Abstract: Lateral diversion from an open channel is a common flow regime that usually produces a larger head loss due to the vortices caused by the diversion. However, most previous studies focused on flow diversion from the channels of fixed cross-sectional shapes and small bottom slopes. In this work, channels of different cross-sectional shapes (rectangle, trapezoid and triangle) and their local head losses around the diverting mouth were studied using numerical simulations based on Mike21, a code for plane-2D flows. A relationship of local head loss coefficient versus Froude number was constructed for different cross-sectional shapes of the channel. The results show that with a fixed channel shape, this minor loss grows gradually with the increasing channel flow rate; under a fixed flow rate, it takes the largest, second largest and smallest values in the cases of triangular, trapezoidal and rectangular cross sections. Under subcritical flow conditions, the minor loss coefficient decreases gradually with the Froude number.