Vahid Chitsaz; Seyed Bagher Fatemi; Zabihollah Eskandari
Abstract
Nowadays, application of remote sensing is common in soil conservation and erosion projects and most of them are used aerial photogarphs and desipte of the numerous advantages, there are some limitations. In this study, replacemen of moderate-resolution satellite data instead of aerial photographs has ...
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Nowadays, application of remote sensing is common in soil conservation and erosion projects and most of them are used aerial photogarphs and desipte of the numerous advantages, there are some limitations. In this study, replacemen of moderate-resolution satellite data instead of aerial photographs has been investigated with emphasis on processing of satellite images and using image filters and the purpose of soil erosion figures detection. Finaly, image processing of area are prepared with maximum capability vitual interpretation of effects associated with erosion, after the study design, atmospheric and geometric corrections and perform pre-processing and initial processing on ETM+ and ASTER images. In order to evaluate the efficiency of filters for detection and identification of soil erosion were used low-pass and high-pass filters such as filters, median, mean, High Pass, Gaussian, Laplacian, Sobel and linear filters on ASTER and ETM images in the part of the Esfahan Dastkan basin. According to the results, using of low pass filters are not recommended because of the resolution reduction of soil erosion. High-Pass filters can be partialy appeard the edages of image and can be help to visual interpretation (especially in combination with the original image). Use of filters is recommended in combination with the image and as an aid to vitual interpretation, due to problems of application the fiters for separate soil erosion units. Regard to the dimension of soil erosion (rill and gully) and compared to the spatial resolution of the used sensor in this study, the erosions are not clearly appeared in the picture and application various image filters to automatically discover and exploit of these effects can not be efficiently. Resolution images of ASTER and ETM+ are not responsive for mapping erosion by using automated method and should be looked for a solution of semi-automated and visual interpretation. Also, because of the similarity between the spectral and geometrical picture was not found a major difference in the results. Therefore, it is recommended to produce a susceptibility map of erosion or erosion risk map instead the variouse types of regional soil erosion.
Mohammad Mehdi Fattahi; Hamid Reza Javidkia
Abstract
Gully erosion is one of water erosion types that happen due to improper management of agricultural lands. The main objectives of this research are zonation and characterisation of gully erosion. For this purpose, affected areas by gully erosion were noticed in Arial photographs and satellite images. ...
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Gully erosion is one of water erosion types that happen due to improper management of agricultural lands. The main objectives of this research are zonation and characterisation of gully erosion. For this purpose, affected areas by gully erosion were noticed in Arial photographs and satellite images. Areas with more than 500 ha and their dominant climates were specified with climate map and for each climate two areas in which one representative gully and two repetition gullies were chosen. Morphology characteristics, soil sampling and other related studies were performed in each gully. Consequently, according to the main characteristics, such as climate and view plan, these gullies were classified by cluster analysis and their digitized zonation maps were provided. According to the results, six regions with a total area of 7437.3 ha were affected by gully erosion with three different types of climates, from which, three regions had moderately arid climate (Qeshlagh Alborz and Naizar) and warm semi-arid (Rahjerd)with more than 500 ha. These regions that are classified in two classes based on cluster analysis, have lateral gullies which are developed beside the natural drainages and are classified as un continuous gullies. The texture of soil surface is usually sandy-loam and in some cases loam and silty-loam and sandy-loam and silty-loam in the subsurface layer. Highly sensitive lands, flood occurrence, past heavy rainfalls and high amount of salts in some areas, are from the most morpho-climatic factors causing gully erosion in dry regions and deserts of Qom province.
Tooraj Asadi; Seyed Saber Shahooei; Mohammad Asadi; Amir Mansour Shahsavar
Abstract
Due to the importance of water erosion in reducing soil fertility many studies have been done on the quantity of this destructive phenomenon. Tamura and Rogowosky found a meaningful relation between water erosion and Cs-137 loss in soil matrix. This report was the first of application of Cs-137 method ...
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Due to the importance of water erosion in reducing soil fertility many studies have been done on the quantity of this destructive phenomenon. Tamura and Rogowosky found a meaningful relation between water erosion and Cs-137 loss in soil matrix. This report was the first of application of Cs-137 method to estimate soil erosion since 1974. From 1974, the method has changed gradually and now is used in many studies. In this study,aerial photographs with scale of 1:20000 and topographic maps with scale of 1:50000 were used. 12 transects on the hilly lands (compound and uniform slopes) and 3 transects on the piedmont plain were studied. Surface samples were collected from different slope situations. The situations were collected from different slope situations.The situations were summits, shoulders, back slopes, foot slopes and toe slopes; gamma spectrometer was used to determine the Cs-137 of the samples. Soil erosion and sediment were calculated by Cochanouski (1993) Equation. Results showed that in summit, shoulder and back slope of the compound slopes, erosion is 68.42, 45.46 and51.16 Ton/ha/yr respectively. On the same situations of uniform slopes 79.6, 65.3 and 84.23 ton /ha/yr of soil losses were expected. In non-erosional situations (toe slopes), soil loss has been deposited. In foot slopes, i.e. dynamic sites, sedimentation process is more dominant than destructive ones. The correlation between USLE and Cs-137 models were statistically signification with % 95 probability.
