Big Sioux River near Florence, SD
River level and flood forecast · Grant County
Normal3.1 ftas of Mon 2 PM
The river is 4.9 ft below flood stage (8 ft).
Flow: 1 cubic feet per second (USGS).
The last 7 days and the forecast
NWS forecast issued Sun, Dec 31, 6 PM. Forecasts change as rain falls and as upstream water arrives.
Flood stages
| Major flood stage | 9 ft |
| Moderate flood stage | 8.5 ft |
| Flood stage | 8 ft |
| Action stage | 7 ft |
| Record crest (April 13, 2023) | 9.7 ft |
What floods at each level
From the National Weather Service, highest first.
- 12 ftThe bridge at the gauge and the bridge 2 miles south of the gauge are both overtopped
- 10.5 ftThe bridge 1 mile north of the gauge is overtopped
- 10 ftThe water reaches the bottom of the bridge at the gauge and the bridge 2 miles south of the gauge the bridge 1 mile east and 1 1/2 mile north of the gauge is overtopped
- 9 ftThe water reaches the bottom of the bridge 1 mile north of the gauge
- 8.5 ftThe water reaches the bottom of the bridge 1 mile east and 1 1/2 mile north of the gauge
Highest crests on record
- 9.7 ft — April 13, 2023
- 9.52 ft — April 2, 1997
- 9.18 ft — July 25, 1993
- 9.08 ft — March 29, 1986
- 9.07 ft — April 7, 2001
Recent crests: 8.97 ft (June 26, 2025) · 9.7 ft (April 13, 2023) · 6.89 ft (May 5, 2020) · 8.95 ft (March 27, 2019) · 6.37 ft (February 22, 2017)
Up and down the river, and nearby
- DownstreamBig Sioux River near Watertown, SD
- Mud Creek near Rauville, SD
- Big Sioux River at Lake Kampeska, SD
- South Branch Tributary Mud Creek near Rauville, SD
- Big Sioux River at Watertown Sioux Conifer Road, SD
- Lake Kampeska at Watertown Water Plant, SD
- Willow Creek near Watertown, SD
- Big Sioux River at Watertown Broadway Avenue, SD
Not an official source. River levels, forecasts, flood stages and impacts are from the National Weather Service (FLOS2); flow from the U.S. Geological Survey. Readings are provisional. In a flood, follow your local officials and the NWS at weather.gov.