Three Gorges primarily famous for its scenery, the Three Gorges region is also historically and culturally important in China. Many settlements and archaeological sites are in danger of being submerged by the rising reservoir of the Three Gorges Dam. Due to the lithological conditions of its different regions, the valleys of the Three Gorges are narrow in some areas and broad in others. Most narrow valleys occur in regions where there is limestone, which is relatively hard and resists erosion. However, water can flow along deep vertical fractures, eroding underneath. As the limestone bed is gradually undercut, parts of it fall into
Three Gorges Dam spillway gates of the dam might pose a risk of cavitation, similar to that which severely damaged the poorly designed and cavitating spillways of the Glen Canyon Dam in the US state of Arizona, which was unable to properly withstand the Colorado river floods of 1983. However, 163,000 concrete units of the Three Gorges dam all passed quality testing and the deformation was within design limits. An experts group gave the project overall a good quality rating. In order to maximize the utility of the Three Gorges Dam and cut down on sedimentation from the Jinsha River, the upper course