Flooding in the Southern Midwestern 

United States, April–May 2017

Open-File Report 2018–1004

U.S. Department of the Interior

U.S. Geological Survey
Above: Rapid-deployment gage installation, Gasconade River near Rich Fountain, Mo., May 1, 2017. Photograph by Larry 

Buschmann, U.S. Geological Survey (USGS).

Front cover. Top center: Floodwater at Current River at Doniphan, Mo., May 1, 2017. Photograph by Shannon Kelly, 

USGS. Upper left: USGS hydrologic technician inspects gage at Big River at Byrnesville, Mo., May 1, 2017. Photograph by 

Aaron Walsh, USGS. Upper right: USGS hydrologic technician inspects gage platform at St. Francis River near Patterson, 

Mo., peak flood, April 30, 2017. Photograph by Josh Keele, USGS. Bottom center: USGS hydrologic technician wading from 

gage at Black River near Poplar Bluff, Mo., May 1, 2017. Photograph by Jarret Ellis, USGS.
Flooding in the Southern Midwestern 

United States, April–May 2017

By David C. Heimann, Robert R. Holmes, Jr., and Thomas E. Harris

Open-File Report 2018–1004

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

RYAN K. ZINKE, Secretary

U.S. Geological Survey

William H. Werkheiser, Deputy Director 

 exercising the authority of the Director

U.S. Geological Survey, Reston, Virginia: 2018

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Heimann, D.C., Holmes, R.R., Jr., and Harris, T.E., 2018, Flooding in the southern Midwestern United States, 

April–May 2017: U.S. Geological Survey Open-File Report 2018–1004, 36 p., https://doi.org/10.3133/ofr20181004.

ISSN 2331-1258 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude .............................1

Antecedent Streamflow and Weather Conditions for the 2017 Southern 

Midwest Flooding....................................................................................................................3

Flood Chronology ..................................................................................................................................3

Magnitude of April–May 2017 Flooding ..........................................................................................16

April–May 2017 Flooding—Comparison with Historic Floods..............................................................17

April–May 2017 Flooding—Annual Exceedance Probability................................................................17

Temporal Changes in Annual Peak Streamflows ...................................................................................18

Summary........................................................................................................................................................31

References Cited..........................................................................................................................................31

Glossary.........................................................................................................................................................35

Figures

1. Map showing the Midwestern United States and flood study area associated 

with the April–May 2017 flood ....................................................................................................2

2. Map showing location of selected U.S. Geological Survey streamgages and 

aerial video documentation locations within the designated flood study area.................8

3. Maps showing streamflow conditions at selected U.S. Geological Survey 

streamgages in the study area before the April–May 2017 flooding including 

January, February, March, and April of 2017 ..........................................................................9

4. Maps showing monthly precipitation conditions in the United States for 

January–April 2017, as a percent of normal ..........................................................................11

5. Map showing the 500 millibar height contours for April 29, 2017, across the 

continental United States..........................................................................................................12

6. Maps showing daily surface weather maps at 7:00 AM Eastern Standard Time 

from April 29 to 30, 2017 .............................................................................................................13

7. Map showing cumulative rainfall totals over the southern Midwest United States 

during April 28–30, 2017 .............................................................................................................14

8. Streamflow hydrographs and precipitation totals and distributions for selected 

U.S. Geological Survey streamgages and precipitation stations within the 

study area ....................................................................................................................................15

9. Graph showing annual number of peak-of-record streamflows and number 

of U.S. Geological Survey streamgages in the study area with peak 

streamflow record ......................................................................................................................17

10. Map showing the spatial distribution of the magnitude of annual exceedance 

probabilities of peak streamflows at 59 U.S. Geological Survey streamgages 

for the April–May 2017 flood.....................................................................................................26

11. Maps showing percentage changes in median annual peak streamflow values 

for selected U.S. Geological Survey streamgages for 1930–2017, 1956–2017, 

1975–2017, and 1989–2017 .........................................................................................................27

12. Maps showing the percentage change in the median annual precipitation by 

climate division within the study area for 1930–2016, 1956–2016, 1975–2016, 

and 1989–2016 .............................................................................................................................29
iv

13. Graphs showing change in frequency of daily high intensity (greater than 2–3 in.) 

precipitation from the long-term (1900–2014) average, by state ........................................30

Tables

1. Peak streamflow and stage data at selected U.S. Geological Survey streamgages

in the flood study area for the flood of April–May 2017 .........................................................4

2. Date, times, and locations of aerial video footage documenting the effects of the

April–May 2017 flood at selected locations in south-central Missouri.............................16

3. Estimated annual exceedance probability of the 2017 flood peaks and weighted

peak streamflow estimates for selected flood quantiles at 59 U.S. Geological

Survey streamgages included in this study ...........................................................................21

Films

1. Daily distribution of streamflow conditions in the study area, 

April 27–May 10, 2017...................................................................................................................3

2. Spring Creek at Highway AP bridge near Willow Springs, Missouri, 

April 30, 2017, at 10:30 a.m.........................................................................................................16

3. North Fork River and Spring Creek at Highway 14, Douglas County, 

Missouri, April 30, 2017, at 12:09 p.m.......................................................................................16

4. North Fork River at Highway CC, Ozark County, Missouri, April 30, 2017, 

at 12:37 p.m ..................................................................................................................................16

5. Bryant Creek at Highway 181, Ozark County, Missouri, April 30, 2017, 

at 13:06..........................................................................................................................................16

6. North Fork River at Highway PP near Tecumseh, Missouri, Ozark County, 

April 30, 2017, at 13:40 ................................................................................................................16

7. Dry Creek at Highway AP near Willow Springs, Missouri, April 30, 2017, 

at 15:29..........................................................................................................................................16
v

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Pressure

millibar (mbar) 0.1 kilopascal (kPa)

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Abbreviations

AEP annual exceedance probability

EMA expected moments algorithm

FEMA Federal Emergency Management Agency

ID identifier

RRE regional regression equations

USGS U.S. Geological Survey 
Above: Peak flood at Saint Francis River near Saco, Mo., 

April 30, 2017. Photograph by Chris Rowden, USGS.
Flooding in the Southern Midwestern United States,

April–May 2017

By David C. Heimann, Robert R. Holmes, Jr., and Thomas E. Harris

Abstract

Excessive rainfall resulted in flooding on numerous rivers 

throughout the southern Midwestern United States (southern 

Midwest) in late April and early May of 2017. The heaviest 

rainfall, between April 28 and 30, resulted in extensive flooding from eastern Oklahoma to southern Indiana including parts 

of Missouri, Arkansas, and Illinois.

Peak-of-record streamflows were set at 21 U.S. Geological Survey (USGS) streamgages in the southern Midwest 

during the resulting April–May 2017 flooding and each 

of the five States included in the study area had at least 

one streamgage with a peak of record during the flood. The 

annual exceedance probability (AEP) estimates for the April–

May 2017 peak streamflows indicate that peaks at 5 USGS 

streamgages had AEPs of 0.2 percent or less (500-year recurrence interval or greater), and peak streamflows at 15 USGS 

streamgages had AEPs in the range from greater than 0.2 to 

1 percent (500- to 100-year recurrence intervals).

Examination of the magnitude of the temporal changes 

in median annual peak streamflows indicated positive 

increases, in general, throughout the study area for each of the 

1930–2017, 1956–2017, 1975–2017, and 1989–2017 analysis 

periods. The median increase in peak streamflows was greatest in 1975–2017 and 1989–2017 with maximum increases 

of 8 to 10 percent per year. No stations in the 1975–2017 or 

1989–2017 analysis period had median negative changes in 

peak streamflows.

Introduction

Excessive rainfall resulted in flooding on numerous 

rivers throughout the southern Midwestern United States 

(hereafter referred to as the southern Midwest) in late April 

and early May of 2017 (fig. 1). Tropical moisture lifted over 

a stalled frontal system and caused heavy rains from Texas 

to Ohio between April 28 and May 10 resulting in extensive 

flooding from eastern Oklahoma to southern Indiana including parts of Missouri, Arkansas, and Illinois. The flooding 

resulted in 12 deaths, 7 in Arkansas and 5 in Missouri (Cable 

News Network, 2017). A total of 84 counties (53 in Missouri 

[Missouri Department of Public Safety, State Emergency 

Management Agency, 2017], 18 in Oklahoma [Federal 

Emergency Management Agency (FEMA), 2017b], and 13 

in Arkansas [FEMA, 2017a]) were declared Federal disaster 

areas. In Missouri alone, the flooding resulted in destruction or damage to more than 1,200 homes and caused at least 

$58 million in damage to roads, bridges, and other public 

infrastructure (Office of Missouri Governor, 2017).

The purpose of this report is to document the flood peaks 

(stage and streamflow) of selected U.S. Geological Survey 

(USGS) streamgages within the southern Midwest that were 

affected by the April–May 2017 floods, placing them in 

hydrologic context at these selected locations in relation to 

timing, rank, flood frequency, temporal trends, and historical flooding. The flood peak data are reported for 59 USGS 

selected streamgages in the southern Midwest including parts 

of Arkansas, Illinois, Indiana, Missouri, and Oklahoma having 

more than 25 years of peak streamflow record and, generally 

having 2017 peak streamflows that were ranked in the top 3 

of the annual peaks of record. Flood frequency characteristics 

for selected stations are provided through the determination of 

the annual exceedance probabilities (AEPs) of the 2017 flood 

peaks for the selected stations. The AEP is the probability, 

or chance, of a flood of a given streamflow magnitude being 

equaled or exceeded in any given year. Documenting the flood 

peaks and AEPs will help put the 2017 floods in historical 

context aiding public and private entities in flood preparedness, protection, and control. The determination of trends in 

annual streamflow peaks will provide insight into potential 

changes in the nature of flooding with time and help further 

inform agencies involved with flood mitigation efforts.

April–May 2017 Flooding—Antecedent 

Conditions, Chronology, and Magnitude

The 2017 flooding in the southern Midwest was widespread in that it included parts of Arkansas, Illinois, Indiana, 

Missouri, and Oklahoma (fig. 1). The April–May 2017 

flooding primarily occurred in small basins of less than about 

1,000 square miles (mi2) but included stations with drainage areas as large as 23,400 mi2

 (table 1). Streamflow peaks 
2 Flooding in the Southern Midwestern United States, April–May 2017

Figure 1. The Midwestern United States and flood study area associated with the April–May 2017 flood.

Mississippi Riv er

Ar kansas River

North Dakota

South Dakota

Minnesota

Wisconsin

Michigan

Nebraska

Kansas

Oklahoma

Arkansas

Tennessee

Kentucky

Ohio

Indiana Illinois

Iowa

Joplin

St. Louis

Georgetown

Willow Springs

Springfield

Wadesville

Missouri

Tecumseh

DeValls Bluff

 Cotton Plant 

 Doniphan

Pleasant View

Eminence

Van Buren

Caddo Gap

105° 100° 95° 90° 85° 80°

45°

40°

35°

EXPLANATION

Flood study area

Midwestern United States

0 75 150 300 MILES

0 75 150 300 KILOMETERS

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

Missouri River
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 3

on the “big” river (Missouri, Mississippi, Ohio) stations in 

the study area during the April–May flooding generally were 

not ranked in the top 5 at any station. Streamflow peaks of 

record occurred at 21 of the 59 streamgaging stations during 

the April–May 2017 flooding included in this report (fig. 2, 

table 1), which is noteworthy given the multi-State spatial 

distribution of the record peaks and that the average record 

length of the 59 streamgages was 67 years.

Antecedent Streamflow and Weather Conditions 

for the 2017 Southern Midwest Flooding

Much of the area in the southern Midwest that was 

affected by flooding in April–May 2017 began the year with 

streamflows in the normal (25 to 75 percentile) to below 

normal (less than 25 percentile) ranges (USGS, 2017b; 

fig. 3A), and only the streamflows in the Illinois section of 

the study area primarily were above normal (greater than 

75 percentile). By February, most of the study area had below 

normal streamflows except some higher than normal streamflows in southwestern Arkansas (fig. 3B). All stations indicated 

below normal to normal conditions in March with near record 

lows occurring at several stations in southeast Oklahoma and 

southwest Arkansas (fig. 3C). These predominantly normal to 

below normal streamflow conditions persisted through midApril (fig. 3D) before the start of heavy rains in the study area 

on April 28.

Because streamflow is primarily reflective of precipitation conditions, it follows that precipitation for January and 

February 2017 also was average to below normal for much of 

the study area [National Oceanic and Atmospheric Administration (NOAA), National Centers for Environmental Information, 2017b; fig. 4]. March totals were normal for much of the 

area with above normal total precipitation in parts of southern 

Missouri and northern Arkansas. Early to mid-April precipitation also was slightly below normal for Springfield, Mo., and 

other than a substantial precipitation event during April 4–5, 

2017, recorded at Saint Louis, Mo., the remainder of April was 

fairly dry over the study area until the last week of the month.

Flood Chronology

A rainfall pattern that led to excessive precipitation 

falling over much of the southern Midwest began as a surface 

low pressure center in the four corners region of the western 

United States on April 27, 2017, that slowly moved southeast over the next 24 hours. On Friday afternoon, April 28, a 

stationary front that extended from southeast Missouri across 

west-central Arkansas into south-central Oklahoma began 

moving north as a warm front. As an upper level system 

moved out of the southern Rockies, tropical moisture from 

the Gulf of Mexico began to get pulled northward up and over 

the stationary front. At the upper levels of the atmosphere, the 

500 millibar low pressure was centered over Arizona and had 

become cutoff from the main flow as it drifted slowly eastward 

(fig. 5; National Centers for Environmental Prediction, 2017). 

The result was a convergence of the two fronts producing 

thunderstorms that trained over the same areas yielding abundant precipitation for the next 24 to 36 hours (fig. 6).

A series of surface lows that moved northeast along 

the front brought waves of showers and thunderstorms and 

resulted in continuous heavy rainfall across the study area 

during the day on Saturday, April 29. Interestingly, this upper 

level atmospheric pattern was very similar to the upper level 

pattern that developed during the last historic flooding of 

December 2015 through January 2016 (Holmes and others, 

2016), which also affected much of the same study area. As 

the warm front continued to move north on Sunday, April 30, 

the cold front swept in behind it from the west bringing an 

end to the rainfall (National Weather Service, 2017b). The 

heaviest rainfall amounts during April 28–30 occurred over 

extreme northeast Oklahoma and northern Arkansas, across 

the southern half of Missouri, southern Illinois, and southern 

Indiana, and included totals of 6 to 10 inches (in.) with some 

isolated higher amounts (figs. 7, 8). Largely as a result of the 

April 28–30 rainfall totals, April 2017 was the second wettest 

April on record in Missouri (123 years of record), the third 

wettest in Oklahoma, the eighth wettest in Arkansas, and the 

fifth wettest in Illinois (National Centers for Environmental 

Information, 2017b). The runoff response from the intense 

precipitation, as indicated by the streamflow hydrographs, 

varied in magnitude and temporal distribution (fig. 8). Flood 

peaks during the event occurred between April 29 and May 

10, 2017, with the timing of the peaks primarily determined 

by the temporal distribution of precipitation and the size of 

the drainage area upstream from the streamgage. Stations 

with peaks occurring on April 29 had drainage areas less than 

825 mi2, whereas those stations with the later peaks (White 

River at Georgetown, Arkansas, May 8, 2017; White River 

at DeValls Bluff, Arkansas, May 10, 2017) were large basins 

(greater than 22,000 mi2). Peak streamflows at streamgages 

along the White River also were affected by regulation, which 

could contribute to the later peaks. The effects of man-made 

regulation and the large drainage area are reflected in the 

hydrograph for the White River at Georgetown, Ark. (station 

number (no.) 07076750), because the peak was 8 days later 

than most streamgages in the study area (fig. 8, table 1). The 

streamflow peak at the Cache River near Cotton Plant, Ark. 

(station no. 07077555), similarly was lagged compared to 

other streamgages (fig. 8, table 1). The flood peaks at this 

streamgage were lagged and extended by a combination of the 

low gradient (less than 1 foot per mile [ft/mi]) and extensive 

storage capacity in the wide flood plain containing numerous wetlands. The April 27 to May 10 chronology and spatial 

progression in streamflow conditions relative to the long-term 

distribution of daily streamflows indicates the effects of the 

heavy precipitation throughout the study area (film 1).

Film 1. Daily distribution of streamflow conditions in the 

study area, April 27–May 10, 2017. Source: U.S. Geological 

Survey, 2017b.
4 Flooding in the Southern Midwestern United States, April–May 2017 Table 1. Peak streamflow and stage data at selected U.S. Geological Survey streamgages in the flood study area for the flood of April–May 2017. [Values in bold denote peak of record streamflows; ID, identifier; USGS, U.S. Geological Survey; mi2, square mile; ft3/s, cubic foot per second; ft, foot; --, data not available] Map ID (fig. 2) USGS streamgage number USGS streamgage name Drainage area (mi2

)

Date of first 

recorded 

peak 

streamflow

1Historical peak streamflow and stage 1Flood of April–May 2017 National 

Weather 

Service 

flood 

stage 

(ft)

Peak 

streamflow

(ft3/s)

Year of 

peak 

streamflow

Peak 

stage 

(ft)

Year of 

peak 

stage

2Peak 

streamflow

(ft3/s)

Date of 

peak 

streamflow

Peak 

stage 

(ft)

3Rank/

number of 

annual peak 

streamflows 

in record

1 03378550 Big Creek near 

Wadesville, Indiana

104 5/18/1966 17,700 2013 21.06 2013 19,000 2017-04-29 21.23 1/52 --

2 03382100 South Fork Saline River 

near Carrier Mills, Illinois

147 4/28/1966 29,500 2008 18.41 2008 12,200 2017-04-30 17.14 2/52 --

3 03612000 Cache River at Forman, 

Illinois

244 2/3/1923 20,400 2008 442.29 1935 11,200 2017-05-02 36.55 3/95 --

4 05587900 Cahokia Creek at 

Edwardsville, Illinois

212 9/17/1969 16,100 2015 27.17 2015 9,090 2017-05-01 23.08 3/49 --

5 05595200 Richland Creek near 

Heckler, Illinois

129 5/1/1970 23,400 1996 44.4 1996 16,000 2017-04-30 43.06 3/48 --

6 05597500 Crab Orchard Creek 

near Marion, Illinois

31.7 4/13/1952 10,000 2008 13.74 2008 10,300 2017-04-29 13.84 1/66 --

7 06909500 Moniteau Creek near 

Fayette, Missouri

75.1 3/6/1948 13,700 1973 22.23 1973 4,010 2017-04-30 19.71 15/60 16

8 06910230 Hinkson Creek at 

Columbia, Missouri

69.8 5/30/1967 14,200 2009 21.88 2009 9,300 2017-04-29 19.21 6/31 15

9 06910750 Moreau River near 

Jefferson City, Missouri

561 6/7/1949 33,000 1985 33.52 2015 32,900 2017-05-01 33.57 2/58 17

10 06918440 Sac River near 

Dadeville, Missouri

257 4/4/1965 36,100 1993 27.56 1993 18,400 2017-04-30 21.85 4/53 --

11 06919020 Sac River at Highway 

J below Stockton, Missouri

1,292 3/10/1974 13,700 2015 23.86 2015 11,400 2017-04-30 22.36 4/44 --

12 06919500 Cedar Creek near 

Pleasant View, Missouri

420 6/10/1923 37,000 1958 527.7 1909 21,000 2017-04-30 24.81 10/74 20

13 06919900 Sac River near 

Caplinger Mills, Missouri

1,810 11/4/1974 61,500 1994 30.95 1994 33,300 2017-04-30 28.39 6/43 16

14 06921070 Pomme de Terre River 

near Polk, Missouri

276 1/30/1969 38,200 2015 27.81 2015 27,600 2017-04-30 24.68 3/49 --

15 06923500 Bennett Spring at 

Bennett Springs, Missouri

100 5/6/1929 12,600 1990 10.55 2015 4,010 2017-04-30 7.46 7/54 --
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 5

Table 1. Peak streamflow and stage data at selected U.S. Geological Survey streamgages in the flood study area for the flood of April–May 2017.—Continued[Values in bold denote peak of record streamflows; ID, identifier; USGS, U.S. Geological Survey; mi2, square mile; ft3/s, cubic foot per second; ft, foot; --, data not available]

Map ID 

(fig. 2)

USGS 

streamgage 

number

USGS 

streamgage name

Drainage 

area 

(mi2

)

Date of first 

recorded 

peak 

streamflow

1Historical peak streamflow and stage 1Flood of April–May 2017 National 

Weather 

Service 

flood 

stage 

(ft)

Peak 

streamflow

(ft3/s)

Year of 

peak 

streamflow

Peak 

stage 

(ft)

Year of 

peak 

stage

2Peak 

streamflow

(ft3/s)

Date of 

peak 

streamflow

Peak 

stage 

(ft)

3Rank/

number of 

annual peak 

streamflows 

in record

16 06927000 Maries River at 

Westphalia, Missouri

257 6/8/1937 41,800 1998 24.84 1998 27,400 2017-04-30 21.00 6/63 10

17 06928000 Gasconade River near 

Hazelgreen, Missouri

1,250 68/1915 90,000 1916 34.92 2008 119,000 2017-04-30 39.74 1/73 21

18 06930000 Big Piney River near 

Big Piney, Missouri

560 4/28/1922 81,200 1982 24.5 1982 90,200 2017-04-30 30.67 1/88 8.5

19 06933500 Gasconade River at 

Jerome, Missouri

2,840 1/6/1897 140,000 2015 31.92 2015 197,000 2017-05-01 35.06 1/99 15

20 06934000 Gasconade River near 

Rich Fountain, Missouri

3,180 1/6/1897 143,000 2015 34.56 2015 190,000 2017-05-02 37.46 1/78 20

21 07010350 Meramec River at Cook 

Station, Missouri

199 2/10/1966 34,900 1966 17.74 1966 26,200 2017-04-30 16.90 3/26 --

22 07013000 Meramec River near 

Steelville, Missouri

781 8/20/1915 60,000 1915 27.22 1998 62,200 2017-04-30 28.71 1/102 12

23 07014500 Meramec River near 

Sullivan, Missouri

1,475 68/1915 90,000 1915 33.5 1915 95,300 2017-04-30 36.38 1/87 11

24 07016500 Bourbeuse River at 

Union, Missouri

808 61897 73,300 1982 34.31 2015 43,800 2017-05-02 29.38 5/104 15

25 07018100 Big River near 

Richwoods, Missouri

735 1/4/1950 59,800 1993 30.33 1993 66,900 2017-04-30 33.54 1/68 --

26 07018500 Big River at 

Byrnesville, Missouri

917 8/21/1915 80,000 1915 30.2 1915 62,600 2017-05-01 30.09 3/96 16

27 07019000 Meramec River at 

Eureka, Missouri

3,788 3/28/1904 175,000 1915 46.06 2015 169,000 2017-05-02 46.11 2/100 19

28 07021000 Castor River at Zalma, 

Missouri

423 5/17/1920 114,000 2008 30.47 2008 69,700 2017-04-30 29.00 3/88 --

29 07035800 St. Francis River near 

Mill Creek, Missouri

505 2/28/1987 130,000 1993 33.1 1993 69,300 2017-04-30 27.32 2/29 16

30 07036100 St. Fancis River near 

Saco, Missouri

664 11/23/1983 161,000 1993 36.1 1993 110,000 2017-04-30 33.42 2/26 21

31 07037500 St. Francis River near 

Patterson, Missouri

956 61915 155,000 1982 35.77 1982 126,000 2017-04-30 37.13 3/96 16
6 Flooding in the Southern Midwestern United States, April–May 2017 Table 1. Peak streamflow and stage data at selected U.S. Geological Survey streamgages in the flood study area for the flood of April–May 2017.—Continued [Values in bold denote peak of record streamflows; ID, identifier; USGS, U.S. Geological Survey; mi2, square mile; ft3/s, cubic foot per second; ft, foot; --, data not available] Map ID (fig. 2) USGS streamgage number USGS streamgage name Drainage area (mi2

)

Date of first 

recorded 

peak 

streamflow

1Historical peak streamflow and stage 1Flood of April–May 2017 National 

Weather 

Service 

flood 

stage 

(ft)

Peak 

streamflow

(ft3/s)

Year of 

peak 

streamflow

Peak 

stage 

(ft)

Year of 

peak 

stage

2Peak 

streamflow

(ft3/s)

Date of 

peak 

streamflow

Peak 

stage 

(ft)

3Rank/

number of 

annual peak 

streamflows 

in record

32 07043500 Little River Ditch No. 1 

near Morehouse, Missouri

450 66/1945 12,200 1989 19.85 1945 9,500 2017-05-01 18.99 10/69 --

33 07050700 James River near 

Springfield, Missouri

246 67/1909 62,000 1909 22.2 2015 38,100 2017-04-30 20.90 4/63 12

34 07052100 Wilson Creek near 

Springfield, Missouri

31.4 11/1/1972 6,710 2015 10.16 2015 4,220 2017-04-29 9.15 6/29 7

35 07052500 James River at Galena, 

Missouri

987 4/1/1922 85,100 2008 35.96 2008 82,800 2017-04-30 35.97 2/96 15

36 07055607 Crooked Creek at Kelly 

Crossing at Yellville, Arkansas

398 2/23/1985 38,500 1990 31.51 2011 95,200 2017-04-30 31.87 1/33 --

37 07057500 North Fork River near 

Tecumseh, Missouri

561 4/15/1945 75,000 1985 28.1 1985 189,000 2017-04-29 41.82 1/73 20

38 07058000 Bryant Creek near 

Tecumseh, Missouri

570 4/14/1945 71,100 1982 26.74 1982 111,000 2017-04-29 33.07 1/63 16

39 07061500 Black River near 

Annapolis, Missouri

484 4/17/1939 109,000 1993 27.38 1993 71,200 2017-04-30 23.3 3/79 8

40 07063000 Black River at Poplar 

Bluff, Missouri

1,245 63/1904 100,000 1904 22.15 2008 29,700 2017-05-01 21.96 12/96 16

41 07066000 Jacks Fork at Eminence, 

Missouri

398 11/19/1921 58,500 1993 4 25.0 1904 106,000 2017-04-30 27.72 1/96 12

42 07067000 Current River at Van 

Buren, Missouri

1,667 3/26/1904 153,100 1904 29.0 1904 179,000 2017-04-30 37.42 1/106 20

43 07068000 Current River at 

Doniphan, Missouri

2,038 63/1904 130,000 1904 25.49 1982 183,000 2017-05-01 33.13 1/101 13

44 07069000 Black River at 

Pocahontas, Arkansas

4,840 4/17/1927 86,600 2011 28.44 2011 105,000 2017-05-02 28.95 1/77 17

45 07071500 Eleven Point River near 

Bardley, Missouri

793 8/20/1915 49,800 1982 21.64 1982 124,000 2017-04-30 28.66 1/97 --

46 07072000 Eleven Point River near 

Ravenden Springs, Arkansas

1,130 1/14/1930 162,000 1982 29.06 1982 137,000 2017-05-01 27.9 1/86 15

47 07074420 Black River at Elgin 

Ferry, Arkansas

8,420 12/4/1982 212,000 2011 34.77 2011 173,000 2017-05-04 33.99 2/27 --
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 7

Map ID 

(fig. 2)

USGS 

streamgage 

number

USGS 

streamgage name

Drainage 

area 

(mi2

)

Date of first 

recorded 

peak 

streamflow

1Historical peak streamflow and stage 1Flood of April–May 2017 National 

Weather 

Service 

flood 

stage 

(ft)

Peak 

streamflow

(ft3/s)

Year of 

peak 

streamflow

Peak 

stage 

(ft)

Year of 

peak 

stage

2Peak 

streamflow

(ft3/s)

Date of 

peak 

streamflow

Peak 

stage 

(ft)

3Rank/

number of 

annual peak 

streamflows 

in record

48 07076750 White River at 

Georgetown, Arkansas

22,400 4/6/1979 179,000 1982 33.95 2011 200,000 2017-05-08 31.5 1/38 21

49 07077000 White River at Devalls 

Bluff, Arkansas

23,400 6/28/1928 220,000 1949 36.1 2011 187,000 2017-05-10 31.31 3/67 --

50 07077555 Cache River near Cotton 

Plant, Arkansas

1,170 7/13/1987 9,950 1987 20.28 2011 10,100 2017-05-05 20.25 1/31 --

51 07185765 Spring River at 

Carthage, Missouri

425 7/6/1967 40,600 2015 20.33 2015 30,400 2017-04-29 18.44 2/30 10

52 07186000 Spring River near Waco, 

Missouri

1,164 61923 151,000 1993 34.06 1993 55,800 2017-04-30 28.14 8/95 19

53 07187000 Shoal Creek above 

Joplin, Missouri

427 7/13/1924 62,100 1943 4 28.0 1941 52,900 2017-04-29 22.96 4/94 14

54 07189000 Elk River near Tiff City, 

Missouri

851 4/12/1940 137,000 1941 28.4 1941 107,000 2017-04-29 27.39 2/78 15

55 07191220 Spavinaw Creek near 

Sycamore, Oklahoma

133 5/6/1960 39,800 1975 22.07 1975 19,900 2017-04-29 16.94 2/58 --

56 07195500 Illinois River near 

Watts, Oklahoma

635 5/15/1956 110,000 2015 28.64 2015 128,000 2017-04-30 30.12 1/62 13

57 07196000 Flint Creek near Kansas, 

Oklahoma

110 5/15/1956 44,400 1974 19.42 1974 19,400 2017-04-29 18.31 3/58 11

58 07261000 Cadron Creek near Guy, 

Arkansas

169 3/21/1955 24,200 1982 29.29 1982 18,000 2017-04-30 23.57 3/61 --

59 07359610 Caddo River near Caddo 

Gap, Arkansas

136 11/19/1988 97,200 1993 26.27 1993 35,800 2017-04-30 23.32 3/29 --

1All peak streamflow and stage information obtained from U.S. Geological Survey (2017a).2At the time of this report, the peak streamflows in water year 2017 (from October 1, 2016, to September 30, 2017) are provisional data subject to revision.3Rank of the maximum instantaneous peak streamflow compared to all systematic and historical annual peaks. A rank of 1 indicates that the April–May 2017 peak streamflow was higher than all other 

recorded annual peak values.

4Stage obtained at different location or datum from current streamgage.5Maximum stage known, 27.7 feet, July 29, 1909, from floodmark.6Month or day of occurrence is unknown or not exact.

Table 1. Peak streamflow and stage data at selected U.S. Geological Survey streamgages in the flood study area for the flood of April–May 2017.—Continued[Values in bold denote peak of record streamflows; ID, identifier; USGS, U.S. Geological Survey; mi2, square mile; ft3/s, cubic foot per second; ft, foot; --, data not available]
8 Flooding in the Southern Midwestern United States, April–May 2017

E E

EE

E

E

#

#

#

#

#

#

#

#

#

#

#

##

# #

#

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

##

#

#

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

##

#

#

9

8

7

6

5

4

3

2

1

59

58

57 56

55

54

53

52 51

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

3433

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15 14

13 12

11

10

White River

2 3

4 5

6

7

94° 92° 90° 88°

40°

38°

36°

34°

Mississippi River

Jac ks Fork

Current River

Missouri River

Ohio

River

EXPLANATION

# U. S. Geological Survey streamgage

and identifier

E Film location and identifier (table 2)

Flood study area

0 25 50 100 MILES

0 25 50 100 KILOMETERS

Kansas

Missouri

Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Arkansas

Mississippi

Alabama

Texas

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD8

27

2

Figure 2. Location of selected U.S. Geological Survey streamgages and aerial video documentation locations within the designated 

flood study area.
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 9

Figure 3. Streamflow conditions at selected U.S. Geological Survey streamgages in the study area before the 

April–May 2017 flooding including A, January ; B, February; C, March; and D, April of 2017.

96° 94° 92° 90° 88° 86°

38°

36°

34°

January 15, 2017

February 15, 2017

96° 94° 92° 90° 88° 86°

38°

36°

34°

0 50 100 MILES

0 50 100 KILOMETERS

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

A.

B.

New low

 Less than 5 to 9 percentile

10 to 24 percentile

25 to 75 percentile

76 to 90 percentile

Greater than 90 percentile

Streamow condition

Flood study area

Kansas

Missouri Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Arkansas

Kansas

Missouri Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Arkansas

Texas

Texas

Mississippi

Alabama
10 Flooding in the Southern Midwestern United States, April–May 2017

96° 94° 92° 90° 88° 86°

38°

36°

34°

96° 94° 92° 90° 88° 86°

38°

36°

34°

0 50 100 MILES

0 50 100 KILOMETERS

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

March 15, 2017

April 15, 2017

New low

Less than 5 to 9 percentile

10 to 24 percentile

25 to 75 percentile

76 to 90 percentile

Greater than 90 percentile

Streamow condition

Flood study area

C.

D.

Kansas

Missouri Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Arkansas Texas

Kansas

Missouri Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Texas Arkansas

Mississippi

Alabama

Figure 3. Streamflow conditions at selected U.S. Geological Survey streamgages in the study area before the 

April–May 2017 flooding including A, January; B, February; C, March; and D, April of 2017.—Continued
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 11

January 2017 February 2017

March 2017 April 2017

Study area boundary

EXPLANATION

Monthly precipitation condition

Figure 4. Monthly precipitation conditions in the United States for January–April 2017, as a percent of 

normal. (Modified from NOAA, National Centers for Environmental Information, 2017b).

USGS hydrologic technician tethering acoustic Doppler current profiler (ADCP), St. Francis River near 

Patterson, Mo., April 30, 2017. Photograph by Aaron Walsh, USGS.
12 Flooding in the Southern Midwestern United States, April–May 2017

Figure 5. 500 millibar height contours for April 29, 2017, across the continental United States (Source: 

National Centers for Environmental Prediction, 2017).

Illinois River near Watts, Okla., April 30, 2017. Photograph by U.S. Geological Survey.
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 13

Figure 6. Daily surface weather maps at 7:00 AM Eastern Standard Time from April 29 to 30, 2017

(Source: National Centers for Environmental Prediction, 2017).

April 29, 2017

April 30, 2017

Precipitation area H 1020 Isobar and value L

High-pressure area

Low-pressure area

Frontal line between high- and low-pressure systems

EXPLANATION
14 Flooding in the Southern Midwestern United States, April–May 2017

Figure 7. Cumulative rainfall totals over the southern Midwest United States during

April 28 - 30, 2017. Source: National Weather Service (2017b).

Missouri

Kansas

Iowa

Nebraska

Oklahoma

Arkansas

Tennessee

Alabama

Georgia

Mississippi

Kentucky

Illinois

Indiana

Wisconsin

Michigan

Texas

Figure 7. Cumulative rainfall totals over the southern Midwest United States during April 28–30, 2017. 

Source: National Weather Service (2017b).

Southern Current River near Doniphan, Mo., May 1, 2017. Photograph by Ben Rivers, USGS.
April–May 2017 Flooding—Antecedent Conditions, Chronology, and Magnitude 15

#

#

#

#

#

0.35

0.95

3.87

0 0

0.3

0.5

0 0 0 0 0 0 0

0.5

1

1.5

2

2.5

3

3.5

4

0 4.5

10,000

20,000

30,000

40,000

50,000

60,000

4/28 4/29 4/30 5/1 5/2 5/3 5/4 5/5 5/6 5/7 5/8 5/9

0

6.05

1.36

1.78

0.02 0

0.95

1.81

0.06 0 0 0 0 0

1

2

3

4

5

6

0 7

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

4/28 4/29 4/30 5/1 5/2 5/3 5/4 5/5 5/6 5/7 5/8 5/9 5/10

0

1.8

6.57

0.66

0 0.09

1.83

0.97

0 0 0 0 0 0

1

2

3

4

5

6

0 7

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

4/28 4/30 5/2 5/4 5/6 5/8 5/10

Streamow, in cubic feet per second

Precipitation, in inches

Daily precipitation and value (National Centers for 

Environmental Information, 2017a)

0.26 Precipitation from Georgetown

 station

Preciptitation from Winona Forest

Ranger Station

Precipitation from Poseyville 2.8 NW 

station

Flood study area

0 0

7.82

0.33

0 0

1.69

0.26 0 0 0 0 0 0

0.38

0

1

2

3

4

5

6

7

8

0 9

2,000

4,000

6,000

8,000

10,000

12,000

4/28 4/30 5/2 5/4 5/6 5/8 5/10 5/12

Precipitation from Georgetown

station

Streamow, in cubic feet per second

Precipitation, in inches

Precipitation, in inches

Precipitation, in inches

Precipitation, in inches

Streamow, in cubic feet per second

Streamow, in cubic feet per second

Streamow, in cubic feet per second

Georgetown

(7.82,10.10)

Clinton 6 SE

(2.95,4.59)

Pocahontas 1

(4.05, 6.77)

Red Bud 5 SE

(5.03,8.36)

Herrin 3.4 S

(8.56,11.49)

Union 0.8 NE

(5.23,9.53)

Mount Ida 4 S

(5.9, 8.35)

Joplin 5.2 SSW

(5.68,8.33)

Westville 0.2 ENE

(5.56,5.61)

Steelville 5.6 SW

(7.70,11.79)

West Plains 1.5 NW

(9.29,13.55) Upper Spavinaw Port

(5.17, 5.97)

Springfield 0.7 ENE

(5.61,7.91)

Poplar Bluff 4.2 NW

 (7.40,8.92)

Jefferson City 5.9 W

(5.81,9.18)

Winona Forest Ranger Station

(9.29,11.92)

Poseyville 2.8 NW

(7.41, 12.03)

Shoal Creek above Joplin, MO

Station 07187000

White River at Georgetown, AR

Station 07076750

Cache River near Cotton Plant, AR

Station 07077555

Current River at Van Buren, MO

Station 07068000

Big Creek near Wadesville, IN

Station 03378550

Oklahoma

Arkansas

Missouri

Illinois

Indiana

Kansas

Red Bud 5 SE

(5.03,8.36)

Precipitation station

(April 28-30 total precipitation,

April 28-May 10 total precipitation, in inches)

0 0

7.82

0.33

0 0

1.69

0.26

0 0 0 0 0 0

0.38

0

1

2

3

4

5

6

7

8

0 9

50,000

100,000

150,000

200,000

250,000

4/28 4/30 5/2 5/4 5/6 5/8 5/10 5/12

EXPLANATION

Streamow hydrograph

Precipitation from Joplin 5.2 SSW

Date

Date

Date

Date

Date

Figure 8. Streamflow hydrographs and precipitation totals and 

distributions for selected U.S. Geological Survey streamgages and 

precipitation stations within the study area.
16 Flooding in the Southern Midwestern United States, April–May 2017

Magnitude of April–May 2017 Flooding

Peak-of-record streamflows were set at 21 USGS 

streamgages in the southern Midwest during the resulting 

April–May 2017 flooding (table 1). Each of the five States 

included in the study area had at least one streamgage with 

a peak of record during the flood. In Missouri, the previous 

peaks of record (for stage) at two rivers (Jacks Fork, Current 

River) had stood since 1904 and included 96 to 106 annual 

peaks. The peak stage of the April–May 2017 flood at the 

Current River at Van Buren, Mo. (station no. 07067000), 

exceeded the previous maximum stage by 8.4 ft (table 1). 

Most remaining streamgages included in the study had peak 

streamflows during the event that ranked in the top three peaks 

of record. Additional USGS streamgages within the study area, 

but on the perimeter of the storm track, had peaks that ranked 

as low as the top 10–15 (table 1) including the Moniteau River 

near Fayette, Mo. (map identifier [ID] 7), and Cedar Creek 

near Pleasant View, Mo. (map ID 12), along the northern 

boundary of the study area (fig. 2).

Flooding is easily summarized numerically as a peak 

stage or streamflow value, but these numbers alone fail to 

convey the physical consequences of such high flows on structures and the lives of those affected. Aerial videos that were 

collected within 24 hours of the flood peaks at several locations (table 2, fig. 2) document the consequences of the floods 

(films 2–7). These videos were collected at locations within 

the greater than 10 in. precipitation areas shown in figure 7, 

and that also were near USGS streamgage locations with 

peaks of record during the flood including North Fork River 

near Tecumseh, Mo. (fig. 2 map ID 37; table 1) and Bryant 

Creek near Tecumseh, Mo. (fig. 2 map ID 38; table 1).

Film 2. Spring Creek at Highway AP bridge near Willow Springs, 

Missouri, April 30, 2017, at 10:30 a.m. (see fig. 2 aerial video 

location 1). (Video footage provided by Aerial Ozarks).

Film 3. North Fork River and Spring Creek at Highway 14, 

Douglas County, Missouri, April 30, 2017, at 12:09 p.m. (see fig. 2 

aerial video location 2). (Video footage provided by Aerial Ozarks).

Film 4. North Fork River at Highway CC, Ozark County, Missouri, 

April 30, 2017, at 12:37 p.m. (see fig. 2 aerial video location 3). 

(Video footage provided by Aerial Ozarks).

Film 5. Bryant Creek at Highway 181, Ozark County, Missouri, 

April 30, 2017, at 13:06. (see fig. 2 aerial video location 4). (Video 

footage provided by Aerial Ozarks).

Film 6. North Fork River at Highway PP near Tecumseh, 

Missouri, Ozark County, April 30, 2017, at 13:40. (see fig. 2 aerial 

video location 5). (Video footage provided by Aerial Ozarks).

Film 7. Dry Creek at Highway AP near Willow Springs, Missouri, 

April 30, 2017, at 15:29. (see fig. 2 aerial video location 6). (Video 

footage provided by Aerial Ozarks).

Table 2. Date, times, and locations of aerial video footage documenting the effects of the April–May 2017 flood at selected locations in

south-central Missouri.

[ID, identifier; Lat, lattitude; Long, longitude; hwy, highway; nr, near; MO, Missouri]

Map ID (fig. 2) Film Lat Long Date Time Description

2 2 36.9074051 -92.0808668 4/30/2017 10:30 Spring Creek at Hwy AP bridge, nr Willow Springs, 

MO.

3 3 36.810436 -92.1498827 4/30/2017 112:09 North Fork River and Spring Creek at Hwy 14, 

Douglas County, MO.

4 4 36.7598273 -92.1556513 4/30/2017 112:37 North Fork River at Hwy CC, Ozark County, MO.

5 5 36.7095049 -92.2690143 4/30/2017 213:06 Bryant Creek at Highway 181, Ozark County, MO.

6 6 36.615802 -92.262483 4/30/2017 113:40 North Fork River at Hwy PP nr Tecumseh, Ozark 

County, MO.

7 7 36.8378767 -92.0559632 4/30/2017 15:29 Dry Creek at Highway AP, near Willow Springs, 

Howell County, MO.

1

The peak at the nearby North Fork River near Tecumseh, Missouri, streamgage was at 4/29/17 at 21:45.

2

The peak at the nearby Bryant Creek near Tecumseh, Missouri, streamgage was at 4/29/17 at 20:00.
April–May 2017 Flooding—Annual Exceedance Probability 17

April–May 2017 Flooding—Comparison 

with Historic Floods

Placing the magnitude of a flood into context is desirable 

for comparison with previous floods. Ranking the observed 

2017 peak streamflows at USGS streamgages against previous streamflow peaks of record indicates the relative magnitude of the 2017 floods (table 1, fig. 9). The benchmark for 

major flooding on many of the major tributaries in the study 

area includes the 1982 (Sauer and Fulford, 1983), 1993 

(Parret and others, 1993), and December–January 2015–16 

floods (Holmes and others, 2016). Each of the 1982, 1993, 

and 2015–16 floods resulted in 8 peaks of record among 

the selected stations included in this study, whereas the 

2017 flood resulted in 21 peaks of record. The number of 

streamgages in operation did vary considerably with time, but 

nearly the same number of streamgages were in operation in 

1982 (54 streamgages) as were in operation during the 1993, 

2015–16, and 2017 floods (59 streamgages; fig. 9).

April–May 2017 Flooding—Annual 

Exceedance Probability

In the past, flood-frequency estimates have been 

presented in terms of the recurrence interval, which represents the average number of years between occurrences of a 

streamflow of equal or greater magnitude. This term, however, 

often results in a misunderstanding that a 100-year flood, once 

it has occurred, will not occur again for another 99 years, 

which is not necessarily true. A 100-year flood means that, if 

all things remain the same in the basin (for example, land use 

and climate conditions), the observed annual floods during 

thousands of years would average around 100 years between 

events of this magnitude. The term annual exceedance probability (AEP) is now more commonly used to refer to floodfrequency estimates because it more clearly conveys that the 

flood-frequency estimates are probabilistic in nature. The AEP 

is the probability that the streamflow of a certain magnitude 

will be equaled or exceeded in any year and is the reciprocal of the recurrence interval. A 0.01 AEP streamflow, for 

example, has a 1-percent chance of occurring in any year and 

is equivalent to a 100-year flood streamflow.

The current (2017) standard methodology for the determination of flood-frequency studies is Bulletin 17C (England 

and others, 2017) of the Advisory Committee on Water 

Information. Similar to the Bulletin 17B method (Interagency 

Advisory Committee on Water Data, 1982), the Bulletin 17C 

method fits a log-Pearson Type III distribution curve to the 

logarithms of annual peak discharges at a given station using 

the method-of-moments to compute a mean, standard deviation, and station skew of the log-transformed peak flow data. 

The user has the option to weigh the individual station skew 

estimate with a generalized/regional skew estimate, which 

typically improves the accuracy because skews tend to follow 

regional trends. Modifications incorporated into the Bulletin 17C method include the adoption of a generalized methodof-moments estimator, known as the expected moments 

algorithm (EMA) procedure (Cohn and others, 1997), and a 

generalized version of the Grubbs-Beck test for low outliers 

Figure 9. Annual number of peak-of-record streamflows and number of U.S. Geological 

Survey streamgages in the study area with peak streamflow record.

0

10

20

30

40

50

60

0

5

10

15

20

25

1900 1920 1940 1960 1980 2000 2020

Number of stati

ons with peak

stream

fl

o

w record

Annual number of peaks of record

Date

Annual number of peaks

of record

Number of stations

with peak streamflow

record
18 Flooding in the Southern Midwestern United States, April–May 2017

(Cohn and others, 2013). The EMA is an updated method for 

fitting the log-Pearson Type III frequency distribution that is a 

more effective means of incorporating historical peak streamflow information into a flood-frequency analysis.

The USGS computer program PEAKFQ (version 7.1; 

Flynn and others, 2006) was used to compute the floodfrequency estimates for the 59 stations in this study. The 

annual peak streamflow data used in the analyses were 

obtained from U.S. Geological Survey (2017a). The program 

automates many of the flood-frequency analyses procedures, 

including identifying and adjusting for high and low outliers and historical periods and fitting the log-Pearson Type III 

distribution to the streamflow data. The program includes the 

EMA procedure for flood-frequency analysis and multiple 

Grubbs-Beck outlier screening (Veilleux and others, 2013). 

The PEAKFQ program and associated documentation are 

available at https://water.usgs.gov/software/peakfq.html.

In addition to estimating the at-site AEP flood quantiles 

by Bulletin 17C methods, another way to obtain an AEP flood 

quantile estimate is by using regional regression equations 

(RREs). The RREs are developed using regression techniques 

that relate the peak flood-probability data at many streamgages 

in a particular region to the basin characteristics upstream 

from the streamgages (Jennings and others, 1994). The RREs 

allow a user to estimate the various AEP flood quantiles for 

any location along a stream (gaged or ungaged) by entering 

the specified basin characteristics (for example, drainage area 

or average precipitation) used as independent variables in the 

equation. Rural regression estimates for the 59 streamgages 

in this study were obtained from the corresponding RRE 

estimates developed for each state in the study area including Arkansas (Wagner and others, 2016), Illinois (Soong 

and others, 2004), Missouri (Southard, 2010; Southard and 

Veilleux, 2014), and Oklahoma (Lewis, 2010). The single 

streamgage in Indiana (Big Creek near Wadesville, Indiana) is 

within 10 mi of the Illinois border, so the Illinois RRE equations were used to obtain the RRE estimates for this station. 

The optimal estimate of the AEP flood quantile for a gaged site 

is determined by weighting the at-site AEP flood quantile estimate determined from the Bulletin 17C methods with the AEP 

flood quantile estimate determined from the RRE as described 

in (Soong and others, 2004; Southard, 2010; Southard and 

Veilleux, 2014; and Wagner and others, 2016).

The AEP estimates for the April–May 2017 flood peak 

streamflows indicate that peaks at 5 USGS streamgages had an 

AEP of 0.2 percent or less, and peak streamflows at 15 USGS 

streamgages had an AEP in the range from greater than 0.2 

to 1 percent (table 3, fig. 10). The weighted estimates of the 

AEP flood quantiles corresponding to the 50-, 20-, 10-, 4-, 

2-, 1-, 0.5-, and 0.2-percent AEPs, along with their respective 

95-percent confidence limits, for the selected 59 streams in the 

southern Midwest included in this study, also were computed 

(table 3).

Temporal Changes in Annual Peak 

Streamflows

Temporal changes in annual peak streamflows are important to investigate because they may indicate to emergency and 

infrastructure managers there are corresponding changes in the 

levels of risk to public safety. Temporal changes in streamflow 

can be the result of changes to such factors as land use and 

land cover, climate, or regulation. The annual peak streamflow 

time series data were analyzed for selected streamgages in the 

southern Midwest to determine the presence and subsequent 

magnitude of changes through time at each site.

The temporal changes in streamflow magnitudes were 

computed based on the Sen’s slope estimator (Sen, 1968) 

using the MAKESENS application from the Finnish Meteorological Institute (Salmi and others, 2002). The Sen’s slope, 

also known as the Kendall-Theil robust line, is a nonparametric estimate of trend magnitude slope for a univariate time 

series when the time interval is constant (equally spaced).

f(t) = Mq×t + B (1)

where

f(t) is the increasing or decreasing function 

of time for the trend magnitudes of the 

streamflows used in the investigation, 

Mq is the Sen’s slope estimate, 

t is time, and

B is a constant.

The Sen’s slope is the median slope of all pairwise 

comparisons with each pairwise difference divided by the 

number of years separating the records. To determine the Sen’s 

slope estimate in equation 2, the slopes of all data pairs are 

calculated:

M

X X

t j k

k j

j k

, ( )

,

= −

∆

 for j=1,..., n−1; j < k ≤ n (2)

where 

Mj,k is the slope between data points Xj and Xk; 

Xj is the data measurement at time j; 

Xk is the data measurement at time k; 

Δt

j,k is the change in time between observations; 

and

n is the number of years of record.

The Sen’s slope estimate, Mq, is equal to the median value of 

all the Mj,k values.
Temporal Changes in Annual Peak Streamflows 19

Streamgages with missing record periods exceeding 

5 percent of the total record were not used in the analyses 

of temporal changes in annual streamflow peaks nor were 

streamgages on regulated rivers. Of the 59 streamgages 

included in the study, 49 were used in the analyses of temporal changes in annual peak streamflows. The start dates of 

documented peak streamflows and record periods for the 

49 stations differed; therefore, four temporal analysis periods 

(1930–2017, 1956–2017, 1975–2017, and 1989–2017) were 

selected to maintain consistency in streamflow record start 

dates, have overlap of record analysis periods, and maximize 

the number of stations and the period of record that could 

be included in the analyses. For comparison of streamgages 

with differing basin sizes, the Sen’s slope for each streamgage 

was divided by the median annual peak streamflow value to 

determine the percentage of change with respect to the median 

annual peak streamflow at each streamgage.

Examination of the magnitude of the temporal changes 

(scaled by median annual peak flood streamflow) in median 

annual peak streamflows from 1930–2017 indicates all but 1 

of the 20 stations included had a systematic positive increase 

in peak streamflows of less than 2 percent per year (fig. 11A). 

The remaining station, Shoal Creek above Joplin, Mo. 

(station no. 07187000, map ID 53), had a negative change 

of -0.12 percent per year during the analysis period. Similarly, the temporal change in peak streamflows at most of the 

34 stations included in the 1956–2017 analysis period had 

median positive increases in annual peak flows of less than 

2 percent (fig. 11B). Two stations (Jacks Fork at Eminence, 

Mo., station no. 07066000, map ID 41; Current River at 

Van Buren, Mo., station no. 07067000, map ID 42), had no 

change and one station had a median decrease in annual peak 

streamflows of -0.12 percent per year over the 61-year period 

(Cadron Creek near Guy, Ark., station no. 07261000, map 

ID 58). Analyses of the 1975–2017 and 1989–2017 periods 

indicated nearly all stations had median positive changes in 

annual peak streamflows of increasing magnitude (fig. 11C). 

Six of the 44 stations in the 1975–2017 analysis period had 

positive changes of greater than 2 percent, whereas 23 of 

49 stations in the 1989–2017 analysis period had median 

positive increases of greater than 2 percent with maximum 

increases of 8–10 percent per year (fig. 11D). No stations in 

either of the 1975–2017 or 1989–2017 analysis periods had 

median negative changes in peak streamflows, but five stations 

in the 1989–2017 analysis period had no change in streamflow 

peaks.

A primary driver of change in peak streamflows is 

precipitation. Similar to streamflow peaks, the annual precipitation within the flood study area was analyzed by climate 

division (NOAA, National Centers for Environmental Information, 2017c) using the Sen’s slope methodology. Changes 

in annual precipitation were analyzed for the same periods as 

peak streamflow except the analysis periods for precipitation 

ended in 2016. Similar to changes in annual peak streamflows, 

median changes in annual precipitation for the 1930–2016 

and 1956–2016 periods generally were small (less than 

2 percent) and positive (fig. 12). Changes in annual precipitation, however, provided little explanation for the substantial 

increase in magnitude of streamflow peaks because, for 

example, nearly one-half of the climate divisions in the 1989–

2016 analysis period indicated no change or a negative change 

in precipitation per year, whereas this was the period of the 

greatest magnitude in positive changes in streamflow peaks in 

the study area. The increase in the frequency of larger magnitude rain events with time may be a better explanatory variable 

for the greater positive changes in annual peak streamflows. 

The frequency of daily precipitation events of greater than 2 

or 3 in. generally increased from 1985 to 2014 in each state in 

the study area (fig. 13). The degree to which land use changes 

may have contributed to the positive changes in peak streamflows was undetermined.
20 Flooding in the Southern Midwestern United States, April–May 2017

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.

[ID, identifier; USGS, U.S. Geological Survey; AEP, annual exceedance probability; ft, foot; ft3/s, cubic foot per second; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold] Map ID (fig. 2) USGS streamgage number USGS streamgage name

2017 flood peak AEP for observed 2017 flood

Expected peak streamflows for selected AEP with 

95-percent confidence limits (ft3/s)

50-percent AEP

(2-year recurrence)

20-percent AEP

(5-year recurrence)

Rank

Number of annual 

peaks in analysis

Date of peak 

streamflow

Peak stage (ft)

Peak streamflow 

(ft3/s)

AEP estimate

Recurrence 

interval (years)

67% confidence 

interval1

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

1 03378550 Big Creek near 

Wadesville, Indiana

1 52 4/29/2017 21.23 19,000 0.83% 123 0.4% 3.4% 5,270 4,710 5,890 7,920 6,930 9,050 

2 03382100 South Fork Saline River 

near Carrier Mills, 

Illinois

2 52 4/30/2017 17.14 12,200 1.4% 72 1.4% 6.1% 3,100 2,720 3,520 5,030 4,310 5,880 

3 03612000 Cache River at Forman, 

Illinois3

3 95 5/2/2017 36.55 11,200 3.8% 27 1.5% 4.7% 3,810 3,430 4,230 6,320 5,620 7,100 

4 05587900 Cahokia Creek at 

Edwardsville, Illinois

3 49 5/1/2017 23.08 9,090 7.3% 14 2.9% 9.1% 5,470 5,030 5,950 7,350 6,700 8,050 

5 05595200 Richland Creek near 

Heckler, Illinois

3 48 4/30/2017 43.06 16,000 4.9% 20 2.9% 9.2% 5,900 5,070 6,870 9,920 8,460 11,600 

6 05597500 Crab Orchard Creek near 

Marion, Illinois

1 66 4/29/2017 13.84 10,300 0.91% 110 0.3% 2.7% 1,950 1,670 2,260 3,600 3,030 4,270 

7 06909500 Moniteau Creek near 

Fayette, Missouri

15 60 4/30/2017 19.71 4,010 27.9% 4 19.3% 29.9% 2,830 2,500 3,200 4,600 4,010 5,270 

8 06910230 Hinkson Creek at 

Columbia, Missouri4

6 31 4/29/2017 19.21 9,300 10.1% 10 12.1% 25.3% 4,560 3,880 5,360 7,400 6,360 8,610 

9 06910750 Moreau River near 

Jefferson City, 

Missouri

2 58 5/1/2017 33.57 32,900 3.1% 32 1.3% 5.5% 13,600 12,100 15,300 20,600 18,300 23,300 

10 06918440 Sac River near Dadeville, 

Missouri

4 53 4/30/2017 21.85 18,400 7.3% 14 4.1% 10.7% 5,270 4,420 6,290 10,500 8,650 12,800 

11 06919020 Sac River at Highway J 

below Stockton, 

Missouri5

4 44 4/30/2017 22.36 11,400 6.6% 15 4.9% 12.8% 6,860 6,120 7,650 9,120 8,180 10,400 

12 06919500 Cedar Creek near Pleasant 

View, Missouri

10 74 4/30/2017 24.81 21,000 13.5% 7 9.6% 17.1% 9,880 8,640 11,300 17,500 15,200 20,000 

13 06919900 Sac River near Caplinger 

Mills, Missouri5

6 43 4/30/2017 28.39 33,300 14.1% 7 8.7% 18.5% 15,300 11,900 19,300 27,900 22,200 36,500 

14 06921070 Pomme de Terre River 

near Polk, Missouri

3 49 4/30/2017 24.68 27,600 5.4% 18 2.9% 9.1% 13,400 11,900 15,100 19,800 17,600 22,200 

15 06923500 Bennett Spring at Bennett 

Springs, Missouri6

7 54 4/30/2017 7.46 4,010 9.4% 11 8.4% 17.0% 1,310 1,040 1,620 2,700 2,160 3,420 

16 06927000 Maries River at 

Westphalia, Missouri

6 63 4/30/2017 21.00 27,400 7.5% 13 5.9% 12.8% 12,800 11,400 14,300 19,800 17,600 22,400 

17 06928000 Gasconade River near 

Hazelgreen, Missouri

1 73 4/30/2017 39.74 119,000 1.4% 73 0.2% 2.4% 25,000 21,300 29,400 48,000 41,200 56,000 

18 06930000 Big Piney River near Big 

Piney, Missouri

1 88 4/30/2017 30.67 90,200 0.22% 453 0.2% 2.0% 13,300 11,500 15,400 25,100 21,700 29,000 

19 06933500 Gasconade River at 

Jerome, Missouri

1 99 5/1/2017 35.06 197,000 0.47% 215 0.2% 1.8% 30,400 26,800 34,400 57,100 50,500 64,500 

20 06934000 Gasconade River near 

Rich Fountain, 

Missouri

1 78 5/2/2017 37.46 190,000 0.54% 186 0.2% 2.3% 34,000 29,800 38,900 61,400 53,800 70,000 

21 07010350 Meramec River at Cook 

Station, Missouri

3 26 4/30/2017 16.90 26,200 5.7% 17 5.5% 16.7% 6,750 4,980 9,150 14,500 11,100 19,000 
Temporal Changes in Annual Peak Streamflows 21

Expected peak streamflows for selected AEP with 95-percent confidence limits 

(ft3/s)

10-percent AEP

(10-year recurrence)

4-percent AEP

(25-year recurrence)

2-percent AEP

(50-year recurrence)

1-percent AEP

(100-year recurrence)

0.5-percent AEP

(200-year recurrence)

0.2-percent AEP

(500-year recurrence)

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

9,870 8,440 11,500 12,500 10,200 15,200 14,500 11,500 18,300 16,700 12,800 21,800 -- -- -- 22,000 15,500 31,200

6,610 5,480 7,980 8,940 7,050 11,300 10,900 8,260 14,400 13,100 9,500 18,000 -- -- -- 18,900 12,500 28,600

8,250 7,180 9,470 11,000 9,200 13,100 13,200 10,700 16,200 15,500 12,200 19,700 -- -- -- 21,400 15,600 29,500

8,500 7,650 9,450 9,870 8,730 11,200 10,900 9,410 12,500 11,800 10,100 13,900 -- -- -- 14,000 11,300 17,200

12,800 10,700 15,300 16,600 13,400 20,700 19,600 15,300 25,200 22,600 17,000 30,000 -- -- -- 29,800 20,600 43,100

4,920 4,020 6,010 6,800 5,310 8,700 8,320 6,250 11,100 9,910 7,140 13,800 -- -- -- 13,900 9,110 21,300

5,900 5,070 6,870 7,700 6,420 9,220 9,120 7,430 11,200 10,600 8,420 13,300 12,200 9,400 15,700 14,200 10,600 19,100

9,330 7,930 11,000 11,900 9,870 14,300 13,900 11,300 17,100 16,900 12,800 22,200 -- -- -- 21,700 15,900 29,600

25,300 22,200 28,900 31,200 26,600 36,500 35,400 29,600 42,300 39,600 32,300 48,500 43,700 34,800 54,900 49,200 37,900 64,000

15,300 12,300 18,900 22,900 18,000 29,200 29,200 22,400 38,100 35,900 27,000 48,000 43,000 31,700 58,400 52,100 37,000 73,500

10,500 9,360 12,200 12,100 10,600 14,800 13,300 11,500 16,900 14,400 12,200 19,100 15,400 12,800 21,400 16,700 13,600 24,800

23,200 20,100 26,800 31,400 26,700 36,900 37,900 31,600 45,500 44,900 36,600 55,000 52,400 41,900 65,500 61,900 48,000 79,900

37,500 29,400 52,000 50,700 38,600 77,600 61,000 44,900 101,000 71,700 50,600 130,000 82,800 55,900 163,000 97,900 62,200 217,000

23,900 20,900 27,200 28,900 24,900 33,500 32,600 27,600 38,600 36,400 30,100 43,900 40,300 32,700 49,500 45,300 35,800 57,300

3,920 3,090 5,230 5,800 4,410 8,560 7,470 5,460 12,000 9,360 6,540 16,500 11,500 7,660 22,400 14,700 9,160 32,800

24,900 21,600 28,600 31,500 26,700 37,100 36,700 30,400 44,300 41,900 34,000 51,800 47,400 37,600 59,700 54,900 42,000 71,700

65,600 56,000 76,900 89,500 74,800 107,000 108,000 87,900 132,000 126,000 100,000 158,000 145,000 113,000 186,000 170,000 128,000 226,000

34,300 29,300 40,200 47,000 39,200 56,400 57,000 46,400 70,000 67,100 53,300 84,400 77,300 60,100 99,300 91,300 68,500 122,000

78,700 68,700 90,100 110,000 94,000 130,000 137,000 113,000 165,000 164,000 132,000 203,000 193,000 153,000 244,000 232,000 177,000 304,000

82,900 71,800 95,700 114,000 96,400 134,000 139,000 115,000 167,000 165,000 133,000 203,000 192,000 152,000 242,000 229,000 175,000 299,000

20,700 15,700 27,300 28,800 21,700 38,300 35,100 26,000 47,300 41,200 30,200 56,300 47,300 34,300 65,400 55,900 39,100 79,800

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.—Continued

[ID, identifier; USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; AEP, annual exceedance probability; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold]
22 Flooding in the Southern Midwestern United States, April–May 2017 Map ID (fig. 2) USGS streamgage number USGS streamgage name

2017 flood peak AEP for observed 2017 flood

Expected peak streamflows for selected AEP with 

95-percent confidence limits (ft3/s)

50-percent AEP

(2-year recurrence)

20-percent AEP

(5-year recurrence)

Rank

Number of annual 

peaks in analysis

Date of peak 

streamflow

Peak stage (ft)

Peak streamflow 

(ft3/s)

AEP estimate

Recurrence 

interval (years)

67% confidence 

interval1

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

22 07013000 Meramec River near 

Steelville, Missouri

1 102 4/30/2017 28.71 62,200 2.0% 49 0.2% 1.7% 15,400 13,600 17,400 28,100 24,700 32,100 

23 07014500 Meramec River near 

Sullivan, Missouri

1 87 4/30/2017 36.38 95,300 1.2% 84 0.2% 2.0% 21,600 19,000 24,500 38,100 33,600 43,300 

24 07016500 Bourbeuse River at 

Union, Missouri

5 104 5/2/2017 29.38 43,800 3.2% 31 2.8% 6.7% 15,200 13,900 16,700 24,200 22,000 26,700 

25 07018100 Big River near 

Richwoods, Missouri

1 68 4/30/2017 33.54 66,900 1.8% 55 0.3% 2.6% 18,800 16,400 21,500 32,200 28,200 36,700 

26 07018500 Big River at Byrnesville, 

Missouri

3 96 5/1/2017 30.09 62,600 1.6% 62 1.5% 4.7% 17,200 15,400 19,300 29,200 26,000 32,900 

27 07019000 Meramec River at Eureka, 

Missouri

2 100 5/2/2017 46.11 169,000 1.1% 87 0.7% 3.2% 40,800 36,700 45,400 69,100 61,800 77,200 

28 07021000 Castor River at Zalma, 

Missouri3

3 88 4/30/2017 29.00 69,700 0.93% 107 1.6% 5.1% 11,900 10,300 13,800 23,700 20,300 27,600 

29 07035800 St. Francis River near 

Mill Creek, Missouri

2 29 4/30/2017 27.32 69,300 2.7% 37 2.5% 10.7% 23,900 19,800 28,900 39,300 32,600 47,400 

30 07036100 St. Fancis River near 

Saco, Missouri

2 26 4/30/2017 33.42 110,000 0.50% 202 2.8% 11.9% 34,500 28,900 41,300 52,900 44,300 63,100 

31 07037500 St. Francis River near 

Patterson, Missouri

3 96 4/30/2017 37.13 126,000 0.50% 191 1.5% 4.7% 33,800 30,700 37,400 53,300 48,000 59,200 

32 07043500 Little River Ditch No. 1 

near Morehouse, 

Missouri

10 69 5/1/2017 18.99 9,500 11.5% 9 10.3% 18.3% 6,430 5,970 6,940 8,500 7,890 9,160 

33 07050700 James River near 

Springfield, Missouri3

4 63 4/30/2017 20.90 38,100 3.1% 32 3.4% 9.0% 12,500 10,800 14,400 21,300 18,400 24,600 

34 07052100 Wilson Creek near 

Springfield, Missouri4

6 29 4/29/2017 9.15 4,220 20.1% 5 13.0% 26.9% 2,920 2,550 3,340 4,220 3,700 4,820 

35 07052500 James River at Galena, 

Missouri

2 96 4/30/2017 35.97 82,800 1.5% 67 0.8% 3.3% 20,700 18,300 23,500 36,400 32,200 41,100 

36 07055607 Crooked Creek at Kelly 

Crossing at Yellville, 

Arkansas

1 33 4/30/2017 31.87 95,200 0.70% 143 0.6% 5.3% 10,100 7,760 13,200 22,900 17,400 30,200 

37 07057500 North Fork River near 

Tecumseh, Missouri

1 73 4/29/2017 41.82 189,000 <0.20% >500 0.2% 2.4% 13,200 11,200 15,600 26,800 22,400 32,000 

38 07058000 Bryant Creek near 

Tecumseh, Missouri

1 63 4/29/2017 33.07 111,000 <0.20% >500 0.3% 2.8% 12,600 10,500 15,200 25,400 21,300 30,300 

39 07061500 Black River near 

Annapolis, Missouri5

3 55 4/30/2017 23.30 71,200 4.9% 20 2.6% 8.1% 23,100 11,800 27,200 41,300 33,100 53,200 

40 07063000 Black River at Poplar 

Bluff, Missouri5

3 70 5/1/2017 21.96 29,700 37.1% 3 2.0% 6.4% 8,040 6,940 9,340 13,500 11,500 16,400 

41 07066000 Jacks Fork at Eminence, 

Missouri

1 96 4/30/2017 27.72 106,000 0.20% 500 0.2% 1.8% 12,600 10,700 14,800 25,700 22,000 30,100 

42 07067000 Current River at Van 

Buren, Missouri

1 106 4/30/2017 37.42 179,000 0.47% 213 0.2% 1.7% 27,800 24,300 31,700 53,400 46,600 61,200 

43 07068000 Current River at 

Doniphan, Missouri

1 101 5/1/2017 33.13 183,000 0.37% 274 0.2% 1.8% 28,300 24,500 32,700 55,300 48,100 63,700 

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.—Continued

[ID, identifier; USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; AEP, annual exceedance probability; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold]
Temporal Changes in Annual Peak Streamflows 23

Expected peak streamflows for selected AEP with 95-percent confidence limits 

(ft3/s)

10-percent AEP

(10-year recurrence)

4-percent AEP

(25-year recurrence)

2-percent AEP

(50-year recurrence)

1-percent AEP

(100-year recurrence)

0.5-percent AEP

(200-year recurrence)

0.2-percent AEP

(500-year recurrence)

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

38,000 32,900 43,800 51,600 43,800 60,900 62,400 51,700 75,400 73,600 59,500 91,000 85,200 67,300 108,000 101,000 76,800 132,000

50,800 44,200 58,400 68,700 58,600 80,600 83,000 69,400 99,300 98,400 80,400 120,000 115,000 92,000 144,000 136,000 105,000 176,000

31,100 27,700 34,900 40,800 35,400 46,900 48,600 41,300 57,100 56,900 47,300 68,400 65,800 53,500 80,900 77,900 61,300 99,000

41,900 36,400 48,200 54,900 46,700 64,600 65,000 54,200 77,900 75,200 61,400 92,200 85,800 68,600 107,000 99,800 77,100 129,000

38,000 33,500 43,100 49,800 42,900 57,900 59,100 49,700 70,300 68,600 56,400 83,400 78,600 63,200 97,700 91,700 71,400 118,000

90,500 80,200 102,000 121,000 105,000 140,000 146,000 124,000 173,000 173,000 143,000 210,000 202,000 163,000 251,000 240,000 188,000 308,000

33,400 28,200 39,500 47,000 38,600 57,300 57,700 46,200 72,200 68,400 53,400 87,600 78,900 60,300 103,000 94,100 69,300 128,000

49,700 40,600 60,900 62,900 50,300 78,600 73,100 57,200 93,300 83,100 63,800 108,000 93,300 70,400 124,000 108,000 78,500 148,000

64,500 53,300 78,100 78,200 63,300 96,700 88,800 70,300 112,000 99,200 77,100 128,000 110,000 83,900 144,000 125,000 92,400 169,000

67,100 59,700 75,300 84,900 73,700 97,800 98,700 83,900 116,000 113,000 93,600 135,000 127,000 103,000 156,000 146,000 115,000 186,000

9,690 8,910 10,500 11,000 9,970 12,100 11,900 10,600 13,200 12,600 11,200 14,300 13,300 11,600 15,400 14,300 12,100 16,800

27,500 23,500 32,100 35,500 29,900 42,100 41,600 34,400 50,200 47,600 38,700 58,600 53,700 42,900 67,300 62,000 48,000 80,100

5,180 4,490 5,980 6,480 5,510 7,620 7,640 6,370 9,160 8,800 7,200 10,800 -- -- -- 11,800 9,210 15,100

48,100 42,000 55,000 64,100 54,700 75,200 76,600 63,900 91,900 89,600 73,100 110,000 103,000 82,300 129,000 121,000 93,200 157,000

34,200 25,600 45,800 51,500 38,000 69,800 66,000 47,900 91,100 81,600 58,400 114,000 -- -- -- 123,000 83,900 180,000

38,500 31,500 47,100 55,700 44,200 70,100 69,300 53,600 89,600 83,000 62,800 110,000 96,900 71,900 131,000 116,000 83,200 163,000

35,700 29,600 43,200 50,400 40,700 62,300 61,700 48,800 78,100 73,300 56,600 94,900 85,000 64,400 112,000 101,000 73,600 138,000

55,200 44,900 79,000 74,500 57,000 136,000 89,900 65,900 212,000 106,000 74,700 311,000 123,000 83,200 422,000 147,000 94,400 613,000

17,800 14,900 23,100 24,300 19,600 34,900 29,900 23,200 46,800 36,100 27,000 62,100 43,000 31,000 81,600 53,400 36,400 116,000

35,900 30,300 42,500 49,400 40,900 59,600 59,700 48,400 73,500 69,700 55,400 87,700 79,400 61,800 102,000 93,000 69,900 124,000

73,900 63,700 85,600 103,000 86,800 123,000 127,000 104,000 154,000 151,000 121,000 189,000 176,000 138,000 225,000 209,000 158,000 277,000

76,000 65,300 88,400 104,000 87,900 124,000 126,000 104,000 153,000 148,000 119,000 183,000 170,000 134,000 216,000 200,000 152,000 262,000

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.—Continued

[ID, identifier; USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; AEP, annual exceedance probability; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold]
24 Flooding in the Southern Midwestern United States, April–May 2017 Map ID (fig. 2) USGS streamgage number USGS streamgage name

2017 flood peak AEP for observed 2017 flood

Expected peak streamflows for selected AEP with 

95-percent confidence limits (ft3/s)

50-percent AEP

(2-year recurrence)

20-percent AEP

(5-year recurrence)

Rank

Number of annual 

peaks in analysis

Date of peak 

streamflow

Peak stage (ft)

Peak streamflow 

(ft3/s)

AEP estimate

Recurrence 

interval (years)

67% confidence 

interval1

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

44 07069000 Black River at 

Pocahontas, Arkansas3

1 77 5/2/2017 28.95 105,000 1.0% 96 0.2% 2.3% 23,550 14,510 27,240 41,970 35,650 50,660 

45 07071500 Eleven Point River near 

Bardley, Missouri

1 97 4/30/2017 28.66 124,000 <0.20% >500 0.2% 1.8% 9,930 8,430 11,700 21,900 18,500 25,800 

46 07072000 Eleven Point River near 

Ravenden Springs, 

Arkansas

1 86 5/1/2017 27.90 137,000 <0.20% >500 0.2% 2.1% 12,700 11,000 14,700 25,500 21,800 29,800 

47 07074420 Black River at Elgin 

Ferry, Arkansas3

2 27 5/4/2017 33.99 173,000 0.83% 120 2.7% 11.5% 41,590 33,000 51,180 67,950 54,720 88,590 

48 07076750 White River at 

Georgetown, 

Arkansas5

1 38 5/8/2017 31.50 200,000 1.1% 90 0.5% 4.6% 69,300 59,400 81,000 102,000 87,000 124,000 

49 07077000 White River at DeValls 

Bluff, Arkansas5

2 47 5/10/2017 31.31 187,000 0.88% 114 2.1% 6.7% 71,900 63,600 80,800 101,000 89,200 115,000 

50 07077555 Cache River near Cotton 

Plant, Arkansas

1 31 5/5/2017 20.25 10,100 9.2% 11 0.6% 5.6% 6,790 6,080 7,590 8,750 7,930 9,660 

51 07185765 Spring River at Carthage, 

Missouri

2 30 4/29/2017 18.44 30,400 8.2% 12 2.5% 10.4% 9,430 7,380 12,000 19,200 15,400 24,000 

52 07186000 Spring River near Waco, 

Missouri

8 95 4/30/2017 28.14 55,800 8.2% 12 5.6% 11.0% 20,000 17,600 22,800 37,100 32,500 42,300 

53 07187000 Shoal Creek above Joplin, 

Missouri

4 94 4/29/2017 22.96 52,900 2.8% 36 2.3% 6.1% 7,700 6,580 9,000 16,500 13,900 19,500 

54 07189000 Elk River near Tiff City, 

Missouri3

2 78 4/29/2017 27.39 107,000 1.4% 70 0.9% 4.1% 22,200 18,700 26,400 43,400 37,000 51,000 

55 07191220 Spavinaw Creek near 

Sycamore, Oklahoma

2 58 4/29/2017 16.94 19,900 6.5% 15 1.3% 5.5% 4,270 3,220 5,660 10,100 8,090 12,500 

56 07195500 Illinois River near Watts, 

Oklahoma3

1 62 4/30/2017 30.12 128,000 0.31% 325 0.3% 2.8% 19,600 16,900 22,900 35,700 30,200 42,300 

57 07196000 Flint Creek near Kansas, 

Oklahoma3

3 58 4/29/2017 18.31 19,400 8.5% 12 2.4% 7.7% 4,170 3,230 5,370 10,800 8,450 13,800 

58 07261000 Cadron Creek near Guy, 

Arkansas

3 61 4/30/2017 23.57 18,000 7.6% 13 2.3% 7.3% 8,520 7,570 9,590 13,200 11,800 14,900 

59 07359610 Caddo River near Caddo 

Gap, Arkansas

3 29 4/30/2017 23.32 35,800 13.6% 7 4.9% 15.0% 19,400 16,300 23,000 30,900 25,800 37,000 

1

66.7% confidence intervals for observed AEP are determined nonparametrically. In some instances, the nonparametric results place bounds outside the estimate, making these 

confidence intervals nonsensical.

2

95% confidence limits or 90% confidence intervals (both imply 5% tails).

3

Streamflow affected to unknown degree by regulation or diversion.

4

Streamflow affected by urbanization.

5

Streamflow affected by regulation or diversion. Flood frequency analysis was conducted using only regulated period of record and at-site estimates of peak streamflows without 

weighting with rural regression equation estimates. 

6

Site is a spring. Expected peak streamflows were determined using only at-site estimates of peak streamflows without weighting with rural regression equation estimates.

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.—Continued

[ID, identifier; USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; AEP, annual exceedance probability; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold]
Temporal Changes in Annual Peak Streamflows 25

Expected peak streamflows for selected AEP with 95-percent confidence limits 

(ft3/s)

10-percent AEP

(10-year recurrence)

4-percent AEP

(25-year recurrence)

2-percent AEP

(50-year recurrence)

1-percent AEP

(100-year recurrence)

0.5-percent AEP

(200-year recurrence)

0.2-percent AEP

(500-year recurrence)

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Estimate

95% confidence 

limits2

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

Lower

Upper

55,890 46,590 71,790 74,960 60,050 108,800 90,050 70,120 144,100 105,700 80,070 185,800 122,100 89,880 233,700 144,700 102,600 306,000

32,300 27,000 38,700 48,200 39,400 59,100 61,100 48,800 76,500 74,700 58,300 95,700 89,000 68,000 116,000 107,000 79,200 146,000

37,300 31,100 44,700 56,600 45,700 70,200 72,800 57,300 92,600 90,300 69,300 118,000 108,000 81,500 144,000 134,000 96,800 184,000

88,090 69,730 123,700 116,400 89,000 184,100 139,600 103,300 243,500 164,400 117,400 317,700 191,200 131,400 410,300 229,700 149,700 568,300

125,000 105,000 160,000 155,000 127,000 216,000 179,000 142,000 266,000 203,000 158,000 325,000 228,000 172,000 394,000 262,500 190,000 502,000

120,000 106,000 141,000 145,000 125,000 179,000 164,000 138,000 212,000 183,000 151,000 248,000 202,000 163,000 289,000 227,000 178,000 350,000

9,920 8,820 11,200 11,300 9,730 13,100 12,200 10,300 14,500 13,100 10,800 16,000 -- -- -- 15,100 11,800 19,400

27,300 21,800 34,300 39,200 30,700 50,200 48,500 37,200 63,300 58,100 43,700 77,300 68,100 50,300 92,200 80,800 57,600 113,000

50,500 43,600 58,500 69,900 58,900 83,000 85,600 70,400 104,000 102,000 82,100 127,000 120,000 94,300 152,000 143,000 108,000 188,000

24,400 20,200 29,600 36,800 29,400 46,100 46,900 36,500 60,200 57,300 43,600 75,300 67,900 50,600 91,000 82,300 59,100 115,000

59,600 49,600 71,500 81,200 65,900 100,000 98,000 77,900 123,000 114,000 89,200 147,000 132,000 101,000 172,000 154,000 114,000 208,000

15,400 12,000 19,800 24,000 17,600 32,800 32,100 22,800 45,200 41,300 28,300 60,300 -- -- -- 67,100 42,000 107,000

48,600 40,100 58,900 67,000 52,800 85,100 81,300 61,700 107,000 96,200 70,200 132,000 -- -- -- 134,000 88,100 203,000

17,200 13,300 22,300 27,700 20,300 37,800 37,100 26,300 52,300 48,000 32,700 70,400 -- -- -- 79,200 48,400 130,000

16,400 14,500 18,700 20,600 17,600 24,000 23,700 19,800 28,400 26,900 21,900 33,000 -- -- -- 34,300 26,300 44,900

38,900 31,700 47,800 49,400 38,800 63,000 57,300 43,600 75,200 65,400 48,200 88,800 -- -- -- 85,000 58,100 125,000

Table 3. Estimated annual exceedance probability of the 2017 flood peaks and weighted peak streamflow estimates for selected flood 

quantiles at 59 U.S. Geological Survey streamgages included in this study.—Continued

[ID, identifier; USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; AEP, annual exceedance probability; %, percent; --, not calculated; stations 

with peak of record during April–May 2017 flood are shown with rank value of “1” in bold]
26 Flooding in the Southern Midwestern United States, April–May 2017

Figure 10. Spatial distribution of the magnitude of annual exceedance probabilities of peak streamflows at 59 U.S. Geological 

Survey streamgages for the April–May 2017 flood.

98° 96° 94° 92° 90° 88° 86°

40°

38°

36°

34°

32°

EXPLANATION

Greater than 10

4.1 to 10

2.1 to 4.0

1.1 to 2.0

0.21 to 1.0

Less than 0.2

0 50 100 MILES

0 50 100 KILOMETERS

Flood annual exceedance probability (AEP)

in percent-- Number is map identifier (table 3)

1

2

3

4

5

6

7

8

9

16

20

26

27 24

25

23

22

21

32

40

28

29

31

30

39

41

42

45 43

46

44

47

48

49

50 58

59

55

56 57

51 52

53

54

11

12 13

10

14

15

34 33

35

36

37 38

17

18

19

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

Kansas

Missouri

Illinois

Indiana

Kentucky

Tennessee

Oklahoma

Arkansas

Mississippi

Texas

Nebraska

Iowa

Ohio

Mississippi Alabama

Georgia

Louisiana
Temporal Changes in Annual Peak Streamflows 27

Figure 11. Percentage changes in median annual peak streamflow values for selected U.S. Geological Survey 

streamgages for A, 1930–2017; B, 1956–2017; C, 1975–2017; and D, 1989–2017.

Ó

# #

#

##

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

9

7

6

3

57

56

54

53

52

46

45 43

41

38 37

35

33

32

31 28

27

26

25

24

23

22

20

19

18

17

16

12

58

42

98° 96° 94° 92° 90° 88° 86°

39°

38°

37°

36°

35°

34°

# 0.10 to 2.0 Ó -0.13 to -0.10

# 2.01 to 4.0

# 4.01 to 6.0

# 6.01 to 8.0

# 8.01 to 10.0

EXPLANATION

Percent change of the median annual peak streamflow per year and map ID (see table 1)

Positive Negative No change

Study area

-0.099 to 0.099

Not all ranges are represented on map

12

12

12

12

12 12 12

Kansas

Oklahoma

Arkansas

Texas Mississippi

A.

B.

#

#

#

#

# #

#

#

#

#

#

#

# #

#

#

#

#

#

Ó

53

3

52

46

45 43

42 41

35

31

28

27

26

24

23

22

20

19

18

17

98° 96° 94° 92° 90° 88° 86°

39°

38°

37°

36°

35°

34°

0 50 100 MILES

0 50 100 KILOMETERS

Alabama

Tennessee

Kentucky

Indiana

Illinois

Missouri

Kansas

Oklahoma

Arkansas

Texas Mississippi Alabama

Tennessee

Kentucky

Indiana

Illinois

Missouri

1930 2017

1956 2017

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)
28 Flooding in the Southern Midwestern United States, April–May 2017

#

#

#

# #

# #

#

#

#

#

#

#

#

# #

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

# # #

#

# #

#

#

#

#

9

7

6

5

4

3

2

1

58

57

56 55

54

53

52

51

46

45 43

41

38 37 35

34

33

32

31 28

27

26

25

24

23

22

20

19

18

17

16

15 14 12

10

42

98° 96° 94° 92° 90° 88° 86°

39°

38°

37°

36°

35°

34°

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

# #

#

#

#

#

9

7

6

5

4

3

2

1

58

57

55 56

54

53

52

51

50

46

45 43

42

41

38 37

36

35

34 33

31 32

30

29

28

27

26

25

24

23

22

20

19

18

17

16

15 14

12

10

59

98° 96° 94° 92° 90° 88° 86°

39°

38°

37°

36°

35°

34°

Kansas

Oklahoma

Arkansas

Texas Mississippi Alabama

Tennessee

Kentucky

Indiana

Illinois

Missouri

Kansas

Oklahoma

Arkansas

Texas Mississippi Alabama

Tennessee

Kentucky

Indiana

Illinois

Missouri

1975 2017

1989 2017

# 0.10 to 2.0 Ó -0.13 to -0.10

# 2.01 to 4.0

# 4.01 to 6.0

# 6.01 to 8.0

# 8.01 to 10.0

EXPLANATION

Percent change of the median annual peak streamflow per year and map ID (see table 1)

Positive Negative No change

Study area

-0.099 to 0.099

Not all ranges are represented on map

12

12

12

12

12 12 12

Base from U.S. Geological Survey, 1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

C.

D.

0 50 100 MILES

0 50 100 KILOMETERS

Figure 11. Percentage changes in median annual peak streamflow values for selected U.S. Geological Survey 

streamgages for A, 1930–2017; B, 1956–2017; C, 1975–2017; and D, 1989–2017.—Continued
Temporal Changes in Annual Peak Streamflows 29

Figure 12. Percentage change in the median annual precipitation by climate division within the study area for A, 1930–2016;

B, 1956–2016; C, 1975–2016; and D, 1989–2016.

Illinois

Indiana

2305

2304

2303

2302

303

306

304

3403

302

2301

3406

305

301

307

1106

1109 1108

2306

1207

96° 94° 92° 90° 88°

39°

38°

37°

36°

35°

34°

2305

2304

2303

2302

303

306

304

3403

302

2301

3406

305

301

307

1106

1109 1108

2306

1207

96° 94° 92° 90° 88°

39°

38°

37°

36°

35°

34°

2305

2304

2303

2302

303

306

304

3403

302

2301

3406

305

301

307

1106

1109 1108

2306

1207

96° 94° 92° 90° 88°

39°

38°

37°

36°

35°

34°

2305

2304

2303

2302

303

306

304

3403

302

2301

3406

305

301

307

1106

1109 1108

2306

1207

96° 94° 92° 90° 88°

39°

38°

37°

36°

35°

34°

1930–2016 1956–2016

1975–2016 1989–2016 Base from U.S. Geological Survey, 

1:2,000,000-scale data, 2005

Albers Equal-Area Projection

North American Datum of 1983 (NAD83)

Kansas

Oklahoma

Texas Arkansas

Mississippi

Missouri

Alabama

Tennessee

Kentucky

Illinois

Indiana

Kansas

Oklahoma

Texas Arkansas

Mississippi

Missouri

Alabama

Tennessee

Kentucky

Illinois

Indiana

Kansas

Oklahoma

Texas Arkansas

Mississippi

Missouri

Alabama

Tennessee

Kentucky

Illinois

Indiana

Kansas

Oklahoma

Texas Arkansas

Mississippi

Missouri

Alabama

Tennessee

Kentucky

0 50 100 MILES

0 50 100 KILOMETERS

EXPLANATION

Flood study area

Climate division and identifier

Percent change of the median annual precipitation, per year

Positive change, 0.1 to 0.62

No change, -0.099 to +0.099

Negative change -0.1 to -0.9

301

301

301

A B

C D
30 Flooding in the Southern Midwestern United States, April–May 2017

Figure 13. Change in frequency of daily high intensity (greater than 2–3 in.) precipitation from the long-term (1900–2014) average, 

by state.

Years

Values are averages

from 21 long-term 

stations

Values are averages

from 43 long-term 

stations

Values are averages

from 16 long-term 

stations

Values are averages

from 22 long-term 

stations

Values are averages

from 28 long-term 

stations

Number of events with

precipitation greater than 2 inches

Number of events with

precipitation greater than 2 inches

Number of events with

precipitation greater than 2 inches

Number of events with

precipitation greater than 2 inches

Number of events with

precipitation greater than 2 inches

Long-term average 
References Cited 31

Summary

Excessive rainfall resulted in flooding on numerous rivers 

throughout the southern Midwestern United States in late 

April and early May of 2017. Tropical moisture lifted over a 

stalled frontal system caused heavy rains from Texas to Ohio 

between April 28 and May 10, resulting in extensive flooding from eastern Oklahoma to southern Indiana including 

parts of Missouri, Arkansas, and Illinois. The heaviest rainfall 

amounts during April 28–30 occurred over extreme northeast 

Oklahoma and northern Arkansas, across the southern half of 

Missouri, southern Illinois, and southern Indiana, and included 

totals of 6 to 10 inches with some isolated higher amounts.

Peak-of-record streamflows were set at 21 U.S. Geological Survey streamgages in the southern Midwest during the 

resulting April May 2017 flooding. Each of the five states 

included in the study area had at least one streamgage with a 

peak of record during the flood. The annual exceedance probability (AEP) estimates for the April May 2017 flood peak 

streamflows indicate that peaks at 5 USGS streamgages had an 

AEP of 0.2 percent or less, and peak streamflows at 15 USGS 

streamgages had an AEP in the range from greater than 0.2 to 

1 percent.

Examination of the magnitude of the temporal changes 

in median annual peak streamflows indicated positive 

increases, in general, throughout the study area for each of the 

1930–2017, 1956–2017, 1975–2017, and 1989–2017 analysis 

periods. The median increase in peak streamflows was greatest in the 1975–2017 and 1989–2017 periods with maximum 

increases of 8–10 percent per year. No stations in either the 

1975–2017 or 1989–2017 analysis period had median negative 

changes in peak streamflows.

A primary driver of change in peak streamflows is 

precipitation, but the changes in annual precipitation provided 

little explanation for the substantial increase in the magnitude 

of streamflow peaks in the 1989–2017 analysis period. The 

increase in the magnitude of the positive changes in annual 

peak streamflows during this period likely is better explained 

by a change in the frequency of larger magnitude rain events 

(greater than 2 or 3 inches) with time.

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Veilleux, A.G., Cohn, T.A., Flynn, K.M., Mason, R.R., and 

Hummel, P.R., 2013, Estimating magnitude and frequency 

of floods using the PeakFQ 7.0 program: U.S. Geological 

Survey Fact Sheet 2013–3108, 2 p.
References Cited 33

Wagner, D.M., Krieger, J.D., and Veilleux, A.G., 2016, 

Methods for estimating annual exceedance probability 

discharges for streams in Arkansas, based on data through 

water year 2013: U.S. Geological Survey Scientific Investigations Report 2016–5081, 136 p., https://doi.org/10.3133/

sir20165081. 

Gasconade River near Rich Fountain, Mo., May 1, 2017. Photograph by Larry Buschmann, USGS.
Above: USGS hydrologist tethering acoustic Doppler 

current profiler (ADCP), Black River near Poplar Bluff, Mo., 

May 1, 2017. Photograph by Chris Rowden, USGS.
Glossary 35

Glossary

Note: Glossary definitions are from Langbein and Iseri (1960), Holmes and others (2010), 

and National Weather Service (2017a).

annual exceedance probability (AEP) The 

probability, or chance, of a flood of a given 

streamflow magnitude being equaled or 

exceeded in any given year. The probability 

can be expressed as a fraction, decimal, or 

percentage. 

annual exceedance probability flood quantile 

(AEP flood quantile) The value of the peak 

streamflow that corresponds to a particular 

annual exceedance probability (for example, 

1-percent AEP flood quantile) 

Bulletin 17B Report by the Interagency 

Advisory Committee on Water Data (1982) 

that delineates the recommended method for 

flood-probability analysis in the United States. 

Bulletin17C Report published by the U.S. 

Geological Survey in 2017 representing the 

efforts of the Advisory Committee on Water 

Information, that updates the methods for 

flood-probability analysis in the United States 

presented in Bulletin 17B.

confidence limits To gauge the accuracy 

of an approximation based on a probability 

distribution, upper and lower confidence 

limits can be estimated based on the properties of the probability distribution. This report 

includes the 95-percent confidence limits of 

the estimate of the flood quantiles as computed by the methods outlined in Bulletin 

17B.

discharge In its simplest concept discharge 

means outflow; therefore, the use of this term 

is not restricted as to course or location, and 

it can be applied to describe the flow of water 

from a pipe or from a drainage basin.

expected moment algorithm The expected 

moment algorithm (EMA) is an updated 

method for fitting the log pearson type III 

probability distribution that is a more effective means of incorporating historical peak 

streamflow information into a flood-frequency 

analysis than the previous Bulletin 17B 

method. The EMA can accommodate interval 

data, which simplifies analysis of datasets 

containing historic data, potentially influential 

low flows (PILFs), and uncertain data points 

while also providing enhanced confidence 

intervals on the estimated peak streamflows.

flood An overflow or inundation that comes 

from a river or other body of water, and 

causes or threatens damage.

flood peak The highest value of the stage 

or streamflow attained by a flood; often 

designated as peak stage or peak streamflow 

respectively.

flood quantile See “annual exceedance 

probability flood quantile.”

flood stage The stage at which overflow of 

the natural banks of a stream begins to cause 

damage in the reach in which the water surface elevation is measured.

hydrograph A graph showing stage, streamflow, velocity, or other property of water with 

respect to time.

log-Pearson Type III probability distribution One of the family of probability 

distributions developed by Karl Pearson that 

is used in the United States as a best-fit for the 

distribution of annual peak flood streamflows 

in the Bulletin 17B analysis procedures developed by the Interagency Advisory Committee 

on Water Data (1982).

peak-of-record streamflow The largest 

instantaneous streamflow value for the period 

that data have been collected.

peak stage See “flood peak.”

peak streamflow See “flood peak.”

precipitation As used in hydrology, precipitation is the discharge of water, in liquid or 

solid state, out of the atmosphere, generally 

upon a land or water surface. It is the common 

process by which atmospheric water becomes 

surface or subsurface water. The term “precipitation” also is commonly used to designate 

the quantity of water that is precipitated.

probability A means to express the likelihood of something occurring, also known as 

chance. The probability can be expressed as a 

fraction, decimal, or percentage.
36 Flooding in the Southern Midwestern United States, April–May 2017

probability distribution Describes the range 

of possible values that a random variable can 

attain and the probability that the value of the 

random variable is within any subset of that 

range.

recurrence interval The average interval of 

time within which the given flood is expected 

to be equaled or exceeded once.

regional regression equation (RRE) Equation developed through use of regression 

techniques that relate the flood-probability 

data at many streamgages in a region to the 

basin characteristics of the streams monitored 

by the streamgages. For any location along a 

stream, a user can enter the basin characteristics (drainage area, basin slope, and so forth) 

as independent variables into the equations 

and compute various flow characteristics 

(for example, 1-percent AEP flood quantile, 

2-percent AEP flood quantile, and annual 

mean streamflow).

Sen’s slope estimate A nonparametric 

estimate of trend based on the median slope of 

data pairs in a time series.

stage Height of a water surface above an 

established datum, also known as gage height.

stationary front A front between warm and 

cold air masses that is moving very slowly or 

not at all.

streamflow The discharge that occurs in a 

natural channel. Although the term discharge 

can be applied to flow in a canal, the word 

streamflow uniquely describes the discharge 

in a surface stream course. The units of measurement often are reported in cubic feet per 

second (ft3/s).

streamgage A particular site on a stream 

where a record of streamflow is obtained.

trend The change of a particular variable 

with either time or spatial location as computed by statistical analysis.

Spavinaw Creek near Sycamore, Okla., April 29, 2017. Photograph by U.S. Geological Survey.

For more information about this publication, contact

Director, USGS Missouri Water Science Center 

1400 Independence Road

Rolla, MO 65401

(573) 308–3667

For additional information visit https://mo.water.usgs.gov

Publishing support provided by the 

Rolla Publishing Service Center
Back cover. USGS hydrologic technician wading St. Francis 

River near Patterson, Mo., April 30, 2017. Photograph by Josh 

Keele, USGS.
Heimann and others—Flooding in the Southern Midwestern United States, April–May 2017—Open-File Report 2018–1004

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20181004