Types of Dams
Today, there are several different types of dams and the man-made ones are classified by their size and structure. Typically a large dam is classified as being higher than 50-65 feet (15-20 meters) while major dams are those over 492-820 feet (150-250 meters).
One of the most common types of major dams is the arch dam. These masonry or concrete dams are ideal for narrow and/or rocky locations because their curved shape easily holds back water via gravity without the need for a lot of construction materials. Arch dams can have one large single arch or they can have multiple small arches separated by concrete buttresses. The Hoover Dam which is on the border of the U.S. stateAnother type of dam is the buttress dam. These can have multiple arches, but unlike a traditional arch dam, they can be flat as well. 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.
Finally, gravity dams are huge dams that are constructed to hold back water using only their own weight. To do this, they are constructed using extensive amounts of concrete, making them difficult and expensive to build. The Grand Coulee Dam in the U.S. state of Washington is a gravity dam.