// Risk Intelligence
| Risk Score | 7 / 10 High |
| Facility Type | 🌊 Major Dam / Flood Control |
| Operator / Branch | US Army Corps of Engineers |
| Host County | Sherman County OR |
| Nearest City | Pepperell MA |
| Primary Risk Radius | 20 miles |
| Secondary Risk Radius | 100 miles |
// Strategic Significance
John Day Dam on the Columbia River is the fourth largest hydroelectric dam in the US. It creates Lake Umatilla stretching 76 miles upstream. As part of the Columbia River dam system a cascading failure scenario involving multiple dams is a documented concern for emergency planners.
// Civilian Impact Assessment
The Columbia River valley communities including The Dalles OR and Kennewick WA would face catastrophic flooding in a failure scenario. Approximately 50,000 people live in the downstream inundation zone.
// Evacuation & Shelter Guidance
US-30, I-84. Sherman County and Wasco County Emergency Management coordinate with Army Corps for dam emergency protocols.