News Flash

Planning & Public Works

Posted on: February 23, 2021

Changes to flood thresholds of White River and South Prairie Creek to aid in flood preparation

To help communities prepare for flood events, flood stages have been updated on the White River and added for the first time to the South Prairie Creek station.

The changes were added to the National Weather Service (NWS) Advanced Hydraulic Prediction Services Map in January at the request of Pierce County. 

Flood stages, including action, minor, moderate, and major, warn communities about possible flooding and help officials determine when to implement evacuations and anticipate road closures. Contributing agencies like Pierce County help inform how stages are set.  

South Prairie Creek additions
New thresholds indicating minor, moderate, and major flooding on South Prairie Creek have been added based on flooding impacts from a moderate flooding event in Orting and the surrounding area in February 2020. The thresholds are 4,000 cubic feet of water per second (CFS) for minor flooding, 5,500 CFS for moderate flooding, and 8,000 CFS for major flooding.

White River changes
Pierce County and local cities also agreed to increasing the threshold for minor flooding on the White River by 1,000 CFS to 7,500 CFS, while the threshold for moderate flooding was raised by 2,000 to 10,000 CFS and the threshold for major flooding was raised by 2,000 to 12,000 CFS. These changes were requested after monitoring water releases from Mud Mountain Dam. The changes more accurately reflect when flooding may occur.  

Learn more about flooding in Pierce County, including ways to prepare, at   

Aaron Copado, Pierce County public outreach specialist
(253) 798-6101
[email protected]

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