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A two-dimensional hydraulic flow model was developed using the SMS software (Surface Water Modeling System) to simulate the flow properties(thalweg line location) for meander in trapezoidal section channel, and its changes when a single emerge spur dike install at mid of the bend. The model was calibrated and verified through matching velocity profiles throughout the study reach. Thalweg line location were found due to the variation of spur dike characteristic including 180 runs, included five different ratios of spur dike length to top channel width (L/Tw), five ratios of spur dike arm to its body length (l/L), and two spur arm`s direction for four different flow rates, as a result, through the flow configuration the new location of the thalweg in the bend channel after using the spur dike was about (44-71)%Tw which mainly affected by spur body length.

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Specific effects of topography over any area watershed erosion are estimated through the LS factor as the product of slope length L and slope steepness factor S using RUSLE equation. The LS factor map of Euphrates watershed was derived from the raw Digital Elevation Model (DEM) by using of ArcMap 10.2 software, the DEM images were provided from United State Geological Survey (USGS) website. The DEM were consisting of sixteen images with cell resolution of 30m*30m, the DEM of Euphrates watershed is ranged from -100 m to 466 m, 98.83% of Euphrates basin area of DEM within the range 0 to 457 m. The slope in percentage rise map of Euphrates watershed is required to estimate the LS factor, the most of slope of this study was ranged from zero to five which represent about 93.12% from total area of basin. The LS factor of Euphrates basin is ranged from (0) to (8010.61), 94.25% of Euphrates watershed area have the LS factor of the range from (0) to (1). Furthermore, the LS factor values more than 500 of watershed have a small area, so the factor value can be considered up to 500 and neglect the other large values of LS factor. The LS values more than 3 were identified the lines of Euphrates river, distributary channel, rills, interrill and gully.

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One of the major causes of serious damage to the bridge is scoured around bridge foundations. In this study, the effect of main parameters (pier shapes, foundations shapes, level of foundation, flow intensity, and Froude number) on local scour with different shapes of non-uniform piers were experimentally investigated. The runs that occurred for three foundation shapes include (rectangular, oblong, and hexagonal), the depth of foundation in this study was 8 cm. The shapes of piers used in this study were (rectangular, oblong, and hexagonal). The results display that the depth of scour depends on the foundation level, shape of pier and foundation. The best foundation shape which gives minimum scour, was hexagonal, oblong, and rectangular shape, respectively. The results also display that positioning of foundation below bed level, leads to less values of scour depth around bridge pier. Also, the best shape of the pier that leads to minimum scour is hexagonal pier because it has minimum exposed area.

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This study is concerned with unsteady flow in open channels in boundary conditions that may exist in river or channel system. A software Hydrologic Engineering Center-River Analysis System (HEC-RAS) was used for a case study. The software contains a hydrodynamic model for simulating the unsteady flow in open channels based on a one-dimensional form of the Saint-Venant equations, by formulating a discrete form using the implicit finite difference scheme, then solving using the Newton-Raphson iteration procedure and the modified Gaussian elimination technique. The case study adopted with the help of HEC-RAS application was applied to a reach of Al Msharah River (channel) between AL Msharah Barrage (upstream)and Al Malah Bridge (Downstream), for a length of (49 Km) divided to (52) cross sections.Model runs and the comparison of results with actual field data indicate that the accuracy of the results obtained for(θ=1 and ∆t=5 minute) is quite acceptable, where θ is a weighting parameter and ∆t is the time interval.The paper covers the case of normal depth of flow and observed water stage data within the period ( from January 2006 to July 2006) . The results demonstrate that the area at Al Am'arah city at distance 17.5 Km from upstream(cross section 30)could be subjected to flooding at High Flow, therefore, it is recommended to adjust cross sections to prevent the flooding in this area.At last , Calibration of the hydrodynamic model is achieved in a study reach using the observed data (water stage) along AL Msharah River and show that a good agreement.

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This research is carried out to evaluate the amount of bed sediment load entering Haditha reservoir. The proper selection of a sediment transport formula to evaluate river's response is important. However, there are no definitive guidelines for the selection of transport formula. Therefore, an analysis was made on six sediment transport formulas, (Engelund-Hansen, Ackers-White, Yang, Maddock, Graf-Acaroglu and Karim-Kennedy) to check the applicability of each transport formula. The data used have been investigated by depth integrated sampling over a period from 26/1/2003 to 10/3/2003 and from 15/6/2003 to 16/9/2003.
Besides, a new formula was developed as sediment transport predictor for expected ranges of hydraulic and sediment characteristics of Euphrates river up-stream of Haditha dam.
It was concluded from the analyses that the used six formulas required adjustments to closely describe the measured data. Engelund-Hansen and Maddock formulas are better than other four formulas in predicting the total sediment load.
The predicted values using the new formula has no significance difference compared
with the observed values? The analysis showed that the new formula is better than the other
ones in predicting the sediment discharge, where the observed data have discrepancy ratio
between (0.5-1.5).

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The three-dimensional numerical computational fluid dynamics “CFD”computer program "SSIIM" was used to predict the flow field downstream theKuffa Barrage. It solved the Reynolds-Averaged Navier–Stokes equations in threedimensions to compute the water flow and used the finite-volume method as thediscretization scheme. The model was based on a three dimensional, nonorthogonal,structured grid with a non-staggered variable placement. Thecomparison between filed measurements and numerical results were considered tomake the correct decision in this model. The results showed that the maximumvelocities were inclined from the river center. The determination coefficients fordistribution of velocities ranged from 0.94 to 0.96.

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Scour is defined as the erosion of streambed sediment around an obstruction in a flow field. Bridge pier scouring is a significant problem in the safety estimation of bridges. In this study, the use of rectangular collar for reducing the effect of local scour at a circular pier in a laboratory flume was presented. The study was conducted using 6.6 m laboratory flume in length and 0.4 m in width. Experiments were conducted for various sizes of rectangular collars fitted at the bed elevation on the scour depth at the circular pier with clear-water scour condition. The time development of scour depth at the circular pier with and without a collar of circular installed was conducted. In collars observed that size of a collar plate increases, the scour decreases. Results showed that the maximum reduction in scour depth equal to 100% (no scour hole). Dimensional analysis technique was used, and from the experimental data an empirical formula was derived. It was found that the predicated scour depth from the formula performs well as compared to the observed scour depth.

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This study based on laboratory experiments for computing depth of local scour around abutment and bridge pier neighboring abutment considering the study of the effects of upstream flow conditions , pier and abutment sizes , median size of bed material and spacing between pier and abutment on the maximum scour depth and scour pattern around a pier and abutment. The study was conducted using a physical hydraulic model of pier and abutment operated under subcritical flow , clear-water condition and using uniform cohesionless sand as bed material . Three different size models of pier and abutment were used to show the effect of the size on the local scour and two different median size (d50) of sand were used in this study. Dimensional analysis techniques and statistical analysis were used to find new formulas with help of the experimental data . One of these formula was to compute the maximum scour depth at pier neighboring abutment and the other to find the maximum scour depth at abutment. There formula were derived to predict the maximum scour depth in terms of Froude number , diameter of pier and abutment , median size of sand , flow depth , flow velocity and spacing between pier and abutment.

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This study is based on laboratory experiments for computing depth of local scour around bridge pier when a downstream bed sill using as a countermeasure.A circular section pier model has been used with clear water flow condition. However, sand was used as a bed sill. Three different size of pier diameter are investigated with four different water depths and four different flow velocities. It is found that the diameter of the pier is an important parameter influencing the scouring process around pier.Bed sills at different distance from pier downstream and with different width and thickness, were used as a countermeasure to reduce the local scour depth. The level of sill crest was the same elevation of bed material. As a results of a study, the analysis of experimental data shows that the usage of sill as a countermeasure structure has a beneficial reduction of scour around pier around 25% for flow intensity 0.95.

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In this research, a study was conducted experimentally to investigate the scour hole dimensions downstream the combined structures which consist of weir and gate. Twelve models have been designed and every model is formed from composite weir consists of two geometric shapes and three types of gates which are rectangular, semi-circular and triangular in shape, where multi factors were studied to find out the effect of changing geometry for both weir and gate, discharge flowing in the flume and particle size of bed material on the dimensions of scour hole. The experiments was conducted in a laboratory channel was constructed from blocks and concrete with length of 18 m, 1 m width and 1 m depth. The laboratory models were installed after 7 m from the main gate which is controlling the passage of water from the main reservoir into the flume. At the beginning, the calibration process was conducted to identify the actual discharge values that pass in the flume, then experiments were conducted to calculate the discharge coefficient for each model, which represents one of the studied factors within the dimensional analysis of the variables to derive the empirical formulas to calculate the dimensions of scour hole. Then the experiments were conducted in order to derive formulas to investigate the depth and length of the scour hole which formed in the sand floor spreading as a layer of 30 cm in thickness for a distance 4 m downstream combined structure. Two samples of sand were used in the experiments with different median size of particles ( d50), the first of 0.7 mm and the second of 1 mm. Using the dimensional analysis by π theorem and IBM SPSS 21 program, Four nonlinear relationships were derived to calculate the dimensionless scour depth (SD / d50) and another four nonlinear relationships calculates the dimensionless length of scour (SL / d50) depending on the laboratory results for each of the relative discharge (Qr), Froude number in terms of mean size of particle of bed material (Frd), non-dimensional difference head between upstream and downstream of combined structure (HD / d50), dimensionless distance between the lower edge of the weir and the upper edge of the gate (y3 / d50), dimensionless head over the crest of compound weir (h/d50) and the discharge coefficient (Cd), where the resulted determination coefficients (R2) from these relationships were good.

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