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Showing 4 results for Bed Load
A Mathematical Model to Evaluate the Bed and Total Load by the Modified Einstein Procedure
M. Shafai Bajestan, M. Ostad Asgari,
Volume 4, Issue 2 (7-2000)
Abstract

The application of “Modified Einstein Procedure” is recommended by the Specialized Committee on Sediment, Iranian Ministry of Energy. However, this method has not been applied to any river in the country. It is the purpose of this study to investigate the total sediment load of the Karun and Karkheh rivers at Ahwas and Hamidieh stations.

The graphical calculations of the method are very complicated and time consuming. Therefore, a mathematical model has been developed in this study to improve the accuracy, simplicity and speed of computations. The required data were obtained from the above stations for seven years (1988-95), and applying these data, the total sediment load was calculated using the model. The bed load for the above stations was also computed and the ratio of bed load to total sediment load was calculated. In addition, measured data from East Fork river (in USA) were applied to examine the accuracy of the method in estimating the bed load. Comparison of the measured and computed results shows that the “Modified Einstein Procedure” estimates the amount of bed load with a high accuracy. The relationship between the bed load and suspended load and also between the total load and the stream discharge have also been established.

Finally, it is concluded that the “Modified Einstein Procedure” with minor modifications can be successfully applied for the above-mentioned rivers of Karun and Karkheh.


Evaluation of Bed Load Hydraulic Formulas in Navrud, Gilan Province
N. Dehghani, M. Vafakhah,
Volume 18, Issue 69 (12-2014)
Abstract

Sediment is as one of problems related to water resources utilization. Numerous formulas have been developed for bed load estimation in rivers. In this study, eleven common formulas including hydrologic and hydraulic methods such as Einstein Tofalti Meyer, Peter and Muller Van Rayne Modified Van Rayne Yalin Bagnold Fraylink Habibi and Sivakumar and Samaga were used for selection of the most suitable bed load estimator formula in Kharajgil hygrometry station on Navrud river. The results showed that Habibi and Sivkumar formula is the most suitable with the mean computed to observed data=1.35, standard deviation computed to observed=1.96, RMSE=1.63 and ill sorted ratio(computed transportation ratio to observed)=33.82% within the range of 0.5 to 2.


Selectivity of Particles through Rill Erosion in Different Soil Textures
N. Sadeghian, A. Vaezi,
Volume 23, Issue 2 (9-2019)
Abstract
Sediment selectivity during transport may provide basic information for evaluating on-site and off-site impacts of the soil erosion. Limited information is, however, available on the selectivity of sediments in rill erosion, particularly in the rainfed furrows. Toward this, the sediment selectivity was investigated in three soil textures (loam, loamy sand sand clay loam) under 10% slope using 90 mm.h-1 rainfall intensity for 40 min. Soil samples were passed from a 10 mm sieve and packed in to the erosion flume with 0.4m × 4 m in dimensions. Particles size distribution (PSD) was determined in the sediments (PSDs) and compared with the original soil PSD (PSDo). The proportion of PSDs and PSDo was stated as PSDs/PSDo to show the selectivity of soil particles by rill erosion. Based on the results, all three soils appeared as the coarse particles (coarse sand and very coarse sand) in sediments with the PSDs/PSDo>1, indicating the higher selectivity of these particles by rill erosion. Loamy sand was the most susceptible soil to rill erosion among the studied soils, which generated a higher runoff (0.0035 m2.s-1) and sediment load (0.1 kg.m-1.s-1) during rainfall. The PSDs of this soil were similar to those of the original soil PSD. This study revealed that the stability of aggregates could be regarded as the major soil factor controlling rill erosion rate and the sediment selectivity in the semi-arid soils. With an increase in the water-stable aggregates, soil infiltration rate and as a consequence, shear stress of flow could be decreased in the rills.

Experimental Study of Bed Shear Stress in Straight Channels Covered with Dunes of Different Sizes
M. Badzanchin, M. Bahrami Yarahmadi, M. Shafai Bejestan,
Volume 27, Issue 1 (5-2023)
Abstract
The formation of bed form in alluvial rivers due to sediment transport has a significant effect on the hydraulic parameters of the flow such as bed shear stress. The formation of the bed form and its shape and geometry depends on the bed shear stress. Therefore, the relationship between bed form and flow parameters (such as bed shear stress) is complicated. In the present study; the effect of dune bed forms with different heights on bed shear stress has been investigated. Artificial dunes made by sand-cement mortar with a length of 25 cm and heights of 1, 2, 3, and 4 cm were used. In the tests of this research, flow discharge of 10, 15, 20, 25, and 30 l/s and bed slopes of 0, 0.0001, 0.0005, 0.001, and 0.0015 were used. The results showed that with increasing the relative submergence and Δ/λ, the bed shear stress increased in dune-covered beds. The formation of the dune bed form and the increase in its height leads to an increase in the bed shear stress. The bed shear stress in dunes with a height of 1, 2, 3, and 4 cm was, on average, 39, 80, 141, and 146% more than in plane beds, respectively. Moreover, form shear stress for dunes with a height of 1, 2, 3, and 4 cm was, on average, 27.37, 43, 57.11, and 58.74% of the total shear stress, respectively.

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