WHAT IS MORPHOLOGICAL DIMENSION OF URBAN DESIGN?
Urban design’s Morphological dimension deals with the configuration of urban form and space, and the spatial patterns of infrastructure that support it. There are essentially two types of urban space system – one is where buildings define space; the other where buildings are objects-in-space. Morphological dimension can be discussed in four parts:
- urban morphology
- morphological transformation
- third & fourth parts deals with aspects of contemporary reaction
Urban morphology – the study of change in the physical form and shape of settlements over time – focuses on patterns and processes of growth and change.
Differences in street and block patterns, plot patterns, the arrangement of buildings within plots and the shapes of buildings create very different environments – the different patterns are commonly referred to as ‘urban tissue’ (Caniggia & Maffel 1979, 1984).
Four main morphological elements by Cozen to see how morphological structures are composed of interrelated layers:
- Land uses – Changes to land uses include both new uses coming in and existing uses moving to other areas.
- Building structures – There has often been a recognisable cycle of building development on each plot.
- Plot pattern – Cadastral units (urban blocks) are typically subdivided or ‘platted’ into plots or lots. These may be ‘back-to-back’ plots, each having a frontage onto a main street or circulation route and a shared or common plot boundary at the rear.
- Cadastral (street) pattern – The cadastral pattern is the layout of urban blocks and public space/movement channels between those blocks. The spaces between the blocks can be considered to be the public space network.
Regular and Deformed Grids:
Regular or ‘ideal grids’:
- characterised by geometric regularity.
- they are typically planned and have some degree of geometric discipline.
due to the ease of laying out streets, the most basic planned layouts have generally been rectilinear and many settlements with regular or semi-regular grids exist.
- characterised by apparent irregularity.
- the cores of pre-industrial cities tend to have ‘deformed’ grids.
- generally based on pedestrian movement and strongly influenced by topography, they were integral parts of the immediate area, rather than through-routes, and evolved and developed through use.
The Public Space Network:
When the principal modes of transport were by foot or horse, the realms of movement and social space had considerable overlap. With the development of new modes of land-based travel, the realms became more separated and increasingly compartmentalised into vehicular movement space and pedestrian movement/social space.
This part discusses the transformation in the public space network’s morphological structure in the twentieth century from buildings as constituent elements of urban blocks defining streets and squares towards buildings as separate freestanding object-buildings standing in amorphous ‘space’.
Buildings Defining Space and Buildings in Space:
In traditional urban space, the urban fabric is relatively dense, and buildings are normally built adjacent to one another and flush with the street. Building facades thus provide the ‘walls’ of open space and also contributes to larger systems of ‘street’ and ‘urban block’.
The Road Hierarchy:
Accommodating different forms of travel has been a historical evolution.
Sidewalks/pavements were for pedestrians, while the centre of the street was for vehicles.
A quasi-road hierarchical pattern was achieved by designating certain streets as major roads with selective widening, waiting restrictions, turning prohibitions, one-way routings and access limited to allow traffic to move more freely and quickly.
By closing off intersections and side streets and consolidating blocks, larger superblocks were created, with the new perimeters of the enlarged street/superblocks becoming large-scale gyratory systems.
A transformation in the morphological structure of urban areas from outward-facing urban blocks to inward-focused complexes of buildings served by an exclusive road connection – often referred to as ‘pods’. In pod development, each use – shopping mall, fast-food outlet, strip mall, office park, apartment complex, medical centre, hotel and convention facility, etc. – is conceived as a separate element, surrounded by its associated parking and usually with its own individual and exclusive access onto a collector or main distributor road.
Residential cul-de-sacs are a particular kind of pod. In its typical suburban manifestation, it is a relatively short, dead-end street with a turning hammerhead or circle, serving perhaps 20 or 30 dwellings.
CONNECTED STREET PATTERNS:
On the spectrum of connectivity, Marshall identified four broad street network pattern types:
- Tributary – deep branching with systematic use of cul-de-sac and/or layered loop roads, and often associated with hierarchically based suburban expansions of the second half of the twentieth century.
- Semi-tributary – with some degree of layering and use of cul-de-sacs, but with less division between minor and major access roads and use of T-junctions, found in older suburban neighbourhoods.
- Semi-gridded – referring to typically distorted grid systems with a variety of T and X junctions, often found in inner areas or traditional settlements.
- Gridded – featuring a high proportion of X-junctions and reflecting the type of planned, regular layouts of grid-iron urban extensions or new cities.
Reaction to object-buildings and pod developments saw a new interest in the conscious design of the space between buildings and in the creation of well-defined, positive space. This has led to explicit attempts to compose and organise the parts so that the whole – the place – is greater than the sum of the parts (individual buildings and developments).
Colin Rowe described the Modernist city’s ‘spatial predicament’ as one of ‘objects’ and ‘texture’: objects are sculptural buildings standing freely in space, while the texture is the background, continuous matrix of built form defining space.
Urban Block Sizes:
Conceived as a public space network, urban block structures open up possibilities and – in conjunction with basic typologies/codes/rules about physical parameters – can provide coherence and ‘good’ urban form without necessarily being overly deterministic about architectural form or content.
The size and shape of urban blocks are also important as it can control the microclimate and issues of wind and sun penetration and thus a balance must be struck within the design process between environmental performance and urban form.
Rather than a single, repeated block size, a range of block sizes (including small blocks) may encourage and facilitate greater diversity of building types and land uses.
Small blocks are nevertheless often advocated for a variety of reasons including vitality, permeability, visual interest and legibility.
Larger blocks are likely to be perimeter blocks where the ribbon of buildings around the edge of the block provides the public front to the development, with private or semi-private space in the block’s interior.
Comparing Block Sizes:
Compared to small block patterns, larger block structures may be more efficient in terms of the distribution of built form and open space because there is less circulation space.
Two interrelated aspects of the evolution of the block and street patterns are of particular interest – their persistence and the size of the circulation meshes.
STREETS AS PLACES:
Instead of treating streets only as ‘channel for efficient movement’ they should be considered as both social space and as connecting spaces; a multi-purpose public space network, where social space and movement space are separated if absolutely necessary, but otherwise have considerable overlap.
Designing for Cars or People:
The combination of vehicular movement space and social space in the same physical space tends to cause a variety of problems:
- major urban roads provide obstructions to pedestrian movement, creating problems of severance and reducing connectivity.
- heavy traffic frustrates the social use of streets.
From Arterial Roads to Streets and Boulevards:
Cities around the world have sought to change the character of urban roads – and to re-discover them as ‘streets’, ‘avenues’ and ‘boulevards’, and to re-conceive them as connectors rather than dividers.
At the more local level, careful design is required to reconcile and integrate the needs and demands of different forms of movement: protecting social space from the impacts of cars and creating areas that, while accessible by cars, are pedestrian-dominant.
Shared space typically involves replacing conventional road priority management systems and devices (kerbs, lines, signs, signals, etc.) and the segregation of vehicles, pedestrians, cyclists and other road users, with an integrated, people-oriented understanding of public space, such that walking, cycling, and driving cars become integrated activities.
Urban design’s morphological dimension focuses on urban form and urban layout, highlighting contemporary preferences for urban block and interconnected street patterns. It has also focused on the public space network and the physical public realm – the physical setting or stage for public life.
This is a Summary of the Dimensions of Urban Design from the Book “PUBLIC PLACES- URBAN SPACES“ by Matthew Carmona, Tim Heath, Taner Oc and Steven Tiesdell, Architectural Press