Arch–gravity dam
An arch–gravity dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the force from the water against the canyon rock walls, which provide the force to compress the dam. It combines the strengths of two common dam forms and is a compromise between the two. They are made of conventional concrete, roller-compacted concrete (RCC), or masonry. A typical example of the conventional concrete dam is the Hoover Dam. Changuinola Dam is an example of the RCC arch–gravity dam. A gravity dam requires a large volume of internal fill. An arch–gravity dam can be thinner than a pure gravity dam and requires less internal fill.