Boundary shear stress and depth-averaged velocity are the most common characteristics of flow in open channels. Using depth integration for velocity distribution, depth-averaged velocity can be calculated. When water flows in an open channel, a force, called boundary shear stress, arises and starts to erode the boundaries. The problem of detaching the bed and the side-wall shear stresses is very important in almost all studies of open channel flows. For example, to study boundary shear stress and velocity profile, one must divide the bed shear stress from the total shear stress to estimate the bed-load traort in open channel flows. Similarly, to study channel migration or to prevent bank erosion, one must know the side-wall shear stress. Moreover, a side-wall correction procedure is often needed in laboratory flume studies of velocity profiles, bed-form resistance and sediment traort. These parameters are useful in various problems such as water conveyance, erosion, river morphology and Pollutants transitions. So knowledge and accurate estimation of these two parameters are basis to safe design of open cannels. Previous investigations demonstrate that, in the absence of secondary currents, the boundary shear stress acting on the bed must be balanced by the downstream component of the weight of water contained within the bounding orthogonals. An efficient way to study the boundary shear stress distribution in open channel flows is the idea of using conformal mapping method. This idea has not rendered any conclusive results but afterwards, researchers used the idea to estimate isovels and orthogonals. Orthogonals have an important role in open channel flow whose their stream wise velocity gradient is almost zero. Hence, one can call them as "zero shear stress surfaces". In case of uniform flow, the weight component between two orthogonals can be balanced by the shear force between them. Modeling boundary shear stress is more difficult than depth-averaged velocity because of the secondary currents. Secondary circulation is a result resolving flow velocity into longitudinal and transverse components respect to the flow direction in the channel. The transverse component of the velocity generates the secondary circulation. It can occur in both straight and curved channels regarding to different flow aspects. Secondary circulation is affected by temperature gradients, sediment, turbulence, non-uniformity of boundary shear, and the curvature of streamlines.