Analyzing the effects of urban development on flooding in the cities (Case study: Birjand City)

It is increasingly recognized that the land-use change, especially urbanization has influenced hydrological attributes intensely. But in most urban designs, flood prediction is considered through type of land use (residential, industrial, and so on) and density. However, experiences show that this method has not been very successful. As a result, the present study aims to investigate and explore a different method in Birjand city. The study primarily emphasizes on the relationship between parameters of hydrologic models and features of urban development as well as scenarios considered in comprehensive plan. Data required for the study were obtained through investigation of existing documents and studies, particularly regarding comprehensive plan of Birjand City. Evaluation has been performed using urban hydrologic models and applying geographic information systems regarding prediction of surface currents corresponding to different urban scenarios. The results showed that in comprehensive plan the effects of increasing impervious surfaces and their effect on increasing water runoff have not been emphasized. This issue has led to an increase in runoff and consequently flooding. The model used in the study indicated that in heavy rains with return period of 25 years, flooding is mainly associated with blocking of water flow at the mouth of bridges. Moreover, this method is compatible enough with conditions of Iran and can be used in similar situations.