Farzaneh Sasanpour; Fateme Mohebbi; َAmir hosein Kazem
Abstract
Extended Abstract
Introduction
Floods are natural hazards that cause a lot of financial and human losses every year. Flood zoning plans contain basic and important information in the study of development projects in the world, sobefore any investment or implementation of development plans, they should ...
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Extended Abstract
Introduction
Floods are natural hazards that cause a lot of financial and human losses every year. Flood zoning plans contain basic and important information in the study of development projects in the world, sobefore any investment or implementation of development plans, they should be reviewed by the relevant organizations. The Taleghan River has faced numerous floods over the years,however, no comprehensive studies have been conducted regarding the damage caused by the flood of Taleghan River and its zoning. Taleghan town, which is the main population settlement in the region, the river passes through and the construction of residential and commercial buildings along the river, is expanding. By Using the ARC GIS software,Taleghan most affected areas by flood risk have been determined in the form of a zoning map. Flood risk zoning map has been preparedby using FuzzyVIKOR method, determining the weight through the critic for 7 effective criteria in evaluating flood zones including: altitude, slope, slope directions, land use, geology, distance from waterway and average rainfall. The results of this study, which has been prepared in five categories, show that 83% of the total area of the basin includes safe or low-risk areas. However, 17% of its lands have moderate and high flood risk, which includes areas around the main waterway and sub-waterways with residential and agricultural uses in the basin. Therefore, in order to reduce floods,in low and medium slope lowlands of Taleghan River, in development of rural urban uses in the region, it should be implemented.
Materials and Methods
The present research is descriptive-analytical in terms of method and applied research in terms of purpose. Many factors must be considered in flood zoning, with different degree of importance. In this study, based on previous experiences, the factors that had the greatest impact on flood occurrence in the Taleghan watershed were selected in the VIKOR Fuuzy model. The data used in this study include sea level elevation, slope, slope directions, average rainfall, distance from waterway lines, land use and formation, which were used to determine areas vulnerable to floods.Some part of the required data including Digital Elevation Model (DEM), land use map of the region and map of geological formations have been collected in raw form with a shape file format in the scale of 1: 250,000 from the rangeland and watershed management department of the Faculty of Agriculture and Natural Resources, University of Tehran. Elevation, slope and geographical aspect, maps were extracted from DEM 10 m. The layer of waterways, including permanent canals and rivers, was provided by the National Forests, Rangelands and Watershed Management Organization. The map contains same rain line that is received from the Meteorological Organization. The raster map of the average precipitation of the basin that was prepared based on the information of the precipitation rain lines and the statistics of rainfall data related to 5 stations of Dizan, Ciancranchal, Gotehdeh, Jostan, Glird, Armut and Zidasht, using the Interpolation technique. The criteria were normalized after preparing the maps (GIS READY) and applying the required edits such as defining the unit coordinate system for the maps, eliminating the errors that occurred during digitization and reducing the descriptive data by adding a new column to the related descriptive information table.
In all of the maps thatwere converted from Vector format to Raster, after the normalization step, the layers were weighed through the Critic method. Using the VIKOR model and the weights obtained by the Critic method, which were calculated in Excel software, the value of the VIKOR index (Q) was obtained for every option (pixel). Finally, the ultimate map of flood risk zoning in Taleghan watershed resulted from assigning the values of VIKOR index (Q) obtained from the previous step for every relevant point (option), by ARC GIS software.
Results and discussion
The results of flood zoning map show that 83% of the total area of the basin includes safe or low risk areas. However, 17% of this area has a moderate and high flood risk, which mostly includes urban, rural settlements, orchards and agricultural lands, which shows the importance of paying attention to proper management in these areas. According to the results, it can be said thatthe distance from the waterway in Taleghan watershed has had a significant effect on the amount of flooding, so by moving away from the main waterway and sub-waterways of the basin, the risk of floods and flooding can be reduced. The results of the terming flood risk zoning, show that 27 villages and settlements out of 68 villages in the region are in high-risk areas, including the villages of Eskan, Gotehdeh, Narian, Prachan, Mehran, Joostan, Nisa Olga, Hasanjoon, Jazan, and Mochan are at the highest risk.
Conclusion
It has been proved that Multi-criteria decision analysis methods in GIS is a robust approach to generating risk maps with acceptable accuracy. The judgment about the acceptabilityof the model can be made byusing external information from real ground data. In this study, relatively high compliance with the final zoning map was obtained by checking the history of floods in the study area.
Zohreh Maryanaji; Hamed Abbasi
Abstract
Abstract
Two important characteristics of Hamedan climate are irregular precipitation time and maximum 24-hour precipitation in the months of March (20th) and April (20th). This factor, namely severe rainfall, has increased the risk of flood in this province. The precipitation is snowy in the winter ...
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Abstract
Two important characteristics of Hamedan climate are irregular precipitation time and maximum 24-hour precipitation in the months of March (20th) and April (20th). This factor, namely severe rainfall, has increased the risk of flood in this province. The precipitation is snowy in the winter season, and the melting time accompanied by the rain, causes rivers to flood. The land’s lack of the crop and vegetation cover in other months of the year and the dryness of the soil and ..., increase the flood. Flooding factors are diverse in Hamadan province. Some of the most important factors influencing the flooding of an area are climate, inequalities of vegetation, etc. In this paper, maximum daily rainfall has been investigated in order to predict the amount of water that can be extracted from floods and to plan for management of the region’s water resources. For this purpose, on the basis of maximum 24-hour precipitation, the map of the elevation and rainfall gradient model and the rain map of the region for the return period of 2,10,25,50 with the ‘best statistical distribution’ method for the region (Gamble distribution) are estimated and zoned in the GIS environment (by Kriging method) and the probable daily precipitation decreases by the reduction in the return period.Accordingly, during the aforementioned return periods, the southeast and northwest regions of Hamadan province (Dasht-e-KaboodarAhang) have the most probable daily precipitation.The abundance of the number of floods in the province reflects the fact that the aforementioned regions have the highest numbers and the (the most terrible floods in the province (1987 flood in KaboodarAhang region). According to these maps, the eastern parts of the province have the least probable daily precipitation. The results of this study can be used in flood zoning and forecasting as well as planning and management of water resources in the region.
Masoud Taghvaei; Fahimeh Soleimani
Volume 20, Issue 79 , November 2011, , Pages 66-73
Abstract
Flood is an exceptional, extreme water stream that may be overflowed from the natural bed of the river and occupy the land around the bed. Flooding can be the result of heavy rain, quick melting of snow and ice, or the destruction of dams. Whatever the reason for this process, when it enters the urban ...
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Flood is an exceptional, extreme water stream that may be overflowed from the natural bed of the river and occupy the land around the bed. Flooding can be the result of heavy rain, quick melting of snow and ice, or the destruction of dams. Whatever the reason for this process, when it enters the urban areas, it causes damage and sometimes heavy casualties, as the city invades the natural hydrological spaces (rivers and river beds) during its development.
Over the past few decades, new methods have been developed to deal with floods, and these methods are of a more pre-emptive and non-therapeutic nature. By laying down and implementing specific plans for urban land use, regulations and laws, as well as education of people, flood damage can be reduced and minimized, while avoiding heavily costs of the construction of flood control structures.
In this regard, the present study, by documentary study, identifies the effects of natural factors (precipitation) and the resulting crisis in urban planning, which results in attention to crisis management in urban planning in order to prevent flooding and reduce rainfall damages as well as extending the optimal use of rainwater in a variety of aspects.
