An arch dam is a type of dam that curves upstream, allowing it to efficiently transfer the water pressure to the rock walls on either side. This design enables the dam to use less material than other types, making it a cost-effective solution for holding back large volumes of water. Arch dams are typically built in narrow, steep-sided canyons. These structures are often made from concrete and can be quite tall, with some famous examples including the Hoover Dam in the United States. Arch dams are particularly suitable for locations with strong geological formations, as they rely on the surrounding rock for stability and support.