JOURNAL OF PHYSICAL GEOGRAPHY
Year:2011 | Volume:4 | Issue:12|Papers Count:8

The Deficiency of Precipitation for Growth of Living Organisms is one of the Permanent Characteristics of Arid Climates. However, the Unexpected Reduction of Precipitation or those Rainfalls Which are Less than Long-Term Range in an Area Which is not Completely Arid Creates Many Risks. This Phenomenon is Called Drought. In this Study the Data on Annual Precipitation for the Stations of Ardebil, Ahar, Pars Abad, Maku, Jolfa, Khoy, and Marand Were Used With the Purpose of Studying the Precipitation Conditions of Aras Drainage Basin, Applying Statistical Analysis and the Calculation of Wet and Dry Years. The Indexes Used in this Study Include Dependable Rainfall Index (DRI), Nitzche Technique, and the Percentage of Normal Precipitation Index (PNPI). Findings of the Adaptation of these Methods Led to the Determination of Precipitation Conditions, and the Stipulation of Frequencies of Dry and Wet Year occurrence in the Stations Under Study. The Results of this Study Indicate that in All Stations the Drought Phenomenon is Coincided With Intensities and Also Weaknesses and in Most Stations the Precipitation is in Normal Situation. Among the Methods Applied, the DRI Method Having Lesser Limitations and More Capabilities is Better than the Other Methods for Determining Dry and Wet Years.

This study was done in order to estimate the erosion rate in the Zidasht – Fashandak watershed (of Talaghan rood sub – watershed) with area over 26/737 km s, and there is no gravimetric station: also, The two models are used, named, EPM and STEHLIK. For doing this work, first, the homogeneous units were provided, and by overlaying the maps of the litho logy, slope, geomorphology facies and combining them, 18 units were made which are the base for estimating and evaluating the erosion rate.The required data are provided by study the watershed management of the watershed which has been done before, and by take the areal photography's and the field studies. For make digit and combining and providing the maps, Arc Gis soft ware is used. By using two models EPM and STEHLIK, was estimated the rate of the erosion at the watershed level, and the results compared. These results of the two models aren’t consistent. It seems that the obtained results of the model STEHLIK aren’t reliable in the target area.

Alamarvdsht area located in north of Lamed township and south of Fars province. This area has hot and dry climate and includes a plains that surrounds by Zagros anticline in north and south of it. In recent years the gully erosion of Alamarvdasht river causing destruction of natural resources and threatened structures that built on the terraces of this river and limited the future development too. The aim of this study is determine the suitable development zones according these limits. To achieve this aim, geomorphological and hydrodynamic variables of the channel has been reviewed. The research tools in this research included types of maps, aerial photos and satellite images of the area to compare period changes of gullies. Also, the GIS software has been used for analysis and zoning development possibilities and limitations too. Among the tasks the field view has been done to review and record changes in the short time and match the finding with GPS. Results of this study show that among the six zones were divided, and the amplitude plains and alluvial fan because of location, soil texture and slope have the most ability to develop and lowland areas of Alamarvdsht plain, especially the lands that locate close the river because of gully erosion have limited developing capability. Perhaps the best way to control development of gullies is engineering methods to reduce and controlling the slope of channels.

Ahwaz has been owned special bio-climate conditions that are based on locating in a special geography location, topography conditions and the atmosphere effective conditions on the area. Thus the air temperature in the coldest month of a year raises to 7/2 C and in the hottest month of a year sometimes is more than 46/3 C. that it make considerable problems foe residents of this city. So, the necessity of survey the climate conditions in relationship to the design of building for reducing these problems. So it uses the synoptic data and survey the bio – climate condition of Ahwaz and the below results have been achieved:For benefiting of the climate condition in the building, the condition of different kinds of building has been drawn on the diagram of the path of sun move according to the geographical width of Ahwaz.

The increasing population rate in urban areas, along with the development of new population centers, lack of policy-making and evaluation of different urban activities and performances based on a general and holistic program (Land use planning), and consistent throwing of a huge variety of waste water and sullage in the environment, are all considered as the crisis-creating factors which has put the environment and the quality of human hygiene and health, specially urbanites subject to many dangers and damages. The aim of the present study is to select a site in order to sanitary landfill solid waste materials in Hajiabad on the basis of site-selecting scales and rules. The methods used in this research are procedures and capabilities based on geographical information system (GIS) and Analytical Hierarchy Process (AHP). At the early stage, the scales and rules for selecting an adequate site to sanitary landfill were identified, such as, slope, land use, distance from city centers and roads, surface and underground waters, soil, geography, and other criteria and required level with the capacity of at least 20-year landfill was estimated and the places where already covered this area of 2416 hc and the larger, out of the whole area of 238396 hc, were selected as the adequate places for sanitary landfill of solid waste materials in Hajiabad.

Sirjan playa with approximately 8027 km2 area is located in Kerman province. The decrease of ground water surface level in the aquifer caused salty water table to move towards Sirjan aquifer, and decrease the quality of ground water this plain. In this study our decision is, using hierarchical analysis and GIS techniques to finding potential sources of ground water playa Sirjan be paid. To ensure from final results, potential layer of studied area has been prepared in three ways Weighted Overlay, Weighted sum and Raster Calculator, has been prepared. The results show that among the above three methods weighted sum up to the high potential area in front of Raster Calculator and the minimum area devoted to high potential. But Weighted Overlay contour method between the two methods and previous results, it has higher reliability. The high potential zone based on more coarse alluvial deposits during the quarter and is Mkhrvth fan. The results of this study can be ground in water management projects and the exploitation of these resources is effective.

The Research Effect of This Maning’s Coefficient of Roughness on Flooding Area and Water Level Was Assessed. First, TIN Layer in Arc Map Was Prepared and Then HEC-GEORAS Extension Was Used to Provide Necessary Information Based on Cross sectional Data Then, The Maning’s Coefficient of Roughness for The Selected Reach of Arak River Was Determined Based on Field Works and Cowen Standard Tables. This Coefficient Was Then Calibrated Using HEC-RAS Model. Furthermore, 5, 10, 25 Percent of The Coefficient Variation Was Considered to Find Out The Effects on The Model. The Flooding Area and Waters Level in Each Cross Section Was Monitored in Each Case and Was Exported to GIS to Study The Flooding Area With Aid HEC-GEORAS Extension. The Results Indicate Increasing The Maning’s Coefficient Will Increase The Flooding Zone and Vice Versa. Also it Showed That Calibration of The Coefficient Has a Considerable Effect on Estimation Flooding Zone and Flood Characteristics. The Results Also Suggest That The Model Has The Highest Sensitivity to Maning’s Coefficient of Roughness.

In Iran. One of the prevalent models for erosion and sediment estimation in watershed scale is erosion potential model (EPM). But according to the reports, in most cases relative differences between measured and estimated amount of erosion and sediment are more than 10 per sent. In order to  increase precision of the EPM model 13 sediment delivery ratio estimation methods were evaluated in the two watersheds with different climatic conditions  including Khomein and Mozleqan in the Central Province of Iran., Results of the study showed that the Rohel method (1977) and SWAT (2001) are the most suitable methods to be applied in the arid and semiarid watersheds, respectively due to the observed minimum difference ratio between measured and estimated amount of erosion and sediment by EPM model (4.1 and 6.4 per cent in the Mozleqan and Khomein, respectively). It can be therefore concluded that the mentioned methods for estimating SDR have to be replace with the SDR estimation method used in EPM model.