Many parameters need consideration in designing a spillway. These include:
- The inflow design flood hydro-graph
- The type of spillway to be provided and its capacity
- The hydraulic and structural design of various components and
- The energy dissipation downstream of the spillway.
The topography, hydrology, hydraulics, geology and economic considerations all have a bearing on these decisions. For a given inflow flood hydro graph, the maximum rise in the reservoir level depends on the discharge characteristics of the spillway crest and its size and can be obtained by flood routing. Trial with different sizes can then help in getting the optimum combination.