Hamed Haghnazar; Ramin Amini; Mojtaba Saneie
Abstract
Evaluation of mining methods and the volume of the bed and flood plain sand and gravel mining show that many problems will be created due to geometry and naturally changing of rivers, increasing of the flood power and environmental and ecological dangers. Hence, applying correct management on river sand ...
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Evaluation of mining methods and the volume of the bed and flood plain sand and gravel mining show that many problems will be created due to geometry and naturally changing of rivers, increasing of the flood power and environmental and ecological dangers. Hence, applying correct management on river sand and gravel mining can create many positive effects. In this research, the effect of locating of the consequent river bed material mining pits on their sedimentation is investigated in order mining management via an experimental study. Results indicated that, there is no perceptible effect on the infilling and migration velocity of the upstream pit by increasing the distance between the pits up to 16 times the flow depth. Also, mining near the wall of the channel (20% width of the channel) leads to decrease infilling volume up to 25% and decreases migration velocity of the upper edge of the upstream pit up to 37%. By increasing of the distance between the pits, infilling of downstream pit is decreased, but it depends on the distance between the downstream pit and the wall. When the distance between the pits doubles, migration velocity of the downstream pit decreases up to 70%. If the mining is located at the center of the channel and the pits are in close proximity, it creates more suitable condition due to the infilling and migration for upstream and downstream pits.
Moien Jahanthigh; Seysd Mohmmad Tajbakhsh; Gholamreza Mirab Shabestari; Hadi Memarian
Abstract
This research was aimed to investigate Hirmand River morphology alterations through the estimation of suspended loads transported by floods. The sediment samples were collected and suspended loads were estimated. The alterations of sediment load along Sistan reach was investigated, spatially and temporally. ...
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This research was aimed to investigate Hirmand River morphology alterations through the estimation of suspended loads transported by floods. The sediment samples were collected and suspended loads were estimated. The alterations of sediment load along Sistan reach was investigated, spatially and temporally. The suitable reaches for sedimentation inspected through the high resolution Satellite imageries of Spot-5 (with the spatial resolution of 2.5-5 m). Through the geo-referencing of aerial photos and satellite images in GIS environment, the changes of river width, meander angel, and sinuosity index were estimated during the last 50 years. The t-student test was employed to assess the changes of river width during time. Results showed that the average suspended sediment load of Sistan River was 32 grL-1 and approximately 7.3 million tones sediment load entered to the study reach. According to the results, the river width has been changed, significantly. The river width in 2016 has been decreased by 0.33 of that in 1965 and 73% of the river has no capacity for flow transport and shows a high density of suspended load. This study established that the hydrology parameters (sediment and flood), biologic and slope changes are the main causes of sediment load and the changes of river morphology from a disorganized sinusoidal meanders to limited meanders. During the period of 1965-2016 the pattern of flow changed from meander to the sinusoidal. The average angel of river from 287.94 changed to 295.26 degree. The average of sinusoidal index changed from 1.39 to 1.18 and the average of flooding bed width from 160.79 m changed to 41.32 m in 2016.
Hossein Rastgar; Mehdi Habibi
Abstract
Sedimentation is one of the most important problems in watershed management. The characteristics of geological formations are the most basic factors which have an important role in sediment yield. There are several methods for sediment estimation, but sediment transport equations and formulas have been ...
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Sedimentation is one of the most important problems in watershed management. The characteristics of geological formations are the most basic factors which have an important role in sediment yield. There are several methods for sediment estimation, but sediment transport equations and formulas have been developed for special conditions which may not represent all conditions. Therefore to find out which method is suitable for a specific river, it is required to compare each method with the measured data. The purpose of this research is to evaluate efficiency of different methods of sediment discharge estimation in Jagin River at Panhan hydrometric station. The methods of modified Einstein, Engelund-Hansen, Yang, Habibi and Van Rijn are used in this investigation. The required data was collected from Water Regional Organization of Hormozgan Province. The sediment yield is estimated based on concentration of collected samples of floodwater. Then, the collected data were checked and corrected. The conclusion shows that the modified Einstein method is the most suitable method for sediment estimation in the study area.
Seyed Ali Asghar Hashemi; Mahmood Arabkhedri
Volume 2, Issue 1 , May 2010, , Pages 25-34
Abstract
Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were ...
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Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were selected in Semnan Province. There is an earth small dam at the outlet of each watershed built in the past 10 years. These dams have not spilled since they were built. Therefore total sediment volume discharged from each watershed was entrapped behind the dams. The amount of deposited sediments in these reservoirs was measured by surveying and estimation of apparent Specific Weight which then compared with estimating values of MPSIAC model by paired t-test. The results showed that the difference between the means for estimated volumes of sediment yield by use of MPSIAC model at the level of 5% had no significant difference while the difference between mean weights of sediments at the level of 5% was significant. Also determination of performance and relative root mean square error showed that MPSIAC model has no appropriate efficiency for application in the region.
