Free jet spillways are most suitable for arch dams where the water jet leaves from either a short crested sill at the top of the dam, or a middle level or low level short length outlet with its exit shaped in the form of a deflector. Arch dams of height exceeding 200 m are not unusual and some dams while in planning or construction will be about 300 m in height. The main concern in the design of free jet spillways is either the deep scour just downstream of the dam (as in the case of a deflected jet) or impact forces on the stilling basin floor at the foot of the dam (with a free falling jet).