Emergency Action Planning



About EAPs

About EAPs

What to Expect When Dams Fail

Vulnerability is the susceptibility of population, human services, transportation, other infrastructure, and the economy to damage. Vulnerability is essentially the linkage between hazard and loss. It is critical to current and future hazard exposure analysis. The Indiana Department of Homeland Security's 2008 Hazard Mitigation Plan states that based upon reported damages from past floods, the following can be considered vulnerable to current and future damage and loss if a dam fails and causes extensive flooding.

  • Loss of human life.
  • Livestock from drowning.
  • Furnishings, equipment, personal property and basements.
  • Roads and ditch lines from mud and rockslides.
  • Roads and bridges due to washout, road surface and road bed failure.
  • Rural water supplies (wells, springs and cisterns) due to contamination from surface water entering the supply source.
  • Heat, water and electrical sources cut off due to rising water.
  • Drainage from catch basins and retention ponds. If they cannot handle the volume of water, they cause back-up flooding.
  • Homes are destroyed by deep, fast moving floods – characteristics of the floodway portion of the floodplain.
  • Municipal water and sewage treatment plants can become inoperable if levees and retaining walls are overtopped and/or if sediment basins are flooded.
  • The supply of raw water from municipal water supply reservoirs and back up water supply reservoirs can be reduced or lost due to the failure of an impounding dam.
  • In essential facilities, electrical panels and circuit breakers are often installed on interior walls below the 100-year flood level. This results in loss of power when the water rises to the level of the panels.
  • Water can enter otherwise protected facilities through non-flood proofed mechanical and electrical rooms and through conduits.
  • Bridges, culverts and stream crossings may be unable to handle the volume, causing backup onto roads and into residential and commercial structures.
  • Backup of water can be caused or increased when automobile-bodies, refrigerators and other appliances that have been discarded into streambeds hinder the natural flow of water. Backup also occurs if drainage systems have not been properly maintained.
  • Backup water can enter storm sewers and cause flooding in areas not threatened by stream flooding.
  • Levees constructed by the Corps of Engineers are sometimes inadequate to hold back the volume of water resulting in the failure of the structure.
  • Many developed areas have failed to provide for the excessive run-off caused by concrete and blacktop ground coverage.
  • Detention basins, retaining walls and berms are designed to redirect water from vulnerable areas. Flooding often results when these protective measures are not in existence or have not been properly maintained.