Inheritance of Geology and Geomorphology Amidst Urban Growth: Historical Development of the Tehran Metropolitan Area, Iran

Rapid population and spatial growth of major cities occur on foundations which primarily depends on the local geological, geomorphological, and environmental conditions. The bedrock and alluvial geology of the cities prescribes ease of excavation and exploitable building materials, as well as arability and permeability of the urban soils, while the neotectonic setting specifies the convenient natural routs and landforms on which the city has to develop. The Tehran metropolitan area provides an interesting anecdote, presented here as an archetype of such social-natural interplay. Early simple urban development of the city was cradled by the ancient Ray city, while Tehran’s rapid growth between the mid-twentieth and early twenty-first century took on a complex pattern affected by the natural background factors discussed in this paper. Geology and geomorphology have imposed limitations and allowances for development of the city which are reflected both in the land use and the urban fabric. It is therefore suggested that the geological grain of the city is inherited and partially recorded by its infrastructure. Meanwhile, protecting the geological heritage using the geosites is highly recommended for such rapidly growing cities. The piedmont location of the city in an active tectonic setting imposes earthquake, flood, and rock avalanche hazards to the city. A fortuitous jumble of such urban development history and the resulting incipient threats implies an “unplanned evolution” or “instinctive growth” of the city which is pushed over its resiliency limits.