Lost Valley

About Lost Valley

Lost Valley is a dam in Adams, Idaho. The dam is private-owned. It impounds the Lost Creek Weiser River near Fruitvale.

The dam stands 31 feet tall and stretches 262 feet across, creates a reservoir covering 633 acres, has a storage capacity of 9,583 acre-feet, and collects water from a drainage area of 29 square miles. Completed in 1910, the structure is over a century old.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 06/18/2019.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Idaho dam safety program can provide more specific information about emergency planning for this structure.

Search for dams near your address to see all dams in your area with hazard classifications and safety data.