What do you need to know the forces for? what are you designing, frames, support wallsgate structures? There are really only three factors effecting the gates, water pressures, water velocity and gravity. Water pressures act directly into the gate face resisting flow. Flow velocity through the gate cause hydrodynamic effects that usually tend to act to force gates open more. Gravity alway pulls all mass in the gate and component structures downwards. On slide gates the loads are translated into the slide frames along the sides of the gate. From the frame they tanslate to the bolts into the wall and the bottom of the structure you have attached the frame to, or if the frame is recessed much of the force translates into the wall directly at the rear contact point and bottom of the frame. In radial gates, the force translates through the support arms, back into the wall, and the weight of the gate is born by the cables that lift the gate and the pin to the wall (depending on configuration).