Diachronic investigation of the urban form of Qom (Iran) through morphometric approach

Qom is one of the oldest cities in Iran, with a multi-millennial history dating back to the 4th millennium BC, according to archaeological excavations. Due to different dominations (from ancient Persian dynasties to Islamic ones), the city has gone through successive phases of development and decay, which stratified in its urban form. More recently, due to its advantageous geographical position, several inter-city roads were constructed to converge in Qom, creating a radial structure, whose accessibility has been constantly improved by adding ring roads and filling gaps with local gridded networks. The sum of these transformations produced over time a complex urban form, which remains largely understudied. The aim of this paper is to investigate the morphology of Qom in a systematic manner through the use of a novel method of morphometric analysis based on multiple indicators of urban form describing aspects of the urban fabric and street network, as well as clustering techniques identifying homogeneous urban types in a hierarchical structure according to similarity. The application of this method to official datasets of plots and street segments, provided by the local administration, reveals 11 urban types with distinctive morphological traits, seemingly matching main phases of urban development. This morphometric analysis provides novel insights on one of the most ancient Iranian cities and can be replicated to investigate urban types in further case studies.