A barrage is simply a large flat wall constructed along the banks of a river or other water resource. A barrage consists of a series of ditches or embankments which are strategically positioned to catch water flowing in different directions and channeling it where it is needed. A barrage consists of a huge number of locks which are placed on the river bank either side of the main channel for a more controlled movement of water. Barrage systems can also include an artificial embankment designed to act as a sediment control to reduce erosion from runoff into channels.
A dam is an artificial construct built to catch falling water. When a dam is built, the water is diverted to a spillway where it is controlled and directed towards a river or lake. This allows for the diversion of large volumes of water and the lower volume of water channels it to a controlled release. A dam can vary in size and height, which allow water to be directed to a particular basin or area. The dam acts as a low-water catchment area which causes the diversion of floodwater running off the side of the dam into the lower areas. If left unchecked, a dam can cause flooding and erosion along its banks and could potentially destroy other vegetation along its length.
An embankment is a type of levee constructed to prevent the rising and falling of water levels in a lake or river. These are normally constructed alongside a levee system so that they do not interfere with each other. The most famous embankment is the Grand Coulee in Scotland which is a massive granite wall which stands hundreds of metres high. Barrage systems are constructed in a similar way to embankments which allow the water to channel down either side of a barrage. The largest dam in the world is the Hoover Dam in the USA, which allows the Colorado River to flow through to the Pacific Ocean.