Flood vulnerability assessment in Tehran city

Flood vulnerability is variable and complex that dependents on very phenomena such as rainfall, runoff and high exposure of the flooding downstreamareas. Flood vulnerability changes over time and from regions due to natural conditions, human activities, and damage culture of the community at risk. Tehran city may be experiences the difference life and property damages because the high varieties in the socio-economic and the life quality level in regions, also structural varieties in the city fabric. In this study, the blocks with weak texture, population density, land use, bridge, slope and drainage density are defined as element at risk to assess the vulnerability differences pattern. Prioritization and the relationship between this variables and vulnerability was done through Analytic Hierarchy Process; based on expert opinions created a matrix with 6×6 dimensions to determine the variables relative weight and vulnerability map. Zonal analysis determined the vulnerability in Tehran, which the weights calculated on the basis of the hierarchical process. Zones 10, 17, 8 and 11 are affected against floods urban very high, while zones 22, 21, 18 and 5 are very low. These zones are lack of the blocks with weak texture and their population is low, especially zone 22 is not weak texture, low density population and high potential of flow of Kan watercourse. The resulted relative weights show the population density with 0.3825 and drainage density with 0.0428 as highest and lowest relative weight, respectively. The vulnerability map defines that 138 km2 of the Tehran city area is located in high and very high categories of the vulnerability. Finally based on zonal statistic municipal 10 and 22 have highest and lowest vulnerability, respectively.