Hossein Karimi; Amir Lakzian; Gholamhossein Haghnia; Hojat Emami; Majid Soufi
Abstract
In the past decades, the study of soil erosion has gained considerable attention by many researchers. This was thorough understanding of soil erosion processes and variable factors affecting it which is essential for making land management decisions. The aim of this study was to investigate the spatial-temporal ...
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In the past decades, the study of soil erosion has gained considerable attention by many researchers. This was thorough understanding of soil erosion processes and variable factors affecting it which is essential for making land management decisions. The aim of this study was to investigate the spatial-temporal coefficient of variation of soil erosion and flow hydraulic parameters in top-down conventional ploughing rills with 20 percent average slope. The artificial rills were produced with a length of 10, 20 and 30 meters. Hydraulic parameters and sediment concentration were measured at three equal time and distance intervals after applying 10, 15 and 20 Lmin-1 inflow rates for 10 minutes. Consequently, sediment detachment and transport rates were calculated. In addition, relative errors (RE) of these parameters were calculated in order to investigate the coefficient of variations. The results showed that there was a significant difference (P<0.01) between sediment (soil detachment rate, transport rate and sediment concentration) and hydraulic parameters. Stream power was significantly different with sediment detachment and transport rates (P<0.05). Temporal evaluation revealed that coefficient of variations in the first and final time intervals of RE values of detachment and transport rates were more than middle time slot. This is perhaps due to stochastically movement of available sediment in the first step and undercutting and bank failure of rills in final stage. Spatial variability showed that the RE in the primary section is significantly (P<0.01) greater than following sections, whereas there was no significant difference between second and third sections.
Heshmatolah Agharazi; Aliakbar Davudirad; Mahdi Mardian; Majid Soufi
Abstract
Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. ...
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Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. In this paper, the area- slope threshold was investigated in Zahirabad Watershed in Markazi province, Iran. First, based on field surveys and digital elevation model, morphometric characteristics of 14 gullies were measured, accompanied by soil sampling and vegetation cover measurements. Second, homogeneous groups of gullies were defined by factor and cluster analysis and power relations of area-slope was prepared. Results demonstrated that there was no considerable correlation between area and slope of gully watersheds. So, coefficient of determination of creation point and head-cut of gullies were 0.111 and 0.181, respectively. According to the results, the dominant process in creation and head cut development of gullies in Zahirabad was related to flow concentration and rill erosion of high slopes. Considering the prevail of loamy texture of soils land use changes and deterioration of vegetation cover, it is suggested to investigate the optimization of land use schemas, and land cover improvement on sloppy lands with the objective of gully control.
Banafsheh Yasrebi; Majid Soufi; Sayed Khalagh Mirnia; Jahangard Mohamadi
Abstract
Gully erosion has an important role in land degradation producing much sediment. Due to development of gully erosion in crop lands of study area, this research deals with assessing the topographic characteristics of bank gullies and assess on effective soil factors controlling gullies advancement in ...
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Gully erosion has an important role in land degradation producing much sediment. Due to development of gully erosion in crop lands of study area, this research deals with assessing the topographic characteristics of bank gullies and assess on effective soil factors controlling gullies advancement in Siekan watershed in Ilam province. For this purpose, 46 bank gullies were selected and morphometric characteristics like initial and advancement contributing area and slope as well were measured. Two compound soil samples were collected from top soil of contributing area and gullies walls then analyzed in the soil lab. Then database formed and effective factors on gullies advancement were recognized by correlation matrix and regression.Correlation matrix results revealed, the higher slope the higher head-cut and gullies volume. A-S relationship is negative and b is 0.31 that shows gullies formed by hortonian overland flow process. Topographic threshold is 0.04 and mean threshold in 10% slope is 0.05 ha and in 2% slope is 2 ha. Critical threshold in 2% slope is 0.07 ha. Correlation matrix showed that increase in gully advancement slope increases head–cut height and gully volume. The index of area of development/ area of initiation is suitablefor gully development stage determination and it has negative relationship with gully length, volume and width/depth index. Increasing in soil organic matter cause an increase in topographical threshold, soil texture and electrical conductivity increase the gully volume. The effect of both topographical parameters and soil material characteristics on total eroded bank gully volume was integrated in multiple regression equations. The models based on all measured parameters explain 85% of the variation ingullies volume.
Abdolali Adelpour; Majid Soufi
Abstract
Erosion and sedimentation study and design of the distance between spreading channels are basic requirement in flood water spreading projects. Different environmental parameters including topography and slope, soil texture, vegetation cover and flow resistance affect the hydraulic characteristics of ...
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Erosion and sedimentation study and design of the distance between spreading channels are basic requirement in flood water spreading projects. Different environmental parameters including topography and slope, soil texture, vegetation cover and flow resistance affect the hydraulic characteristics of the flood water spreading area. So it isnecessary to investigate the effect of environmental parameters according to natural conditions and simulation of overland flow. This study was done in the Gareh Bygone plain, in the south of Fasa city. An open hydraulic flume with 120 m length, 0.4 m width and 0.25 depth was used to simulate concentrated overland flow with 0.1 mdepth. Three experiments were examined and for each experiment, discharge flow and mean flow depth were measured directly and other parameters such as mean velocity and shear stress were calculated. Erosion or sedimentation depths were calculated by comparing flume bed elevations in the cross sections with one meter intervals. Results of this study show that erosion and sedimentation phenomena were changed with theincrease or the decrease in trends of shear stress along the flume and shear stress parameter were also changed with bed slope and roughness coefficient and became maximum at 75 m from the top end of the flume. On the other hand, according to the bed elevations of cross sections in two steps maximum erosion depth occurred at 75 mfrom the start of the flume which was confirmed with maximum shear stress. So, we can conclude that channel erosion threshold was established in 75 m from the top end of the flume and it can be considered as channel spreading distance.
Mohammad Nekouiemehr; Said Naim Emami; Ravanbakhsh Raisian; Majid Soufi; Msoud Goodarzi
Abstract
Applied research about preventing gully initiation and expansion, needs basic knowledge about the types and morphometric characteristics of gullies. The purpose of current research is the classification of gullied regions based on morpho-climatic characteristics in Chaharmahal and Bakhtiary province. ...
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Applied research about preventing gully initiation and expansion, needs basic knowledge about the types and morphometric characteristics of gullies. The purpose of current research is the classification of gullied regions based on morpho-climatic characteristics in Chaharmahal and Bakhtiary province. In this research, two gullied regions covering an area about 500 ha were selected in each climate zone and three representative gullies were chosen in each region. The morphometric characteristics were measured in each studied area. Classification of gullied regions was done using cluster analysis based on quantitative characteristics. The results indicate that gullied regions in Chaharmahal and Bakhtiary province can be divided to three groups base on morpho-climatic characteristics. Maximum similarity level was 94.12 percent. A comparison of variance analysis and mean value of variables in groups shows that, annual rainfall, elevation above sea level, gully length, gullied region area and top width of gullies were the most important variables in separating of the groups. Generally, we can emphasize that among all morphometric characteristics; only gully length and top width have the main role in morpho-climatic classification.
Majid Soufi; Hossein Esaei
Volume 2, Issue 2 , July 2010, , Pages 73-82
Abstract
Gully erosion is more important than both rain splash and sheet erosions due to both higher sediment productions. Estimation of the volume of gully erosion requires some indices that could be measured easily in the field. This research aims to present simple models to estimate the volume of gully erosion ...
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Gully erosion is more important than both rain splash and sheet erosions due to both higher sediment productions. Estimation of the volume of gully erosion requires some indices that could be measured easily in the field. This research aims to present simple models to estimate the volume of gully erosion with minimum cost. After determining influenced regions, using anecdotal, historical and field surveying, two regions in each modified Dumartin climate zone and region, three representative gullies were selected. Then, morphometric and edaphic characteristics such as length, depth, top and bottom width, clay, silt, sand, Ca, Na and Mg percentages of the gullies were measured both in their heads and cross sections in 25, 50 and 75% of their length from the headcut. The volume of gully erosion was calculated by the sum of partial volumes in each gully. The results revealed that gullies were initiated and developed in two arid and semi-arid climates on the loess sediment with little cohesion. Gully widening is higher than deepening and silt has an important role in it. Statistical analysis indicated that linear relationship with R2 of 0.86 is more suitable than power relationship with R2 of 0.54 for estimation of the volume of gully erosion. Results indicated that the volume of the gullies had a significant linear relationship with gully length, depth and top width in 0.01 level. Results also, revealed that gully length with 86% interpretation of changes in gullies volume and had the most impact among the variables. These results prove that suggested comments in literature using gully length to sediment yield estimation in EGEM is applicable in the northeast of Iran.
