Rivers in Iowa

Floyd River at Alton

Sioux County, IowaNWS ALTI4USGS 06600100Sioux Falls office

Below flood stage
5.94ftStage

Observed Mon, Sep 21, 11:00 PM CDT

Flood stage
12.00 ft
Record crest
26.81 ft2024

Open the live map with the river flood outlook

Flood stages and impacts

CategoryStage
Major flood22.00 ft
Moderate flood16.00 ft
Minor flood12.00 ft
Action10.00 ft
  1. 26.00 ftHwy 10 is flooded and substantial flooding is ongoing near the river throughout Alton.
  2. 24.00 ftSeveral houses on the north side of Alton flood. Water approaches Hwy 10 on the north side of Alton. The railroad tracks are also flooded.
  3. 22.00 ftMore substantial street flooding begins in Alton including 3rd Ave south of the bridge. Additional structures are also in danger of flooding.
  4. 20.00 ftThe lower levees in Alton may begin to be overtopped flooding some nearby industrial businesses. Hwy 60 south of Alton is flooded. Portions of Division St in Alton may also begin to flood and the bridge on 3rd Ave may also be closed.
  5. 18.00 ftThe entire flood plain is under water and the river is about 1/2 mile wide. The flooding still primarily only affects agricultural land and county roads.
  6. 16.00 ftSignificant amounts of crop and pasture land are flooded.
  7. 15.00 ft410th Street and Larch Avenue is inundated. Also 440th Street and Kingbird Avenue is flooded, and the water reaches the bottom of the bridge at CR L14 and 440th Street.
  8. 12.00 ftFlooding begins to affect the lower lying agricultural lands along the river.

Flood outlook

Chance of flooding, September to November

CategoryChance
Minor flooding10%
Moderate flooding7%
Major floodingUnder 5%

The three-month chances are the River Forecast Centers’ long-range flood outlook, issued August 26, 2026.

Crest history

69 crests on NOAA’s list since 1956.

#DateStage
1June 22, 202426.81 ft
2September 20, 201821.96 ft
3March 14, 201920.87 ft
4June 21, 201820.50 ft
5May 27, 201319.19 ft
6June 20, 198318.54 ft
7March 23, 197918.40 ft
8March 28, 196218.35 ft
9June 18, 201418.04 ft
10July 23, 201017.97 ft
11March 4, 196917.78 ft
12March 28, 199317.46 ft
13April 1, 196517.36 ft
14June 13, 199417.34 ft
15March 28, 196017.27 ft
16February 19, 197117.17 ft
17April 23, 198516.93 ft
18February 9, 196616.62 ft
19June 13, 198416.58 ft
20June 5, 197516.55 ft
21July 6, 198216.39 ft
22March 3, 197315.95 ft
23March 3, 196115.73 ft
24March 13, 199715.66 ft
25March 12, 197215.59 ft

Most recent crests

  • July 31, 2025: 13.43 ft
  • June 22, 2024: 26.81 ft
  • May 13, 2023: 9.09 ft
  • June 25, 2022: 6.43 ft
  • July 14, 2021: 6.16 ft
  • May 27, 2020: 8.82 ft
  • March 14, 2019: 20.87 ft
  • September 20, 2018: 21.96 ft
  • June 21, 2018: 20.50 ft
  • September 18, 2016: 11.07 ft

Nearby

Upstream, downstream and the gauges around this one.

What this means

Forecasts by the Missouri Basin River Forecast Center. Forecasts are issued as needed during times of high water, but are not routinely available. River forecasts for this location take into account past precipitation and the precipitation amounts expected approximately 48 hours into the future from the forecast issuance time. River forecasts for this location take into account past precipitation and the precipitation amounts expected approximately 24 hours into the future from the forecast issuance time. Gauge reading may be affected by ice.

Sources

Stage, flood stages, impacts and crest history from NOAA’s National Water Prediction Service. Streamflow and the daily record from the U.S. Geological Survey.