Flood Risk Assessment Using GIS (Case Study: Golestan Province, Iran)

In recent years humans have endured increasing numbers of natural disasters, of which flooding is the greatest and most common throughout the world. Iran is also exposed to floods, considering the severe damage recently incurred in Golestan province, particularly Gorganroud watershed. Due to the importance of the subject and lack of comprehensive studies on flood risk in the country's watersheds, it is crucial to perform flood risk assessment using appropriate tools, such as Landsat ETM+ imaging and digital elevation model data collections in geographic information system throughout the region. For this purpose, database maps of 6 sub-watersheds in Gorganroud watershed were prepared in 5 layers affecting flooding in the region. By overlaying and weighing three layers in GIS software, a layer of flood hazard intensity was obtained. Next, by means of obtained numbers and scoring, the overuse layer priorities were determined. Then, these two flooding layers were overlaid with the help of a two-dimensional matrix, and the final map of flood risk was obtained. Finally, it was found that Chelichay and Sarab Gorganroud, making up to 24.59% of the Gorganroud watershed, are the most risky sub-watersheds. In light of the fact that the data pertaining to Gorganroud watershed have never been entirely used to sort out the risk priorities in the region, the new method presented in this paper can lead to a more accurate and comprehensive understanding about what is really taking place in it.