Editing Dam (section)

=== Other types ===
==== Cofferdams ====
{{main|Cofferdam}}
[[File:Dam Coffer.jpg|thumb|A cofferdam during the construction of [[canal lock|locks]] at the Montgomery Point Lock and Dam]]

A [[cofferdam]] is a barrier, usually temporary, constructed to exclude water from an area that is normally submerged. Made commonly of wood, [[concrete]], or [[steel]] sheet [[Deep foundation|piling]], cofferdams are used to allow construction on the [[Foundation (engineering)|foundation]] of permanent dams, bridges, and similar structures. When the project is completed, the cofferdam will usually be demolished or removed unless the area requires continuous maintenance. (See also [[causeway]] and [[retaining wall]].)

Common uses for cofferdams include the construction and repair of offshore oil platforms. In such cases, the cofferdam is fabricated from sheet steel and welded into place under water. Air is pumped into the space, displacing the water and allowing a dry work environment below the surface.

====Natural dams====
Dams can also be created by natural geological forces. [[Lava dam]]s are formed when lava flows, often [[basalt]]ic, intercept the path of a stream or lake outlet, resulting in the creation of a natural impoundment. An example would be the eruptions of the [[Uinkaret volcanic field]] about 1.8&nbsp;million–10,000 years ago, which created lava dams on the [[Colorado River]] in northern [[Arizona]] in the [[United States]]. The largest such lake grew to about {{convert|800|km|mi|abbr=on}} in length before the failure of its dam. [[Glacier|Glacial activity]] can also form natural dams, such as the damming of the [[Clark Fork River|Clark Fork]] in [[Montana]] by the [[Cordilleran Ice Sheet]], which formed the {{convert|7780|km2|mi2|abbr=on}} [[Glacial Lake Missoula]] near the end of the last Ice Age. [[Moraine]] deposits left behind by glaciers can also dam rivers to form lakes, such as at [[Flathead Lake]], also in Montana (see [[Moraine-dammed lake]]).

Natural disasters such as earthquakes and landslides frequently create [[landslide dam]]s in mountainous regions with unstable local geology. Historical examples include the [[Usoi Dam]] in [[Tajikistan]], which blocks the [[Murghab River]] to create [[Sarez Lake]]. At {{convert|560|m|ft|abbr=on}} high, it is the tallest dam in the world, including both natural and man-made dams. A more recent example would be the creation of [[Attabad Lake]] by a landslide on [[Pakistan]]'s [[Hunza River]].

Natural dams often pose significant hazards to human settlements and infrastructure. The resulting lakes often flood inhabited areas, while a catastrophic failure of the dam could cause even greater damage, such as the failure of western [[Wyoming]]'s [[Gros Ventre landslide]] in 1927, which wiped out the town of [[Kelly, Wyoming|Kelly]] resulting in the deaths of six people.

===== Beaver dams =====
{{main|Beaver dam}}
[[Beaver]]s create dams primarily out of mud and sticks to flood a particular habitable area. By flooding a parcel of land, beavers can navigate below or near the surface and remain relatively well hidden or protected from predators. The flooded region also allows beavers access to food, especially during the winter.