Flood Vulnerability Assessment in Northwestern Areas of Tehran

Nowadays, population increase, progress in science and technology and development of industrial installations with the shortage of places in metropolitan areas made considerable changes in the morphology of watersheds. Violation to territory of rivers, channels, and streams causes alterations in natural drainage pattern and overflowing due to the lower capacity of the changed channels and streams. This can increase the risk of flooding and inundation of the streets and also the costs of urban maintenance. Moreover, this will considerably increase the possible financial and life damages. The results of vulnerability assessment in the study area indicated that a combination of upstream natural factors and urban agents make these areas vulnerable against the floods. Although in outside the urban areas the lands near the channels and streams are more vulnerable, as also confirmed by field observations, there are some other factors affecting the vulnerability of urban areas. The old texture is greatly important in the vulnerability because it does not have a suitable drainage ability and the available drainage networks are also mainly in the ending part of the areas. Thus, the inundation can intensify the floods or even cause them. The vertical slope surfaces and the curvature in north and northwestern areas of Tehran also show conformity and non-conformity with the drainage and watercourses. The jumps of peak flow in the hydrograph of October 2012 make it necessary to pay more attention to the runoffs of Kan drainage basin as the Tehran City is experiencing events related to the watershed.