جستجوی مقالات مرتبط با کلیدواژه « فرسایندگی » در نشریات گروه « علوم انسانی »

Erosion is primarily caused by precipitation and runoff, while erodibility results from the type of the formations at the catchment scale, which is subject of this study. The objective of this study was to investigate the relationship between geologic units and erosion intensity. Initially, two models of MPSIAC and Fargas were used to study erosion intensity. The Fargas model was presented based on the theoretical principles of two erosion and the erodibility factors, while MPSIAC model was based on 9 factors. BLM method was used to separate the intensities of a type of erosion according to the S.S.F table. RUSLE model was used to estimate soil erosion in the studied sub-basins. To determine the risk of erosion using the value coefficient, Fargas model was used. In the MPSIAC model, coefficients were considered for each of the nine factors. Based on the results of MPSIAC model, 79% of the basin surface had high erosion intensity and 21% had very high erosion intensity, while according to Fargas model, 0.3% had moderate erosion intensity, 10% had high erosion intensity, and 4.7% and 85% were characterized with severe erosion and very severe erosion, respectively. Moreover, in both models, 18% corresponded to very high erosion intensity (very severe), while 7.2% had high erosion intensity. In Fargas model, E1t1, E1t2, E2ig3, Q2f, Qt1, and Qt2 had very strong erosion intensity, whereas, in MPSIAC model, E1t1, Qt1, and Qt2 had high erosion intensity on their surfaces. One reason for this phenomenon could be the erodibility of the formations. Most of E1t2 and Q2t are highly eroded, which contributes to a large amount of drainage in addition to the erodibility of the formations.

Arid and semi-arid regions of the world cover more than 30% of the earthchr('39')s surface. Wind, as one of the erosive agents of the earthchr('39')s surface, causes the transport of sand and deformation in arid areas. Wind erosion is directly related to wind speed. The higher the wind speed is above the threshold value, the more increase in wind speed. This issue increases wind erosion and thus, it intensifies wind erosion. The Iranian plateau is one of the most sensitive areas of the world to wind erosion due to its location on the arid belt of the northern hemisphere. The Lut Desert is one of the most active places for changes in wind speed and direction with its huge volume of sand masses. The eastern part of this region, which includes the largest sand mass in Iran, namely Yalan sand, is dominated by 120-day winds, which doubles the importance of studying winds and its shaping role in the wind season. The main purpose and assumption of this study is to analyze the frequency of erosive winds and estimate the potential and final direction of sand transport flow in the Lut plain and to investigate its relationship with the geomorphology of existing wind forms using time series data of wind direction and speed recorded in Synoptic stations are located around this plain.

In this study, in order to analyze the wind situation and study the erosive winds in the Lut plain, the available meteorological data for 4 synoptic stations around this plain were used. WRPLOT view 7 software was used for statistical calculations of wind and drawing of wind rose. Sand Rose Graph 3 software was also used to draw the sand rose of the stations around Lut plain due to the high volume of calculations. To calculate the values of sand transport potential (DP) in different geographical directions, the Freiberger-Dean relationship based on the basic equations of Begnold and Leto-Leto was used. From the sum of DP values in different directions, the total sand carrying capacity (DPt) is obtained and in fact it is an indicator that represents the total wind energy to carry sand to the desired station. RDP stands for the amount or size of the output vector (resulting vector) of sand carrying capacity, which is obtained by summing the DP values in 8 or 16 different directions and shows the final status of sand transport in the study area. RDD indicates the net direction of sand movement (result vector direction) during the year, month or season. In order to determine the amount of sand transferred per unit time, a unit of width is used from the equations presented by Begnold, Xing, 1953, Kawamura, 1964, Hesu, 1973 and Leto-Leto, 1978.

At Shahdad station, about 40% of the winds blow from the north, north-northwest and north-northeast, and the rest of the winds often blow from the east and west. At Nehbandan station, about 20% of the winds blow from the north and northeast, and the rest of the winds have a great variety in the directions. At Bam station, about 36% of the winds blow from the west and west-northwest and the rest of the wind blows from the north and its surroundings. At Nusratabad station, about 31% of the winds blow from the east and southeast, about 27% of the winds from the west and northwest, and the rest of the winds from other directions with great variety. The results of annual hurricanes indicate that winds with north, north-northwest and north-northeast are the dominant winds in Nehbandan and Shahdad stations. At Bam station, in addition to the north directions, these winds also blow from the west and west-northwest directions. At Nusratabad station, there is a great variety of wind directions, but unlike other stations, the wind does not blow from the north. Analysis of net direction of sand movement (RDD) of the studied stations shows that the direction of sand movement in Bam and Shahdad stations is south-southeast, in Nehbandan station to the south and in Nusratabad station is to north-northeast. The analysis of the direction of movement of the sandrose shows the complete correspondence with the hurricane rose of the studied stations. Total sand carrying capacity (DPt) indicates moderate erosion power for Bam and Nusratabad stations and high erosion power for Shahdad and Nehbandan stations. The highest value of vector output of sand carrying capacity (RDP) is related to Shahdad station, followed by Nehbandan, Nusratabad and Bam stations, respectively. For Shahdad, Bam and Nehbandan stations, the maximum amount of one-way winds occurs in autumn and in Nusratabad station in late winter and spring. The maximum amount of sand flow for Bam, Shahdad, Nehbandan and Nusrat Abad stations is 165, 320, 233 and 202 kg/m/s, respectively.

The results indicated that in Shahdad and Nehbandan stations located in the northern half of Lut plain, most of the winds blow from the north, but in Bam and Nusratabad stations located in the southern half of Lut plain, most of the winds are concentrated towards Lut. The highest percentage of occurrence of winds above the threshold speed for Shahdad, Nehbandan and Bam stations occur in summer and the highest percentage of occurrence in Nusratabad station is related to spring. Analysis of net direction of sand movement (RDD) shows that the direction of sand movement in Bam and Shahdad stations is to the south-southeast, in Nehbandan station is to the south and in Nusratabad station is to the north-northeast. Total sand carrying capacity (DPt) indicates moderate erosion power for Bam and Nusratabad stations and high erosion power for Shahdad and Nehbandan stations. The highest value of vector output of sand carrying capacity (RDP) is related to Shahdad station, followed by Nehbandan, Nusratabad and Bam stations, respectively. The study of sand homogeneity index (UDI) indicates one-way winds for Nehbandan station and two-way winds with aperture angle for Bam, Shahdad and Nusratabad stations. The highest flow rate of sand is related to Shahdad station with 320 kg/m/s and the lowest is related to Nusratabad station with 50 kg/m/s.

The soil is one of the most important factors of production that has a great influence on human economic and social life. The surface of the earth is generally covered by soil and other surface deposits. Soil erosion is one of the most important problems and problems we face today. Increasing exploitation and lack of proper human management of the natural environment have a great effect on the intensification of soil degradation and erosion processes. In this research, the effective parameters analysis of erosion and sediment production in Dakehah basin with a total area of 9923.2 ha in southern Kerman province was studied using the Revised Universal Soil Erosion Model (RUSLE). Data and tools used in the research include data from meteorological stations, digital elevation model (DEM), ETM 2015 satellite imagery, GIS and remote sensing (RS) It should be. By studying the effective factors in this model, which includes rainfall erosivity factor, soil erodibility factor, topographic factor, and vegetation, the purpose of this study is to estimate the annual soil erosion in the study area. The erosion rate of the basin is estimated. Accordingly, annual soil erosion in the whole study area is estimated at 67 tons per hectare per year. The results of this study show that the highest effect on the estimation of erosion, a topographic factor with the highest coefficient of explanation was 92.6 In this research, the effectiveness of RUSLE technologies of annual soil erosion is confirmed by the new model of GIS and remote sensing for quantitative estimation of soil erosion values.

This study tries to investigate relationship between rainfall parameters and USLE R factor. To gain R-factor, at first, shower kinetic energy was calculated and then its erosivity computed by using maximum 30 minutes rainfall intensity. Therefore 3 meteorological stations in Khuzestan province and one station per Kohgiloyeh & BoyerAhmad and Boushehr provinces were selected and their recorded hyetographs of 13 years were analyzed. For any hyetographs, rainfall erosivity was computed in any one month, season, or year and corresponding rainfall parameters were extracted too. Temporal and spatial variation of rainfall erosivity was studied and relationships between R factor and rainfall characteristics were investigated by using regression analysis. It was resulted that February to March and winter season has the most erosivity risk. Spatial analysis of rainfall erosivity in selected area showed that Dezful and Ramhormuz have the maximum erosivity factor. Mean annual erosivity factor of Khuzestan province was computed 28.07 ton.m/ha.h. Regression analysis showed strong relationships between rainfall amount (mm) and maximum 30 minutes rainfall intensity (cm/h) with R factor. A model that computes R-factor by means of rainfall amount was suggested.