(1) “Emergency action plan” means a plan developed by the owner that establishes procedures for notification of the department, public off-site authorities, and other agencies of the emergency actions to be taken prior to and following an impending or actual failure of a dam.

  (2) “Enlargement” means any change in or addition to an existing dam which raises or may raise the design flood elevation of the water impounded by the dam.

  (3) “Failed dam” means a dam not capable of impounding water at its intended level due to a structural deficiency.

  (4) “Failure” means an incident resulting in an unplanned or uncontrolled release of water from a dam.

  (5) “Flood of record” means the greatest flow rate determined by the department to have occurred at a particular location.

  (6) “Freeboard” means the vertical distance between the design flood elevation and the lowest point of the top of the dam.

  (7) “Half probable maximum flood” means the largest flood that may reasonably occur over a watershed, and is derived from the combination of hydrologic runoff parameters and the half probable maximum storm that produces the maximum runoff.

  (8) “Half probable maximum storm” means the spatial and temporal distribution of the probable maximum precipitation, divided by 2, that produces the maximum volume of precipitation over a watershed.

  (9) “Hazard potential classification” means a reference to the potential for loss of life, property damage, and environmental damage in the area downstream of a dam in the event of failure of the dam or appurtenant works.

  (10) “Height” means the difference in elevation measured vertically between the natural bed of a stream or watercourse at the downstream toe of the dam, or, if it is not across a stream channel or watercourse, from the lowest elevation of the downstream toe of the dam, to the design flood elevation or to the lowest point of the top of the dam, whichever is less.

  (11) “High hazard potential dam” means a dam located in an area where a failure may cause serious damage to inhabited homes, agricultural buildings, campgrounds, recreational facilities, industrial or commercial buildings, public utilities, main highways, or class I carrier railroads, or where environmental degradation would be significant, or where danger to individuals exists with the potential for loss of life.