جستجوی مقالات مرتبط با کلیدواژه « arid » در نشریات گروه « جغرافیا »

For this purpose, the data of 13 climatic variables in 14 synoptic stations in a period of 44 years (from 1977 to 2020) used and a 13x14 matrix (rows; climatic elements and columns; number of stations) was created. In order to generalize the station data to the area, a grid with 15x15 km pixel was formed in central Iran and a matrix with dimensions of 446x15 (rows; digital pixel and columns; number of stations) It was found that the basis of the calculations will be factor analysis with varimax rotation and cluster analysis with Ward integration. The results of measuring the relationship between altitude and climatic variables indicate that in Central Iran, there is a direct and significant relationship between these two factors. However, due to the influence of local and macro-scale climatic factors, this relationship is not the same throughout the area and sometimes creates climatic nesting. In addition, the results showed that the 4 main and effective factors that make the climate of central Iran are: precipitation, temperature, humidity and dust storm. These factors explain 86.2 percent of the climatic behavior of this area. So that the rainfall with 35 percent is the most important climatic element in this area, which often dominates in cold mountainous regions and high altitudes. The temperature is 27.3 percent in the central deserts and the sides of Lut desert in Kashan, Khourbiabanak, Lar and Bam. Humidity is effective with 15.3 percent in parts of hot and humid southern areas in Baft, Abadeh and even cold and humid northern areas in Daran, Isfahan. Dust storms with 8.8 percent are the least effective factor in the climate of central Iran, which are scattered in Khourbiabanak, Bafaq, Yazd, and Kashan

Atmospheric aerosols are a colloid of solid particles or liquid droplets suspended in the atmosphere. Their diameter is between 10-2 to 10-3 micrometers. They directly and indirectly affect the global climate by absorbing and scattering solar radiation, and they also have a serious impact on human health by emitting harmful substances. In addition, high concentrations of aerosols on a local scale due to natural or human activities have adverse effects on human health, including cancers, pulmonary inflammation, and cardiopulmonary mortality. Monitoring the temporal and spatial variability of high concentrations of aerosols requires regular measurement of their optical properties such as aerosol optical depth (AOD).

Algeria is a large country with little knowledge of the spatial and temporal diversity of AOD, and the low spatial resolution of existing products makes it very difficult to predict aerosols (airborne particles) at the local scale, especially in arid southern regions. As a result, AOD recovery with data with higher spatial resolution is crucial for determining air pollution and air quality information. Several AERONET stations have been installed in Algeria. The Tamanrasset_INM station has been selected based on its location and the availability of historical AOD data for the period (2015-2016).
In this study, Landsat-8 / OLI image from tile 192/44 was used for satellite images. To this end, 23 TOA-corrected L1G-level Landsat-8 / OLI cloudless scenes were downloaded from January 2015 to December 2016 in the study area. DN values ​​are converted to TOA reflections using the scaling factor coefficients in the OLI Landsat-8 metadata file. In this study, the minimum monthly reflectance technique was used to recover AOD in this area. As a result, LSR images were used in the recovery process in different months of 2015 and 2016. The process of selecting reference LSRs was initially based on the selection of clear, foggy / cloudless sky images. The selected images were then used to construct artificial images in which each pixel corresponds to the second lowest surface reflection of all selected monthly images to be the LSR pixel for the respective month. The AOD retrieval method developed in this study is based on a LUT, using the 6S radiative transfer model. The advantage of using the 6S model is its ability to estimate direct components and scattering using a limited number of inputs for each spectral band in the entire solar domain. The effect of the viewing angle is limited because Landsat data are usually obtained with a fixed viewing angle. Surface reflectance can be estimated from a pre-calculated LSR database. The accuracy of AOD recovery depends on the use of the appropriate aerosol model. A continental model was selected from the available aerosol models. Other atmospheric parameters such as ozone, carbon dioxide, carbon monoxide and water vapor are considered by default. The AOD values ​​used to make LUT are set as follows: 0.0, 0.05, 0.1, 1.5, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 and 1.5. The zenith angles of the sun and the sensor range from 0 to 70 degrees with a step of 5 degrees and the range of azimuth angles from 0 to 180 degrees with a step of 12 degrees. Using these parameters, the radiative transfer equation was run in forward to obtain the TOA reflection. Different combinations of input and TOA output parameters are stored in LUT. AOD retrieval is based on a comparison between the TOAs estimated with the model and the observed items using the best fit approach. Using such an approach, the estimated AODs are simulated in accordance with those used in the production of TOAs, using a competency function that minimizes the distance.

In this study, the AODs recovered at 550 nm in a 5-by-5-pixel window around the AERONET site were averaged. The considered AERONET values ​​are the average of all measurements taken within ± 30 minutes of image acquisition time. Observation regression results (AOD from Landsat 8 images and AERONET stations) showed that the correlation coefficient is about 84%. This study shows a good fit of the model on the research data and shows the high capability of the model. This study showed a strong recovery of AOD against AERONET data of more than 70% at . The differences can be attributed to a limited number of points or hypotheses related to the aerosol model used in this study. The assumption of using a pre-calculated LSR does not limit the accuracy of this method because we have shown that in arid regions where the change in land cover in different months of the year is small, a pre-calculated LSR image can be representation used the share of surface reflection in the radiative transfer model throughout the month.

In this study, an AOD derived from a high-resolution satellite at an urban scale was produced in the city of Tamanrasset, Algeria. The developed method assumes that the change in land cover is minimal and the temporal change in LSR is not significant. A pre-calculated LSR image is created to show the surface reflection in the retrieval process. Based on the 6S radiative transfer model, an LUT was constructed to simulate the TOA reflection of the built-in LSRs and a set of geometric and atmospheric parameters. The retrieved AODs were compared with the AERONET ground data. The results show that this approach can achieve reasonable accuracy in AOD recovery, which reaches about 70.9% at . In addition, this approach is suitable for estimating AOD in urban areas compared to existing AOD products with low spatial resolution. The results of this study show a 4% improvement compared to the results of Omari et al. (2019). The results of this study showed that ignoring the monthly changes in LSR values leads to good results in AOD recovery.

In recent years, the population growth, the increase in irrigated land and economic development have caused the increase in the demand for groundwater resources all over the world. In arid and semi-arid regions where surface water does not have a significant amount due to low rainfall and high evapotranspiration, people lives mainly depend on groundwater. As a result, it is necessary to identify the groundwater potential areas and determine its recharge areas using accurate technologies. So, the aim of this research is to compare the method of multi- influencing factors with the fuzzy method for determining the potential of groundwater in a part of Kebar-Fordo watershed, Qom city, Iran.

For this purpose, a part of Kebar-Fordo watershed located in Qom province was selected. Six factors layer, viz. slope, annual rainfall, distance from river, geology, soil, and landuse were considered and classified based on groundwater potential susceptibility in different scales. Multi-influencing factor method can determine the groundwater potential of the region by assigning appropriate weight to different effective factors. In this approach, the layers were combined in Arc-GIS after determining the weight of the layers. In the fuzzy method, the layers of six factors were converted to fuzzy based on the linear function, and then the layers were incorporated using the gamma function. Finally, the statistics of observation points and accuracy index were used in order to evaluate the models,

The slope map represents that most part of the studied area (78.56%) has a "0-1" class while "1-3", "3-9" and "9-25" slope classes could be observed in 19.97, 1.29 and 0.18% of the total area, respectively. The soil texture has a significant effect on the infiltration and percolation of the surface water movement towards the groundwater. Therefore, in this research, the soil factor has been investigated as one of the input factors to the models. Soils with high permeability are more suitable for groundwater recharge and vice versa. The soil texture of the area consists of sandy loam, loam, sandy clay loam, and clay loam textures, which cover 3.73, 90.72, 0.23, and 5.32% of the total area, respectively, with a rank of four to one  for groundwater potential. In this study, geology map showed that Qft2 formation has the largest area (88.98%) and Plc formation is in the second rank (4.9%). Qft1, Qs.d and Mur units have an area of 2.22, 2.12 and 1.10% and the smallest area belongs to OMq formation (0.68%). Also, different types of land use in the study area were agriculture, garden, rangeland, bareland, and resendential area. The land use map showed that the largest area of this area was ariculture landuse (77.18%), while garden and rangeland covered 0.07 and 6.5% of the total area, respectively. Bareland and residential area comprise 2.94%, 13.31% of the total area, respectively. Among the different landuses, agriculture and residential area have the highest and lowest ranks in groundwater recharge. The rainfall map was categorized with four classes. The classes of 140-156, 156-168, 168-182, and 182-203 mm layers include 14.15, 48.92, 21.84 and 15.09% of the total area with the rank of one to four for groundwater recharge, respectively. The map of distance from the stream was divided into four categories: "0-659", "659-1480", "1480-2675" and "2675-4939" meters, which comprise 46.33%, 34.15%, 15.72% and 3.8% of the total area, respectively. In the method of multi influencing factor, the distance from the stream (8.33%) and the geological factor (25%) were the lowest and highest weights. In this regard, the factors of rainfall, slope, soil, landuse have 20.83%, 16.67%, 16.67% and 12.5% weights, respectively. Then, the groundwater potential map was prepared through overlaying in ArcGIS and the studied area was classified into suitable and unsuitable classes. The suitable class covers 75.15% of the studied area and the unsuitable class covers 24.85% of the total area. In the fuzzy method, the unsuitable class comprises 43.63% and suitable class covers 56.37% of the area. In order to evaluate the models, the statistics of the observation points were applied which the accuracy of the multi- influencing factor and fuzzy models was calculated as 71.42 and 78.57%, respectively.

Preparation of groundwater potential map is necessary to adopt management measures of rainfall storage and groundwater recharge in arid and semi-arid regions and it can be used for sustainable management of groundwater resources. The findings of this research revealed both model's accuracy in the studied area.

Land vulnerability one of the major global challenges as an objective case of degradation of arid, semi-arid and semi-humid ecosystems caused by natural processes and human activities. However, in order to assess the vulnerability of the land, it is necessary to know exactly the degree of tolerance of ecosystems and the use of indigenous knowledge systems to external conditions.The present study was based on the IDI hybrid index algorithm to assess the severity of Khorasan Razavi vulnerability over a 16-year period (2001-2016). For this purpose, two indicators of vegetation status (VCI) (MOD13Q1) and temperature status (TCI) (MOD11A2) based on the opinion of experts, and according to the availability of these indicators, based on satellite data and in The desired time period was selected. Then, the images of Modis sensor products were prepared and normalized, and the indices were scaled in the range of zero and one, and the hierarchical method in EDRISI software was used to evaluate the weights. Using 250 ground harvest points, the accuracy of the model was determined using kappa coefficient for vegetation status. Then, using IDI combination model and implementation of the model, the area has very low vulnerability (0-15 . 0), low vulnerability (0.3-0.3), medium vulnerability (3.5-3.0) 0), high vulnerability (0.5-0.7) and very high vulnerability (1-7 . 0). The results showed that the highest vulnerability in 2001 with more than 50 percent of the province's average in the middle class and in 2016, the highest vulnerability in the two medium and high classes is approximately equal to the proportion of 44 percent. The overall accuracy of the model for the IDI combination model was 78.6% and the Kappa coefficient was 0.7.

In this research, in order to investigate the effect of short and long term observational data on the quality of predicting climate parameters, the LARS-WG6 statistical downscaling model is performed for EC-EARTH model and the optimistic scenario RCP4.5 and the pessimistic scenario RCP8.5. Also the HadGEM2-ES model with the optimistic scenario RCP2.6 and the moderate scenario RCP4.5 and the optimistic scenario RCP8. 5 are investigated. Forecasts are applied on the next three 20-year periods (2021-2040, 2041-2060, 2061-2061). Three daily statistical periods of the Drudzen Dam Synoptic Station including the 30-year period (1988-2017), the 20-year period (1998- 2017) and the 18-year period (1988-2005), were used. The 18-year period was determined by examining the 30-year trend. A fractal based procedure is employed for extracting a complete pattern of repeating weather events including rainfall, minimum and maximum temperatures. The modelchr(chr('39')39chr('39'))s capability in the simulation was measured according to the base period and the accuracy of the anticipations was evaluated using MAD, MSE and RMSE statistical tests. Studying the results clearly shows the effect of time scale changes on the accuracy of predictions. Accordingly the 20 year time period showed the least error, especially for the precipitation parameter. In general, it was revealed that this model predicts minimum and maximum temperatures with high accuracy and the rainfall prediction holds less accuracy. The prediction of models under different scenarios and different time intervals showed an increase in minimum and maximum temperatures. Moreover, the model indicates while the average annual precipitation increases in the coming years, the pattern of precipitation will change. In April, January and December, we will see an increase in precipitation and a decrease will be experienced in February.

Vegetation is one of the essential factors in structure and function of terrestrial ecosystem and it is one of the principal loops in water-soil-plant-atmosphere continuum. Several studies have demonstrated that vegetation covers are sensitive to alteration of climatic, edaphic, topographic and human activities. Thus, alteration in vegetation and its relation with the mentioned factors are important of high importance. In order to investigation of vegetation changes and its effective factors, the current study was conducted in Kharestan region placed in Fars province, Iran. In this regard, the images obtained from ETM Landsat 7 (2000-2017) and meteorological data gained from local and 17 regional meteorological stations were used. Using these images, temporal and spatial changes NDVI and NDVI anomaly were studied. A supervised classification method was used to extract land use map. Finally, the relationship of NDVI with climatic, topographic and anthropogenic factors was investigated. Relationship between NDVI and climatic and topographic factors was estimated using GWR and OLS methods, respectively. Generally, temporal variations showed a slow increasing trend in NDVI value. NDVI anomaly was mostly negative before 2008 but it turned to positive after 2009. NDVI spatial distribution showed an increasing tendency from north toward center and continued to south-west of the study area. The study shows that the vegetation cover change was caused by both natural factors and human activities. NDVI increased in agricultural and pasture lands. Also, natural vegetation has been affected by climatic factors more than irrigated vegetation (agricultural and gardens). Furthermore, vegetation variation influenced by topographic factors likes height, slope and aspect. Also, with an altitude over than 2500 m, NDVI showed a decreasing trend, on slopes lower than 5° it increased. NDVI values in north and east directions were higher than in southern aspects. The overall trend indicates an increase in temperature and a decrease in precipitation during the study period. The maximum positive and negative correlation between mean annual precipitation and NDVI using ordinary least squares method were 0.93 and 0.83, respectively. Also the maximum negative and positive correlation between NDVI and temperature were 0.65 and 0.5, respectively. The highest local R2 values between NDVI with precipitation and temperature were 0.45 and 0.44, respectively, which was observed in the central parts of the region. According to the obtained results through the present study, it can be stated that environmental factors like precipitation, altitude, slope and aspect are the Influential factors controlling vegetation in Kharestan (Fars province, Iran).

The aim of this modeling initiative is to gain insight into the energy needs at dawn (6.30 o'clock in Tehran) in seven provinces including Qazvin, Qom, Central, Isfahan, Yazd, Fars and Kerman (i.e. Iran's arid and desert regions). For this purpose, the dynamical model data of EH5OM were downloaded from the Max Planck Physics Center under the A1B propagation scenario for the period from 01/01/2015 to 03/13/2010 at 03Z for 03Z. In the next step, for the microscale, the output data of the model were used using the REGCM4 model, and the data of the model were obtained with a spatial resolution of 0.27 × 0.27 arcs and an array of outputs of 13410 × 705. After the temperature of the heating clock (HDH) was calculated, the fractal theory was used to assess the behavioral outlook of this climate parameter. The results show that the maximum demand for the temperature of the hexagonal tail in the arid and desert regions of the country is 595 ° C in December and the minimum is 21 ° C in July. The results of fractal geometry also showed that the temperature of dawn warming in Iran's dry and desert regions serves as a sensitive nonlinear system that is more subject to long-term changes in the early and late months of the year and to short-term changes in summer. The trend evaluation and trend slope proved that, in most months of the year, the degree of warming of the dawn is reduced.

Iran is located in the desert and sandy location because the large sections of this country is on arid and semi arid belt of the world. Due to the dust and Haze in these areas is a major problem that has plagued the residents and bystanders and so lives of them is disrupted every so often. Airflow of the monsoon winds, which caused a mass of clay and silt as so as spread dust and smoke in the atmosphere, it does limit sometime visibility between 1 and 2 km in the horizontal. In addition to the environmental problems of this phenomenon, it has many hazards for heart disease - cardiovascular and respiratory and so be detrimental to the children. In this regard, the subject soil stabilization using polymer as a way to reduce the production of dust is defined for prone area. In this paper, the effect of polymer acrylic on a mass of fine-grained soil has been studied. The soil has been simulated for different sizes of fine grains. Samples in this study were uncompacted particles of soil with different amount of water-solvated polymer (0, 5, 10, 15,20,25,30 grams per meter squared) poured over them. These samples are kept in experimental environment for 7 days. After ensuring complete dryness, their stabilities are tested against wind flow with 72 km/h speed. Results show that adding more polymers to soil would considerably increase its particles’ stabilities. This stability is due to positive reaction of polymer with soil particles. The effect of this stability is maintained during sample drying time in the lab and the soil maintains its characteristics during testing. The best results are obtained for 4% polymer, where caused increase in stability to about 15 times that of the soil without polymer

Study the behavior of the rivers at arid and semi arid areas is of the main and basic activities in the country (since a great portion of Iran has arid and semi arid climate). The main differences of arid areas from humid areas are the different climatic factors including the precipitation amount and pattern. This issue can cause the change of flow regime and sedimentation regime (FSR) and their ratios in these areas. Also temporary flood ways of arid areas, in which the water flow is limited to heavy rainy and wet seasons, has a great influence on flow and sediment regime (FSR). In this research, by statistical review of flows discharge in arid and semi arid areas at the west part of country, it is tried to review the effect of climate on flow and sediment regime.For this purpose, flood discharge with different return periods were estimated by the best statistical distribution of 21 hydrometric stations. Then by using rating flow of sediment, sediment amount was measured in different return periods. At the next step, flow and sediment regime was calculated and the relationship between flow and sediment regime and the area of relevant up stream sub-catchment areas was determined. Also the results of this study show that the relation of up stream sub-catchment areas of each station will increase with FSR increase in high return periods.

Flood spreading is among preventing method from damage of deluge, especially perishing of water and soil in latrine basins of arid and semiarid regions. Accumulation of sediments on the flood spreads regions lead to changes in soil fertility, revival and support of plant covering and controlling of desertification and change in physicochemical properties of soil in these regions. In order to measure of soil changes in the station of flood spreading Hashtbandi, Minab, Hormozgan, were dipped 12 cavities in two regions: flooded and control. Sampling was done from 0-30 cm and 30-60 cm depth. Physicochemical properties were evaluated in the samples. The obtained results indicated that the average of organic carbon, total nitrogen, amount of potassium and phosphorous, EC as well as sand percent significantly increased in the flood spreading region than control region and clay percent, pH and saturating percent (SP) decreased in the flood spearing region than control region. Beside, silt amount non-significantly decreased in the flood spreading region than control region. Generally, can be said flood spreading system changes the soil texture during the time and has positive effect on soil fertility. Increasing amount of macro elements such as N, P and k as well as reduction of pH are positive effects for enhancing soil fertility, although increasing EC may be limited planting of some sensitive crops.

Researches indicate that around one third of lands are located in arid areas and Islamic republic of Iran is also located in arid and semi-arid area of the world. Apart from aridity, a significant part of the country, i.e. around 25 million hectares are wastelands. But beyond this most permanent, seasonal and temporal rivers and many important inland lakes have saltwater which worsen this sad situation. On the other hand, more water is extracted from groundwater sources to satisfy ever increasing demands. For example, 79837 million m3 water was extracted from ground water resources in 2002-2003 water year which compared to 2001-2002 water year has increased up to 2.5 percent. Inappropriate and wasteful use of groundwater also results in salinization of freshwater resources.
Southern provinces and cities bordering the desert have lots of saltwater. Water shortage and water saltiness along with salt salinization have even reached agricultural villages and lands are no longer profitable. Most aqueduct, especially those in southern parts of the country and those bordering the desert have dried. There were around 40000 aqueduct which reached 26307 in 2004. Many lands are now barren and desolate. Irregular and unplanned extraction of water from aqueducts, springs and freshwater resources by deep and semi-deep wells have decreased freshwater resources to a great degree and have gradually increased saltwater, water shortage crisis and drought crisis. This crisis is an alarm indicating a massive crisis of water shortage. Planners and authorities should see this crisis as an important religious and divine responsibility and try to find a compassionate and responsible solution. Before it is too late, they should manage and protect water resources, try to preserve rural agriculture and avoid wasting water and polluting its resources, which are shortly discussed in the present article.

Meanders are of dynamic landscapes and important shapes affecting on the characteristics of flood plains, which are formed for different reasons and displaced under some conditions in various shapes.These geomorphologic and hydrological phenomenon are the most important factors of changing the flood plains and also are the main reason of increasing the entering sediments in to the rivers. By knowing this fact that the type of configuration at the rivers’ flow path especially the existence of meanders are not accidental at most of the times, therefore through the study of the configuration of the rivers’ path and recognition of the factors effective on changing their flow path, it is possible to recognize the dominant dynamism on the river’s flow in the time period of the study and also the manner and trend of changes’ occurrence in the current situation in the flood plains and manner of dominancy of possible conditions in the future. by the study of these phenomenon and referring to the existing heritages, which indicates the displacement of the rivers’ flow paths in the past, it is possible to comment on the manner of pervious changes and also about the features of the processes and the dominant dynamism on the rivers from the view point of erosion or sedimentation and settlement of deposits. Garaagaj is considered as the most meander rivers of Garangoo (having geographical coordinates of 37 °00 ' to 37 20' of north latitude and from 46° 45 ' to 47 ° 15 ' of east longitude). This river with having different meanders in its path and the changes has made in the path, has increased the sedimentation load of the river. regarded that a lot of dams and weirs have been established at the path of this river, the creation of meanders and consequently increase of the lateral erosion during the time, in addition to the entrance of lateral soils of large flood beds in to the river,the increase of resulting sediments has changed to a great and severe problem for the established dams at the route of these rivers.Research Areal photos have been used for the review and analysis of displacement rate of active channels in Garaagaj flood plain, and the new and old routes have been fixed and traced from areal photos, the rate of displacements have been measured from the remaining lines and signs and the required 23 calculations have been made by the resulting data. Sinuosity rate of araagaj river has been calculated by using (S=T/L) S relation. In this paper, for the review of displacements made in meander route and along Garaagaj River, firstly the radius of meanders’ arch and then the bed width has been calculated and then by the use of the resulting data of these easurements, the ratio of these two parameters (R/W) has been obtained. For estimating the required time for displacements in active channels, the relation of (Wt=Wcb/V) has been used.Discussion and The produced meanders at the path of Garaagaj River have various configuration and magnitude along different parts of the river. Review of the river meanders with S index shows that out of 25 parts of the under study, 8 parts are of sinuosity type and 17 parts are of meander type. Sinuosity rate of Garaagaj is more at the river outlet and at the end of the path, but sinuosity change is relatively low at the path length, in fact it can be said that more than 70% of the path along the under study parts are of meander type path and considering that each arch at meander path is considered as the exciter and displacement motor for the next arch and finally for displacement of the flow path, therefore increase of meander type parts of the path indicates the high potential of the flow path for more and faster displacement. The studies show that there exists a relationship between meander radius (R) and width (W), type and size of sedimentation load and also lateral erosion. When the rate of R/W reaches to maximum, flow turbulence also increases which leads to the increase of erosion power of the flow at meanders’ part. Review and study of the rates obtained from estimating the ratio of canal radius (R/W) with displacement rate of flow path in Garaagaj River and canal width specifies maximum amount of displacements happened in the past at the river path. Displacement of the path is together with creating cesspits and bank sides and as a whole erosion of the bed, so such phenomenon can be seen in the path of the said river. Studying the type of displacements in the path of different parts of Garaagaj river shows that different types of displacements have been happened at the river path. study of Garaagaj river bed shows that the required time for canal displacement at Garaagaj path is various in different parts. The lowest time for displacement of channel is 4 years and maximum time required for displacements is more than 17 years. This river at the areas near to confluence place of Garangoo changes its path rapidly and in a short time, but in middle parts, this time decreases and again at the ending part of path, the time of displacement will increase. Type of soil at flow bed and flood bed has a great effect on the severity and weakness of lateral erosion. When the soil shows sensitivity to thelateral erosion, the amount of material left in to the water will increase at the same rate and the width of flood bed will increase. Studying the soil type of surface formations of Garaagaj path shows that the type of formations at the under study area is sensitive to lateral erosion.Meanders are the main causes of lateral erosion and are considered as the changing factor of flood plains. In semi arid areas that the flood plain banks do not protected by vegetation cover, the occurrence of such changes is great and lateral erosion has been intensified. On eastern slope of Sahand Mountain, as a semi arid area, the most typical meanders have been formed on the river path.One of these meander paths is Garaagaj Chai, which by creating various and different arches along its path has great displacements which has intensified the lateral erosion. With respect to the type of surface formations at the flow path of this river, frequent displacements at the flow arch and meeting the meander part of the flow with uncovered sides made the flood plain to become wider and middle bank sides at the flow path to be displaced rapidly.Investigation and Analysis of the Type and Time Length of Displacements...Geography and evelopment, 10nd Year, No.27,Summer 2012 24 The results suggested that R/W on Graagaj River is not same in all parts of path, in some parts is high and in other parts is low. This range shows the change of type, features and displacement rate throughout river length. With respect to the results of performed studies, these changes can be related to the type of flow paths and the impact of tectonic factor. In the under study area, in parts meander and Sinuosity can be seen, except active tectonic, no other reason can be find for changing configuration of Garaagaj Chai river. In performing development operations in meander paths of semi arid areas, which lateral erosions resulting from displacements can produce major ad great problems,review and estimation of the required time for displacements has a great importance.The obtained results of the studies at Garaagaj Chai river flow path shows that the required time for displacement of channel at Garaagaj Chai river is various in different parts. Minimum time required for displacements is 4 years and maximum time is more than 17 years. It can be said that 4 years is a short time for displacements and the river at this time can make major changes in its middle and lateral part.

This paper presents the processes and forms that are shaped in loess deposit in the south and east of Aghband. The study area is the Centre of agriculture of Golestan- province. Therefore the investigation of erosion outcrops such as gully erosion, badland and landslide in the study area is important. Another important processes are  the characteristics of arid and semi arid climate as well as other natural factors involved. Using the laboratory methods which were carried out on soils of the study area has shown that the presence of limestone, silt, clay and gips of the loess- deposit has led to the forming of Gully erosion in arid- central part, piping in semi- arid- part and landslide in humid sourthern part and badland topography in  most parts of northern and southern parts of the study area.