عنوان مقاله [English]
Rivers of the most important factors affecting geomorphological processes and cycles of erosion, till now studies extensively on morphological changes in rivers and the factors affecting them are taken. The aim of this study was to study morphological changes Khorramabad River - Doab Veysian and factors contributing to the change geometry and create relationships between them. In order Estimated Discharge with different return periods from Discharge Chamanjir station and Doab Veysian statistical period (1335-1334) and (1392-1391) was used. After completing the Statistics by software SMADA statistics maximum discharge Chamanjir station and Doab Veysian were fitted with different statistical distributions and Statistics for the Log Pearson Type III distribution was the best fit. To simulate the hydraulic flow in this research, according to the information available, was considered unsteady flow. For this purpose, after entering geometric data and flow data,the boundary conditions for a range of upstream, hydrograph and for limiting downstream, rating curve was considered. Then, execution models and the results were extracted. Sediment simulation was done at a later stage. For this purpose along the river Khorramabad - Doab Veysian, four samples of the materials were taken from the river bed and banks. Samples taken place, due to changes in grain size distributions, changes in slope (topography) and connecting tributaries of the main river was important. Accordingly, in Chamanjir station, Veysian-e olya, Shurab-e Sofla and Doab Veysian station According to uniform materials, samples were taken. After the harvest, samples for gradation testing were transferred to Technical and Soil Mechanics Laboratory. After this stage, sediment data entered into the application and boundary conditions for a range of upstream and downstream for the period discharge - sediment curve were selected. Ruby equation was used to determine fall velocity and sediments transport. To perform simulations of sediment need to enter the data was unsteady quasi After entering this data and the boundary condition for a range of upstream flow series and discharge - scale curve interval for downstream, Calculation of the simulation of sediment is done and results were extracted. Since some of the sedimentary particles fall velocity calculation methods such as Ruby need to water temperature, information on water temperature in part due to the Quasi unsteady flow input into the software. Sediment boundary condition as a sediment rating curve gives the relationship between flow and sediment discharge, the software was defined. According to a survey carried out and it was found that due to the high number of input data that To fully understand and carry out successful model calibration, sensitivity analysis will be necessary to model parameters. At this stage in order to examine the relationship between geometric data and outputs hydraulic the resulting hydraulic model HEC-RAS, the proportion of simple linear regression, grade 2, grade 3 and was exponential. After heterogeneity test data, Normal set of original data (each variable) and determine correlations between variables, Regression equations, using the software SPSS, was determined and the relations between the two variables (independent variable and dependent variable) with the highest coefficient of determination, the lowest standard error and the lowest level of significance had was chosen as a suitable relationship. The results of the regression relationship between the dependent variable discharge (Q) and the independent variable width (W), hydraulic depth (D), the flow cross section (A) and flow velocity (V) based on a significant level values, the coefficient of determination and error standard indicated that Simple linear equations (grade 1) often has a R2 relatively high, SE low and P-value high. In grade 2 and 3 models due to a problem is linearity, these models were not credible. In addition, grade 2 and 3 models both in terms of Significant level and standard error are not credible. Thus, the reasons are not linear exponential model, P-value less than 1% and standard error is less than the other models, suitable model are introduced. Regression relationship between the dependent variable sediment capacity (SC) nd independent variables shear stress (SH), discharge (Q) and flow velocity (V) based on the P values, the determination coefficient and standard error were investigated. The coefficient of determination obtained in the exponential function for V, Q, SH Grade 2 and grade 3 lower values and regression equations and simple linear regression function further and P-value is seen as the values of all variables at 1% (99% confidence interval) are significant. Also, in the function variables have the lowest standard error and significance level than linear, Grade 2 and Grade 3 so are the appropriate models for the studied river. In grade 2 and 3 models due to a problem is linearity, these models were not credible. In addition, grade 2 and 3 models both in terms of Significant level and standard error are not credible. Thus, the reasons are not linear exponential model, P-value less than 1% and standard error is less than the other models, suitable model are introduced. According to the Manning coefficient, three parameters water surface width, velocity and flow depth review and to obtain the results of the model in sensitivity analysis, with regard to the accuracy of 80%, The number sections that sensitivity percentage was more than 20%, It was considered as an error. The results of the study showed that sediment transport capacity in the range under study of Khorramabad river-Doab Veysian is variable. Results, Sediment values are calculated by By equation Ackers-White as the appropriate relationship between the independent variables showed that the sediment capacity is more dependent on the discharge. This means that runoff greatest impact in changing the morphology of the river. The amount of sediment capacity and shear stress is directly proportional to the flow velocity This means that with increasing shear stress and flow velocity, sediment transport capacity is also increasing And also by increasing sediment transport capacity, shear stress and flow velocity increases. According to the above cases and the particles size of the studied river it was found that in the first range (Chamanjir station), Sedimentation, in the second range (between two stations), erosion and the third range (Doab Veysian station), sedimentation as well as occurs.