Identifying Effective Indicators for Typology of Urban Fabrics

An unexampled rate of transformation in urban fabric of Iranian metropolises causes many unprecedented physical changes on it. Because of these physical changes, the city's morphology has changed dramatically and in so many cases, because of unplanned / anti - planned changes, urban fabric's morphology does not follow regularity and continuity. This trend cause that planning for these kind of urban fabric confronts with difficulty because of great diversity of form in these urban fabric. This research is an attempt to determine effective indicators for classifying urban fabric types in order to plan them. The research used documentary method in compiling theoretical framework for typological and morphological studies, so tries to find some regulative principles for classification. This documentary research showed that there are two paradoxical paradigms: first, researchers need some kind of classification which contain maximum information and attributes on itself and this will lead to increase in number of types; and second, for making an reasonable classification and manageable set which facilitate planning on it, researchers need minimum types. These two paradoxical paradigms always manifest in complicated fields of classification which have great diversity in itself. Also research finds that there are three approaches in urban morphology: first, environment and behavior with concentration on relations between human behavior and built environment; second, place and its image with concentration on relationships between human experience and built environment; and third, structure and procedure with concentration on built environment evolution with help of analyzing typological elements in urban morphology. Because of its relevance, the research chose third approach. Then by using analytical - comparative method and reviewing some documents and researches, three criteria for defining typologies were determined. These criteria include form and layout, height, streets network. In accordance with two paradigms, research had to choose and analytical unit in urban fabric. Literature review showed that there are three analytical level in urban fabric research: parcels, blocks and neighborhoods. According to the goals of this research, block level was selected. Then from these three criteria, nine indicators were manifested. These indicators include average area of parcels in block, average frontage of parcels in block, average ratio of width to length of parcels, area of block, maximum slope of block, floor area ratio, ground space index, open space ratio, average number of floors in block, average visible surface, average ratio of street width to buildings height, and half of area of adjacent streets to a block as block permeability index. Paradigms of research showed that it is not possible to use all nine indicators together for classifying urban fabric, but it can be classified to main types by using essential indicators and in two stage processes. First, by using more important indicators according to purposes of planning which would be included average area of parcels in block, ground space index, floor area ratio and open space ratio. Then these main types can be subdivided by using remaining indicators to identify sub-types, and this would be a systematic approach for classifying urban fabric.