Sediment transport under unsteady flow condition is studied experimentally. In the first step, Sediment transport under different steady flow conditions was measured and an empirical equation was derived for its calculation. In the next step, two continuous and three stepwise hydrographs were generated in the flume, and their Sediment transport rate was measured. The continuous hydrographs were then approximated by different number of steps. Sediment transport for the hydrographs was then calculated by assuming a steady state condition in each step employing the empirical equation derived in the first step of the study. Results showed that in continuous as well as the stepped hydrographs the difference between the calculated and measured Sediment rates is less than 10%. This shows that in the range of the tested hydrographs which conforms to many rivers in Iran, approximating the hydrograph with steady state steps for Sediment transport calculations leads to acceptable results. In the next step, the flow and Sediment transport in the flume under the tested hydrographs were simulated by using HEC-RAS software. Various Sediment transport equations were used and calculated results were then compared with experimental measurements. Results showed that by increasing the number of steps in stepped hydrograph in HEC-RAS, calculated Sediment transport rates by each equation tend to constant values.

Flow unsteadiness in flood events has a significant effect on the structure of the flow field and motion of Sediment particles, thereby affecting dispersion of pollutants and river ecology. The aim of the present article was to evaluate state-of-the-art research efforts concerning flow characteristics and Sediment transport in unsteady flow condition. The paper is organized in four sections: The first section deals with the unsteady parameters which affect Sediment transport. In the second section, the flow characteristics in unsteady open channel flow are presented. Different studies showed that the flow characteristics which affect Sediment transport including velocity distribution or shear stress during passage of a hydrograph differ from steady flow condition. In addition, measurements during passage of a hydrograph show that turbulence intensity is generally larger in the rising limb of the hydrograph rather than in the falling limb. This causes the peak of Sediment load and pollutants occur during the rising limb of the storm hydrograph. The third and forth sections deal with bed load and suspended load in unsteady flow condition, respectively. Studies show that the methods which are based on steady flow conditions generally underestimate the Sediment transport rates in unsteady flows. The larger the unsteadiness, the bigger is the difference. Finally, with considering different findings from previous studies, suggestions are presented for further research.

In this paper, the longshore Sediment transport in littoral zones is investigated. For investigation of Sediment transport in the nearshore zone, the effects of waves, currents and topographical conditions of the coast, are considered. Linear wave theory is used for investigation of wave behavior. Governing equations of littoral current are continuity and momentum, and for calculating the concentration profile of suspended Sediments at depth, convection-diffusion equation must be solved. A computer program called “PLSTP” (Prediction of Littoral Sediment transport Program) is developed for investigation of Sediment transport process in littoral zones. The finite difference method is used for solving the governing equations. The results show a good agreement between this model and existing measurements.

In this paper, the large amount of Sedimentation and the resultant shoreline advancements at the breakwaters of Beris Fishery Port are studied. A series of numerical modeling of waves, Sediment transport, and shoreline changes were conducted to predict the complicated equilibrium shoreline. The outputs show that the nearshore directions of wave components are not perpendicular to the coast which reveals the existence of longshore currents and consequently Sediment transport along the bay. Considering the dynamic equilibrium condition of the bay, the effect of the existing Sediment resources in the studied area is also investigated. The study also shows that in spite of the change of the diffraction point of Beris Bay after the construction of the fishery port, the bay is approaching its dynamic equilibrium condition, and the shoreline advancement behind secondary breakwater will stop before blocking the entrance of the port. The probable solutions to overcome the Sedimentation problem at the main breakwater are also discussed.

Several types of Sediment transport equations have been developed for estimation of the river Sediment materials during the past decades. The estimated Sediment from these equations is very different, especially when they applied for a specific river. Therefore, choice of an equation for estimation of the river Sediment load is not an easy task. In this study 10 important Sediment transport equations namely; Meyer-Peter and Muller (1948), Einstein (1950), Bagnold (1966), Engelund and Hansen (1972), Toffaleti (1969), Yang (1996), Van Rijn (2004), Wiuff (1985), Samaga et al. (1986) and Beg (1995) are used to estimate Sediment load of the Karun River in Iran. The estimated Sediment load compared with the measured field data by using statistical criteria such as root mean square error (RMSE), mean absolute error (MAE) and correlation coefficient (R2). Results showed that Engelund and Hansen formula can provide reliable estimates of Sediment load of the Karun River which have high suspended Sediment load concentration with RMSE of 3725 ton/day, MAE of 1058.82 ton/day and R2 of 0.41. Bagnold and Wiuff formulas estimated the total Sediment load 280 % and 700% more than the measured values and the Van Rijn, Tofaleti and Bagnold formulas estimated the Sediment load 99 %, 71% and 93 % lower than the measured values, respectively. The comparison indicated that Samaga, Einstein, Tofaleti and Yang equations with low accuracy are not suitable for estimation of Sediment load of the Karun River. The main reason for this difference is related to fact that the Karun River carries fine Sediment (wash load) which these equations not considered it.

Many Sediment transport equations have been developed for estimation of the river Sediment materials during the past four decades. There are significant differences in the results from these equations when applied to compute Sediment transport for a specific river. Therefore, application of an equation for estimation of a river Sediment load is not an easy task. In this study, 12 important Sediment transport equations including Meyer-Peter and Muller, Einstein, Bagnold, Engelund and Hansen. Toffaleti, Ackers and White, Yang, Van Rijn, Wiuff, Samaga et al, Beg and Fazel were tested against the measured field data of four maior Khuzestan rivers, namely, the Karoon, the Dez, the Karkheh, and the Maroon. For accurate results and rapid computation, a computer program was developed for this purpose. Over 490 measured data from the gauging stations of these rivers are selected. Using these data, the hydraulic parameters and the bed material of the gauging stations are determined. The results of the computer program are analyzed and compared with the measured data. The results from this study show that those equations which are based on the energy exchange of the flow, are generally in good agreement with the measured data for Khuzestan Rivers. From these equations, the Engelund s for the all gaugings stations except for the Maroon River gauging station. And finally if the Sediment load computed by the method is multiplied by a factor of 0.1, the results approximately match those obtained from the Engelund.      

Wave-induced hydrodynamics within the near shore region and the subsequent Sediment transport and evolution of beaches under wave attack are important elements governing the stability of coastal zone. Based on surf zone hydrodynamics several efforts have been made to estimate the Sediment transport and beach profile evolution during storm conditions. Recently, it has been found that the dominant processes responsible for along-shore and cross-shore Sediment transport in coastal zone can be categorized in to two major parts: long shore transport due to wave-induced current resulted from oblique wave breaking and on-offshore transport due to the combination of wave orbital velocity and mean return flow or undertow in the surf zone. One of the main steps in calculating morphological changes of a beach profile is the determination of Sediment transport rate due to the main flow pattern in the surf zone. In this paper the effect of geotechnical parameters such as medium grain size of the bed, internal friction angle of Sediments, density and void ratio of Sediments on Sediment transport rate are investigated analytically and through field measurements. Field data have been collected from different locations along Caspian Sea coast (from Astara region on the west toward the eastern coast of guilan province). Different soil mechanics tests have been performed in the laboratory on the samples and the results are plotted compared with those estimated by a numerical model. Using the Advanced Near shore Profile Model (ANPM) developed by Nairn (1990), the sensivity of the transport rate results to different parameters are considered. The results obtained from the present work indicate that the geotechnical parameters have remarkable effect on Sediment transport rates in the surf zone. It has been also found that the direction of long-shore Sediment transport rate is from the west toward the eastern coast due to the change in the medium grain size of the Sediments. Moreover, the major behavior of Caspian Sea coast in terms of cross-shore Sediment transport is erosional which results of current research can be implemented in the different coastal projects along the Caspian Sea coast.

Approach of organic material anaerobic biodegradation and species of organic matter in Sediment are discussed, and then a classifying method of the species is proposed on a new viewpoint. The pore water Sediment oxygen demand (SOD) numerical model in bottom Sediment system is proposed originally, which differs from other advection-dispersion-sorption (ADS) model in adding a SOD-creating term. The model was preliminarily validated via pilot experiment. Finally, this model was used to simulate SOD concentration of pore water in bottom Sediment, and the sensitivity of parameters in the model was analyzed. The results indicate that SOD-creating factor at beginning stage and pore water SOD-attenuating factor in bottom Sediment are the most important coefficients in the new model and should be estimated accurately. Because of the assumption of equilibrium of sorption/desorption, the new model appears to be valid only with less than 5 m/ d vertical velocity of pore water.