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

Nationally, the main reasons that dams fail are: 
  • 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

Some incidents can lead to a catastrophic release of water which may cause loss of life, damage to property, and environmental harm. We refer to these events as failures.  Below is a list of notable failures and some details on recent events.

Ongoing incidents

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.