فصلنامه مطالعات جغرافیایی مناطق خشک
پیاپی 38 (زمستان 1398)

Dust phenomenon is one of the most common and destructive phenomena in the dry and desert regions of the world and Iran, which can have harmful effects on human life and the environment. Wind erosion and the removal and transport of soil particles by wind create dust. Controlling wind erosion will be effective when enough information is available on the factors affecting it. The results of the related studies show that wind erosion phenomenon is very complex and controls many factors. Soil characteristics influence the severity of wind erosion through its impact on its erosion. However, in most researches conducted on wind erosion throughout the world, the role of soil characteristics has been confirmed in wind erosion, but few studies have been conducted in Iran, and the Alborz province, which has been exposed to wind erosion and dust storms in recent years, has not been investigated in these studies. Considering the importance of the issue in this area, the present study was conducted to investigate the role and effect of soil characteristics on the wind erosion threshold velocity and the occurrence of dust phenomenon. In this study, the wind erosion threshold velocity was measured in normal conditions using desert wind tunnel device, and the physical, chemical and mechanical characteristics of the soil were also obtained after sampling in the laboratory and compared with the estimated threshold velocity. Also, using wind velocity data and velocity thresholds, wind rose and storm rose area of the area were drawn and examined. The characteristics of the soil samples examined with high-precision included limestone, sodium, phosphorus, calcium, magnesium, organic matter, nitrogen, humidity content, shear strength, compressive strength, EC, pH, and d.( In this study, using grading of the soil samples , a variable called d has been measured. This variable indicates the percentage of particles with diameters between 0.1 to 0.5 mm as the most sensitive particles for wind erosion in the collected samples.) The results of measuring the threshold velocity using a wind tunnel device showed that the minimum and maximum wind speed thresholds in the area were 7.5 m / s, and 9 m / s, respectively. The range of 7.5 to 9 m / s indicates the high sensitivity of the region to the wind erosion; this is while the width of these areas is also high and this could be a serious threat to the province of Alborz and its neighboring provinces. Studies of the wind rose and storm rose in the region showed that the dominant winds in the region are from the northwest. And more than half of the winds erupted in the area are erosive and have the ability to move particles of soil and create dust. The relationship between soil characteristics and threshold velocity was investigated using the stepwise regression test. The results showed that the most effective parameters on soil moisture threshold velocity included particle size, lime content and shear and pressure strength of the soil. That is, as the amount of lime in the soil increases, the adhesion of the particles and consequently the pressure and shear strength of the soil increase. Moreover, when the percentage of particles with a diameter of 0.1 to 0.5 mm in the soil increases, threshold velocity decreases. In this study, soil moisture has the highest effect on the threshold velocity and has a direct relation with the velocity of wind erosion. The percentage of sodium in the sampled soils was very high, and this caused the disintegration of soil particles and reduction in the wind erosion threshold velocity. The study showed that the risk of wind erosion and dust-fogging greatly threatens the Alborz province. The actual focal points for the production of dust constitute a vast area of the province. These areas, integrated into the central part of the Eshtehard plain and being bordered by the deserts of the Buinzahra plain in Qazvin province, have placed a wider field of dust in front of the wind and are regarded as a serious threat and would have harmful consequences in the provinces of Alborz, Tehran and other neighboring provinces. Therefore, it is necessary to take a special look at these areas in order to prevent the risks of this problem from being exacerbated in the first stage and to reduce the risks in the next stage.

One of the most important problems facing desert areas today is the growing trend of desertification and land use change. Land use is a special use of man from the earth. These uses are changing over time and these changes lead to increased land degradation and ecosystem destruction, especially in arid and semi-arid regions. Accordingly, in this research, the trend of land use change in the east of Kerman Province from Fahroj to Bam's new citadel has been evaluated. In this research, satellite images of the years 2000, 2010 and 2017 have been used to monitor land use change. The methodology is that by using the controlled classification method, the land use map was prepared for these years and then, using the Land Change Modeler (LCM), the amount of variation of the calculation and the trend of the modifications were modeled. The results of this study indicate that in the study area of agricultural land and vegetation has the most change, so that during the study period, along with the growing trend of residential areas, agricultural lands and vegetation, the trend has decreased. In addition to the trend of increasing the residential areas, the areas of the Bayer area of study have also increased during the open time, which, given the environmental conditions governing the area, could be a serious threat to the inhabitants of the region.

In this study the recharge and discharge of Isfahan-borkhar aquifer was investigated. This leads to long-term management of the aquifer and will make appropriate decisions by planners. The results of this study showed that the water table was constantly decreasing over the selected statistical period. The water table level was reduced by 0.46m per year, which reflects the fact that the aquifer is in critical conditions. In the present study, the recharge rate was determined by three factors including leakage from the river, rainfall infiltration and agricultural wastewater by using MODFLOW and then the correlation coefficient above 0.97% indicated high accuracy of the simulation. According to the results, it was found that recharge by agricultural wastewater is more than recharge by rainfall (about 32% of total irrigation water), which is due to the type of irrigation in the area (check-basin irrigation) and after that the influence of rainfall (about 10% of the total rainfall), which is a low contribution to this area due to high evaporation rates in the region. Thus, it can be concluded that the most important source of aquifer recharge is agricultural wastewater, which is necessary to be accurately calculated according to the type of product, irrigation, soil characteristics and climatic conditions of the study area in hydrological modeling studies. In case study of Isfahan-Borkhar, there is no possibility of exploitation of the aquifer due to the continuous decrease of the water table of groundwater that is clearly evident in the aquifer hydrograph, as well as the negative balance of groundwater resources.

Like developing countries, our country faces the problem of poverty and the spread of this phenomenon in rural areas and is one of the most important problems in rural areas. Measuring and identifying poverty is an integral part of the knowledge needed to formulate programs and policies for poverty alleviation in society and can be a powerful tool for policymakers' attention to the living conditions of the poor. The purpose of this study is to investigate and explain the rural poverty situation in Kouhdasht county. 2- Identify the spatial distribution of rural poverty in Kouhdasht county. The present research is an exploratory and question-oriented one. It is also an applied research based on descriptive-analytical method. Data collection tools were library and field studies (questionnaire, observation). The statistical population includes the villages of Kouhdasht county. To determine the sample of 26 villages an appropriate spatial distribution across all districts were selected. In summing up the results of this study, it can be said that the most important factors affecting rural poverty and its spatial distribution in Kouhdasht county related to income and facilities indices, education, environmental index, service-physical index, food costs, Side jobs and employmen,.respectively. In demographic indices, equality is above 3 which indicates favorable status of these indices compared to other indices and t values of 6.99 and 2.20 respectively and the lowest mean is related to index. Environmental and training indicators that indicate their undesirable status with t-values of -13.98 and -8.04.

Today, the major source of income for Iranian municipalities is the unstable resources such as construction fines and charges and Such an approach has led them to the financial crisis, the challenge of urban management and ultimately to citizens' dissatisfaction. So, in the developed cities of the world, tourism is used as one of the main and influential drivers in analyzing the urban economy in order to sustain and monetize the economy of municipalities. Therefore, the main purpose of this research is to present a comprehensive model of municipalities' sustainable income generation based on tourism. For the research method, interpretive and systematic meta-synthesis approach has been used and the statistical population is based on the findings of qualitative studies of other researchers in the field of sustainable income of the municipalityS based on tourism in the period of 1370-1388 solar years and systematic sampling method has selected 26 articles from 315 articles, based on the title, abstract, content analysis of articles with dimensions and components related to the capability of innovation based on sustainable income of municipalities from the tourism industry. Data were coded using Maxqda software based on content analysis strategy and based on the "double coding" index to evaluate the reliability and quality control of the findings, with 0.92 excellent agreement was reached between the two evaluators.  The findings of the present study show that 131 initial codes, 15 codes with concepts and with 6 main categories and effective in creating sustainable income of municipalities based on tourism are effective in holding festivals, special ceremonies and communication, leisure planning, development of urban transportation infrastructure, Using the hidden capacity of urban tourism attractions, constructing tourist spaces and environments, reinforcement the multiple roles of tourism and tourism They can be considered as a strategy, finally, the result of the research is the presentation of a practical concept model for stabilizing the income of municipalities based on tourism.