ABSTRACT
This chapter provides the procedures and data necessary to calculate discharges over and through hydraulic structures. Discharge through a structure when the upstream and downstream water levels are given or can be calculated from a set of boundary conditions. Sizing a structure to pass given discharges for specified upstream and downstream water levels. Guidance is given when two or more mechanisms affect a structure's discharge capacity, such as a weir influenced by a high downstream water level. Special consideration should always be given to the design of closed conduit systems when the discharge through the system is controlled by a critical section at the conduit inlet. Free surface flows are much more complex than internal flows because of the extra parameters involved. Orders of magnitude more model studies are required to provide comprehensive data for free surface flows as compared to internal flows.
