Videos from the Association of State Dam Safety Officials show several ways dams can become more hazardous, including some ways they can catastrophically fail.
Over time, without maintenance, safe dams can become dangerous:
Dams built in rural areas can begin to threaten homes and roads built later. Dam breaks can flood beyond the floodplain.
In dam slide failures, water seeps through the face of a dam, leading to a landslide that collapses the dam:
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In some dams, water erodes the insides of the dam, leading to cavities known as piping:
When too much rain falls, water levels can rise beyond the ability of regular and emergency spillways to remove the water. In extreme flooding, water can rise over the edges of the dam, eroding it and causing a catastrophic release.