A study commissioned by the King County Flood Control District in the wake of the emergency evacuation of communities near Northern California’s Oroville Dam in February is showing the impact that a potential dam failure could have in the region.

The report recommends updating emergency action plans and the development of “inundation maps” showing the potential areas that could be underwater if a dam fails or water needs to be released from the dam.

“This study and its recommendations provide steps forward to strengthen our evacuation plans, coordination between jurisdictions, and planning for potential flood events,” said Reagan Dunn, chair of the Flood Control District’s Board of Supervisors, in a Monday county media release. “The close call at the Oroville Dam was a good opportunity to update our region’s emergency action plans and find ways to improve.”

“Upwards of 22,000 people and over $4 billion in economic activity would be disrupted in the Kent Valley alone in the event of a failure at the Howard Hanson Dam,” said Dave Upthegrove, vice chair of the Flood Control District’s Board of Supervisors, about the dam that helps prevent Green River flooding in Kent, Auburn, Renton and Tukwila. “The recommendations in this study will help the county achieve a critical level of preparedness in the event of a dam failure.”

The study, done in collaboration with the King County Office of Emergency Management and King County Water and Land Resources Division was presented to the Flood Control District’s Executive Committee at its Sept. 18 meeting.

The report illustrates the Emergency Action Plans required by the state Department of Ecology for the 82 dams in King County shows gaps that could impact the readiness and ability to respond to a dam failure emergency. Less than a third of the emergency plans have been updated in the last year, with the majority having no update in the last five years.

Sixty of the emergency action plans either did not have or had no current inundation map, which would show emergency responders the areas that would be impacted by either a dam failure or the need to release water to prevent the failure of a dam.

The study also stated the need to develop a countywide dam safety education program. With more than 25,000 people could be required to evacuate in the case of a dam failure, the study calls for the development of a comprehensive program that will educate municipalities and residents on the steps they will need to take safe and effective evacuation from areas at risk.

Along with the creation of an education program, there is also need to assess the capability of regional entities to shelter and care for those who must evacuate because of a dam failure. The study calls for an assessment of what may be needed versus what is available to identify any potential gaps relative to a dam failure event.