Investigation of flood vulnerable regions in Urmia in order to decrease the hazards and damages

Introduction: Conversion of runoff into flood can cause irreparable damage to urban water gathering channels. A ۲۰-fold increased of Urmia, new constructions development on the urban areas over the past five decades particularly on hills constructions and vegetation loss enormously and replacing with asphalt made this area prone to flooding and rainfall runoff especially during heavy rains at rainy seasons.  According to the morphological specification, Urmia and its surroundings (about ۲۰۰ Km۲) were divided into different zones and investigated the torrents and vulnerable regions. Due to evaluation of more than ۴۰۰۰ data collected from Urmia Regional Water and Metrological Organization, about ۲۷ million m۳ rain and snow come to city annually. Primary evaluation shows that about ۵ million m۳ annually in spring seasons flow through the city. Methods: In this study, zones prone to runoff in Urmia city, margin, and residential areas have been identified. The flood-prone areas were determined by using TOPSIS method and obtaining data from Meteorology Organization of West Azerbaijan during heavy rain for a five-year return period by combining existing data. Findings: According to this project, ۱۷ separate regions are distinguished with respect to different morphological features. The studies showed that region No.۱۲ (about ۷۵۷۰۰۰ m۲) with the ultimate point to ideal situation was the most flood-prone regions due to the cause and flow runoff and urban flooding; in a heavy spring rain about to ۱۹۲ m۳/min rainfall occurs, given the affecting coefficients much of it became runoff. Region No.۱۷ with about ۱۷۶۳۰۰۰ m۲, the closet point to ideal situation, was the most secure one on which heavy rain more than ۲۷۵ m۳ was coming down.        Conclusion: Weighting to the effective parameters involved in runoff showed that the connecting angle between natural draining systems and urban water gathering channels on the one hand, and the indicator of the length of channels and significant difference in height on the other hand had the maximum and minimum weight (effect) on the vulnerable criterion respectively. Accordingly, the regions ۴, ۱۲, ۱۵ and ۱۶ with about ۳.۴ Km۲ are the most vulnerable zones but on the other hand, the regions ۱۷, ۱, ۲ and ۳ are located on the low risk vulnerable zones. For this purpose, constructing the water gathering channels in urban areas, especially in the ۴-۶ and ۸-۱۶ regions is necessary to reduce the damages and hazards in these regions and unpleasant sights in the heavy rains.

کلیدواژه ها:

run off ، vulnerable regions ، TOPSIS method ، Urmia city ، رواناب ، مناطق آسیب پذیر ، روش تحلیل تاپسیس ، شهر ارومیه.