Rivers are a dynamic and increasingly important part of our physical environment. 
Their behavior is of interest in a wide variety of contexts, ranging from disaster 
prevention, such as by flood control, to water resources development for navigation 
and recreation. For these reasons, studies of river flow and morphology are 
urgently needed. One of the parts of rivers is bends that calls Meander. The flow 
pattern in river bends is known to be fairly complex due to presence of strong 
secondary flow or spiral (helical) flow, in a direction perpendicular to the 
longitudinal direction of flow. Secondary flow is due mainly to 1-difference 
between velocities near the center of the channel and near the walls due to 
friction on the channel walls, 2- centrifugal force, which deflects the particles 
of water from a rectilinear, or straight-line motion, and 3- a vertical velocity 
distribution which exists in the approach channel and thus initiates a spiral 
motion in the flow. In this research a two dimensional mathematical model for a 
meandering river is developed in a curvilinear co-ordinate system. Grid mapping for 
the computational domain of the entire area is developed based on sine-generated 
curve plan-form. The model is based on the integration of depth-averaged main flow 
equations including the convective influence of secondary flow. In this model we 
suppose that the depth is small compared with the width, the width is constant and 
its small compared with the radius of curvature, Froude number is small, the flow 
is mainly friction controlled and the longitudinal component of the velocity 
dominates the other velocity components. The model is developed, tested and 
verified with flume experiments. The results show that there are good agreements 
between flow distributions that simulated by the numerical model and the 
experimental results.
