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.
Amir Hossein Kazem; Farhad Hosseinali; Ali Asghar Ale-sheikh
Abstract
Modeling urban growth and land use changes are an integral part of planning for sustainable development. The present research intends to model the urban growth and development for Tehran metropolis from the aspect of timeand spatial distribution. To this end, land-use maps for the years 1988, 2002 and ...
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Modeling urban growth and land use changes are an integral part of planning for sustainable development. The present research intends to model the urban growth and development for Tehran metropolis from the aspect of timeand spatial distribution. To this end, land-use maps for the years 1988, 2002 and 2013 were categorized with the object-based approach using Landsat satellite time series images. In the next step, using the logistic regression model, the effect of independent variables in relation to urban growth including 14 variables in the form of two groups of environmental-natural and socio-economic variables during the period of 1988 to 2002 was calculated as the coefficient in the regression equation, and the potential map of urban expansion was produced. The evaluation of the logistic regression function using two Pseudo R2 and ROC indexes with values of 0.32 and 0.89 showed good regression fit and proper description capability. Subsequently, the area of change for the expected year was quantitatively predicted using Markov chain analysis.Finally, by using the outputs of the two models of logistic regression and Markov chain analysis and using the Cellular Automata Model, urban growth was modeled for the year 2013, comparison of which with the 2013 classified image, shows that the used model with a 93% relative accuracy for the estimated area and a Kappa coefficient of 0.87 has been a successful model. Accordingly, the same model was used to estimate the urban growth in 2025,using images from the years of 2002 and 2013.
