چکیده:
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.
خلاصه ماشینی:
"First it should be noted that hydrologic parameters which are used to indicate urban development features include: Impervious surface area which is determined as ratio of the area where rainfall directly enters into drainage network of surface water; and Focus time and speed of water in the basin.
However, since these conditions are not available in most Iranian cities (Rasouli, 2015), the present study aims to consider population density and type of land use along with scenarios for each urban industrial area as main parameters.
Concentration time for the basin is obtained according to the following formula: tc tcb tcc (3) Using these models and some other parameters will make it possible to determine hydrographic features of the study area and consequently access the following information which can be useful in investigation of the effects of development on produced runoff and eventually potential flooding in each urban area such as Birjand: The amount of rainfall regarding intensity, duration, and return period; Features of watersheds such as the area, type of soil, and vegetation; Features of urban areas such as waste (drainage) network regarding engineering, structure, and local as well as total permeability conditions.
Given the necessity of determining runoff direction in urban basins and their difference with rural areas, digital model of land (DTM) proposed by Jensen and Doming (1988: 1597) was used.
This relationship has been considered for impermeable surfaces and concentration time for Birjand City in the present study and determines prediction of concentration time with different degrees of urban development in a basin."