Y. Ramezani; M. Ghomeshi; H. Khozeyme Nejad
Abstract
Bridge failures due to scour at bridge abutments clarify importance of scour prediction and scour countermeasures. Most of bridge abutments are located in floodplains. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is investigation on effect of vegetated ...
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Bridge failures due to scour at bridge abutments clarify importance of scour prediction and scour countermeasures. Most of bridge abutments are located in floodplains. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is investigation on effect of vegetated floodplain on vertical wall abutment scour in compound channels. Results show, for constant abutment length and flow depth, with increasing the vegetation concentration, scour depth decreased with an increasing rate. For constant vegetation concentration and abutment length, with increasing the flow depth, effect of vegetation in reduction of scour depth decreased. In abutment with the lengh of 26 cm and concentration with s=8, with increasing the flow depth from 4.8 to 11.8 cm, percentage reduction in scour depth decreased from 40 to 22 percent. Also, vegetation reduces scour hole dimensions and has effect on downstream topography.
N. Azam; M. Ghomeshi; Zh. Fayezizade; M. Mansouri Hafshejani
Abstract
The operation dredging of river bed and also creating a cut off for removing sharp meander and maintain proper alignment is effective non-structural methods for decreasing the flood level. This study compared the effects of 1) Dredging karoon river at ahvaz range, 2) Removing heterogeneity height in ...
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The operation dredging of river bed and also creating a cut off for removing sharp meander and maintain proper alignment is effective non-structural methods for decreasing the flood level. This study compared the effects of 1) Dredging karoon river at ahvaz range, 2) Removing heterogeneity height in order to make uniformly downstream slope, 3) Removing ahvaz downstream horseshoe Meander, which has been analyzed by HecRas4 model. Data modeling analysis showed that dredging in the form of bed dig in ahvaz range will not have significant effect on water level profile. This method only increase sedimentation and erosion rate in ahvaz range. Achieving to better results, the idea of dredging ahvaz downstream between two meander in order to regulate hydraulic gradient through removing heterogeneity height was proposed. Findings showed that this method has significant effect on improving of Hydraulic of flow and dredging effectiveness. Finally, it will be found that removing of the ahvaz downstream horseshoe meander is the most effective method for reducing level of flood and sedimentation rate in ahvaz range.
P. Varjavand; A. Hosseinzadeh Dalir; M. Ghomeshi; Davoud Farsadi
Abstract
Instantaneous velocity fluctuations are very important insuspended sediment load transportation. In this study experiments were performed toinvestigate the effects of artificial bed roughness on the instantaneous velocity fluctuations of saline density currents. Conic and cylindrical shapes of roughness ...
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Instantaneous velocity fluctuations are very important insuspended sediment load transportation. In this study experiments were performed toinvestigate the effects of artificial bed roughness on the instantaneous velocity fluctuations of saline density currents. Conic and cylindrical shapes of roughness with three heights were used. Velocity profiles were measured with an acoustic profiler velocity meter. Velocity and concentrationprofiles were measured in 3 and 4 cross-sections, respectively. The results show that increasing inrelative roughness height has a little impact on instantaneous velocity fluctuations in the entrainment region of the body of current. Also results of theinstantaneous velocity fluctuations profile on the rough bed show that turbulence intensity at the boundary of the ambient fluid and body of the current for cylindrical and conic roughness were 48 and 32 percent of shear velocity, respectively.
Y. Ramezani; M. Ghomeshi
Abstract
Abstract
Turbidity current is one of the most important factors that effect the sediments distribution and also their transportation and release from reservoir. In this study, effects of these currents on sedimentation process in Sefidroud dam were simulated by TCM model in 30 years period. Comparison ...
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Abstract
Turbidity current is one of the most important factors that effect the sediments distribution and also their transportation and release from reservoir. In this study, effects of these currents on sedimentation process in Sefidroud dam were simulated by TCM model in 30 years period. Comparison between the case of turbidity currents that reach to the dam wall and release from the reservoir, and the case of neglecting the effects of these currents (all sediments deposit approximately) were conducted. The results show that in the case of releasing the turbidity currents from the reservoir, the trap efficiency of Ghazalozan branch would decrease about 30 percent in comparison with the other case. Also, this reduction would be about 20 percent in Shahroud branch. Comparison between the two cases of operations show that the average of annual volume reduction of the Ghazalozan branch would decrease from 1.07 to 0.73 and 0.55 to 0.43 in Shahroud branch, if Turbidity currents release from the reservoir.
Keywords: Reservoir Sedimentation, Turbidity Current, Trap Efficiency, Sefidroud Dam, TCM Model
