The Use of Dam Failure Inundation Maps in Exercises

The purpose of the Emergency Action Plan is to minimize the likelihood of life and property loss due to a breach of a dam. The inundation map is a useful tool, but it can be intimidating or confusing to local Emergency Management Agencies (EMAs). The transition to virtual exercises during the pandemic offered an opportunity to use the virtual platform for detailed discussions with EMAs concerning interpretation and use of TVA’s inundation maps.
The key points for the EMAs to consider during a Dam Safety exercise, and in an actual emergency, are: 1. Notifications. What are their emergency notification plans and processes? How much time is there to make the notifications? 2. Evacuation planning. What routes will be used to move people out of inundation areas? Have alternate routes been identified? How will people on or near the water engaged in recreational activities be warned and evacuated? How quickly will people respond to the warning? 3. Transportation impacts. What is the level of inundation compared to the elevation of roadways and bridges? Which transportation routes will be impacted and to what degree? Will bridges that are not inundated still be safe to cross and at what point might bridges become inundated? Will traffic congestion be a major issue? How will loss of electric power affect the transportation network? 4. Critical infrastructure impacts. Will utilities such as electric power, water and communications be impacted by flooding? What are the expected impacts to emergency response facilities and high occupancy buildings?
During discussion of these key points, the inundation maps are overlaid on local street maps or shown next to aerial photographs. The exercise staff calls attention to critical information displayed on the inundation maps or aerial photographs. For example, flood wave arrival and peak times along with elevations are highlighted, major transportation routes impacted by flooding are reviewed, and high occupancy or critical structures such as schools, hospitals, emergency response facilities, and major industries that are within the inundation areas are identified. Areas that may be above the inundation elevation, but could be isolated and potentially not accessible, are also emphasized and discussed.
Virtual exercises have proved to be an excellent forum for educating local EMAs on the interpretation and use of inundation maps. This information can be used by local EMAs to prepare better, more focused evacuation plans which should result in reduced impacts in the event of a dam failure.