فهرست مطالب m.r. majdzadeh tabatabaee

Morphological river models are designed to provide physical insight into the morphological response and to assist river engineers and managers in the design, operation and maintenance of river systems. Here deterministic modeling weak for a dynamic and stochastic of nature river environment. Specially, these could not predict the exact shape of the river bed, Specially e.g. for braided river because the bed level variability and variations in cross-sectional. Since a stochastic model approach copes with the variability of system behavior of the time, therefore need for Stochastic modeling on the location of morphological changes in rivers and variations in river bed seems necessary. Many large rivers in the world have recently undergone through a great deal of morphological changes, Which has led to the development of local scouring, therefore, it has become an important problem for the river engineering. The change of river morphology is evaluated by braid parameter in braided rivers. A decrease in braid parameter results in a braided channel changes to meandering. As a result, local scouring process is accelerated. Since Process of the changes in river cross section are usually caused by change in water and sediment discharges or by river works. Moreover, river gradient plays a key role in channel morphological changes therefore In this research, local scouring relationship with river morphologic changes are investigated by stochastic modeling in braided rivers based upon for parameters such as maximum water, sediment discharges, river bed gradient river and bed elevation. The model was then tested by data obtained from Yahagi river in Japan. That the month Maximum Stream flow data is predicted by time series models (ARIMA) and three sediment transport equation were used to calculate the bedload such as Bagnold, Meyer-peter and Einstien Brown. predicted results show If calculate the bedload with the Bagnold equation, this model could predict significantly in cross-sectional and local scour depth, predict river morphological changes.

The diversion flow pattern is quite 3-D and nonuniform. In general, diversion flow occurs either naturally like streams or artificially like lateral intakes. According to the performed investigations the intake location affects the rate of diversion discharge and entry of sediments to the diversion channel. Since the main purpose of lateral intakes is to facilitate water transfer without sediments, and most rivers are zigzagged through their path, therefore, more research on the location of the lateral intake and its angle in the bending channels seems necessary. For this purpose, to determine the velocity and secondary flow fluctuations caused by hydraulic parameters changes in domain of lateral intakes with no diversion dam in winding channels a U-shaped flume with rectangular cross section was built. A straight channel with rectangular cross-section was used as a diversion channel. Based on the past researches, water intake was performed from the outer bend with 60˚ diversion angle at different locations (40˚, 75˚, 115˚) and with Froude numbers 0.27, 0.41, and 0.55, respectively. The obtained results of velocity distribution, secondary flow strength and radial flow momentum in a bend channel with diversion channel showed that the maximum variation of the above hydraulic parameters occur in the intake entrance.