Yet it would not
seemto be outside the realms of possibility that,given an
appropriate point of reference, themodels might be calibrated to
complementmore accurately other forms of description.
The configurational approach
Space syntax represents the configurationalapproach to urban
morphology, which seeks to
Figure 1. Graphic output from an agent-based computer model of a
sub-regional urban system (reproduced from Batty, 2007, p.
253).
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Aspects of urban form 111
understand the spatial structure of settlementsthrough a range
of analytical methods. At thescale of settlements, the theoretical
basis of theapproach is the relationship between spatialstructure
and the generic function ofmovement.
The... fundamental correlate of the spatialconfiguration is
movement. This is the caseboth in terms of the determination of
spatialform, in that movement largely dictates theconfiguring of
space in the city, and in termsof the effects of spatial form, in
that movementis largely determined by spatial
configuration(Hillier, 1996, p. 152).
Like Batty, Hillier sees configuration asemergent, with global
structure arising out oflocal processes.
With respect to the notion of form, spacesyntax takes a distinct
view because of itsemphasis on space and spatial
configuration,rooted in the analysis of buildings (Hillier
andHanson, 1984). The concepts and analyticalmethods focus almost
entirely on the voids ofa structure, principally the street spaces
withina settlement, though some consideration isgiven to the spaces
around buildings within aplot.
For Hillier, spatial form is the arrangementof spaces, with
explicit reference to the
position of any given space within thestructure of the
configuration as a whole. Thisformulation necessarily implies or
assumes thesolid that defines the space or void. Thedifferent
analytical techniques employedwithin the space syntax represent the
structureof solid and void in different ways. In themore abstract
techniques such as j-graphs, thesolid is not explicitly represented
at all (Figure2). To make sense of the analysis, however,the solid
must still be assumed to define thevoid. In the case of axial and
convex spacemapping, the solids are explicitly drawn, or areat
least used to generate the axial and convexmaps, and correspond to
street-blocks (Figure3). It is important to note that axial
andconvex space mapping are intended torepresent what can be seen
by a human withina space. The approach therefore implicitlyincludes
the relation between humans andphysical form. In terms of the
aspects set outabove, space syntax includes:
space/physical form use/occupation/movement perception
The process typological approach
The process typological approach to urbanmorphology is rooted
principally in the workof the Italian architect Saverio Muratori
but isbest represented by the work of the architectand urbanist
Gianfranco Caniggia, who studiedunder Muratori. The approach they
developedseeks to inform their architectural and urbanproposals
with an understanding of the builtenvironment by examining its
detailedstructure and the historical process of itsformation. They
begin with the generaldistinction between spatial and
temporalrelations, which they refer to, respectively, ascopresence
and derivation (Caniggia andMaffei, 2001, pp. 62-5). The analysis
ofcopresence proceeds from an abstract set orschema of component
subdivisions that formsa hierarchy: elements, structures of
elements,systems of structures, and organisms ofsystems. This
schema is first applied to indi-
Figure 2. Examples of j-graphs, whichillustrate the abstract
connections and relative
positions of a spatial configuration(reproduced from Hillier,
1996 p. 102).
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112 Aspects of urban form
vidual buildings, with building materials suchas bricks,
timbers, tiles etc. taken as theelements. The structures of
elements are thenthe associations of building materials withinsuch
things as walls, interior floors, roofs etc.Systems of structures
are arrangements of thelatter into rooms, stairs, corridors etc.,
theorganism being the building. The samescheme is applied to towns,
taking buildings aselements. The structure of elements is
anassociation of buildings or an urban tissue, ingeneral referred
to as an aggregate (Figure 4).The system of structures is then a
combinationof tissues forming regions or districts, whichtaken
together form the organism of the town(Caniggia and Maffei, 2001,
pp. 73-4).
The forms found at the different levels areidentified as types
which are conceived ascultural entities rooted in, and specific to,
thelocal process of cultural development. Theoperation of the
process over time and indifferent places leads to development
andchange and diversification of forms. Functionis therefore
implicit in the type concept in thatany form will have been
initially conceivedand developed to satisfy a particular humanneed
or desire. Throughout their texts,Caniggia and Maffei refer to the
functions ofthe different types of forms at the differentlevels in
the hierarchy. While different localprocesses lead to distinct
forms, there is a
generic similarity to the process which ischaracterized as
derivation. At the time ofconstruction, the form of a building is
basedon an idea or concept derived from the sharedexperience of
previous buildings ormodifications of them. The idea of thebuilding
and the act of construction ormodification are thus essential parts
of thecultural process and are distinct in terms ofclasses,
relations and properties. The ideainvolves the relation between the
sharedcultural concept and the population that holdsit and the act
of construction involves therelation between the builders and what
is built.Caniggia and Maffei thus identify thefollowing distinct
aspects of urban form:
physical form function/use the idea of the building or form the
act of construction/modification the cultural process of derivation
and/or
development/change
The historico-geographical approach
The historico-geographical approach to urbanmorphology is rooted
in and well summarizedby the work of the geographer M. R. G.Conzen.
The aim of Conzens town-plan
Figure 3. Superimposed mapping of convex spaces and axial lines
for part ofcentral London (reproduced from Hillier, 1996, p.
157).
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Aspects of urban form 113
analysis is to explain the geographicalstructure and character
of towns through asystematic analysis of their constituentelements
and development through time. Asset out in his seminal study of
Alnwick (1969,pp. 3-5), he begins by distinguishing fivegeneral
aspects:
site function townscape social and economic context
development
Within the townscape, he distinguishes threeform complexes:
town plan land utilization pattern building fabric
The town plan is itself subdivided into threecomplexes of
plan-elements:
street system plot pattern building pattern
The constituent element of the street-system isthe street; the
element of the plot pattern is theplot and the element of the
building pattern isthe block-plan of the building. Further,distinct
combinations of streets, plots, andblock-plans are identified as
plan-units (Figure5).
Looking at the five general aspects in termsof classes,
relations and properties, functionand social and economic context
are bothbased on the relations of use or activitiesbetween humans
and built form. Function ismore limited and specific to particular
classes
Figure 4. The formation of urban tissue or aggregates in
differentgeneralized situations (reproduced from Caniggia and
Maffei,
2001, p 130).
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114 Aspects of urban form
of activities, for example residential orcommercial. The social
and economic contextis the combination and interaction of
differentactivities and functions over a wider area. Inthis respect
any given function is a part ofthe social and economic context.
Site isdefined principally in terms of the spatialrelations and
distribution of natural physicalfeatures such as geology,
topography,hydrology and vegetation. As with Lynchschange, the
process of development involvesthe temporal relations between
elements and
aspects from one time to the next. Examination of the townscape
as defined by
Conzen raises a number of ambiguitiesconcerning the element of
the plot. Despitefunction having been identified as a
distinctgeneral aspect, the townscape includes theform complex of
land utilization pattern withthe plot identified as a unit of land
use(Conzen, 1969, pp. 5, 79, 128). The town planalso includes the
element complex of the plotpattern. The plot is thus defined in
terms ofboth land use and physical form. This raises
Figure 5. Examples of plan units: Alnwick,
Northumberland(reproduced from Conzen, 1969, p. 72).
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Aspects of urban form 115
the issue flagged up by Lynch of conflatingform and use and
therefore blurring orobscuring the dynamic associations betweenthe
two. Conzen himself openly recognizesthe importance of these links,
noting that
town plan and to a lesser extent building fabricare conservative
in that they tend to reflect thepattern of past landownership and
capitalinvestment longer ... The land-use patternresponds more
easily to changing functionalimpulses (Conzen, 1981, p. 80).
To be more consistent, the categories of socialand economic
context, function and landutilization pattern, which are all
defined bythe human-built form relation, would be betterincluded
together as a separate aspect.
Conzens mention of land ownership in theabove quotation and
illustration of propertyholdings in his study of Alnwick (Figure
6)raises a further point of ambiguity associatedwith the plot. In
common use, the plot refersto a unit of property. As with form and
use,there is the tendency to conflate the physicalform of plots and
their status as an object ofownership or, more generally, control.
Whilethe physical boundaries of plots generallycorrespond to the
boundaries of control, it isnot always the case (Kropf, 1997).
Morefundamentally, the concept of ownership andother forms of
control involves a sociallydefined relationship between the
controller andthe thing controlled. One does not make sensewithout
the other. Just as with use, however,control is a fundamental
aspect of urban formand is an essential factor in understanding
theprocess of development. The issue of controlis the subject of an
entire chapter in LynchsGood city form and is central to a number
ofother works within the typological approach,in particular
Habraken (1998), as well asMoudon (1986) and Castex et al. (1980,
2005).
In accord with the foregoing analysis,Conzens method identifies
four principal aspectsof urban form:
site social and economic context, function, land
utilization townscape development.
The further aspect of control is implied byConzen in the
identification of the plot as anelement. This is reinforced by the
explicitinclusion of control as an aspect by otherswithin related
approaches.
The case for physical form as the referenceaspect
The results of the analysis are presented inTable 1, which
groups the different aspects bygeneral class and relationship, the
four broadgroups being spatial relation of physicalobjects,
interrelations between humans and
Figure 6. The pattern of pre-industrialproperty holdings in
Alnwick, Northumber-
land (based upon Conzen, 1969, p. 35).
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116 Aspects of urban form
Table 1. General aspects of urban form as identified in the
various approaches to urbanmorphology
Spatial relations of physical features
Site/environment Spatial relations of natural features unaltered
by humans (the substrateof built form).
Built form Spatial relations of features built or modified by
humans, encompassingboth solid and void and including planted
vegetation.
Interrelations between humans and physical features
Social and economic context/local culture
Collective relations between human activities and between
humanactivities and physical forms.
Function/use/activity Relations between humans and physical
forms for particular purposesincluding movement and occupation.
Control (e.g. ownership) Socially acknowledged relations between
an individual or group and aphysical form conferring powers of
action and determination over theform.
Intention/design The sense or mental image motivating the
modification or constructionof built form including representations
such as drawings.
Construction The act of modifying or constructing built
form.
Perception Mental and physiological response or experience of
being in a place andthe image or sense retained in memory.
Flows of resources
Natural Sunlight, wind, water etc.
Human The movement of goods, information, energy, waste.
Temporal relations
Change/development Short-term cyclical changes in patterns of
activity and long termtransformation of the natural and built
environments necessarilydescribed in terms of states at two or more
points in time.
physical form, flows of resources and temporalrelations. The
different aspects are thendistinguished by the specific classes
andrelationships. The aspect of resource flows,which is included by
Lynch as a distinct partof built form, is noted and very
usefullyelaborated by Osmond (2008), as is theimportance of
vegetation.
The aim here is not, however, to set out acomprehensive set of
aspects. It is to identifywhich amongst the commonly identified
aspects provides the best reference key orregistration mark for
co-ordinating the otheraspects so that different descriptions can
becorrelated in a rigorous way. Whicheveraspect is chosen, if it is
to function as thereference key, it should be common to all
theapproaches and defined consistently as distinctfrom other
aspects in order to avoid theproblems of conflation.
Of all the aspects identified, physical formand use are common
to all the different
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Aspects of urban form 117
approaches. There is, however, an importantdistinction between
these two aspects that is anessential consideration for choosing
areference aspect that can be defined in a waythat is consistent,
coherent and comprehensive.If defined strictly, physical form is
the spatialrelations of physical objects. Function, useand activity
are interrelations between humansand some physical form. When we
refer touse, we talk about the use of some object orspace defined
by objects within a town.Functions such as residential or
employmentpresuppose the infrastructure, building andequipment that
accommodate the activities. Itis this fact that leads to the
tendency noted byLynch to conflate the two.
There is no question that activities and usescan be defined
without reference to physicalform. But the very fact that
activities such asresiding, worshiping, working and playing are,on
their own, relatively fluid and flexible, bothin their constituent
elements and where theytake place, means they are less suited as
areference aspect. Use is more evanescent andchanges more quickly
than form, as was longago noted by Conzen. Physical form is themost
tangible and persistent of all the aspects.
A point related to the general persistence ofform relative to
other aspects is the fact thatmost representations of settlements
primarilydepict physical form. As the most tangible andubiquitous
aspect, it is the easiest to representby drawing and other graphic
means. In caseswhere other aspects are represented, such asproperty
boundaries on cadastral maps, theultimate reference point is still
physicalfeatures on the ground (Kropf, 1997). If weare to
reconstruct the process of developmentof settlements, the source
material with whichto do so is most likely to be representations
ofphysical form.
The tangibility, ubiquity and persistence ofphysical form make
it the most suited to act asthe point of reference for
co-ordinating andcomparing aspects. This seems at once bothobvious
and too simple and naive to justifymention. But the cost of the
neglect of such afundamental matter is a field of enquiry, takenas
a whole, that is surprisingly incoherent andunco-ordinated.
Consolidating the insights of
different groups to build a more effective bodyof knowledge and
understanding is extremelydifficult.
Pertinent features of physical form
Focusing on physical form as a referenceaspect out of a range of
co-dependent aspectsof urban form is not as simple as it
mightappear. If it is obvious that physical formshould be the point
of reference, it is equallyobvious that the physical form of
humansettlements itself presents a diversity ofaspects. The
different approaches to the studyof form tend to abstract different
features ofphysical form as pertinent to theirinvestigations and
represent them in differentways. At a general level, features
andrelations include the following:
Features line (net) area/patch space module (solid/void)
Relations between features network patchwork
aggregate clustercellular matrix (aggregate of uniformdefined
planes)fractal
hierarchy palimpsest
To an extent, the different approaches can becharacterized by
the features they take aspertinent and the relations between
them:
spatial analytical (patch, aggregate cluster,matrix)
configurational (line, space, network) process typologogical
(module, modular
hierarchy) historico-geographical (area or patch, patch
hierarchy, palimpsest)
Just as all of the different aspects of urban
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118 Aspects of urban form
form are co-dependent facets of the samephenomenon, the
different features andstructures are different views of the
sameaspect. As such, there must be points ofcontact when different
views are overlaid.Finding those points of contact is the
challengeto be met in seeking to co-ordinate thedifferent views so
that they might worktogether and reinforce each other.
To put the issue in these terms is in someways to overstate the
case. Identifyingcommon features to use as the registrationmark
should not be a major intellectual feat.The analogy with
multi-plate printing impliedby the term registration mark can be
used asa pragmatic methodological pointer. If thedifferent aspects
of urban form and thedifferent features of physical form are seen
asdifferent colours, each with its own patternapplied to a separate
plate, it is the registrationmarks applied to each plate that make
itpossible to co-ordinate the printing of all theplates and
generate a coherent image.
The analogy is plausible in the first placebecause virtually all
of the approaches to urbanmorphology make use of
two-dimensionalgraphic representations of urban form,typically
using the conventions of ortho-graphic projection in plan. For the
analogywith printing to work, the first obviouspractical point to
acknowledge is that all thedifferent aspects need to be shown from
thesame point of view at the same scale. As inprinting, the
registration marks might theneven be independent of the image and
worklike a grid reference in mapping. The benefitof a reference
aspect that is part of the image isthat it is always there to be
used whatever theview.
Conclusion
It may seem perverse to pick apart urban formonly to try to put
the pieces back together. Toa large extent, however, this is the
essence ofmorphology. The purpose of the analysis andsynthesis is
not to compile an exhaustive tableof deracinated parts. To go
beyond a mindlessdisassembly, there is an absolutely essential
third component to the process which iscomparison. To a large
extent comparison isat the core of perception and operates at
asubconscious level. Goethes brilliance was tobring that intuitive
capacity into consciousapplication. He compared one form
withanother. He compared the different compo-nent parts and their
relationships and hecompared the different stages in
thedevelopment, growth and transformation offorms. He also overlaid
and compared theinformation about the forms provided bydifferent
fields and disciplines.
What emerges from the process is afundamentally composite view
that isconceptually more integrated and articulated asa whole than
the view provided by any singleperspective. For Goethe, these were
neverpurely mental abstractions but essentiallybased on experience.
Nor were they staticconceptions but capable of modification asnew
forms were investigated through cycles ofhypothesis, deduction and
induction (Wilkin-son, 1962, pp. 177-8). This paper has soughtto
apply this method to urban form itself byundertaking a deductive
and comparativecritical analysis of key texts from the
differentapproaches to urban morphology. The resulthighlights that
there are at least four broadtypes of aspect and eleven logically
distinctgeneral aspects:
spatial relations of physical featuresnatural physical formbuilt
physical form
interrelations between humans and physicalfeatures
social and economic
contextuse/function/activitycontrolintentionconstructionperception
flowsnaturalhuman
changeformation/transformation/cyclical change
At first sight this may appear unduly
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Aspects of urban form 119
complicated. The provisional list of aspectsmust, however, be
seen in the context of thephenomena that we are seeking to
understand.If we acknowledge that cities are almostintractably
complex and diverse, can weexpect to have a simple explanation for
themthat can be understood at a single sitting? Theanalysis shows
there is a clear logical basis forthe distinctions. If they are to
have explanatoryvalue we need to identify how they fit togetherin
some coherent way, not just statically, butas part of a process of
formation and trans-formation. And just as it is comparison
thatallows us to distinguish the aspects, it isfurther comparison
that is necessary todetermine how they fit together.
Identifying consistently defined aspects ofform only clears the
ground for and facilitateslooking in more detail at the
individualaspects, comparing them and investigatingtheir
interrelationships, associations andcorrespondences in order to
identify the partthey play in the processes of formation
andtransformation of urban form.
What is also clear from the results set outhere is that further
comparison and criticalanalysis is needed, especially on the aspect
ofphysical form, not only to determine how itmight best function as
a reference key but alsoto ensure that our view of physical form is
ableto pick up the full range and diversity ofspecific forms and
features and the relation-ships between them.
One starting point would be to confront theambiguity that dogs
particular features such asthe plot and find their place in the
overallstructure of elements. Some initial work inthis direction
shows positive results (Kropf,1996, 1997, 1998). Another starting
pointwould be to fully acknowledge the differenttypes of overall
structure that can be identifieddepending on the base elements
chosen aspertinent. The most obvious examples ofdifferent
structures are the network patterns oflinear features identified in
the configurationalapproach, the patch hierarchies of
morpho-genetic regions in the historico-geographicalapproach and
the modular hierarchies of theprocess typological approach.
Are these views mutually exclusive or can
they be correlated by the use of a reference keyfor rigorous and
consistent comparison?Using physical form as a common
referenceaspect to co-ordinate different descriptions ofurban form
would be a significant step towardbuilding a more coherent
understanding ofhuman settlements. The alternatives wouldseem to be
either viewing human settlementsas indivisible wholes or discrete
and irrecon-cilable parts. If urban form remains mono-lithic we
must be satisfied with a fascinatingbut ultimately mysterious
phenomenon. If weseparate aspects but leave them isolated
andfree-floating, we must be content withlistening simultaneously
to a number ofunrelated conversations.
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The Codes Project
This project is a compilation of the codes, laws andrelated
documents that have created, or sought tocreate, particular urban
forms. Code is broadlydefined: it includes not only legal documents
butalso social customs in other words, both legally-binding codes
and customs that may not haveinvolved a governing authority. These
documentsprovide a rich resource for urban planners,architects and
others.
A website had been set up (http://codesproject.asu.edu/) to
which all are invited to
contribute. Types of codes that are beingcontributed include
unified development codes,architectural codes (building scale
designregulations), building codes (health and safetyregulations),
state enabling legislation, designguidelines, pattern books and
master plans.
Further information is available from ProfessorEmily Talen,
Arizona State University, PO Box875302, Tempe AZ 85287-5302, USA
(E-mail:[email protected]).
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