Organizing Farahzad City-Floodway in Northern Tehran Metropolis view of geomorphology

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 of concern to the applied geomorphologist is that in which geomorphologist events have a direct impact on man. The irregular development in Tehran, over the past half-century, addition to the destruction of parts a coherent historical context and cultural assets and historical heritage surviving the cause is of a large part the natural heritage of floodways.
Farahzad stream is one floodways in north of the metropolitan Tehran. Farahzad basin in terms of geological structure is part of Central Alborz and has semi-dry climate. With the 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 the organizing the floodways. Farahzad basin at coordinates of geographical longitude of 51ú 19´, and 00 up to east 51ú ,22´, and 00 and geographical latitude 35ú ,45´, and 00 up to north 35ú,53´, and 00 with an area of 28 square kilometers in north Tehran city (North of Tehran Province) is located. The maximum amount of rainfall in the area is more than 600 mm and its average of 422 mm per year.
This study aims to assessment the organizing appropriateness the Farahzad city-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 done. 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 Farahzad city-floodways based on the geomorphological factors have been proposed.
Among layers used in this study, the most weight allocated to elevation. The next layer in order of importance include: slope, aspect, rainfall, vegetation, soil, distance from streams, faults and roads have been. Among the factors and layers used in this paper, the lowest relative weight assigned to the layer distance from the road.
Knowledge of key geomorphological processes is integral to the understanding of the evolution of any landscape. Results of this study show that most organized floodways area of geomorphological factors in considering a very low and low status proportion (44 per cent). Also, 33 per cent of the area has been organizing high and very high to fit the situation with the geomorphological factors. The results show that in environmental management and urban planning have not been paying attention to the morphological parameters.
In this paper, the Farahzad Basin was studied using topography maps with 1:50000 scales and geology 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 organizing) and their comparison revealed that the Farahzad floodways vegetation after the organizing than in the previous year’s organizing has grown to 26 per cent. Also, hazards such as landslides, slope instability and even protection of the environment, was affected from landforms and geomorphological parameters.