Historical incidents & failures
Despite our best efforts to promote dam safety and assist owners in maintaining their dams in a safe manner, incidents and failures sometimes occur.
Why dams fail
- Overtopping — 34 percent of all failures
- Inadequate spillway design
- Debris blocking the spillway
- Settlement of dam crest
- Foundation defects — 30 percent of all failures
- Differential settlement
- Sliding and slope instability
- High uplift pressures
- Uncontrolled foundation seepage
- Piping and seepage — 20 percent of all failures
- Internal erosion through the dam caused by seepage — "piping"
- Seepage and erosion along hydraulic structures, such as an outlet
- Conduits or spillways, or leakage through animal burrows
- Cracks in the dam
- Conduits and valves — 10 percent of all failures
- Piping of embankment material into conduit through joints or cracks
- Other — 6 percent of all failures
Dam failures in Washington
If conditions at a dam under our jurisdiction prompt an emergency declaration or the involvement of local/state emergency response staff, we track it here. This does not necessarily mean that a failure is imminent. In these cases, we work with local emergency management and the dam owner to take steps to reduce the risks posed by the dam.