Changes to Flood Stages and Severity Categories on Select Rivers

A combination of recent in-person river surveys, LiDAR analysis,
archived satellite imagery, impacts from previous flood events and
consultation with local and state emergency management officials
have concluded that adjustments to the flood severity categories at
select river gauge locations within the Big Sioux River and Floyd
River basins in southeastern South Dakota and northwest Iowa would
better align the categories with the noted impacts.

Structures being moved out of the floodplain, roads and highways
being raised or new river gauge installations impacting the river
reach of an associated gauge are factors that have contributed to
the changes in impacts over the past several years. Below are the
impacted river gauge locations and new category levels:

Big Sioux River near Dell Rapids (DERS2)
Previous Action Stage: 11.0 ft      New Action Stage: 10.0 ft
Previous Minor Stage: 12.0 ft       New Minor Stage: No Change
Previous Moderate Stage: 14.0 ft    New Moderate Stage: No Change
Previous Major Stage: 15.0 ft       New Major Stage: No Change

Skunk Creek at Sioux Falls (SIFS2)
Previous Action Stage: 9.5 ft       New Action Stage: No Change
Previous Minor Stage: 11.5 ft       New Minor Stage: No Change
Previous Moderate Stage: 15.0 ft    New Moderate Stage: 14.0 ft
Previous Major Stage: 17.0 ft       New Major Stage: 18.0 ft

Split Rock Creek near Corson (COSS2)
Previous Action Stage: 7.5 ft       New Action Stage: No Change
Previous Minor Stage: 8.5 ft        New Minor Stage: No Change
Previous Moderate Stage: 11.0 ft    New Moderate Stage: No Change
Previous Major Stage: 14.0 ft       New Major Stage: 16.0 ft

Floyd River at Sheldon (SHLI4)
Previous Action Stage: 10.0 ft      New Action Stage: No Change
Previous Minor Stage: 12.0 ft       New Minor Stage: No Change
Previous Moderate Stage: 14.0 ft    New Moderate Stage: No Change
Previous Major Stage: 16.0 ft       New Major Stage: 18.0 ft

Big Sioux River Sioux Falls Western Ave (WAVS2)
Previous Action Stage: 7.0 ft       New Action Stage: 6.5 ft
Previous Minor Stage: 8.0 ft        New Minor Stage: No Change
Previous Moderate Stage: 12.0 ft    New Moderate Stage: No Change
Previous Major Stage: 14.0 ft       New Major Stage: No Change

Big Sioux River near Brandon (BBSS2)
Previous Action Stage: 1302.0 ft    New Action Stage: No Change
Previous Minor Stage: 1304.0 ft     New Minor Stage: No Change
Previous Moderate Stage: 1307.0 ft  New Moderate Stage: 1309.0 ft
Previous Major Stage: 1309.0        New Major Stage: 1312.0 ft

Big Sioux River near Canton (CBSS2)
Previous Action Stage: 1233.0 ft    New Action Stage: No Change
Previous Minor Stage: 1235.0 ft     New Minor Stage: No Change
Previous Moderate Stage: 1238.0 ft  New Moderate Stage: No Change
Previous Major Stage: 1240.0        New Major Stage: 1245.0 ft

This change is planned to go into effect on or around June 25, 2026.

If you have any questions or comments, please contact:

Andrew Kalin
National Weather Service Sioux Falls, SD
26 Weather Lane
Sioux Falls, SD 57104
605-330-4247
andrew.kalin@noaa.gov