Floodgates are devices that are designed to allow for the controlled flow of water from various types of water systems. The floodgate is a common component in all sorts of systems ranging from reservoirs, dams, and spillways. Essentially, any human constructed system that is used to control the level and flow of water in a river, lake, or stream will be equipped with some type of floodgate.
The exact design of floodgates will vary, depending on the overall design of the dam or spillway. In some cases, the main function of the floodgates is to direct the flow of water from one section of the water system to another. At other times, the floodgates operate as a means of lowering the water level of the section of river or lake that is found behind a dam or spillway. This is often an important function that can be used to lower the amount of pressure on the dam or reservoir when rain or melting snow has generated an amount of water in the system than is considered desirable or safe.
While the design for floodgates may vary somewhat based on purpose and the structure of the retaining water system, all types will have a few elements in common. Valves are a common component on all floodgate designs. Most valve designs today allow for both automated and manual operation. When the valves are engaged, the mechanism of the floodgates allows for the opening of the gates and the release of a controlled amount of water. The valves help to control the rate and speed that the water is released, so that flooding is not likely to occur as a result.
Several types of floodgates are in common use today. Radial gates are a rotating design that features gates composed of cylindrical sections. Clamshell gates have a design that allows the gate to open in a fashion that is similar to the opening of the two sections of a clamshell. Fusegates make use of free standing blocks that are set into the spillway sill and allow for the orderly release of water at various points along the face of the spillway.