Mohammad Khosroshahi; Ahdei Kali rad; Hamid Hossaini Marandy
Volume 18, Issue 2 , September 2011, , Pages 336-352
Abstract
In this research, deserts domain of Iran was studied and compared in view of the geological and climatological specifications.Geological deserts domain was made as digital maps with considering saline and evaporate formations which have been effective in their development. To determine climatological ...
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In this research, deserts domain of Iran was studied and compared in view of the geological and climatological specifications.Geological deserts domain was made as digital maps with considering saline and evaporate formations which have been effective in their development. To determine climatological deserts domain, climatological factors including amount of precipitation, rainfall coefficient variation, rainfall irregularity coefficient, the average intensity of daily precipitation, annual average temperature and amount of evaporation were calculated for all studied stations. Using Geographical Information System (GIS), the isohyets digital maps were prepared for each factor. With overlaying layers, a transitional boundary was made through which non-desert areas were separeted from deserts. All (geological and climatological) desert units were set up on the country map with utilization of the coordinate system and georeference. According to the results, climatological and geological deserts respectively encompassed 42.5 % (700991 km2) and 12.6% (208041 km2) of Iran map. Each individual layer covered different desert area on the map. Crossing and matching of two layers (common parts of overlaying) was 22.6% of the geo-climatological deserts of Iran which indicates differences between spatial distribution of geological and climatological deserts.
Ebrahim Farahani; Mohammad Khosroshahi; Majid Hosseni; Seyamak Loghmani
Volume 14, Issue 4 , February 2008, , Pages 490-499
Abstract
Vegitation cover is one of the important environmetal factors which can determine desert areas. In this article, we determine desert areas in Tehran province by GIS. In the study area, dominant plant types and some of main ecological properties of them were assigned. Finally, by available information ...
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Vegitation cover is one of the important environmetal factors which can determine desert areas. In this article, we determine desert areas in Tehran province by GIS. In the study area, dominant plant types and some of main ecological properties of them were assigned. Finally, by available information and public characteristics of every plant type, desert area was separated. In this area, we distinguish 43 plant groups that 7 types of them belong to desert areas. This area is 307647 hectares which is formed 16.43 % of Tehran province.
Abol ghasem Dadrasi; Mohammad khosroshahi
Volume 15, Issue 2 , January 2008, , Pages 227-241
Abstract
One of the major consequences of desertification is development of destructive floods in spite of ground water level falling in the lower parts of basins, which will lead to water quality/ quantity decline, landslide and blending of saline and fresh water tables. Each of these symptoms individually or ...
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One of the major consequences of desertification is development of destructive floods in spite of ground water level falling in the lower parts of basins, which will lead to water quality/ quantity decline, landslide and blending of saline and fresh water tables. Each of these symptoms individually or in combination with the others clearly notifies the development of desertification. Identification of suitable areas for flood control will assist the natural aquifer recharge in the basin’s upstream and will reduce the development saline and gypsiferrous waters in the ground water of basin’s downstream and surrounding area, which in turn will cause secondary salinization in the lower parts of basins. Off course computer models are the most suitable methods for determination of the best sites in this regard, and because of variety of available models in the first step we should determine the best model. In this research compiling of effective factors using establishment of information layers and then regionalization in conceptual models which were applicable in GIS media like as Boolean logic model, overlap index model and Fuzzy logic model was used. The main research technique is analytical comparison of results using these models. These models were done in GIS media by scoring to the variables affecting flooding and aquifer recharge based on their effectiveness. We compared models due to natural conditions of the region to determine the best model for quantitative analysis of flooding in 6 towns of Khorasan-e-Razavi province, with emphasis on determination of flood control capability of these regions to combat desertification. Results showed that Fuzzy model with summation operator gives the best adaptivity compared to the other models to determine the floodable and capable for flood control areas.
Saeid Choopani; Mohammad khosroshahi; Mohammad Gholampoor; khosro Mirakhorlo
Volume 13, Issue 1 , February 2006, , Pages 17-26
Abstract
The country of Iran is situated in an arid and semi-arid zone, with an average precipitation of about 250 mm per year. Hormozgan province in southern Iran, is one of the most arid parts of Iran with an average annual rainfall of only 170mm. The study area is located ...
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The country of Iran is situated in an arid and semi-arid zone, with an average precipitation of about 250 mm per year. Hormozgan province in southern Iran, is one of the most arid parts of Iran with an average annual rainfall of only 170mm. The study area is located in the Zagros and Makran geological zones.. In the study area the oldest formations are of Palaeozoic age. Another characteristic of the Zagros zone are diapirs. Diapirs rise up from the deepest part of sedimentary rocks, and after cutting through the upper layers, they may appear at the surface, which seriously affect groundwater quality and land use. Desertification; in Iran has occurred from Neosene and Quaternary. Geological formation have important effect on salinisation and desertification. Thus, the geographical investigation of desert area is very important. This investigation is based on GIS method Applications, geological map (1:250000) and supported by, fieldwork. At the first, prepared and digitizing of geological maps by Ilwis program and was carefully checked and corrected where possible. The next step prepared evaporation formation and Quaternary maps and its overlying. Prepared cross map of Quaternary and Hydrographic network and determination of primary and secondary deserts area. The final step was prepared a cross map of primary and secondary desert area map and checked by fieldwork. To comparison between units of desert area map, can be result, more than 78 percent of study area is situated in the deserts area.