Somaiyeh Khaleghi; MohammadMahdi Hosseinzadeh; Payam Fathollah Atikandi
Volume 6, Issue 21 , March 2020, , Pages 43-64
Abstract
1-IntroductionOne of the methods used in river surveys is river classification. The main aim of the classification of the river is simplify the processes of hydrology and sedimentation, and ultimately predict river behavior. So far, rivers have been categorized from different perspectives and the basics ...
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1-IntroductionOne of the methods used in river surveys is river classification. The main aim of the classification of the river is simplify the processes of hydrology and sedimentation, and ultimately predict river behavior. So far, rivers have been categorized from different perspectives and the basics of these categories are including topography, slope, flow discharge, river age, and pattern in the plan. The first classification Recognized by Davis in 1899. Davis classified the rivers according to their evolution and modification into three groups of young, mature, and old. Leopold and Welman (1957) divided the form of alluvial rivers based on the sinuosity coefficient and the ratio of width to Depth into three straight, meandering and braided groups. A descriptive classification by Shumm (1963) presented based on two factors of river stability and sediment transport. The objectives of this research are to identify the factors affecting the bank erosion of the Kaleybarchai River, identifying the damages incurred in the construction and banks of the river, runoff and preventing possible floods. In this research, the river classification system is based on the Rosgen method, which is presented by the American researcher Rosgen (1994) to the river engineering community. The Rosgen method is the most complete and comprehensive method provided so far and includes many of the features of previous systems. Rivers are living beings that constantly change their beds and banks, and this causes the river to undergo major changes over time. In addition, human activities, such as the utilization of riverine material and river modification, will cause the river to be moved.2-MethodologyTo evaluate the classification of the flow pattern in the Kaleybarchai River, the Rosgen model has been used at levels I, II, III. A reach of 3 km between the two villages of Pazhagh and Gheshlag was determined, and then 8 cross sections were selected in this reach. To simulate the river and extract the required parameters from geological maps, topography, land use and ARC GIS software was used. After determining the river reaches, based on field observations and topographic maps, classification in level I and level II were carried out in 8 cross-sections at the Kaleybarchai River, which are based on the slope, curvature coefficient, bankfull width, mean flood plain depth, flood plain width and bed material.3-ResultsAfter crossing the river route with field observations and then analyzing data and general calculations, 8 cross sections from the entire river course were extracted in all of the studied river and all the parameters required for classification and geometrical identification of the channel wrer calculated.In order to obtain the average size of channel material, 16 samples were taken at river in different reaches and were analzed in the laboratory (Table 2). According to the obtained data, the highest percentage of particles along the river were average sand with 26.6% and cobble up to 14.7%, which were evaluated for the Rosgen classification, according to the results, the total of river is in groups B and C.To determine the channel type at level I, after obtaining the slope of the Kaleybarchai River in the study area, four sections of the river were in type B and four sections in type C.4-Discussion and conclusionBased on morphological indices, sediment content and flow conditions, two different types of channels including B and C were identified in the study area and evaluated level according to the Rosgen in level I, II and III.Morphological study of type B in relation to the evaluation of the correspondence and efficiency of the Rosgen model showed that their dominant morphology consisted of narrow valleys with relatively low widths and moderate slopes and relatively stable banks. Type C has meandering and high sinuosity, valleys with floodplain and point bars in low slope.The high instability of the river bed in the reaches of 3, 5, 7, is a threat to the agriculture land land and surrounding buildings. Due to the fact that the braided rivers are not stable and the flow and position of the sedimentary islands and the width of this rivers are constantly changing, it is necessary to manage and organize the operations in this section with regard to the morphological variables and Flow conditions. The results of the Kaleybarchai River assessment based on the Rasgen classification system at level I, II and III showed that the Rosgen system present good the patterns of the channel in the Kaleybarchai River and, consequently, the effective parameters in the classification and separation of the channels. In this way, there are differences in the quantities and the parameters due to the specific conditions of the factors affecting in the locality.
Foruzan Ahmadi; Kazem Nosrati; Mohamad Mehdi Hoseinzadeh
Volume 6, Issue 20 , December 2019, , Pages 141-164
Abstract
1-IntroductionAccelerated soil erosion is a serious problem in Iran, leading to degradation of soil and water resources, reduction of soil fertility, destruction of range and agricultural lands, desertification, recurring floods, sedimentation of reservoirs, and pollution of fishery habitats. Hence, ...
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1-IntroductionAccelerated soil erosion is a serious problem in Iran, leading to degradation of soil and water resources, reduction of soil fertility, destruction of range and agricultural lands, desertification, recurring floods, sedimentation of reservoirs, and pollution of fishery habitats. Hence, understanding of the potential soil erosion process and opposition to this erosion are necessary environmental. To this end, uptake and refinement of sediment source tracing or fingerprinting techniques has expanded dramatically as an alternative approach to traditional methods of identifying key sediment sources. Sediment source fingerprinting involves discriminating potential sediment sources on the basis of differences in source material properties or tracers and determining the relative contributions of these sources to sampled target sediment. different kinds of sediment sources have been used so far in sediment fingerprinting techniques (e. g., land use, geology, sub-basins, surface and subsurface erosion) but, there is a little attention paid to the selecting the soil erodibility groups as sediment sources. Therefore, the main objective of this study are the Kouhdasht watershed dividing into different erodible units based on soil erodibility index and determination of the contribution of each unit in sediment yield using an un-mixing Bayesian uncertainty model and to find its relationship with soil organic carbon stock. 2- MethodologyKouhdasht basin with 1138 km2 area located in 33° 17´ to 33° 41´ north latitude and 47° 20´ to 47° 50´ eastern longitude in western of Lorestan province. samples were collected in two stages; first, 81 samples in order to estimate erodibility, second, in order to determine the contribution of each source to sediment yield, 70 soil samples were collected form sources and 12 sediment samples collected at the basin outlet. The soil erodibility was calculated based on the soil texture and based on the geometric mean of the soil particle diameter. Based on the amount of soil erodibility, the area was divided into three different erosion units as sediment sources. To determine the contribution of sediment sources to sediment yield used fingerprinting technique is based on estimation of uncertainty.3- ResultsThe erodibility of the study area varied from 0.0386 to 0.0663. Erodible units were identified as sediment sources based on the values obtained from the erosion parameter and according to the results of selecting the optimal combination of tracers. The results showed that the first erosion unit 2%, the second erodible unit 5%, and the third erosion unit 93% contributed in the region's sediment yield. The relative importance of erodible units in sediment yield was obtained by dividing the share of each resource in the production of sediment into the percentage covered by each source. The relative importance of the first, second and third erosion units is 0.08, 0.28, and 1.57, respectively. Regarding the role of organic carbon in erosion, the amount of organic carbon storage in different erosion units of the area was also measured. The amount of organic carbon storage in each erosion unit is first, second and third ones were 70.5, 64.3 and 54.6 mg / ha respectively. 4- Discussion and conclusionThe third unit with 93% has the largest contribution in sediment yield and with 54.6 mg / ha, it has the lowest amount of organic carbon storage in the area. Considering that this unit is most used in agriculture and geologically under quaternary sediments, showed that the parts that are under cultivation and quaternary sediments have both high erodibility and the highest contribution to sediment yield. Measurements of organic carbon storage also showed, there is the least amount of organic carbon storage in this unit and this suggests that in the third unit, the damage caused by the loss of fine sediments such as clay is higher. Given that the third unit is under agricultural use this can be attributed to the type of land use and exploitation. Therefore recommended more attention to the type of use of land and soil management and conservation programs implemented in the region.
