عنوان مقاله [English]
Urban streams have great potential for building a green space network for an entire city. In essence, urban streams have great potential to function as a key part of an urban green infrastructure providing valuable ecosystem services to urban residents. Urban stream organizing has one of the key topics in water management and land use planning in Iran. There are still ongoing controversies associated with organizing plan. Vegetation is one of the key components of urban stream restoration to increase its natural and esthetic attributes. However, formulating and maintaining planting/vegetation is not easy because it requires consideration of not only the usual factors for general open space design such as ground-level ecological capacity and residents’ preference, but also plants’ hydrophilic aspects. To be selected for stream basin vegetation, plants and vegetation should not be easily washed away during ﬂooding and have a high survival rate even with extended submergence. One of the situations that concerns the applied geomorphologist, is that geomorphological events have a direct impact on man. The irregular development in Tehran, over the past half-century, in addition to the destruction of parts of a coherent historical context and cultural assets and historical heritage surviving the cause is a large part of the natural heritage of floodways.
Materials and Methods
Farahzad stream is one of the floodways in the North of the metropolitan Tehran. Farahzad basin in terms of geological structure is part of Central Alborz and has semi-dry climate. By organizing floodways, urban landscape, walkways and recreational confines as well as environmental and urban landscape conservation sustainable development will be realized. In the urban areas, sections of society play an important role in organizing the floodways. Farahzad basin witha geographical longitude of 51ْ19´ 00 to 51ْ 22´ 00 E and a geographical latitude of 35ْ45´ 00 to 35ْ 53´00 N with an area of 28 square kilometers is located in the North of Tehran city (North of Tehran Province). The maximum amount of rainfall in the area is more than 600 mm with an average of 422 mm per year.
This study aims at assessing the organizing appropriateness of the Farahzad city’s floodways with the geomorphological factors such as elevation, slope, aspect, precipitation, soil, land use and land cover (vegetation), distance from liner features (such as fault, river, road), and overlying of them, with emphasis on organizing floodways using geographical information system (GIS), remote sensing (RS), and AHP. Methods based on analytical - descriptive, library studies using geographical Information system (GIS) software and analytic hierarchy model in Expert choice software over the map of organizing proportion of Farahzad city-floodways based on the geomorphological factors have been proposed.
Among layers used in this study, the most weight was allocated to elevation. The next layer in order of importance includes: slope, aspect, rainfall, vegetation, soil, distance from streams, faults and roads. Among the factors and layers used in this paper, the lowest relative weight was assigned to the layer distance from the road.
Results and Discussion
Knowledge of key geomorphological processes is an integral part of understanding the evolution of any landscape. Results of this study show that most organized floodway areas of geomorphological factors is considered as a very low and low status proportion (44 per cent). Also, 33 per cent of the area has been organized highly and very highly to fit the situation with the geomorphological factors. The results show that no attention has been paid to the morphological parametersin environmental management and urban planning.
In this paper, the Farahzad Basin was studied using topographical maps with 1:50000 scales and geological maps with 1:100000 scales, Landsat satellite imagery with high resolution and the overlying and weighed methods. The Landsat ETM+ satellite image analysis during 2005 and 2010 (before and after the organization) and their comparison revealed that Farahzad floodways vegetation had grown 26 per cent after the organization with respect to the previous year’s organization. Also, hazards such as landslides, slope instability and even protection of the environment, were affected by landforms and geomorphological parameters.