Search
Menu

Explore

Hazards

Analysis

Rankings

Reference

Floyd River at Alton

Highest listed crest 26.81 ftFlood stage 12.0 ft69 crests since 1956

The Floyd River at Alton crested at major flood stage 1 time among the 69 crests the National Weather Service lists from 1956 to 2025. The highest, 26.81 ft on June 22, 2024, was major flooding, 14.81 feet above flood stage. 5 other gauges on the Floyd River crested above flood stage within a week of it, 4 at their own highest listed crest.

The gauge

Highest listed crest
26.81 ft
June 22, 2024
Flood stage
12.0 ft
Major flooding from 22.0 ft
Crests at major
1
93rd of 203 gauges in Iowa
Most recent flood crest
July 31, 2025
13.43 ft, minor flooding
Location
Sioux County
Iowa

Flood stages

The thresholds the National Weather Service uses for this gauge today, and how many listed crests reached each.

Flood categories, Floyd River at Alton
Action stage10.08Sep 18, 2016The level at which the NWS or its partners begin to take action
Flood stage (minor)12.022Jul 31, 2025Minimal or no property damage, but possibly some public threat
Moderate flood stage16.020Mar 14, 2019Some inundation of structures and roads near the stream
Major flood stage22.01Jun 22, 2024Extensive inundation of structures and roads

Every listed crest

69 crests from 1956 to 2025. Filled: at or above flood stage. Hover a crest for its date and stage.

Listed crests at the Floyd River at Alton, 1956 to 2025 51015202530ft Flood stage 12.0 ftMajor 22.0 ft Jul 11, 1956: 9.45 ft, below flood stage; 287 cubic feet per secondJul 4, 1957: 10.54 ft, action stage; 440 cubic feet per secondJun 3, 1958: 9.82 ft, below flood stage; 336 cubic feet per secondJun 1, 1959: 12.77 ft, minor flooding; 1,130 cubic feet per secondMar 28, 1960: 17.27 ft, moderate flooding; 4,150 cubic feet per secondMar 3, 1961: 15.73 ft, minor flooding; 2,100 cubic feet per secondMar 28, 1962: 18.35 ft, moderate flooding; 12,200 cubic feet per secondMar 17, 1963: 8.80 ft, below flood stage; 150 cubic feet per secondJul 11, 1964: 10.89 ft, action stage; 565 cubic feet per secondApr 1, 1965: 17.36 ft, moderate flooding; 5,340 cubic feet per secondFeb 9, 1966: 16.62 ft, moderate flooding; 3,600 cubic feet per secondJun 16, 1967: 13.75 ft, minor flooding; 1,400 cubic feet per secondJul 20, 1968: 8.61 ft, below flood stage; 198 cubic feet per secondMar 4, 1969: 17.78 ft, moderate flooding; 8,510 cubic feet per secondMar 3, 1970: 15.47 ft, minor flooding; 2,280 cubic feet per secondFeb 19, 1971: 17.17 ft, moderate flooding; 4,000 cubic feet per secondMar 12, 1972: 15.59 ft, minor flooding; 2,620 cubic feet per secondMar 3, 1973: 15.95 ft, minor flooding; 2,750 cubic feet per secondJun 22, 1974: 14.00 ft, minor flooding; 1,500 cubic feet per secondJun 5, 1975: 16.55 ft, moderate flooding; 3,490 cubic feet per secondMar 16, 1976: 9.16 ft, below flood stage; 427 cubic feet per secondJul 24, 1977: 7.46 ft, below flood stage; 148 cubic feet per secondMar 19, 1978: 13.37 ft, minor flooding; 1,450 cubic feet per secondMar 23, 1979: 18.40 ft, moderate flooding; 14,000 cubic feet per secondJun 6, 1980: 12.68 ft, minor flooding; 1,230 cubic feet per secondJun 15, 1981: 14.17 ft, minor flooding; 1,440 cubic feet per secondJul 6, 1982: 16.39 ft, moderate flooding; 3,270 cubic feet per secondJun 20, 1983: 18.54 ft, moderate flooding; 16,300 cubic feet per secondJun 13, 1984: 16.58 ft, moderate flooding; 4,990 cubic feet per secondApr 23, 1985: 16.93 ft, moderate flooding; 5,660 cubic feet per secondMar 19, 1986: 14.38 ft, minor flooding; 2,320 cubic feet per secondMar 24, 1987: 12.35 ft, minor flooding; 1,610 cubic feet per secondMar 2, 1988: 10.46 ft, action stageMar 10, 1989: 9.76 ft, below flood stage; 596 cubic feet per secondJun 28, 1990: 14.05 ft, minor flooding; 2,240 cubic feet per secondApr 14, 1991: 7.71 ft, below flood stage; 357 cubic feet per secondJul 10, 1992: 10.94 ft, action stage; 1,180 cubic feet per secondMar 28, 1993: 17.46 ft, moderate flooding; 6,580 cubic feet per secondJun 13, 1994: 17.34 ft, moderate flooding; 6,220 cubic feet per secondAug 8, 1995: 15.05 ft, minor flooding; 2,740 cubic feet per secondJun 22, 1996: 12.50 ft, minor flooding; 1,070 cubic feet per secondMar 13, 1997: 15.66 ft, minor floodingApr 16, 1998: 7.48 ft, below flood stage; 365 cubic feet per secondJun 10, 1999: 8.34 ft, below flood stage; 532 cubic feet per secondJun 15, 2000: 6.83 ft, below flood stage; 221 cubic feet per secondApr 23, 2001: 12.84 ft, minor flooding; 1,850 cubic feet per secondJun 12, 2002: 7.42 ft, below flood stage; 333 cubic feet per secondJul 9, 2003: 11.86 ft, action stage; 1,520 cubic feet per secondMar 2, 2004: 12.15 ft, minor flooding; 1,616 cubic feet per secondMay 14, 2005: 9.98 ft, below flood stage; 915 cubic feet per secondMay 2, 2006: 10.34 ft, action stage; 1,050 cubic feet per secondJun 13, 2008: 12.07 ft, minor flooding; 1,600 cubic feet per secondFeb 11, 2009: 14.17 ft, minor flooding; 2,320 cubic feet per secondJul 23, 2010: 17.97 ft, moderate flooding; 8,580 cubic feet per secondFeb 19, 2011: 13.54 ft, minor flooding; 2,080 cubic feet per secondMar 8, 2012: 11.26 ft, action stage; 1,300 cubic feet per secondMay 27, 2013: 19.19 ft, moderate flooding; 13,800 cubic feet per secondJun 18, 2014: 18.04 ft, moderate flooding; 8,830 cubic feet per secondMay 17, 2015: 6.24 ft, below flood stage; 149 cubic feet per secondSep 18, 2016: 11.07 ft, action stage; 1,360 cubic feet per secondJun 21, 2018: 20.50 ft, moderate floodingSep 20, 2018: 21.96 ft, moderate flooding; 21,700 cubic feet per secondMar 14, 2019: 20.87 ft, moderate flooding; 24,900 cubic feet per secondMay 27, 2020: 8.82 ft, below flood stage; 832 cubic feet per secondJul 14, 2021: 6.16 ft, below flood stage; 161 cubic feet per secondJun 25, 2022: 6.43 ft, below flood stage; 155 cubic feet per secondMay 13, 2023: 9.09 ft, below flood stage; 945 cubic feet per secondJun 22, 2024: 26.81 ft, major floodingJul 31, 2025: 13.43 ft, minor flooding; 2,630 cubic feet per second Highest, 26.81 ft, Jun 22, 2024 1960197019801990200020102020

Crests at or above flood stage, by decade

Crests at or above flood stage per decade, Floyd River at Alton 1950s: 1 1960s: 7 1970s: 8 8 1980s: 8 1990s: 6 2000s: 4 2010s: 7 2020s: 2 1950s1960s1970s1980s1990s2000s2010s2020s
  1. These are the crests the local National Weather Service office lists for the gauge: the highest on record and recent crests. Lesser floods between them may be missing, so counts by decade are a floor.
  2. Categories use today's flood stages. Levees, dams and channel changes since a crest can make old and new stages not directly comparable.

Highest crests

The 50 highest of 69 listed crests.

Highest listed crests, Floyd River at Alton
1Jun 22, 202426.81+14.81Major—
2Sep 20, 201821.96+9.96Moderate21,700
3Mar 14, 201920.87+8.87Moderate24,900
4Jun 21, 201820.50+8.50Moderate—
5May 27, 201319.19+7.19Moderate13,800
6Jun 20, 198318.54+6.54Moderate16,300
7Mar 23, 197918.40+6.40Moderate14,000
8Mar 28, 196218.35+6.35Moderate12,200
9Jun 18, 201418.04+6.04Moderate8,830
10Jul 23, 201017.97+5.97Moderate8,580
11Mar 4, 196917.78+5.78Moderate8,510
12Mar 28, 199317.46+5.46Moderate6,580
13Apr 1, 196517.36+5.36Moderate5,340
14Jun 13, 199417.34+5.34Moderate6,220
15Mar 28, 196017.27+5.27Moderate4,150
16Feb 19, 197117.17+5.17Moderate4,000
17Apr 23, 198516.93+4.93Moderate5,660
18Feb 9, 196616.62+4.62Moderate3,600
19Jun 13, 198416.58+4.58Moderate4,990
20Jun 5, 197516.55+4.55Moderate3,490
21Jul 6, 198216.39+4.39Moderate3,270
22Mar 3, 197315.95+3.95Minor2,750
23Mar 3, 196115.73+3.73Minor2,100
24Mar 13, 199715.66+3.66Minor—
25Mar 12, 197215.59+3.59Minor2,620
26Mar 3, 197015.47+3.47Minor2,280
27Aug 8, 199515.05+3.05Minor2,740
28Mar 19, 198614.38+2.38Minor2,320
29Jun 15, 198114.17+2.17Minor1,440
30Feb 11, 200914.17+2.17Minor2,320
31Jun 28, 199014.05+2.05Minor2,240
32Jun 22, 197414.00+2.00Minor1,500
33Jun 16, 196713.75+1.75Minor1,400
34Feb 19, 201113.54+1.54Minor2,080
35Jul 31, 202513.43+1.43Minor2,630
36Mar 19, 197813.37+1.37Minor1,450
37Apr 23, 200112.84+0.84Minor1,850
38Jun 1, 195912.77+0.77Minor1,130
39Jun 6, 198012.68+0.68Minor1,230
40Jun 22, 199612.50+0.50Minor1,070
41Mar 24, 198712.35+0.35Minor1,610
42Mar 2, 200412.15+0.15Minor1,616
43Jun 13, 200812.07+0.07Minor1,600
44Jul 9, 200311.86−0.14Action1,520
45Mar 8, 201211.26−0.74Action1,300
46Sep 18, 201611.07−0.93Action1,360
47Jul 10, 199210.94−1.06Action1,180
48Jul 11, 196410.89−1.11Action565
49Jul 4, 195710.54−1.46Action440
50Mar 2, 198810.46−1.54Action—

The worst floods along the Floyd River

For this gauge's highest crests, the other gauges on the Floyd River that crested above flood stage within a week.

June 22, 2024: 26.81 ft here, major flooding

  • Le MarsIA · Jun 23, 2024 · 27.97 ft · Major · its highest
  • MerrillIA · Jun 23, 2024 · 20.19 ft · Major · its highest
  • StrubleIA · Jun 22, 2024 · 18.47 ft · Major · its highest
  • JamesIA · Jun 23, 2024 · 32.39 ft · Moderate · its highest
  • SheldonIA · Jun 22, 2024 · 17.62 ft · Moderate

September 20, 2018: 21.96 ft here, moderate flooding

  • Le MarsIA · Sep 21, 2018 · 26.40 ft · Major
  • MerrillIA · Sep 21, 2018 · 17.00 ft · Major
  • StrubleIA · Sep 21, 2018 · 16.24 ft · Moderate
  • JamesIA · Sep 22, 2018 · 27.70 ft · Minor

March 14, 2019: 20.87 ft here, moderate flooding

  • MerrillIA · Mar 15, 2019 · 17.60 ft · Major
  • JamesIA · Mar 15, 2019 · 31.48 ft · Moderate
  • Le MarsIA · Mar 14, 2019 · 25.84 ft · Moderate
  • StrubleIA · Mar 14, 2019 · 16.41 ft · Moderate
  • SheldonIA · Mar 14, 2019 · 13.70 ft · Minor

Gauges on the Floyd River

Flood gauges sharing the river's name, linked within 80 miles of one another.

Flood gauges on the Floyd River
Alton this gaugeIA12.026.81 ft, Jun 22, 20241
JamesIA26.032.39 ft, Jun 23, 20240
Le MarsIA20.027.97 ft, Jun 23, 20243
MerrillIA12.020.19 ft, Jun 23, 202413
SheldonIA12.019.96 ft, Jun 7, 19531
StrubleIA14.018.47 ft, Jun 22, 20241

Other gauges in Sioux County

Flood gauges in Sioux County
Perkins16.023.06 ft, Jun 22, 20241
Struble14.018.47 ft, Jun 22, 20241
Rock Valley16.027.70 ft, Jun 22, 20246

Sioux County: every hazard · River floods across the country · Iowa

NOAA National Water Prediction Service, gauge ALTI4, retrieved October 30, 2026. Stages in feet on the gauge's own datum, not elevation. Crests are as the National Weather Service lists them; preliminary values may be revised.