County presents 'Swift Exit' evacuation modeling and zones for Sun Valley

County emergency planning staff presented the Swift Exit/Safe Outcomes evacuation study and demonstrated how new evacuation zones and computer modeling will be used to inform response decisions for Sun Valley.

"We started the swift exit safe outcomes evacuation study," Kelly said, explaining that the project collected three months of public comment and is using a modeling workflow that pairs fire-behavior modeling (SimTable) with traffic/perimeter modeling and CNA analysis. Kelly said the team builds worst-case fire-weather scenarios (very high temperatures, very dry fuels, fast winds), overlays those runs on evacuation zones intended for first responders, and then uses historical population data to stress-test traffic flow during large events.

The project team has created responder-focused evacuation polygons so incident commanders can select a zone and set a status (evacuate/soon-to-be-evacuated), reducing the risk that hand-drawn polygons in the field will cut off properties. The team also plans to incorporate event peaks (for example, large concerts or peak shopping events) by using historical cellphone-derived population estimates to estimate people-at-risk during worst-case timing.

Kelly told the board the target for finishing the analysis is "before June," barring other critical incidents that divert staff resources. Truckee‑area and district fire partners are participating in scenario planning; the county said it will return with results and recommended operational procedures after model runs are completed.

No formal evacuation order was issued at the meeting; staff requested continued community input via the project website and said public feedback received during the comment period will be included in the modeling prioritization.