Normally buttress dams are made of concrete and feature a series braces called buttresses along the downstream side of the dam to prevent the natural flow of water. The Daniel-Johnson Dam in Quebec, Canada is a multiple arch buttress dam.In the U.S., the most common type of dam is the embankment dam. These are large dams made out of soil and rock which use their weight to hold back water. To prevent water from moving through them, embankment dams also have a thick waterproof core.The Tarbela Dam in Pakistan is the world’s largest embankment dam. reservoir is a man-made lake that is primarily used for storing water. They can also be defined as the specific bodies of water formed by the construction of a dam. For example, the Hetch Hetchy Reservoir in California’s Yosemite National Park is the body of water created and held back by the O’Shaughnessy Dam.