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 emergency management officials have
concluded that raising the flood stages and/or flood severity
categories at select river gauge locations along the Big Sioux,
Floyd, Little Sioux, and Redwood Rivers would better align the
categories with the noted impacts. These changes in documented
impacts over the past years may be caused by such factors as
structures being moved out of the flood plain, roads and highways
being raised or new river gauge installations impacting the river
reach of an associated gauge. Below are the impacted river gauge
locations and new category levels:

Big Sioux River near Bruce (BRCS2)
Previous Action Stage: 7.0 ft       New Action Stage: No change
Previous Minor Stage: 8.0 ft        New Minor Stage: No change
Previous Moderate Stage: 9.5 ft     New Moderate Stage: 10.0 ft
Previous Major Stage: 11.5 ft       New Major Stage: 13.0 ft

Big Sioux River near Brookings (BRKS2)
Previous Action Stage: 8.0 ft       New Action Stage: No change
Previous Minor Stage: 9.0 ft        New Minor Stage: No change
Previous Moderate Stage: 10.5 ft    New Moderate Stage: No change
Previous Major Stage: 12.0 ft       New Major Stage: 15.0 ft

Big Sioux River near Hawarden (HWDI4)
Previous Action Stage: 18.5 ft      New Action Stage: No change
Previous Minor Stage: 20.5 ft       New Minor Stage: No change
Previous Moderate Stage: 24.0 ft    New Moderate Stage: No change
Previous Major Stage: 27.0 ft       New Major Stage: 30.0 ft

Big Sioux River near Richland(BSRS2)
Previous Action Stage: 1116.0 ft      New Action Stage: No change
Previous Minor Stage: 1117.0 ft       New Minor Stage: No change
Previous Moderate Stage: 1119.0 ft    New Moderate Stage: No change
Previous Major Stage: 1121.0 ft       New Major Stage: 1123.0 ft

Floyd River near Struble (STUI4)
Previous Action Stage: 12.0 ft      New Action Stage: No change
Previous Minor Stage: 14.0 ft       New Minor Stage: No change
Previous Moderate Stage: 15.0 ft    New Moderate Stage: No change
Previous Major Stage: 16.0 ft       New Major Stage: 18.0 ft

Floyd River at Alton (ALTI4)
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: 16.0 ft    New Moderate Stage: No change
Previous Major Stage: 18.0 ft       New Major Stage: 22.0 ft

Floyd River at Le Mars (LMRI4)
Previous Action Stage: 18.0 ft      New Action Stage: No change
Previous Minor Stage: 20.0 ft       New Minor Stage: No change
Previous Moderate Stage: 21.0 ft    New Moderate Stage: No change
Previous Major Stage: 24.0 ft       New Major Stage: 26.0 ft

Little Sioux River near Milford (MIFI4)
Previous Action Stage: 11.0 ft      New Action Stage: No change
Previous Minor Stage: 12.0 ft       New Minor Stage: 13.0 ft
Previous Moderate Stage: 14.0 ft    New Moderate Stage: 16.0 ft
Previous Major Stage: 16.0 ft       New Major Stage: 20.0 ft

Little Sioux River near Lake Park (LPRI4)
Previous Action Stage: 1395.0 ft      New Action Stage: No change
Previous Minor Stage: 1396.0 ft       New Minor Stage: No change
Previous Moderate Stage: 1398.0 ft    New Moderate Stage: No change
Previous Major Stage: 1400.0 ft       New Major Stage: 1404.0 ft

Redwood River at Marshall (MSHM5)
Previous Action Stage: 12.0 ft      New Action Stage: No change
Previous Minor Stage: 14.0 ft       New Minor Stage: No change
Previous Moderate Stage: 15.0 ft    New Moderate Stage: 17.0 ft
Previous Major Stage: 16.5 ft       New Major Stage: 18.5 ft

This change will be effective December 17, 2024.

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