U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1301

Prepared in cooperation with the Iowa Department of Transportation and Iowa Highway 

Research Board (Project HR–140)

Floods of July 23–26, 2010, in the Little Maquoketa River 

and Maquoketa River Basins, Northeast Iowa

Maquoketa River 

Basin 

Little Maquoketa

River Basin

IOWA
Cover. Map of Iowa showing location of Little Maquoketa River and Maquoketa River Basins.
Floods of July 23–26, 2010, in the Little 

Maquoketa River and Maquoketa River 

Basins, Northeast Iowa

By David A. Eash

Prepared in cooperation with the Iowa Department of Transportation and Iowa 

Highway Research Board (Project HR–140)

Open-File Report 2011–1301

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Eash, D.A., 2012, Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast 

Iowa: U.S. Geological Survey Open-File Report 2011–1301, 45 p. with appendix.

ISBN 978–1–4113–3317–8
iii

Acknowledgments

The author expresses his gratitude to the following: Harry Hillaker, State Climatologist, Iowa 

Department of Agriculture and Land Stewardship, for providing an isohyetal map of rainfall for 

the 72-hour period ending 7:00 a.m. on July 24, 2010; Bonnie Shepard, National Flood Insurance 

Program Bureau and Statistical Agent, Federal Emergency Management Agency, for providing 

private property damage claims for nine counties in Iowa; and Dennis Harper, State Hazard 

Mitigation Officer, Iowa Homeland Security and Emergency Management Division, for providing 

public assistance project costs for nine counties in Iowa. 

The author also expresses gratitude to the following U.S. Geological Survey employees: Mike 

Linhart, Brian Imig, Doug Goodrich, Kevin Townsend, Garret Welsh, Jon Nania, and Clint Van 

Schepen for collecting field data for the determination of water-surface and bench-mark elevations listed in this report; and Kaylene Carney for obtaining newspaper articles for the compilation of flood description information.

Contents

Acknowledgments........................................................................................................................................iii

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

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

Purpose and Scope ..............................................................................................................................3

Study Area..............................................................................................................................................4

Flood History...................................................................................................................................................5

Floods of July 23–26, 2010.............................................................................................................................6

Annual Flood Probability......................................................................................................................6

Storm Description.................................................................................................................................9

Flood Description................................................................................................................................12

Little Maquoketa River Basin...................................................................................................12

Maquoketa River Basin ............................................................................................................12

Chronology of Flood Impacts ............................................................................................................14

Breach of Lake Delhi Dam.................................................................................................................14

Flood Profile..................................................................................................................................................15

Summary........................................................................................................................................................17

References Cited..........................................................................................................................................17

Figures 5–18..................................................................................................................................................19

Appendix........................................................................................................................................................35

List of Bench Marks and Reference Points....................................................................................36
iv

Figures

1. Map showing Little Maquoketa River and Maquoketa River Basins and lines of equal 

rainfall for 72 hours ending at 7:00 a.m. on July 24, 2010 .......................................................2

2. Map showing Little Maquoketa River and Maquoketa River Basins and landform 

regions of Iowa .............................................................................................................................4

3. Graphs showing hourly rainfall for July 22–24, 2010, at three rain gages in the 

Maquoketa River Basin and vicinity........................................................................................10

4. Graphs showing discharge hydrographs for streamgages on the Maquoketa River and 

the North Fork Maquoketa River, July 22–29, 2010 ...............................................................13

5. Graph showing profile of the July 23, 2010, flood for the Little Maquoketa River and the 

North Fork Little Maquoketa River, river miles 4 to 23..........................................................20

6. Graph showing profile of the July 23, 2010, flood for the Little Maquoketa River and the 

North Fork Little Maquoketa River, river miles 4 to 12..........................................................21

7. Graph showing profile of the July 23, 2010, flood for the North Fork Little Maquoketa 

River, river miles 12 to 23 ...........................................................................................................22

8. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 2 to 144 ...............................................................................................................................23

9. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 2 to 30 .................................................................................................................................24

10. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 30 to 60 ...............................................................................................................................25

11. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 60 to 90 ...............................................................................................................................26

12. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 90 to 120 .............................................................................................................................27

13. Graph showing profile of the July 23–26, 2010, flood for the Maquoketa River, river 

miles 120 to 144 ...........................................................................................................................28

14. Graph showing profile of the July 23–24, 2010, flood for the North Fork Maquoketa 

River, river miles 0 to 90 .............................................................................................................29

15. Graph showing profile of the July 23–24, 2010, flood for the North Fork Maquoketa 

River, river miles 0 to 25 .............................................................................................................30

16. Graph showing profile of the July 23–24, 2010, flood for the North Fork Maquoketa 

River, river miles 25 to 50 ...........................................................................................................31

17. Graph showing profile of the July 23–24, 2010, flood for the North Fork Maquoketa 

River, river miles 50 to 75 ...........................................................................................................32

18. Graph showing profile of the July 23–24, 2010, flood for the North Fork Maquoketa 

River, river miles 75 to 100 .........................................................................................................33
v

Tables

1. National Flood Insurance Program Bureau and Statistical Agent Iowa claims

closed with payment for selected counties, July 23–26, 2010, dates of loss, as of

February 28, 2011 ..........................................................................................................................3

2. Iowa Public Assistance Program project costs for selected counties for disaster

number 1930, June–August 2010, as of April 29, 2011 ............................................................3

3. Maximum stages and discharges for 2010 and selected largest-flood years, and

the corresponding annual flood-probability ranges, at streamgages in the Little

Maquoketa River and Maquoketa River Basins, Iowa...........................................................7

4. Annual flood probability and equivalent flood recurrence interval for selected

probabilities ...................................................................................................................................9

5. Twenty-four-hour rainfall amounts at selected rain gages in northeast and

east-central Iowa during July 22–24, 2010 .............................................................................11

6. Magnitude and annual probability of theoretical rainfall amounts for selected

storm periods in the East-Central and Northeast Iowa Climatological Divisions............11

7. Locations and elevations of high-water marks used in the Little Maquoketa River

and North Fork Little Maquoketa River flood profiles of July 23, 2010...............................15

8. Locations and elevations of high-water marks used in the Maquoketa River flood

profile of July 23–26, 2010..........................................................................................................16

9. Locations and elevations of high-water marks used in the North Fork Maquoketa

River flood profile of July 23–24, 2010 .....................................................................................16

Appendix Table

1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa

River, North Fork Little Maquoketa River, Maquoketa River, and North Fork

Maquoketa River flood profiles ................................................................................................37
vi

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

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

Elevation or vertical coordinate information is referenced to the National Geodetic Vertical 

Datum of 1929 (NGVD 29). Elevation refers to distance above or below NGVD 29. NGVD 29 can 

be converted to the North American Vertical Datum of 1988 by using the National Geodetic 

Survey conversion utility available at http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html.

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

Map projections are Universal Transverse Mercator, Zone 15

Water year is the 12-month period from October 1 through September 30. The water year 

is designated by the calendar year in which the water year ends and that includes 9 of the 

12 months. Thus, the water year ending September 30, 2010, is called the “2010 water year.”
Floods of July 23–26, 2010, in the Little Maquoketa River 

and Maquoketa River Basins, Northeast Iowa

By David A. Eash

Abstract

Minor flooding occurred July 23, 2010, in the Little 

Maquoketa River Basin and major flooding occurred 

July 23–26, 2010, in the Maquoketa River Basin in northeast Iowa following severe thunderstorm activity over the 

region during July 22–24. A breach of the Lake Delhi Dam 

on July 24 aggravated flooding on the Maquoketa River. Rain 

gages at Manchester and Strawberry Point, Iowa, recorded 

72-hour-rainfall amounts of 7.33 and 12.23 inches, respectively, on July 24. The majority of the rainfall occurred during 

a 48-hour period. Within the Little Maquoketa River Basin, 

a peak-discharge estimate of 19,000 cubic feet per second 

(annual flood-probability estimate of 4 to 10 percent) at the 

discontinued 05414500 Little Maquoketa River near Durango, 

Iowa streamgage on July 23 is the sixth largest flood on 

record. Within the Maquoketa River Basin, peak discharges 

of 26,600 cubic feet per second (annual flood-probability estimate of 0.2 to 1 percent) at the 05416900 Maquoketa River at 

Manchester, Iowa streamgage on July 24, and of 25,000 cubic 

feet per second (annual flood-probability estimate of 1 to 

2 percent) at the 05418400 North Fork Maquoketa River near 

Fulton, Iowa streamgage on July 24 are the largest floods on 

record for these sites. A peak discharge affected by the Lake 

Delhi Dam breach on July 24 at the 05418500 Maquoketa 

River near Maquoketa, Iowa streamgage, located downstream 

of Lake Delhi, of 46,000 cubic feet per second on July 26 is 

the third highest on record.

High-water marks were measured at five locations along 

the Little Maquoketa and North Fork Little Maquoketa Rivers 

between U.S. Highway 52 near Dubuque and County Road 

Y21 near Rickardsville, a distance of 19 river miles. Highwater marks were measured at 28 locations along the Maquoketa River between U.S. Highway 52 near Green Island and 

State Highway 187 near Arlington, a distance of 142 river 

miles. High-water marks were measured at 13 locations along 

the North Fork Maquoketa River between Rockdale Road near 

Maquoketa and U.S. Highway 52 near Luxemburg, a distance 

of 90 river miles. The high-water marks were used to develop 

flood profiles for the Little Maquoketa, North Fork Little 

Maquoketa, Maquoketa, and North Fork Maquoketa Rivers.

Introduction

Severe thunderstorms during July 22–24, 2010, following record statewide precipitation in June, caused minor 

flooding on the Little Maquoketa River and record flooding on the Maquoketa and North Fork Maquoketa Rivers, in 

northeast Iowa during July 23–26, 2010. New maximum peak 

discharges were recorded on July 24, 2010, at streamgages 

05416900 Maquoketa River at Manchester, Iowa (fig. 1, site 

8) and 05418400 North Fork Maquoketa River near Fulton 

(fig. 1, site 15). Record flooding on the Maquoketa River in 

the vicinity of Manchester led to the breach of the Lake Delhi 

Dam downstream of Manchester on July 24. The July 22–24 

storms also caused significant flooding in parts of adjacent 

watersheds and along reaches of the Turkey, Volga, and Wapsipinicon Rivers (fig. 1). 

Because of the flooding in the Little Maquoketa River 

and Maquoketa River Basins, the counties of Buchanan, 

Clayton, Delaware, Dubuque, Jackson, and Jones were added 

to a State disaster proclamation during July 23–26, 2010, 

which authorized implementation of the State Individual 

Assistance Grant Program to assist eligible residents of those 

counties (http://www.iowahomelandsecurity.org/news_room/

press_releases.html, accessed July 5, 2011). A Federal disaster 

declaration (number 1930) was issued on July 29, 2010, to 

help Iowans recover from losses caused by severe storms, 

flooding, and tornados for the incident period June 1 to 

August 31, 2010 (Federal Emergency Management Agency, 

2010). The Federal disaster declaration requested individual 

assistance for 38 counties and public assistance for 59 counties 

in Iowa. Private property damage claims reported for residential and nonresidential buildings in nine selected counties in 

northeast Iowa are shown in table 1 (Bonnie Shepard, Federal 

Emergency Management Agency, National Flood Insurance 

Program Bureau and Statistical Agent, written commun., 

May 2011). Approved public assistance costs (assistance to 

local governments for the repair of disaster-damaged public 

facilities) for the same nine counties in Iowa are shown in 

table 2 (Dennis Harper, Iowa Homeland Security and Emergency Management Division, State Hazard Mitigation Officer, 

written commun., April 2011).
Williams

Creek

Oelwein

Stanley

FAYETTE CO

CLAYTON CO

Gutte

Coggon 

Anamosa

DUBUQ

BUCHANAN

CO

DELAWARE

CO

LINN CO JONES CO

4

6 8

12

10

10

8

6

4

2

1

Maquoketa River  Basin

Little Maquoketa River Basin

WISCONSIN

ILLINOIS

IOWA

Turkey

W

River

apsipinicon River

VolgaRiver

20

52

187

38

38

20

6

3

Sherrill

7

2 5

1

9

12

13

4

8

11

16

17

14

15

18

0 5 10 MILES0 5 10 KILOMETERS

4

4

151

61

3

13

136

62

64

38

136

StrawberryPoint

Lamont

Dundee

10

Manchester Earlville

Delhi

Dyersville

Worthington

Hopkinton

Quaker Mill

Dam

New Vienna

Luxemburg

Rickardsville

Sageville

Dubuque

Graf

Arlington

Maquoketa Maquoketa

River

South Fork

Lamont Creek

Coffin s Creek

Honey

Creek

Plum

River

Creek

Lake Delhi

Dam

Little

Maquoketa

Middle Fork

North

Fork

Little Maquoketa Rivertributary

Bloody Runtributary

Durango

Spragueville

Charlotte

Maquoketa

Canton Fulton Andrew

Baldwin

Monmouth

Onslow

ScotchGrove

Monticello

Cascade

Langworthy

Kitty

Cr

Bear

Creek

Fork

Maquoketa

River

River

Maquoketa

North Base from U.S. Geological Survey digital data, 2006, 1:24,000 Universal Transverse Mercator projection

Zone 15

EXPLANATION

Municipal area within basinsRiver reach profiled in this reportDrainage basin boundaryLine of equal rainfall

—In inches, for 

72 hours ending at 7:00 a.m., July 24, 2010 (Harry Hillaker, State Climatologist, Iowa Department of Agriculture and Land Stewardship, written commun., 2011)

Streamgage and map number (table 3)Crest-stage gage and map number (table 3)Ungaged bridge site used in profile

109

91°30’

90°30’

42°

42°30’

12

12

10

12

10

8

8

6

4

2

6

BACKBONE

STATE PARK

Sand Creek

Lakehurst

Dam

Figure 1. Little Maquoketa River and Maquoketa River Basins and lines of equal rainfall for 72 hours ending at 7:00 a.m. on July 24, 2010.
Introduction 3

Table 1. National Flood Insurance Program Bureau 

and Statistical Agent Iowa claims closed with payment 

for selected counties, July 23–26, 2010, dates of loss, 

as of February 28, 2011.

[Source: Bonnie Shepard, Federal Emergency Management 

Agency, National Flood Insurance Program Bureau and Statistical Agent, written commun., May 2011. NC, no claims]

County Number

of claims

Damage payment 

(dollars)

Buchanan 18 97,125

Clayton 1 35,754

Clinton NC NC

Delaware 27 1,425,560

Dubuque 8 178,003

Fayette 7 31,185

Jackson NC NC

Jones 12 1,244,501

Linn 4 40,883

Total 77 3,053,011

Purpose and Scope

This report is part of an on-going program of preparing 

water-surface profiles of major floods on streams in Iowa. The 

program is managed by the U.S. Geological Survey (USGS) 

in cooperation with the Iowa Department of Transportation 

(Iowa DOT) and the Iowa Highway Research Board (Project 

HR–140). Flood-peak and water-surface-elevation profile 

information is needed for the economical and safe location and 

design of bridges and other structures on or over streams and 

the adjacent flood plains. Defining the limits of flood inundation and establishing encroachment limits on flood plains are 

related issues dependent on this information. Data for major 

floods are needed to compute annual flood-probability discharges and to calibrate water-surface-elevation profile models 

for sites along streams. A list of other USGS flood-profile 

reports for Iowa can be obtained by accessing http://ia.water.

usgs.gov/projects/profiles/.

This report provides information about July 22–24, 

2010, rainfall and flooding during July 23–26, 2010, in the 

Little Maquoketa River and Maquoketa River Basins, and 

estimated annual flood-probability ranges at eight continuousrecord streamgages and ten crest-stage gages (CSG) in the 

basins. High-water marks (HWMs) at selected sites along the 

Little Maquoketa and North Fork Little Maquoketa Rivers 

are presented in a flood profile from U.S. Highway 52 near 

Dubuque to County Road Y21 (not shown in fig. 1) near 

Rickardsville, a distance of 19 river miles. HWMs at selected 

sites along the Maquoketa River are presented in a flood 

profile from U.S. Highway 52 near Green Island (not shown 

in fig. 1) to State Highway 187 near Arlington, a distance of 

142 river miles. HWMs at selected sites along the North Fork 

Table 2. Iowa Public Assistance Program project costs for selected counties for disaster number 1930, June–August 2010, as of 

April 29, 2011.

[Source: Dennis Harper, Iowa Homeland Security and Emergency Management Division, State Hazard Mitigation Officer, written commun., April 29, 2011. 

NC, no claims]

County 

Number

of 

applicants

Debris 

removal

Emergency 

protective 

measures 

Roads and 

bridges

Water 

control 

facilities

Buildings 

and 

equipment

Utilities Parks 

and other Total

Cost (dollars) 1

Buchanan 9 26,254 55,037 121,139 NC 3,849 1,370 27,378 235,027

Clayton 6 2,085 14,947 476,510 NC NC NC 4,522 498,064

Clinton 0 NC NC NC NC NC NC NC NC

Delaware 10 64,971 111,463 426,762 14,139 NC 183,060 66,447 866,843

Dubuque 13 121,208 97,095 459,521 29,346 22,572 64,954 97,072 891,768

Fayette 3 3,420 15,729 232,176 28,263 3,400 9,908 7,770 300,667

Jackson 5 17,965 91,999 154,818 NC NC 4,426 58,955 328,163

Jones 12 46,785 124,761 90,860 0 78,388 251,489 36,716 629,001

Linn 0 NC NC NC NC NC NC NC NC

Total 58 282,688 511,031 1,961,787 71,749 108,210 515,207 298,860 3,749,532

1Cost rounded to whole dollars.
4 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

Maquoketa River are presented in a flood profile from Rockdale Road (not shown in fig. 1) near Maquoketa to U.S. Highway 52 near Luxemburg, a distance of 90 river miles.

Study Area

The Little Maquoketa River and Maquoketa River 

Basins are adjacent watersheds in northeast Iowa with the 

Little Maquoketa River Basin draining from west to east 

and the Maquoketa River Basin draining from northwest to 

southeast. The two drainage basins, the river reaches profiled, 

the location of USGS streamgages within these river basins, 

and the location of bridge sites used in the July 23–26, 2010, 

flood profiles are shown in figure 1. The Little Maquoketa 

River and Maquoketa River Basins lie within three of Iowa’s 

landform regions (fig. 2), the Iowan Surface, the East-Central 

Iowa Drift Plain, and the Paleozoic Plateau. The Iowan 

Surface landform region is a low-relief plain with wellestablished, low-gradient drainage networks. Topography of 

this region appears slightly inclined to gently rolling with 

long slopes and open views to the horizon (Prior, 1991). 

Soils of this region are characterized as thin, discontinuous 

loess or loam and clay loam over glacial drift (Prior, 1991; 

Oschwald and others, 1965). The East-Central Iowa Drift 

Plain is similar to the Southern Iowa Drift Plain, and was 

formerly included as part of the Southern Iowa Drift Plain 

and the Iowan Surface, but is now considered a separate 

landform because of its uniqueness (Prior and others, 2009). 

This region differs from the Southern Iowa Drift Plain with 

41°

42°

43°

96° 95° 94° 93° 92°

91°

Landform region

[Priot, Kohrt, and Quade, Iowa Geological Survey, 2006 (edited 2009)]

East-Central Iowa Drift Plain

Des Moines Lobe

Iowa-Cedar Lowland

Iowan Surface

Loess Hills

Missouri River Alluvial Plain

Mississippi River Alluvial Plain

Northwest Iowa Plains

Paleozoic Plateau

Southern Iowa Drift Plain

0 15 30 KILOMETERS

0 15 30 MILES

EXPLANATION

Main branch Little Maquoketa and Maquoketa Rivers

Drainage basin bounday 

Base from U.S. Geological Survey digital data, 2006, 1:24,000

Universal Transverse Mercator projection

Zone 15

Little Maquoketa River

Basin

Maquoketa River

Basin

Figure 2. Little Maquoketa River and Maquoketa River 

Basins and landform regions of Iowa.
Flood History 5

bedrock closer to the surface and more bedrock outcropping. 

Topography of the region consists of steeply rolling hills 

and valleys. A mantle of loess covers the uplands and upper 

hill slopes. Soils in this region are characterized as loess 

over glacial till or limestone bedrock (Oschwald and others, 

1965). The Paleozoic Plateau landform region has a bedrockdominated, erosional topography that is characterized by 

plateau-like uplands, integrated drainage networks with steep 

gradients, and deeply entrenched valleys (Prior, 1991; Horick 

and Soenksen, 1989; Iowa Natural Resources Council, 1958). 

Stream erosion and hillslope development have stripped away 

glacial deposits from all but limited areas of this region. Karst 

topography exists in the Paleozoic Plateau where carbonate 

rocks are present at depths of less than 50 feet (ft) beneath the 

land surface. Dissolution of these carbonate rocks (limestone 

and dolomite) by groundwater enlarges cracks and crevices in the bedrock which can result in surface depressions, 

sinkholes, caves, caverns, and springs. Where sinkholes have 

formed in streambeds, streams can abruptly disappear, as 

surface-water runoff is captured and redirected to groundwater flow or to re-emerge at springs. Soils in this region 

are characterized as thin loess and glacial drift over bedrock 

or clay loam till (Prior, 1991; Oschwald and others, 1965). 

Extensive descriptions of the landform regions are available 

from Prior (1991) and Prior and others (2009).

The Little Maquoketa River Basin lies entirely within 

Dubuque County just northwest of the city of Dubuque, Iowa 

and drains 157 square miles (mi2)(Larimer, 1957). The Little 

Maquoketa River flows about 30 miles (mi) from drainage divide to its mouth at the Mississippi River in northeast 

Dubuque County; major tributaries include the Middle Fork 

Little Maquoketa River with a drainage area of 33.2 mi2 and 

the North Fork Little Maquoketa River with a drainage area of 

70.0 mi2 that includes the entire Middle Fork Little Maquoketa 

River Basin (Larimer, 1957). Basin topography is rugged, 

with many small valleys bounded by steep hills. The lowlands 

are predominately agricultural and the hillslopes are in forest 

and pasture. The region is sometimes referred to as the “Little 

Switzerland of Iowa” (Heinitz, 1973). No dams have been 

constructed across the Little Maquoketa River or its tributaries 

(Iowa Conservation Commission, 1979).

The Maquoketa River Basin originates in Fayette County 

and flows about 150 mi through the cities of Manchester, 

Monticello, and Maquoketa to its mouth at the Mississippi 

River in eastern Jackson County (fig. 1). The Maquoketa River 

Basin includes parts of nine counties and drains 1,879 mi2

(Larimer, 1957). The North Fork Maquoketa River, a major 

tributary to the Maquoketa River with a drainage area of 

592 mi2 (Larimer, 1957), originates in Dubuque County 

and flows about 97 mi through the cities of New Vienna, 

Dyersville, and Cascade to its mouth in Jackson County. 

In northwest Delaware County, the Maquoketa River valley changes for a few miles from a gently sloped valley to a 

rugged gorge in Backbone State Park. Farther downstream 

in central Delaware County, a few miles southeast of Manchester, the Maquoketa River enters a canyon-like valley that 

persists throughout much of the remaining length of the river 

(Iowa Natural Resources Council, 1958). Land use in the 

basin is predominately agricultural and includes some wooded 

areas. Eight low-head dams have been constructed across the 

Maquoketa River (Iowa Conservation Commission, 1979); no 

dams have been constructed across the North Fork Maquoketa 

River. Six of the dams on the Maquoketa River were originally 

built for hydroelectric power (Iowa Natural Resources Council, 1958); only the Lakehurst Dam upstream from the city of 

Maquoketa in Jackson County (fig. 1) is currently operating as 

a hydroelectric dam. Prior to its breach on July 24, 2010, the 

Lake Delhi Dam was the largest dam on the Maquoketa River, 

at a height of 38 ft (Iowa Conservation Commission, 1979). 

Lake Delhi (federally recognized as Hartwick Lake) was 

approximately 8 mi in length and 450 acres in area prior to the 

breach of the dam. The local name “Lake Delhi” was adopted 

by area residents in recognition of the nearby town of Delhi in 

Delaware County (fig. 1).

Flood History

Floods on the Little Maquoketa River have been well 

documented during the operation of the streamgage 05414500 

Little Maquoketa River near Durango (fig.1, site 4) during 

water years 1935–2000. The only other flood data recorded 

in the Little Maquoketa River Basin prior to streamgage 

operation were for the 1925 flood that was documented by 

the U.S. Army Corps of Engineers (Heinitz, 1973). Heinitz 

(1973) briefly describes six major storm events (1876, 1918, 

1919, 1925, 1937, and 1947) that occurred in the Dubuque 

area; descriptions for three of these storms are noteworthy for 

reprinting in this report.

Storm of 1876.—One of the largest storms recorded in the 

area occurred on July 4, 1876, when 40 people were drowned 

at Rockdale (not shown in fig. 1) on the outskirts of Dubuque. 

Rainfall of 4.55 inches in 2 hours and 5 minutes was recorded 

at Dubuque.

Storm of 1919.—A storm on July 9, 1919, caused the 

deaths of seven people. Flooding was the result of 3.81 inches 

of rain in 4 hours. Great damage occurred to streets in all 

portions of the city (Dubuque) lying below the bluffs. The 

USGS made a computation of discharge on the Little Maquoketa River tributary at Dubuque. This is the same stream on 

which the streamgage 05414600 was located (fig. 1, site 5); 

however, the discharge computation of 3,000 cubic feet per 

second (ft3/s) was made for a site 0.25 mi upstream from the 

streamgage with a drainage area of 1.07 mi2 and this discharge 

is not entered into the flood record for the streamgage.

Storm of 1925.—Rainfall for the month of June at 

Dubuque was 10.80 inches with most of this resulting from 

four heavy rainstorms between June 11 and 24. The greatest 

of these storms occurred on the night of June 14–15 when 

3.15 inches of rain fell between 10 p.m. and 4 a.m. A discharge of 29,000 ft3

/s for the Little Maquoketa River near 
6 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

Durango was computed by the U.S. Army Corps of Engineers 

by an indirect measurement. On the Sageville road, this flood 

was reported to be 0.4 ft higher than the previous record of 

July 1919.

The flood of August 2, 1972, is the largest known flood 

in the Little Maquoketa River Basin. A peak discharge of 

40,000 ft3/s (annual flood-probability estimate of less than 

0.2 percent) was recorded at the discontinued streamgage 

05414500 Little Maquoketa River near Durango (fig. 1, 

site 4). The 1972 flood is also the greatest flood on record at 

streamgage 05414400 Middle Fork Little Maquoketa River 

(fig. 1, site 2) with a discharge of 23,000 ft3/s (annual floodprobability estimate of 0.2 to 1 percent). As much as 9 inches 

of rain fell in the headwater of the Middle Fork Little Maquoketa River with 6 to 7 inches occurring over most of the Little 

Maquoketa River Basin (Heinitz, 1973). Flood damages were 

extensive to crops, roads, and bridges. Many of the homes in 

Durango, Daytonville (not shown in fig. 1), and Sageville were 

inundated to some extent and were evacuated. Flood damages 

were estimated to be greater than 1 million dollars (Heinitz, 

1973). 

Continuous records of streamflow have been collected 

in the Maquoketa River Basin since September 1913 at 

streamgage 05418500 Maquoketa River near Maquoketa 

(fig. 1, site 17). Descriptions of historic floods in the Maquoketa River Basin are limited; available information is summarized for floods that occurred in the Maquoketa River Basin in 

1925, 1944, 1947, and 2002 in the report Flood of June 4−5, 

2002, in the Maquoketa River Basin, East-Central Iowa (Eash, 

2005), and is summarized for the flood that occurred in 2004 

in the report Flood of May 23, 2004, in the Turkey and Maquoketa River Basins, Northeast Iowa (Eash, 2006). 

Peak stages and discharges, and the corresponding annual 

flood-probability ranges for the largest known floods, including the July 2010 flood, are listed in table 3 for streamgages 

in the Little Maquoketa River and Maquoketa River Basins. 

The streamgages listed in table 3 also are listed in the USGS 

National Water Information System (NWIS) database, and 

users may obtain surface-water data for Iowa streamgages, 

including information on types of data available and years of 

data collection, at http://waterdata.usgs.gov/ia/nwis/sw.

Floods of July 23–26, 2010

The floods of July 23–26, 2010, are some of the largest floods on record in the Maquoketa River Basin (table 3). 

The 2010 flood is the largest flood on record at streamgages 

05416900 Maquoketa River at Manchester (fig. 1, site 8) and 

05418400 North Fork Maquoketa River near Fulton (fig. 1, 

site 15). At streamgage 05418500 Maquoketa River near 

Maquoketa (fig. 1, site 17), the 2010 flood is the third largest 

flood on record; the peak discharge of the 2010 flood at this 

site was affected by the Lake Delhi Dam breach on July 24. 

Within the Little Maquoketa River Basin, the flood at the 

discontinued streamgage 05414500 Little Maquoketa River 

near Durango (fig. 1, site 4) is the sixth largest flood on record.

Annual Flood Probability

Annual flood probability, also referred to as annual 

exceedance probability, is an estimate of the likelihood of a 

flood of a specific magnitude occurring in any 1 year, and an 

annual flood-probability range expresses the uncertainty of 

estimating precise annual flood probabilities. The reporting 

ranges are as follows: greater than 10 percent, 4 to 10 percent, 2 to 4 percent, 1 to 2 percent, 0.2 to 1 percent, and less 

than 0.2 percent. The range is determined from the estimated 

annual flood-probability discharges that bracket the observed 

flood-peak discharge. If the observed peak discharge is the 

same value as an estimated annual flood-probability discharge, the lower annual flood-probability range is used. In 

the “Flood Description” section, flood discharges and their 

respective annual flood-probability ranges are discussed and 

are listed in table 3. Unless noted otherwise, annual floodprobability estimates listed in table 3 were computed using the 

Weighting of Independent Estimates (WIE) program (Charles 

Berenbrock and Tim Cohn, U.S. Geological Survey, written 

commun., 2008) following guidelines in appendix 8 of Bulletin 17B (Interagency Advisory Committee on Water Data, 

1982). The WIE program uses the variance and estimate of 

the Bulletin 17B annual streamgage-probability analysis and 

the variance and estimate of the regional-regression annual 

probability calculation (Eash, 2001) to compute a weighted 

estimate and variance at a streamgage. As noted in table 3, the 

WIE program was not used to estimate annual flood probabilities for streamgages with basin characteristic values outside of 

the applicable range of characteristic values used to develop 

the regional-regression annual probability calculations, in 

which case only Bulletin 17B annual streamgage-probability 

analyses were used. 

Annual flood probabilities change as streamflow records 

get longer. Bulletin 17B annual probability analyses are 

computed for streamgages using annual peak-discharge 

data. As additional annual peak discharges are measured at 

streamgages, Bulletin 17B annual probability estimates are 

updated and become more statistically reliable. A minimum of 

10 years of record is required to compute Bulletin 17B annual 

streamgage-probability estimates. 

Annual flood probabilities formerly were reported as 

flood recurrence intervals expressed in years. For example, 

a 1-percent annual flood-probability discharge is the same as 

the 100-year recurrence-interval flood discharge. But, because 

of widespread confusion caused in recent years by two or 

more “100-year floods” occurring in a period of much less 

than 100 years, the scientific and engineering community has 

begun expressing the annual likelihood of occurrence of flood 

discharges as a probability. Percent probability is the inverse 

of the recurrence interval multiplied by 100. Selected annual 

flood probabilities and equivalent flood recurrence intervals 
Floods of July 23–26, 2010 7

Table 3. Maximum stages and discharges for 2010 and selected largest-flood years, and the corresponding annual flood-probability 

ranges, at streamgages in the Little Maquoketa River and Maquoketa River Basins, Iowa.

[mi2, square miles; ft, feet; ft3/s, cubic feet per second; (ft3/s)/mi2, cubic feet per second per square mile; >, greater than; < , less than; --, not determined]

Map 

number 

(fig. 1)

Streamgage number and name

Peak-flow 

record 

(water years)

Drainage 

area 

(mi2

)

Date of 

peak

Peak 

stage 

(ft)

Peak 

discharge 

(ft3/s)

Annual flood 

probability 

range 1

 

(percent)

Unit runoff 

[(ft3/s)/mi2]

Little Maquoketa River Basin

1

2

3

4

5

6

05414350 Little Maquoketa River near Graf, 

Iowa

05414400 Middle Fork Little Maquoketa 

River near Rickardsville, Iowa

05414450 North Fork Little Maquoketa 

River near Rickardsville, Iowa

05414500 Little Maquoketa River near Durango, Iowa (discontinued)

05414600 Little Maquoketa River tributary 

at Dubuque, Iowa

05414605 Bloody Run Tributary near 

Sherrill , Iowa

1951–2010

1951–2010

1951–2010

1925, 

1935–2000, 

2010

1951–2002

1991–2010

39.6

30.2

21.6

130

1.54

0.59

6/4/2002

6/8/2008

7/23/2010

8/2/1972

4/13/1991

7/23/2010

8/2/1972

6/8/2008

7/23/2010

8/2/1972

6/15/1925

7/23/2010

7/31/1957

6/8/2008

7/23/2010

15.93

16.47

13.15

27.70

21.81

19.86

14.02

12.58

10.54

23.13

22.10

20.76

7.98

22.71

13.06

7,700

8,370

4,830

23,000

13,400

8,690

7,180

8,040

4,200

40,000

2 29,000

2 19,000 

2 1,650

1,110

144

2–4

2–4

>10

0.2–1

1–2

4–10

1–2

0.2–1

4–10

<0.2

0.2–1

4–10

2–4

3 2–4

3>10 

194.4

211.4

122.0

761.6

443.7

287.7

332.4

372.2

194.4

307.7

223.1

146.2

1,071.4

1,881.4

244.1

Maquoketa River Basin

7

8

9

10

11

12

13

14

05416200 Lamont Creek tributary near 

Lamont, Iowa

05416900 Maquoketa River at Manchester, 

Iowa

05416972 Sand Creek near Manchester, Iowa

05417000 Maquoketa River near 

Manchester, Iowa (discontinued)

05417500 Maquoketa River near Delhi 

(discontinued)

05417530 Plum Creek at Earlville, Iowa 

(discontinued)

05417590 Kitty Creek near Langworthy, 

Iowa (discontinued)

05417700 Bear Creek near Monmouth, Iowa 

(discontinued)

1991–2010

2001–10

1991–10

1925, 

1928–30, 

1933–73, 

1976–83

1929, 

1933–40

1966–91

1966–92

1944, 

1958–76

1.78

275

11.0

305

347

41.1

14.4

61.3

4/25/2008

7/23/2010

5/23/2004

5/26/2008

7/24/2010

6/4/2002

10/8/2007

7/23/2010

6/15/1925

6/13/1947

7/9/1951

3/14/1929

9/13/1972

6/21/1974

9/26/1981

7/19/1969

7/8/1986

6/--/1944

9/21/1965

9 

23.18

20.22

21.66

20.80

24.48

19.31

20.95

15.48

--

21.36

19.65

89.82

88.34

88.75

88.22

90.24

88.68

21.50

13.76

5 

1,190

647

26,000

22,100

26,600

2 4,290

5,090

2,390

25,400

20,000

16,800

7,360

2 4,800

2 6,200

2 4,500

8 3,700

2,100

--

7,340

6 

4–10

>10

4 0.2–1

4 1–2

4 0.2–1 

2–4

1–2

>10

6 1–2

6 2–4

4–10

7 --

4–10

2–4

4–10

2–4

4–10

--

2–4

668.5

363.5

94.5

80.4

96.7

390.0

462.7

217.3

83.3

65.6

55.1

21.2

116.8

150.9

109.5

256.9

145.8

--

119.7
8 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

Table 3. Maximum stages and discharges for 2010 and selected largest-flood years, and the corresponding annual flood-probability 

ranges, at streamgages in the Little Maquoketa River and Maquoketa River Basins, Iowa.—Continued

[mi2, square miles; ft, feet; ft3/s, cubic feet per second; (ft3/s)/mi2, cubic feet per second per square mile; >, greater than; < , less than; --, not determined]

Map 

number 

(fig. 1)

Streamgage number and name

Peak-flow 

record 

(water years)

Drainage 

area 

(mi2)

Date of 

peak

Peak 

stage 

(ft)

Peak 

discharge 

(ft3/s)

Annual flood 

probability 

range 1

(percent)

Unit runoff 

[(ft3/s)/mi2]

Maquoketa River Basin—Continued

15 05418400 North Fork Maquoketa River near 

Fulton, Iowa

1999–2010 505 6/5/2002 19.87 22,600 10 2–4 44.8

6/13/2008 18.67 20,700 10 2–4 41.0

7/24/2010 22.44 25,000 10 1–2 49.5

16 05418450 North Fork Maquoketa River at 

Fulton, Iowa (discontinued)

1974, 

1977–91, 

2002

516 6/5/2002 21.21 222,600 2–4 43.8

17 05418500 Maquoketa River near Maquoketa, 

Iowa

1903, 

1914–2010

1,553 --/--/1903 1123.50 43,200 2–4 27.8

6/27/1944 1124.70 48,000 1–2 30.9

6/5/2002 34.09 47,900 1–2 30.8

7/26/2010 35.26 12 46,000 13 -- 12 29.6

18 5418645 Williams Creek near Charlotte, 

Iowa

1989–2010 1.77 5/29/1996 13.02 2990 4–10 559.3

7/24/2010 11.76 598 >10 337.9

1

Annual flood-probability ranges reflect the uncertainty of estimating annual flood-probability discharges. The annual flood probability is calculated using 

established techniques but then reported in one of the following ranges: greater than 10 percent, 4 to 10 percent, 2 to 4 percent, 1 to 2 percent, 0.2 to 1 percent, 

and less than 0.2 percent. Unless noted otherwise, annual flood-probability ranges are based on a weighted average of two independent probability estimates. 

The WIE (weighting of independent estimates) program was used to estimate annual flood probabilities following guidelines in Appendix 8 of Bulletin 17B 

(Interagency Advisory Committee on Water Data, 1982; Charles Berenbrock and Tim Cohn, U.S. Geological Survey, written commun., 2008). The WIE program 

uses the variance and estimate of the Bulletin 17B annual streamgage-probability analysis and the variance and estimate of the regional-regression annual probability calculation (Eash, 2001) to compute a weighted probability estimate and variance at a streamgage. 

2Estimate.

3Computed using Bulletin 17B annual streamgage-probability analysis (Interagency Advisory Committee on Water Data, 1982) because regional-regression 

equations are not applicable.

4Annual flood-probability estimates are based on inclusion of additional annual-peak discharges from discontinued downstream streamgage (05417000).

5Discharge computed by Prof. F.A. Nagler, University of Iowa (U.S. Geological Survey, 1964).

6Flood-probability estimates are based on inclusion of additional annual-peak discharges from active upstream streamgage (05416900).

7Annual flood probability not determined because all peak discharges are regulated by upstream dam.

8Discharge computed from indirect measurement.

9Stage affected by backwater.

10Annual flood-probability estimates are based on inclusion of additional annual-peak discharges from discontinued downstream streamgage (05418450).

11Prior to Sept. 30, 1972, streamgage at different site and datum.

12Peak discharge affected by Lake Delhi Dam failure on July 24. 

13Annual flood probability not determined because peak discharge affected by Lake Delhi Dam failure. Magnitude of peak discharge is equivalent to that of a 

natural flood with an annual flood-probability range of 1 to 2 percent.
Floods of July 23–26, 2010 9

are listed in table 4. Although the annual probability is an 

estimate of the likelihood of a flood discharge of a specific 

magnitude occurring in any one year, more than one flood discharge with a specific magnitude and annual probability could 

occur in the same year.

Table 4. Annual flood probability and equivalent flood 

recurrence interval for selected probabilities.

Annual flood probability 

(percent)

Recurrence interval 

(years)

20 5

10 10

4 25

2 50

1 100

.5 200

.2 500

Storm Description

The floods of July 23–26, 2010, were the result of a 

series of thunderstorms that crossed northeast Iowa during July 22–24. The storms were part of an exceptionally 

wet period for Iowa from June through September 2010 

that followed a wetter than normal first half of the year. A 

new statewide rainfall record of 10.34 inches was set for 

the month of June; the old record of 10.33 inches occurred 

in 1947. Overall, 2010, with an average statewide rainfall of 44.81 inches, was the second wettest year in Iowa 

in 138 years of record (Hillaker, Iowa Preliminary Annual 

Weather Summary–2010, http://www.iowaagriculture.gov/

climatology/weatherSummaries/2010/pas2010.pdf; accessed 

June 28, 2010). Although rainfall during July 2010 was not 

as great as in June, it was more intense for shorter periods of 

time, which resulted in greater flooding; the greatest rain event 

in July occurred on the night of the 22nd when the Oelwein 

rain gage officially recorded 9.93 inches. An additional 3 to 

4 inches of rain fell over the same areas of northeast Iowa the 

next night. An exceptional rainfall total of 20.33 inches for the 

month of July at Oelwein far exceeded the old monthly record 

of 13.30 inches for June 1925 (Hillaker, 2010). 

The following rainfall and flood information is from 

the U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, and National Climatic Data 

Center (2010a) http://www4.ncdc.noaa.gov/cgi-win/wwcgi.

dll?wwEvent~storms (search terms Iowa, 7/22/2010 to 

7/24/2010, and flood were entered to obtain a list of 61 flood 

events; the following quotes were obtained from event numbers (22) Oelwein, (24) Lamont, (38) Backbone State Park, 

and (46) Arlington).

“Several rounds of thunderstorms [beginning on 

July 22] developed along a slow moving cold front. 

These thunderstorms stretched across much of 

southern Wisconsin into north central and central 

Iowa. The thunderstorms tracked repeatedly over 

the same areas dropping several inches of rain 

across Fayette and Clayton Counties which resulted 

in flooding problems on July 22nd into the 23rd. 

Thunderstorms with extremely heavy rain developed 

[overnight on July 22] along a stationary front and 

moved from northeast Iowa into northwest Illinois. 

Some locations measured 5 to 7 inches of rainfall, causing localized flash flooding and pushing 

numerous creeks out of their banks. The North Fork 

Maquoketa River through Dubuque County was 

particularly hard-hit. This round of rainfall further 

set the stage for the extreme flooding that developed 

with the next round of storms later that night [July 

23]. After about 10 inches of rain fell in the upper 

Maquoketa River basin, the river surged to record 

stage levels. Thunderstorms developed along a cold 

front and swept across northeast Iowa for a second 

[consecutive] night [July 23]. These storms brought 

additional heavy rains producing more flood problems on July 23 and 24th.”

Hourly rainfall amounts for July 22–24, 2010, for rain 

gages at Cascade, Dubuque, and Strawberry Point are shown 

in figure 3 (U.S. Department of Commerce, National Oceanic 

and Atmospheric Administration, and National Climatic Data 

Center, 2010b). The graphs provide a general indication of 

the timing and intensity of the rainfall in the Little Maquoketa 

River Basin and the upper and central parts of the Maquoketa River Basin. The greatest 1-hour rainfall intensity of 

1.5 inches occurred at Strawberry Point ending at 8 a.m. on 

July 23 (fig. 3C). Data from the three rain gages (fig. 3) indicate that much of the rainfall occurred during a 48-hour period 

from 6 a.m. on July 22 to 6 a.m. on July 24, and also indicate that Strawberry Point recorded the greatest 24-hour and 

48-hour rainfall of 8.2 inches and 11.8 inches, respectively. 

An isohyetal map of the areal distribution of rainfall for 

the 72-hour period beginning at 7:00 a.m. on July 21 and ending at 7:00 a.m., on June 24, 2010, is shown in figure 1; data 

were provided by Harry Hillaker, State Climatologist, Iowa 

Department of Agriculture and Land Stewardship (written 

commun., June 2011). The isohyetal map shows a band of 

over 12 inches of rainfall in the headwaters of the Maquoketa 

River Basin upstream of Backbone State Park. Each 24-hour 

rainfall amount from July 22 to July 24, 2010, for 12 selected 

rain gages in northeast and east-central Iowa is listed in table 5 

(Hillaker, 2010). The 72-hour rainfall total listed in table 5 

from July 22–24 is the time period for which the most significant rainfall could be considered directly contributing to the 

flooding of July 23–26; although, essentially all rainfall within 

the Little Maquoketa River and Maquoketa River Basins fell 

within a 48-hour period (Harry Hillaker, State Climatologist, Iowa Department of Agriculture and Land Stewardship , 

written commun., June 2011). Seventy-two hour rainfall totals 

ending on July 24 of 7.33 and 12.23 inches were recorded at 

Manchester and Strawberry Point, respectively.
10 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

0

0.5

1.0

1.5

2.0

0

0.5

1.0

1.5

2.0

0

0.5

1.0

1.5

2.0

A. Cascade

Hourly rainfall shown for hour ending.

Greatest 24-hour rainfall shown is 3.6 inches.

Greatest 48-hour rainfall shown is 5.2 inches.

Total 72-hour rainfall shown is 5.2 inches.

B. Dubuque Weather Service Office Airport

Hourly rainfall for hour ending.

Greatest 24-hour rainfall shown is 5.03 inches.

Greatest 48-hour rainfall shown is 8.93 inches.

Total 72-hour rainfall shown is 8.93 inches.

C. Strawberry Point

Hourly rainfall shown for hour ending.

Greatest 24-hour rainfall shown is 8.2 inches.

Greatest 48-hour rainfall shown is 11.8 inches.

Total 72-hour rainfall shown is 11.8 inches.

24-hour period

48-hour period

24-hour period

48-hour period

24-hour period

48-hour period

Rainfall, in inches

July 22 July 23 July 24

Figure 3. Hourly rainfall for July 22–24, 2010, at three rain gages in the Maquoketa River Basin and vicinity. 

(Central Daylight Time; U.S. Department of Commerce, National Oceanic and Atmospheric Administration, 

and National Climatic Data Center, 2010b).
Floods of July 23–26, 2010 11

Table 5. Twenty-four-hour rainfall amounts at selected rain gages in northeast and east-central Iowa during July 22–24, 2010.

[T, Trace]

Rain gage Observation 

time

24-hour rainfall, in inches 1 Greatest 48-hour 

rainfall total, 

in inches

72-hour rainfall 

total, 

in inches July 22, 2010 July 23, 2010 July 24, 2010

Anamosa 1 WNW 8 a.m. 0 0.95 1.50 2.45 2.45

Bellevue Lock and Dam 12 7 a.m. 0 3.85 2.45 6.30 6.30

Cascade 8 a.m. .13 2.50 2.86 5.36 5.49

Coggon 7 a.m. .15 .25 3.08 3.33 3.48

Dubuque Lock and Dam 11 7 a.m. .15 7.18 2.10 9.28 9.43

Dubuque Airport 1 a.m. 2 2.84 3 4.59 4 1.5 7.43 8.93

Guttenberg Lock and Dam 10 7 a.m. .05 3.94 2.70 6.64 6.69

Manchester-2 8 a.m. .52 3.89 2.92 6.81 7.33

Maquoketa 4 W 8 a.m. T .43 2.50 2.93 2.93

Oelwein 1 E 8 a.m. .22 9.93 3.16 13.09 13.31

Stanley 4 W 7 a.m. .39 6.84 3.22 10.06 10.45

Strawberry Point 8 a.m. .53 8.51 3.19 11.70 12.23

1 Iowa Climate Review (Hillaker, 2010).

2 July 23, 2010.

3 July 24, 2010.

4 July 25, 2010

The Rainfall Frequency Atlas of the Midwest (Huff 

and Angel, 1992) provides a table of the mean distribution 

of theoretical rainfall amounts for climatological divisions 

in Iowa for selected rain periods and annual probabilities 

(recurrence intervals). The magnitude and annual probability of theoretical rainfall amounts for selected rain periods 

(durations) from the table in Huff and Angel (1992) for 2 of 

the 9 climatological divisions in Iowa are listed in table 6. 

Eight of the 12 rain gages listed in table 5 are in the Northeast Iowa Climatological Division and four are located in 

the East-Central Climatological Division (Hillaker, 2010). A 

map showing the location of climatological divisions in Iowa 

is available on page 4 of Huff and Angel (1992) at http://

www.isws.illinois.edu/pubdoc/B/ISWSB-71.pdf, accessed 

July 6, 2011. The greatest 48-hour rainfalls listed in table 

5 exceeded 6.34 inches at seven rain gages all located in 

the Northeast Climatological Division (Dubuque Lock and 

Dam 11, Dubuque Airport, Guttenberg Lock and Dam 10, 

Manchester, Oelwein, Stanley, and Strawberry Point). 

Annual rainfall probabilities for greatest 48-hour rainfalls 

for two of these rain gages (Guttenberg and Manchester) are 

estimated to be 1 to 2 percent, and for the other five of these 

seven rain gages, annual rainfall probabilities are estimated 

to be less than 1 percent (table 6).

Table 6. Magnitude and annual probability of theoretical rainfall 

amounts for selected storm periods in the East-Central and 

Northeast Iowa Climatological Divisions.

[Rainfall amounts from Huff and Angel, (1992)]

East-Central

Duration

(hours)

Rainfall (inches) for indicated annual probabilities

10 (percent) 4 (percent) 2 (percent) 1 (percent)

24 4.44 5.42 6.25 7.13

48 5.05 6.02 6.87 7.83

72 5.31 6.42 7.35 8.42

120 5.61 6.70 7.75 9.00

240 7.12 8.25 9.27 10.35

Northeast

Duration

(hours)

Rainfall (inches) for indicated annual probabilities

10 (percent) 4 (percent) 2 (percent) 1 (percent)

24 4.31 5.11 5.73 6.36

48 4.69 5.62 6.34 7.09

72 5.14 6.19 7.00 7.84

120 5.64 6.84 7.75 8.77

240 7.07 8.29 9.20 10.19
12 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

Annual probabilities for two different components of a 

hydrologic event—rainfall and runoff, respectively—and for 

various locations in the Little Maquoketa River and Maquoketa River Basins are listed in tables 3 and 6. Similar to the 

concept of annual flood probability, annual rainfall probability 

is an estimate of the likelihood of a rainfall of a specific magnitude occurring in any one year, more than one rainfall with 

a specific magnitude and annual probability could occur in the 

same year.

Flood Description

Minor flooding occurred July 23, 2010, in the Little 

Maquoketa River Basin and major flooding occurred 

July 23–26, 2010, in the Maquoketa River Basin as a result 

of the intense rain that fell during July 22–24. The 2010 peak 

discharges for 11 streamgages in the Little Maquoketa River 

and Maquoketa River Basins are listed in table 3. Also listed 

in the table are selected historical peak discharges for the 

largest-flood years.

Hydrographs of instantaneous discharges measured 

at continuous-record streamgages on the Maquoketa River 

and the North Fork Maquoketa River are presented in 

figure 4. The period shown is July 22 to July 29, 2010. The 

streamgages record instantaneous values at 15-minute time 

intervals. Also shown on the hydrographs are lines denoting 

discharge estimates for selected annual flood probabilities. 

The annual flood-probability range listed in table 3 for the 

sites is the range between the annual flood-probability discharges that bracket the flood peak discharge. For example, 

the 2010 peak discharge at streamgage 05416900 Maquoketa 

River at Manchester, Iowa (fig. 1, site 8) falls between the 

1-percent and 0.2-percent annual flood-probability estimates 

(table 3; fig. 4). 

Little Maquoketa River Basin

The 2010 flood caused minor flooding (annual flood 

probability greater than 4 percent) in the Little Maquoketa 

River Basin on July 23, 2010, at four active streamgages 

located on small drainage-area tributaries (fig.1, sites 1–3 

and 6) and at a discontinued mainstem streamgage located in 

the lower reach of the basin (fig. 1 site 4). Of the four tributaries, the streamgage 05414450 Middle Fork Little Maquoketa 

River near Rickardsville recorded the greatest peak discharge 

of 8,690 ft3/s (table 3). The 2010 flood at this site is estimated 

to have an annual probability of 4 to 10 percent. At the discontinued streamgage 05414500 Little Maquoketa River near 

Durango, a peak discharge of 19,000 ft3/s was estimated on 

the basis of the stage-discharge rating curve that was in effect 

during the 2000 water year. The 2010 flood at this site is the 

sixth largest known flood in the basin since at least 1925, and 

the annual probability of this peak discharge is estimated to be 

4 to 10 percent (table 3).

Maquoketa River Basin

Flooding began on July 23 at streamgages 05416900 

Maquoketa River at Manchester (fig. 1, site 8) and 05418400 

North Fork Maquoketa River near Fulton (fig. 1, site 15). 

The peak discharge at both of these streamgages occurred on 

July 24 (fig. 4); the flood peaked at the Manchester streamgage 

at 12:30 p.m. with a discharge of 26,600 ft3/s and at the Fulton 

streamgage at 11:00 p.m. with a discharge of 25,000 ft3/s. The 

2010 flood is the largest known flood at both the Manchester 

and Fulton streamgages. The annual flood-probability range of 

the 2010 flood at the Manchester streamgage is estimated to be 

0.2 to 1 percent and at the Fulton streamgage is estimated to 

be 1 to 2 percent (table 3). The peak discharge at streamgage 

05418500 Maquoketa River at Maquoketa (fig. 1, site 17) on 

July 26 at 4:15 a.m. (fig. 4) occurred after the breach of the 

Lake Delhi Dam on July 24. The dam is located approximately 

74 river miles upstream from the Maquoketa streamgage. 

Because the peak discharge of 46,000 ft3

/s at the Maquoketa 

streamgage was affected by the dam breach, an annual flood 

probability was not determined for the 2010 flood at this site 

(table 3). The magnitude of the 2010 peak discharge at the 

Maquoketa streamgage is equivalent to that of a natural flood 

with an annual flood-probability range of 1 to 2 percent. Peak 

discharges at the three streamgages shown in figure 4 were 

determined from rating curves that were verified by discharge 

measurements made near the time of occurrence of the respective peaks.

For informational purposes, also shown on two of the 

hydrographs, are the discharges corresponding to the National 

Weather Service (NWS) designated flood stage (fig.4). The 

flood stages represent “an established gage height for a 

given location at which a rise in water surface level begins to 

impact lives, property, or commerce” (http://www.weather.

gov/directives/sym/pd01009050curr.pdf, accessed September 13, 2011). The discharges corresponding to the NWS 

flood stages were determined from the respective USGS 

stage-discharge rating curves in use at the time of the flood. 

At streamgage 05416900 Maquoketa River at Manchester, the 

NWS flood stage is 14.0 ft (discharge 5,550 ft3

/s), which is the 

stage that water affects West Main Street and residences on the 

south side of town (at http://water.weather.gov/ahps2/hydrograph.php?wfo=dvn&gage=mchi4&view=1,1,1,1,1,1,1,1”, 

accessed September 13, 2011). The streamgage Maquoketa 

River at Manchester was above flood stage during July 23–25, 

and the peak stage of 24.48 ft (table 3) exceeded the flood 

stage by 10.48 ft. At streamgage 05418500 Maquoketa River 

near Maquoketa, the NWS flood stage is 24.0 ft (discharge 

13,300 ft3/s), which is the stage that water affects agricultural 

land in the Maquoketa area and several storm sewers in town 

(at http://water.weather.gov/ahps2/hydrograph.php?wfo=dv

n&gage=maqi4&view=1,1,1,1,1,1,1,1”, accessed September 13, 2011). The streamgage Maquoketa River near Maquoketa was above flood stage during July 24–27, and the peak 

stage of 35.26 ft (table 3) exceeded the flood stage by 11.26 ft. 
Floods of July 23–26, 2010 13

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

July 2010

Discharge at indicated

annual flood probabilities

0.2 percent

1 percent

2 percent

05416900 Maquoketa River at Manchester, Iowa

0.2 percent

1 percent

2 percent

05418400 Nork Fork Maquoketa River near Fulton, Iowa

0.2 percent

1 percent

2 percent

05418500 Maquoketa River near Maquoketa, Iowa

Discharge for National Weather Service (NWS) flood stage of 14 feet

Discharge for NWS flood stage of 24 feet

Flood peak July 24, discharge

26,600 cubic feet per second

Flood peak July 24, discharge

25,000 cubic feet per second

Flood peak July 26, discharge

46,000 cubic feet per second

Discharge, in cubic feet per second

22 23 24 25 26 27 28 29

Figure 4. Discharge hydrographs for streamgages on the Maquoketa River and the North Fork Maquoketa 

River, July 22–29, 2010.
14 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

The NWS has not determined a flood stage at streamgage 

05418400 North Fork Maquoketa River near Fulton.

Chronology of Flood Impacts

The following flood description information was 

obtained from newspaper articles posted online by the Des 

Moines Register (Finney, July 24, 2010), the Gazette (David 

DeWitte, July 26, 2010a, July 26, 2010b), the Associated Press

(July 25, 2010), and the Telegraph Herald (Andy Piper and 

Michael Schmidt, July 24, 2010; Eileen Mozinski Schmidt, 

July 26, 2010); and from on-line sources obtained from the 

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, and National Climatic Data Center 

(2010a) and from KCRG-TV (Dave DeWitte, July 26, 2010c).

In New Vienna, near the headwaters of the North Fork 

Maquoketa River, Fire Chief Henry Westhoff, reported the 

river crested at 5:30 a.m. on July 23, 2010, about 2 ft higher 

than ever before, and that the river returned to within its banks 

at about 11 a.m. Further downstream in Dyersville, Candy 

Cane and West Side parks were inundated with several feet 

of water where the North Fork Maquoketa River, Bear Creek, 

and Hewitt Creek converge on the southwest side of the city. 

Tim Pins, Dyersville Fire Chief, reported the flood water 

rose very quickly, noting that the North Fork Maquoketa 

River topped its banks at about 3 a.m. and crested at 14 ft 

at 9:20 a.m. on July 23. Residents on the west side of Third 

Avenue in Dyersville suffered flooded basements. Also on 

the morning of July 23, in the upper part of the Maquoketa 

River Basin, flash flooding occurred in Lamont where city 

crews had to sandbag the lift pump station due to rising flood 

waters. In Manchester, the Maquoketa River was reported 

to have been rising at about 1-foot per hour; the Delaware 

County Emergency Management and the City of Manchester 

decided to close West Main Street between Franklin Avenue 

and Legions Street around 11:30 a.m. Jack Klaus, Delaware 

County Emergency Management noted the closing of West 

Main Street usually occurs when the river stage reaches 17 ft. 

Several Manchester streets and county roads were closed due 

to dangerous conditions. Numerous homes in Manchester and 

several buildings in the downtown area were flooded, and 

utilities were shut off to parts of the city that were considered 

to be at risk of flooding. Four to five ft of water filled some 

homes and businesses; many basements filled with water 

and several basement walls were reported to have collapsed. 

A man in town escaped a life-threatening situation when a 

sinkhole developed in a parking lot and the skidloader he was 

driving collapsed into the raging Maquoketa River beneath the 

parking lot. Downstream of Manchester, some campers and 

residents on Lake Delhi had to be rescued by boat overnight 

on July 23. Numerous properties were damaged along the 

Maquoketa River, including about 500 homes and the marina 

bordering Lake Delhi. Also, overnight on July 23, the main 

street in Arlington, in southeastern Fayette County, was 

reported impassable due to rising waters.

On July 24, water from the Maquoketa River began flowing over the Delhi Dam at 10:30 a.m.; by 1:00 p.m., a 30-ft 

section of road, rock, and earthen embankment broke loose 

and a torrent of river water raged through, destroying at least 

five homes and threatening the town of Hopkinton downstream. Boats, propane tanks, and a construction barge crashed 

through the breach and tumbled downstream. Downstream of 

the dam, County Road D47 was closed as water from the dam 

submerged the bridge near Hopkinton. Craig Wilson, Hopkinton Fire Chief, ordered half the town to evacuate; he began 

allowing residents to return to their homes in the afternoon 

of July 24. Aircraft from the Iowa State Patrol monitored 

the surge of water from the dam breach and reported that the 

surge slowed upstream of Hopkinton where the flood plain 

attenuated the flood waters. On the southeast side of Hopkinton, about five homes were flooded. Police Chief Britt 

Smith reported that downstream along the Maquoketa River 

in Monticello about 50 homes, including two mobile home 

parks, were evacuated. U.S. Business Highway 151/Main 

Street in Monticello was one of about a dozen roads closed 

by the weekend flooding of the Maquoketa and Wapsipinicon 

Rivers in Jones County, reported Mike McClain, Jones County 

Engineer, the road closures also included County Road E17 

and State Highway 136 north of Onslow. Minor damage was 

reported for a stretch of State Highway 38. Downstream of 

Monticello near Scotch Grove, the Maquoketa River flood 

washed away the privately owned Corbett’s Mill Bridge, a 

historic bowstring (or tied-arch bridge) built in 1871. Further downstream along the Maquoketa River in the city of 

Maquoketa, emergency workers and area residents teamed up 

on July 25 to build a wall of sandbags at the intersection of 

North Main Street and Pershing Road to prevent flooding of 

the city’s wastewater plant, electric plant, and water treatment 

facility, reported Al Muhlhausen, Assistant Fire Chief for the 

City of Maquoketa. The dam breach at Lake Delhi flooded 

agricultural land downstream of the dam. On July, 26, 2010, 

Keith Krause, Delaware County District Conservationist, 

Natural Resources Conservation Service (NRCS), estimated 

that 2,000 acres of crop land and 2,000 acres of pasture were 

inundated along the Maquoketa River; Virgil Schmitt, extension field agronomist for Iowa State University, said it was too 

late in the year for farmers to replant lost crops.

Breach of Lake Delhi Dam

Lake Delhi Dam was built between 1922 and 1929 by the 

Interstate Power Company for hydroelectric power generation. 

In 1974, the Lake Delhi Recreation Association bought the 

dam and has owned it since then. Jon Garton, Iowa Department of Natural Resources dam safety engineer, reported that 

Lake Delhi Dam was used to maintain water levels in the 

upper and lower parts of the lake for recreational purposes and 

it was not used for flood control downstream of Lake Delhi 

(Lynch, The Gazette, July 26, 2010). Detailed information on 

the breach of Lake Delhi Dam is available from the Report on 
Flood Profile 15

Breach of Delhi Dam (Independent Panel of Engineers, 2010). 

The crest of Lake Delhi Dam is at elevation 904.8 ft and the 

spillway crest is at 879.8 ft NGVD 29 (the peak-flood elevation at the dam determined by the USGS was 905.55 ft). The 

cause of the dam breach was internal erosion in the embankment coupled with overtopping flow which resulted in an estimated peak breach outflow of about 69,000 ft3

/s (Independent 

Panel of Engineers, 2010). 

Flood Profile

To develop profiles of the 2010 floods for the Little 

Maquoketa, North Fork Little Maquoketa, Maquoketa, and 

North Fork Maquoketa Rivers, the USGS measured highwater marks (HWMs) at 46 locations. The HWMs that 

were used in the profiles were measured at all Federal and 

State Highway bridges, at USGS streamgages, at selected 

county and local bridges, and at selected dams. The HWMs 

at bridges were located immediately downstream from a 

bridge and one bridge-length upstream from the bridge. The 

distances between most of the profile points are less than 

about 12 mi (fig. 1). The distance between Ebys Mill Road 

and U.S. Highway 151 on the Maquoketa River is about 13.8 

mi, and between 21st Avenue and 1st Avenue on the North 

Fork Maquoketa River is about 18.3 mi. River miles were 

determined using a geographic information system (GIS) to 

measure the distance along each river reach from its mouth 

using USGS 1:24,000-scale topographic-map data. 

The HWMs were surveyed to bench marks (see appendix) at bridges, dams, and intermediate sites within one week 

of the flood peak, and were later referenced to the NGVD 29 

by differential leveling or differential positioning using a 

global positioning system (GPS). In addition, bridge-deck, 

low-bridge-chord, and reference-point elevations were measured with respect to the bench marks. The elevations for the 

bridge deck and low-bridge chord were generally measured 

on the lowest end of the bridge. The reference points were 

established so that low-flow water-surface elevations could 

be measured by using a weight suspended on a measuring 

tape. Low-flow water-surface elevations were obtained during 

November 2010 to indicate the range in stage along the river 

and to define the low-water slope. 

The HWMs are profiled in figures 5–18 and listed in 

tables 7–9. The profile lines connecting the HWMs in the figures approximate the flood elevation between marks. The lines 

do not account for any intermediate features that could affect 

flood elevation such as channel morphology or bridges and 

dams where HWMs were not measured. Primary highways 

referenced in the report are shown in figure 1; secondary roads 

are not shown in the figure.

The July 23, 2010, flood along the Little Maquoketa 

and North Fork Little Maquoketa Rivers is profiled from 

U.S. Highway 52 near Dubuque upstream to County Road 

Y21 near Rickardsville (fig. 1). The 19-mi river reach is 

shown in figure 1, and the five stream sites where HWMs were 

measured are listed in table 7. 

Table 7. Locations and elevations of high-water marks used in 

the Little Maquoketa River and North Fork Little Maquoketa River 

flood profiles of July 23, 2010.

[HWM, high-water mark; NGVD 29, National Geodetic Vertical Datum of 

1929; USGS, U.S. Geological Survey]

Distance 

from mouth 

(river miles)

Location

Downstream 

HWM 

(feet above 

NGVD 29)

Upstream 

HWM 

(feet above 

NGVD 29)

4.13 U.S. Highway 52, south of 

Sageville

621.82 621.98

6.48 Clay Hill Road, east of 

Durango, discontinued USGS streamgage 

05414500

632.79 635.63

10.62 U.S. Highway 52, west of 

Durango

662.42 663.43

16.40 South Mound Road, east 

of Rickardsville, USGS 

streamgage 05414450

755.81 757.57

23.03 County Road Y21/James 

Road, northwest of Rickardsville

849.26 850.54

The July 23–26, 2010, flood along the Maquoketa River 

is profiled from U.S. Highway 52 near Green Island upstream 

to State Highway 187 near Arlington (fig. 1). The 142-mi 

river reach is shown in figure 1, and the 28 stream sites where 

HWMs were measured are listed in table 8. A flood profile 

measured in June 2002 and a low-water profile measured 

in December 2002 (Eash, 2005) are shown in figures 8–12 

for the Maquoketa River from U.S. Highway 52 near Green 

Island upstream to U.S. Highway 20 south of Manchester. A 

flood profile measured in May 2004 and a low-water profile 

measured in November 2004 (Eash, 2006) also are shown in 

figures 8, and 12-13, for the Maquoketa River from County 

Road D47 near Hopkinton upstream to State Highway 187 

near Arlington.

The July 23–24, 2010, flood along the North Fork 

Maquoketa River is profiled from Rockdale Road near 

Maquoketa upstream to U.S. Highway 52 near Luxemburg 

(fig. 1). The 90-mi river reach is shown in figure 1, and the 

13 stream sites where HWMs were measured are listed in 

table 9. A flood profile measured in June 2002 and a low-water 

profile measured in December 2002 (Eash, 2005) are shown 

in figures 14–18 for the North Fork Maquoketa River along 

the entire North Maquoketa River reach profiled for the 2010 

flood with the exception of the reach between State Highway 

136 at New Vienna and U.S. Highway 52 near Luxemburg.
16 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

Table 8. Locations and elevations of high-water marks used in the Maquoketa River flood profile of July 23–26, 2010.

[HWM, high-water mark; NGVD 29, National Geodetic Vertical Datum of 1929; USGS, U.S. Geological Survey; ND, not determined]

Distance from 

mouth 

(river miles)

Location

Downstream 

HWM 

(feet above 

NGVD 29)

Upstream 

HWM 

(feet above 

NGVD 29)

2.20 U.S. Highway 52 , northwest of Green Island 601.44 604.86

11.22 County Road Z20/387th Avenue, north of Spragueville 623.55 625.14

19.51 County Road E23Y/Iron Bridge Road, southeast of Andrew 641.13 641.55

27.60 USGS streamgage 05418500, State Highway 62, northeast of Maquoketa 661.22 ND

31.72 U.S. Highway 61, Maquoketa 669.10 669.31

32.61 Lakehurst Dam, west of Maquoketa 671.31 677.87

44.30 County Road Y34/50th Avenue, north of Baldwin 707.96 708.64

47.06 30th Avenue, north of Monmouth 716.79 716.86

59.02 Temple Hill Road, northwest of Canton 743.47 743.68

61.86 State Highway 136, northeast of Scotch Grove 749.19 749.41

66.84 Ebys Mill Road, northeast of Scotch Grove 764.45 765.08

80.61 U.S. Highway 151, east of Monticello 805.97 806.46

81.50 Main Street, Monticello 807.62 808.79

83.00 State Highway 38, Monticello 811.66 813.07

92.17 County Road D47/Marion Street, southwest of Hopkinton 846.36 846.51

101.58 County Road X31/230th Avenue crossing Lake Delhi Dam, southwest of Delhi 889.17 905.55

103.58 County Road X29/220th Avenue, southwest of Delhi 906.08 906.32

109.40 County Road X21/240th Street, southeast of Manchester 911.23 911.45

113.25 USGS streamgage 05416900, U.S. Highway 20, south of Manchester 924.89 925.46

114.42 Marion Street, Manchester 931.99 932.78

114.76 State Highway 13/West Main Street, Manchester 933.26 933.56

116.98 195th Street, northwest of Manchester 938.61 938.67

117.03 Quaker Mill Pond dam, northwest of Manchester 938.67 948.01

125.52 County Road C64/Richland Street, Dundee 982.13 982.21

127.82 Backbone State Park Dam 996.30 1,003.57

131.32 Backbone State Park Road, near road leading to County Road C57/120th Street 1,016.68 1,016.68

139.73 State Highway 3, west of Strawberry Point 1,077.65 1,078.32

143.71 State Highway 187, southeast of Arlington 1,104.08 1,105.08

Table 9. Locations and elevations of high-water marks used in the North Fork Maquoketa River flood profile of July 23–24, 2010.

[HWM, high-water mark; NGVD 29, National Geodetic Vertical Datum of 1929; ND, not determined; USGS, U.S. Geological Survey; NA, not applicable]

Distance from 

mouth 

(river miles)

Location

Downstream 

HWM 

(feet above 

NGVD 29)

Upstream 

HWM 

(feet above 

NGVD 29)

0.27 Rockdale Road, north of Maquoketa 666.44 666.49

8.24 U.S. Highway 61, south of Fulton, discontinued USGS streamgage 05418450 686.88 ND

12.37 USGS streamgage 05418400, County Road E17/150th Street, northwest of Fulton 701.44 702.04

22.12 60th Avenue, northeast of Canton 733.34 733.47

26.24 21st Avenue, northeast of Canton 747.30 748.50

44.58 1st Avenue West, Cascade 814.82 818.87

45.29 U.S. Highway 151, north of Cascade 820.97 822.03

47.50 State Highway 136, northwest of Cascade 830.70 830.82

57.74 Along 305th Street, south of Worthington 874.20 NA

63.90 County Road D35/272nd Street, west of Worthington 897.61 897.94

71.52 U.S. Highway 20, Dyersville 944.06 944.13

80.67 State Highway 136/Columbus Street, New Vienna 993.05 993.84

90.07 U.S. Highway 52, east of Luxemburg 1,058.76 1,060.06
References Cited 17

Summary

Information on flood peaks and water-surface-elevation 

profiles is needed for the planning and safe design of bridges 

and other structures along rivers and streams and also for 

effective management of flood plains. Data for major floods 

are needed to compute flood-peak discharges and calibrate 

water-surface-elevation models. This report was prepared in 

cooperation with the Iowa Department of Transportation and 

the Iowa Highway Research Board.

As a result of intense periods of rainfall 

July 22–24, 2010, minor flooding occurred in the Little 

Maquoketa River Basin and major flooding occurred in 

the Maquoketa River Basin during July 23–26. Seventytwo-hour rainfall amounts recorded at Manchester and 

Strawberry Point on July 24 were 7.33 and 12.23 inches, 

respectively. The majority of the rainfall occurred during a 

48-hour period. Within the Little Maquoketa River Basin, 

a peak-discharge estimate of 19,000 ft3/s (annual floodprobability estimate of 4 to 10 percent) at the discontinued 

streamgage 05414500 Little Maquoketa River near Durango, 

Iowa on July 23 is the sixth largest flood on record. Within 

the Maquoketa River Basin, peak discharges of 26,600 ft3/s 

(annual flood-probability estimate of 0.2 to 1 percent) at the 

05416900 Maquoketa River at Manchester, Iowa streamgage 

on July 24, and of 25,000 ft3/s (annual flood-probability estimate of 1 to 2 percent) at the 05418400 North Fork Maquoketa River near Fulton, Iowa streamgage also on July 24 are 

the largest floods on record for these sites. A peak discharge 

of 46,000 ft3/s on July 26 at the 05418500 Maquoketa River 

near Maquoketa, Iowa streamgage is the third highest on 

record. The July 24 breach of Lake Delhi Dam, located 74 

river miles upstream of the Maquoketa River near Maquoketa streamgage, affected the flood peak at the Maquoketa 

streamgage.

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18 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

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576 p.
Figures 5–18 19

Figures 5–18
1 Flood profile, July 2010 Low-flow profile, Novem

Bridge-deck elevation Low-bridge-chord eleva

EXPLANATION 580 600 620 640 660 680 700 720 740 760 780 800 820 840 860 Little Maquoketa River | North Fork Little Maquoketa River

Elevation, in feet above NGVD 29

Locations indicated by these vertical lines are described in figures 6 and 7

Distance upstream from mouth of Little Maquoketa River, in river miles

0 2 4 6 8 10 12 14 16 18 20 

Figure 5. Profile of the July 23, 2010, flood for the Little Maquoketa River and the North Fork Little Maquoketa River, river miles 4 to 23.
Distance upstream from mouth of Little Maquoketa River, in river miles

Little Maquoketa River | North Fork Little Maquoketa River

Elevation, in feet above NGVD 29

Flood profile, July 20Low-flow profile, NoBridge-deck elevatiLow-bridge-chord e

EXPLANATION

580600620640660680700720740760780

Flood peak July 23, 2010, 

discharge estimate 

19,000 cubic feet per second

0 1 2 3 4 5 6 7 8 9 10 

U.S. Highway 52, T90N R02E 34SW

Clay Hill Road, T89N R02E 05NE

Mouth of the North Fork Little 

Maquoketa River

Mouth of the Middle Fork Little 

MkRi

Figure 6. Profile of the July 23, 2010, flood for the Little Maquoketa River and the North Fork Little Maquoketa River, river miles 4 to 12.
Figure 7. Profile of the July 23, 2010, flood for the North Fork Little Maquoketa River, river miles 12 to 23.

Flood peak July 23, 2010, 

discharge 

4,200 cubic feet per second

Distance upstream from mouth of Little Maquoketa River, in river miles

Elevation, in feet above NGVD 29

Flood profile, July 20Low-flow profile, NoBridge-deck elevatiLow-bridge-chord e

EXPLANATION

12 13 14 15 16 17 18 19 20 21 22 

660680700720740760780800820840860

USGS streamgage 05414450, South 

Mound Road, T90N R01E 28NW
Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

0 10 20 30 40 50 60 70 80 90 100 110 120 13

Locations indicated by these vertical lines are described in figures 9 through 13.

560600640680720760800840880920960

1,0001,0401,0801,120

Flood profile, July 2010Low-flow profile, November 15–17Flood profile, May 2004Low-flow profile, November 10, 20Flood profile, June 2002Low-flow profile, December 3–4, 2Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Figure 8. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 2 to 144.
Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

0 5 10 15 20 25 

Flood profile, July 2010Low-flow profile, November 16, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Flood peak July 26, 2010, 

discharge 

46,000 cubic feet per second

Flood peak June 5, 2002, 

discharge 

47,900 cubic feet per second

Spragueville 

November 16, 2010, 

discharge 

953 cubic feet per second

550560570580590600610620630640650660670680690700710720

U.S. Highway 52, T85N R05E 23NE

Mouth of Deep Creek

County Road Z20/387th Avenue, 

T84N R04E 13SE

Mouth of Brush Creek

County Road E23Y/Iron Bridge Road, 

T84N R04E 08NE

Figure 9. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 2 to 30.
Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

30 35 40 45 50 55 

Flood profile, July 2010Low-flow profile, NovemFlood profile, June 2002Low-flow profile, DecemBridge-deck elevationLow-bridge-chord eleva

EXPLANATION

Maquoketa

620630640650660670680690700710720730740750760770780790

Mouth of North Fork Maquoketa River

U.S. Highway 61, T84N R02E 24NW

Lakehurst Dam, T84N R02E 23NW

Mouth of Bear Creek

74th Street, T84N R01E 13NW

County Road Y34/50th Avenue,

T84N R01E 03NE

30th Avenue, T85N R01E 33SW

Mouth of Mineral Creek

Jackson-Jones County Line

Jones-Jackson County Line

Jackson-Jones County Line

Figure 10. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 30 to 60.
Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

60 65 70 75 80 85 

Flood profile, July 2010Low-flow profile, November 16–17, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Flood peak June 4, 2002, 

discharge 

47,500 cubic feet per second

Monticello

700710720730740750760770780790800810820830840850860870

State Highway 136, T85N R01W 06NW

Ebys Mill Road, T85N R02W 03SE

U.S. Highway 151, T86N R03W 23NW 

Mouth of Kitty Creek

Main Street, T86N R03W 22SE 

State Highway 38, T86N R03W 16NE

Mouth of Silver Creek

Figure 11. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 60 to 90.
Flood profile, July 2010Low-flow profile, November 15–16, 2010Flood profile, May 2004Low-flow profile, November 10, 2004Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

90 95 100 105 110 115 

Flood peak July 24, 2010, 

discharge 

26,600 cubic feet per second

Flood peak May 23, 2004, 

discharge 

26,000 cubic feet per second

Flood peak June 4, 2002, 

discharge 

10,800 cubic feet per second

November 16, 2010, 

discharge 

173 cubic feet per second

Hopkinton Mancheste

Lake Delhi

810820830840850860870880890900910920930940950960970980

County Road D47/Marion Street, 

T87N R04W 24NW

Mouth of Buck Creek

Mouth of Plum Creek

County Road X31/230th Street, 

Lake Delhi Dam, T88N R04W 30NE

County Road X29/220th Avenue, 

T88N R04W 30NW

County Road X21/240th Street, 

T88N R05W 15NE

USGS streamgage 05416900, 

U.S. Highway 20, T89N R05W 33SW

Marion Street Dam, T89N R05W 32NE

State Highway 13/West Main Street, 

T89N R05W 32NW

Mouth of Coffins Creek

Figure 12. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 90 to 120.
Distance upstream from mouth of Maquoketa River, in river miles

Elevation, in feet above NGVD 29

120 125 130 135 140 145 

Flood profile, July 2010Low-flow profile, November 15–16, 2010Flood profile, May 2004Low-flow profile, November 10, 2004Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Dundee Backbone State Park

0.9940

950960970980990

1,0001,0101,0201,0301,0401,0501,0601,0701,0801,0901,1001,110

County Road C64/Richland Street, 

T90N R06W 27SW

Backbone State Park Dam, 

T90N R06W 22NE

Mouth of South Fork Maquoketa River

Backbone State Park Road, 

T90N R06W 09SW

State Highway 3, T91N R07W 24NE

State Highway 187, T91N R07W 02SW

Figure 13. Profile of the July 23–26, 2010, flood for the Maquoketa River, river miles 120 to 144.
Distance upstream from mouth of North Fork Maquoketa River, in river miles

Elevation, in feet above NGVD 29

0 10 20 30 40 50 60 70 80 

Flood profile, July 2010Low-flow profile, November 17, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Locations indicated by these vertical lines are described in figures 15 through 18

640660680700720740760780800820840860880900920940960980

1,0001,0201,0401,0601,080

Figure 14. Profile of the July 23–24, 2010, flood for the North Fork Maquoketa River, river miles 0 to 90.
Distance upstream from mouth of North Fork Maquoketa River, in river miles

Elevation, in feet above NGVD 29

0 5 10 15 20 

Flood peak July 24, 2010, 

discharge 

25,000 cubic feet per second

December 4, 2002, 

discharge 

289 cubic feet per second

Flood peak June 5, 2002, 

discharge 

22,600 cubic feet per second

November 17, 2010, 

discharge 

366 cubic feet per second

Flood profile, July 2010Low-flow profile, NovemFlood profile, June 2002Low-flow profile, DecemBridge-deck elevationLow-bridge-chord elevat

EXPLANATION

Fulton

600610620630640650660670680690700710720730740750760

Rockdale Road, T84N R02E 13NE

Mouth of Farmers Creek

U.S. Highway 61, T85N R02E 25NE

USGS streamgage 05418400, County 

Road E17/150th Street, T85N R02E 16SE

Mouth of Lytle Creek

Figure 15. Profile of the July 23–24, 2010, flood for the North Fork Maquoketa River, river miles 0 to 25.
Distance upstream from mouth of North Fork Maquoketa River, in river miles

Elevation, in feet above NGVD 29

25 30 35 40 45 

Flood profile, July 2010Low-flow profile, November 17, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Cascade

700710720730740750760770780790800810820830840850860

21st Avenue, T85N R01E 05SW

Jackson-Jones County Line

Jones-Jackson County Line

Jackson-Jones County Line

Mouth of Whitewater Creek

Jones-Dubuque County Line

Dubuque-Jones County Line

Jones-Dubuque County Line

1st Avenue West, T87N R01W 31SW

U.S. Highway 151, T87N R02W 36NE

Figure 16. Profile of the July 23–24, 2010, flood for the North Fork Maquoketa River, river miles 25 to 50.
Distance upstream from mouth of North Fork Maquoketa River, in river miles

Elevation, in feet above NGVD 29

50 55 60 65 70 

Flood profile, July 2010Low-flow profile, November 17, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

Worthington Dyers

820830840850860870880890900910920930940950960970980

Dubuque-Delaware County Line

Delaware-Dubuque County Line

Along 305th Street, T87N R02W 18SW

Dubuque-Delaware County Line

Delaware-Dubuque County Line

Dubuque-Delaware County Line

County Road D35/272nd Street, 

T88N R03W 36NE

Delaware-Dubuque County Line

U.S. Highway 20, T88N R02W 06NW

Mouth of Bear Creek

Figure 17. Profile of the July 23–24, 2010, flood for the North Fork Maquoketa River, river miles 50 to 75.
Distance upstream from mouth of North Fork Maquoketa River, in river miles

Elevation, in feet above NGVD 29

75 80 85 90 95 

Flood profile, July 2010Low-flow profile, November 17, 2010Flood profile, June 2002Low-flow profile, December 3–4, 2002Bridge-deck elevationLow-bridge-chord elevation

EXPLANATION

New Vienna

920930940950960970980990

1,0001,0101,0201,0301,0401,0501,0601,0701,080

State Highway 136, T89N R02W 05SW

U.S. Highway 52, T90N R02W 23NE

Figure 18. Profile of the July 23–24, 2010, flood for the North Fork Maquoketa River, river miles 75 to 100.
34 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa
Appendix 35

Appendix
36 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

List of Bench Marks and Reference Points

To facilitate measuring and referencing the high-water 

marks (HWMs) used in the flood profiles to a common datum, 

bench marks (BMs), temporary bench marks (TBMs), and 

reference points (RPs) were found or established by the 

U.S. Geological Survey (USGS) at selected bridges along 

the profiled river reaches. All BM, TBM, and RP elevations 

listed in appendix table 1 are referenced to the National Geodetic Vertical Datum of 1929. The list of 46 sites where the 

USGS measured HWMs for the July 2010 floods is shown in 

tables 7–9. Of these 46 sites, BMs or TBMs are listed for 44 of 

the sites and RPs are listed for 39 of the sites in appendix 

table 1. For 8 of the 46 sites listed in this appendix, elevations for BMs and TBMs were established by other agencies 

and these agencies are listed in appendix table 1. At USGS 

streamgages, BMs or TBMs are identified as reference marks 

(RMs) that are listed in appendix table 1 with an RM number. 

BM, TBM, and RP elevations established by the USGS were 

determined from a combination of global positioning system 

(GPS) technology and differential leveling. For 31 of the 

46 sites listed in this appendix, elevations were established by 

the USGS using GPS and are noted in the BM, TBM, and RP 

descriptions. GPS data were collected by the USGS using two 

different methods. Static surveys of GPS data were submitted 

for processing to the Online Positioning User Service (OPUS), 

an Internet service provided by the National Geodetic Survey 

(http://www.ngs.noaa.gov/OPUS/). The quality of the OPUS 

GPS data is based on the guidelines of “What to look for in a 

quality solution” (http://www.ngs.noaa.gov/OPUS/about.html, 

accessed May 27, 2011). Real Time Kinematic (RTK) surveys 

of GPS data were processed using the IaRTN SmartNet, a 

Global Navigation Satellite System (GNSS) reference station 

network service provided by Iowa DOT and Leica Geosystems 

(http://spiderweb.iartn.com/spiderweb/frmIndex.aspx). The 

quality of the RTK GPS data is based on an average of multiple sets of GPS data collected using satellite configurations 

spaced at least 30 minutes apart, and on comparisons of elevations between RTK GPS surveys of GPS BMs and published 

elevations.

In general, BMs are points that were specifically designed 

to mark an elevation, such as USGS elevation disks and Iowa 

DOT BMs (round-top rods embedded in concrete at one or 

more corners of a bridge). Marks—such as squares and crosses 

that were chiseled or filed on concrete or metal, or existing bolts on bridges—were used as TBMs or RPs. RPs were 

established to permit water-surface elevations to be determined 

by use of a tape and weight. The terms "right" and "left" in 

the descriptions are determined as viewed while facing in the 

downstream direction.

The BMs, TBMs, and RPs are designated by an index 

number or legal description derived from their respective 

locations using Public Land Survey System coordinates 

(township, range, section). Within the section, the quarter 

section in which the BM, TBM, or RP is located is designated by NE, SE, NW, and SW. For example, T90N R02E 

34 SW refers to a location in Township 90 North, Range 2 

East, southwest quarter of section 34. A number in parentheses following the quarter-section designation indicates 

the sequence number of the BM, TBM, or RP in that particular quarter section. The index number serves to describe 

the legal description of the mark without further reference 

in the body of the description. The physical location of 

the BM or TBM on a bridge dictates the appropriate legal 

description. The RPs, and any additional BMs or TBMs, 

are listed with the related BMs or TBMs and are identified 

by the same legal description though, at times, they are in 

a different section, range, or township as determined by 

upstream or downstream location.

The BMs, TBMs, and RPs are listed in appendix table 1 

in upstream order for the Little Maquoketa, North Fork Little 

Maquoketa, Maquoketa, and North Fork Maquoketa Rivers. 

The user of this information is cautioned that BMs, TBMs, 

and RPs listed herein might have been disturbed, destroyed, or 

moved since elevations were established. It is the responsibility of the user to determine the condition and the suitability of 

the BM, TBM, or RP.
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.

, reference point; GPS, Global Positioning System; USGS, U

-section designation indicates the sequence number o

[Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RPtownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarterparticular quarter section]

Public Land Survey Elevatio

System Mark in feet Location Mark 

(township, range, section, classification (NGVD 

quarter section) 1929)

Little Maquoketa River

T90N R02E 34 SW (1) BM About 0.25 mile south of Sageville, on U.S. Highway 52 bridge over Little Iowa Department of Transportation 634.25 

Maquoketa River, on left downstream wingwall. bench mark

T90N R02E 34 SW (2) RP About 0.25 mile south of Sageville, on U.S. Highway 52 bridge over Little Chiseled arrow 633.52 

Maquoketa River, at 2nd drain from right downstream end of bridge.

T89N R02E 05 NE (1) BM About 1.5 miles east of Durango, site of discontinued streamgage 05414500 USGS bench mark 643.40 

Little Maquoketa River near Durango, on Clay Hill Road bridge over Little Maquoketa River, on left upstream wingwall.

T89N R02E 05 NE (2) RP About 1.5 miles east of Durango, site of discontinued streamgage 05414500 Chiseled arrow 643.08 

Little Maquoketa River near Durango, on Clay Hill Road bridge over Little Maquoketa River, between 18th and 19th vertical concrete pillars from end of bridge. 

North Fork Little Maquoketa River

T90N R01E 35 NE (1) BM About 1.5 miles northwest of Durango, on U.S. Highway 52 bridge over National Geodetic Survey U.S. Coast 669.85 

North Fork Little Maquoketa River, on concrete rail at left downstream & Geodetic Survey bench mark end of bridge. stamped “R177 reset 1995” 

T90N R01E 35 NE (2) RP About 1.5 miles northwest of Durango, on U.S. Highway 52 bridge over Chiseled arrow 668.06 

North Fork Little Maquoketa River, on downstream concrete lip between 1st and 2nd drains.

T90N R01E 28 NW (1) TBM About 1.3 miles east of Rickardsville, site of streamgage 05414450 North Chiseled cross. 760.71 

Fork Little Maquoketa River near Rickardsville, on South Mound Road bridge over North Fork Little Maquoketa River, on bolt head 1 foot below curb at left upstream end of bridge.

T90N R01E 28 NW (2) RP About 1.3 miles east of Rickardsville, site of streamgage 05414450 North Three filed marks 766.14 

Fork Little Maquoketa River near Rickardsville, on South Mound Road bridge over North Fork Little Maquoketa River, on largest metal rail about 30 feet from left downstream end of bridge.

T90N R01E 19 NW (1) TBM About 0.75 mile northwest of Rickardsville, on James Road bridge over Chiseled square. 857.85 

North Fork Little Maquoketa River, on right downstream wingwall. 

T90N R01E 19 NW (2) RP About 0.75 mile northwest of Rickardsville, on James Road bridge over Chiseled arrow 856.79 

North Fork Little Maquoketa River, on downstream concrete rail at middle of bridge. 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued [Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section] Public Land Survey System (township, range, section, quarter section) Mark classification Location Mark Elevatio

in feet (NGVD 1929) 

Maquoketa River T85N R05E 23 NE (1) BM About 1 mile northwest of Green Island, on U.S. Highway 52 bridge over Maquoketa River, on right downstream wingwall. Iowa Department of Transportation bench mark 615.70 

T85N R05E 23 NE (2) BM About 1 mile northwest of Green Island, on U.S. Highway 52 bridge over Maquoketa River, on left upstream wingwall. Iowa Department of Transportation bench mark. 615.69 T85N R05E 23 NE (3) BM About 1 mile northwest of Green Island, on U.S. Highway 52 bridge over Maquoketa River, on concrete platform at curb level at left upstream end of bridge. Iowa Department of Transportation bench mark. 613.57 T85N R05E 23 NE (4) RP About 1 mile northwest of Green Island, on U.S. Highway 52 bridge over Maquoketa River, on concrete platform behind 7th drain from left down- stream end of bridge. Chiseled square. 614.29 T84N R04E 13 SE (1) TBM About 0.75 mile north of Spragueville, on County Road Z20/387th Avenue bridge over Maquoketa River, on outer wingwall about 1.5 ft from guard- rail at left downstream end of bridge. Chiseled square. 635.01 T84N R04E 13 SE (2) RP About 0.75 mile north of Spragueville, on County Road Z20/387th Avenue bridge over Maquoketa River, behind 18th guardrail post from right down- stream end of bridge. Three filed marks 638.93 T84N R04E 08 NE (1) TBM About 5 miles southeast of Andrew, on County Road E23Y/Iron Bridge Road over Maquoketa River, on corner of lower wingwall at left upstream end of bridge. Chiseled square 647.40 T84N R04E 08 NE (2) RP About 5 miles southeast of Andrew, on County Road E23Y/Iron Bridge Road over Maquoketa River, on guardrail about 8 feet left of 2nd vertical truss member from right downstream end of bridge. Three filed marks 661.14 T84N R03E 17 NE (1) TBM About 1.5 miles northeast of Maquoketa, site of streamgage 05418500 Maquoketa River near Maquoketa, on State Highway 62 bridge over Maquoketa River, on right downstream abutment. Chiseled square (RM 19) 670.77 T84N R03E 17 NE (2) TBM About 1.5 miles northeast of Maquoketa, site of streamgage 05418500 Maquoketa River near Maquoketa, on State Highway 62 bridge over Maquoketa River, on right upstream abutment. Chiseled square (RM 20) 670.78 T84N R02E 24 NW (1) BM At Maquoketa, on northbound lane of U.S. Highway 61 bridge over Maquoketa River (downstream bridge), on right upstream wingwall. Iowa Department of Transportation bench mark 683.94 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued[Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section]

Public Land Survey Elevatio

System Mark in feet Location Mark 

(township, range, section, classification (NGVD 

quarter section) 1929)

Maquoketa River—Continued

T84N R02E 24 NW (2) BM At Maquoketa, on southbound lane of U.S. Highway 61 bridge over Iowa Department of Transportation 699.76 

Maquoketa River (upstream bridge), on right downstream wingwall. bench mark 

T84N R02E 24 NW (3) RP At Maquoketa, on northbound lane of U.S. Highway 61 bridge over Chiseled square 683.08 

Maquoketa River (downstream bridge), on concrete platform behind 7th drain from either end of bridge. 

T84N R01E 03 NE (1) TBM About 3.2 miles northeast of Baldwin, on County Road Y34/50th Avenue Chiseled square 728.72 

bridge over Maquoketa River, on left downstream concrete rail.

T84N R01E 03 NE (2) RP About 3.2 miles northeast of Baldwin, on County Road Y34/50th Avenue Three filed marks 725.82 

bridge over Maquoketa River, on meatal rail at 4th drain from left downstream end of bridge. 

T85N R01E 33 SW (1) TBM About 3.5 miles north of Monmouth, on 30th Avenue bridge over Maquoketa Filed cross 713.56 

River, on threaded bolt on outer downstream end of left downstream pier.

T85N R01E 33 SW (2) RP About 3.5 miles north of Monmouth, on 30th Avenue bridge over Maquoketa Three file marks 719.18 

River, on guardrail about 0.5 foot left of guardrail post between 2nd and 3rd vertical truss members from left downstream end of bridge.

T85N R01W 08 SE (1) TBM About 4.25 miles northwest of Canton, on Temple Hill Road bridge over Chiseled cross 749.79 

Maquoketa River, on right downstream wingwall.

T85N R01W 08 SE (2) RP About 4.25 miles northwest of Canton, on Temple Hill Road bridge over Chiseled square 746.61 

Maquoketa River, on concrete barrier wall at 20th concrete post from left downstream end of bridge.

T85N R01W 06 NW (1) BM About 5.75 miles northeast of Scotch Grove, on State Highway 136 bridge Iowa Department of Transportation 756.74 

over Maquoketa River, on left upstream wingwall. bench mark

T85N R01W 06 NW (2) RP About 5.75 miles northeast of Scotch Grove, on State Highway 136 bridge Chiseled square 757.03 

over Maquoketa River, on concrete platform behind 4th drain from left downstream end of bridge.

T85N R02W 03 SE (1) BM About 3 miles northeast of Scotch Grove, on Ebys Mill Road bridge over Brass tablet 774.43 

Maquoketa River, on right downstream concrete rail.

T85N R02W 03 SE (2) RP About 3 miles northeast of Scotch Grove, on Ebys Mill Road bridge over Chiseled arrow 772.74 

Maquoketa River, on downstream concrete rail at 27th vertical rail from right end of bridge.
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued [Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section] Public Land Survey System (township, range, section, quarter section) Mark classification Location Mark Elevatio

in feet (NGVD 1929) 

Maquoketa River—Continued T86N R03W 23 NW (1) BM About 1 mile northeast of Monticello, on northbound lane of U.S. Highway 151 bridge over Maquoketa River (downstream bridge), on right down- stream concrete rail. Iowa Department of Transportation bench mark. 854.86 

T86N R03W 23 NW (2) RP About 1 mile northeast of Monticello, on northbound lane of U.S. Highway 151 bridge over Maquoketa River (downstream bridge), on downstream concrete rail at 4th drain from right end of bridge. Chiseled arrow 860.12 

T86N R03W 22 SE (1) BM At Monticello, on Main Street bridge over Maquoketa River, on outside curb behind guardwall at left upstream end of bridge. Iowa Department of Transportation bench mark 813.68 T86N R03W 22 SE (2) RP At Monticello, on Main Street bridge over Maquoketa River, on concrete platform behind 7th drain from left downstream end of bridge. Chiseled square 814.16 T86N R03W 16 NE (1) BM At Monticello, on State Highway 38 bridge over Maquoketa River, on left upstream wingwall. Iowa Department of Transportation bench mark 823.96 T86N R03W 16 NE (2) RP At Monticello, on State Highway 38 bridge over Maquoketa River, on concrete platform right of 21st metal bracket from right downstream end of bridge and across from center of 3rd and 4th drains from right upstream end of bridge. Chiseled square 824.68 T87N R04W 24 NW (1) BM About 0.5 mile southwest of Hopkinton, on County Road D47/Marion Street bridge over southern channel of Maquoketa River, on left downstream end of sidewalk concrete barrier wall. Delaware County bench mark 846.90 T87N R04W 24 NW (2) RP About 0.5 mile southwest of Hopkinton, on County Road D47/Marion Street bridge over southern channel of Maquoketa River, on downstream side of cyclone fence at 12th fence post from right downstream end of bridge. Edge of concrete sidewalk 844.83 T88N R04W 30 NE (1) TBM About 1.5 miles southwest of Delhi, on County Road X31/230th Avenue 

crossing Lake Delhi dam on Maquoketa River, on end of right downstream wingwall.

Chiseled cross 907.37 

T88N R04W 30 NW (1) BM About 2 miles southwest of Delhi, on County Road X29/220th Avenue bridge 

over Lake Delhi, on concrete rail at left upstream end of bridge.

Delaware County bench mark 909.60 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued[Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section]

Public Land Survey 

System 

(township, range, section, 

quarter section)

Mark 

classification Location Mark

Elevatio

in feet 

(NGVD 

1929)

Maquoketa River—Continued

T88N R04W 30 NW (2) RP About 2 miles southwest of Delhi, on County Road X29/220th Avenue bridge 

over Lake Delhi, on 22nd vertical concrete post from left downstream end of bridge.

Chiseled arrow 913.54 

T88N R05W 15 NE (1) TBM About 4 miles southeast of Manchester, on County Road X21/240th Street 

bridge over Maquoketa River, on corner of wingwall near guardrail at right upstream end of bridge.

Chiseled square 915.58 

T88N R05W 15 NE (2) RP About 4 miles southeast of Manchester, on County Road X21/240th Street 

bridge over Maquoketa River, on metal guardrail behind 3rd drain from right downstream end of bridge.

Three filed marks 917.32 

T89N R05W 33 SW(1) BM About 0.5 mile south of Manchester, on eastbound lane of U.S. Highway 

20 bridge over Maquoketa River (downstream bridge), on left upstream abutment.

Iowa Department of Transportation 

bench mark (RM 1)

938.14 

T89N R05W 33 SW(2) TBM About 0.5 mile south of Manchester, on eastbound lane of U.S. Highway 20 

bridge over Maquoketa River (downstream bridge), on left downstream abutment.

Chiseled square (RM 2) 938.34 

T89N R05W 32 NE (1) TBM At Manchester, on Marion Street bridge over Maquoketa River, at left downstream end of bridge underneath Marion Street bridge sign. Chiseled cross 939.00 T89N R05W 32 NE (2) TBM At Manchester, on Marion Street bridge over Maquoketa River, on retaining 

wall at left upstream abutment.

Chiseled cross 938.93 

T89N R05W 32 NE (3) RP At Manchester, on Marion Street bridge over Maquoketa River, beneath 

metal box attached to downstream guardrail.

Edge of concrete sidewalk 940.72 

T89N R05W 32 NW (1) BM At Manchester, on State Highway 13/West Main Street bridge over Maquoketa River, on left downstream end of sidewalk concrete barrier wall at 

end of metal rail.

Iowa Department of Transportation 

bench mark

944.30 

T89N R05W 32 NW (2) RP At Manchester, on State Highway 13/West Main Street bridge over Maquoketa River, on downstream side of cyclone fence at 10th fence post from 

left downstream end of bridge.

Edge of concrete sidewalk 945.08 

T89N R05W 19 NE (1) TBM About 0.5 mile northwest of Manchester, on 195th Street bridge over Maquoketa River, on right upstream end of lower wingwall. Chiseled square 943.11 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued [Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section] Public Land Survey System (township, range, section, quarter section) Mark classification Location Mark Elevatio

in feet (NGVD 1929) 

Maquoketa River—Continued T89N R05W 19 NE (2) RP About 0.5 mile northwest of Manchester, on 195th Street bridge over Maquoketa River, on downstream metal rail between 3rd and 4th drains from left end of bridge. Three filed marks 945.78 

T90N R06W 27 SW (1) TBM At west edge of Dundee, on County Road C64/Richland Street bridge over Maquoketa River, on right upstream end of concrete rail. Chiseled square 991.96 

T90N R06W 27 SW (2) BM At west edge of Dundee, on County Road C64/Richland Street bridge over Maquoketa River, on left downstream concrete rail. Delaware County bench mark 996.20 

T90N R06W 27 SW (3) RP At west edge of Dundee, on County Road C64/Richland Street bridge over Maquoketa River, on downstream concrete rail near middle of channel. Chiseled arrow 994.59 

T90N R06W 22 NE (1) TBM At Backbone State Park, on southeast dam of two dams across Maquoketa River, below cyclone fence on downstream end of upper horizontal con- crete structure on left end of dam. Chiseled square 1007.34 

T90N R06W 22 NE (2) RP At Backbone State Park, on southeast dam of two dams across Maquoketa River, below cyclone fence on upstream end of upper horizontal concrete structure on left end of dam. Most upstream edge of upper hori- zontal concrete surface 1007.48 

T90N R06W 22 NE (3) RP At Backbone State Park, on southeast dam of two dams across Maquoketa River, behind cyclone fence post on upstream end of lower horizontal concrete structure on left end of dam. Most upstream edge of lower hori- zontal concrete surface 996.08 

T90N R06W 09 SW (1) BM At Backbone State Park, on County Road C57/ 120th Street bridge over Maquoketa River, on right downstream wingwall. Iowa Department of Transportation bench mark 1,010.28 

T90N R06W 09 SW (2) RP At Backbone State Park, on County Road C57/ 120th Street bridge over Maquoketa River, on downstream concrete barrier wall about 1 foot right of center of concrete sections. Chiseled square 1,010.27 

T91N R07W 24 NE (1) BM About 3.5 miles west of Strawberry Point, on State Highway 3 bridge over Maquoketa River, on left downstream lower wingwall. Iowa Department of Transportation bench mark 1,088.42 T91N R07W 24 NE (2) RP About 3.5 miles west of Strawberry Point, on State Highway 3 bridge over 

Maquoketa River, on outer concrete platform behind 8th guardrail post from left downstream end of bridge.

Chiseled square 1,089.44 

T91N R07W 02 SW (1) BM About 2.25 miles southeast of Arlington, on State Highway 187 bridge over 

Maquoketa River, on left downstream wingwall.

Iowa Department of Transportation 

bench mark 

1,109.99 

T91N R07W 02 SW (2) RP About 2.25 miles southeast of Arlington, on State Highway 187 bridge over 

Maquoketa River, on outer concrete platform behind 3rd drain from right 

downstream end of bridge.

Chiseled square 1,108.37 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued[Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section]

Public Land Survey 

System 

(township, range, section, 

quarter section)

Mark 

classification Location Mark

Elevatio

in feet 

(NGVD 

1929)

North Fork Maquoketa River

T84N R02E 13 NE (1) BM About 1 mile north of Maquoketa, on Rockdale Road bridge over North Fork 

Maquoketa River, on right downstream wingwall.

Iowa Department of Transportation 

bench mark

674.39 

T84N R02E 13 NE (2) RP About 1 mile north of Maquoketa, on Rockdale Road bridge over North Fork 

Maquoketa River, on guardrail about 3 inches right of 28th guardrail post from left downstream end of bridge.

Three filed marks 675.24 

T85N R02E 25 NE (1) BM About 0.5 mile south of Fulton, site of discontinued streamgage 05418450 

North Fork Maquoketa River at Fulton, on southbound lane of U.S. Highway 61 bridge over North Fork Maquoketa River (upstream bridge), on left downstream wingwall.

Iowa Department of Transportation 

bench mark

699.52 

T85N R02E 25 NE (2) BM About 0.5 mile south of Fulton, site of discontinued streamgage 05418450 

North Fork Maquoketa River at Fulton, on northbound lane of U.S. Highway 61 bridge over North Fork Maquoketa River (downstream bridge), on 

right downstream wingwall.

Iowa Department of Transportation 

bench mark

700.05 

T85N R02E 25 NE (3) RP About 0.5 mile south of Fulton, site of discontinued streamgage 05418450 

North Fork Maquoketa River at Fulton, on northbound lane of U.S. Highway 61 bridge over North Fork Maquoketa River (downstream bridge), on 

concrete platform behind 4th drain from right downstream end of bridge.

Chiseled square 697.68 

T85N R02E 16 SE (1) TBM About 2.75 miles northwest of Fulton, site of streamgage 05418400 North 

Fork Maquoketa River near Fulton, on County Road E17/150th Street bridge over North Fork Maquoketa River, on left downstream wingwall.

Chiseled square (RM 1) 711.21 

T85N R02E 16 SE (2) TBM About 2.75 miles northwest of Fulton, site of streamgage 05418400 North 

Fork Maquoketa River near Fulton, on County Road E17/150th Street bridge over North Fork Maquoketa River, on right upstream wingwall.

Chiseled square (RM 3) 711.16 

T85N R01E 10 SW (1) TBM About 3.25 miles northeast of Canton, on 60th Avenue bridge over North 

Fork Maquoketa River, on right upstream bolt on right upstream pier.

Filed cross 732.21 

T85N R01E 10 SW (2) RP About 3.25 miles northeast of Canton, on 60th Avenue bridge over North 

Fork Maquoketa River, on guardrail about 10 feet left of 2nd vertical truss member from right downstream end of bridge.

Three filed marks 736.15 

T85N R01E 05 SW (1) TBM About 2.5 miles northeast of Canton, on 21st Avenue bridge over North Fork 

Maquoketa River, on roadside end of concrete curb next to metal bracket at left downstream end of bridge.

Chiseled square 758.63 

T85N R01E 05 SW (2) RP About 2.5 miles northeast of Canton, on 21st Avenue bridge over North Fork 

Maquoketa River, on metal guardrail at 4th drain from right downstream end of bridge.

Three filed marks 767.33 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued [Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section] Public Land Survey System (township, range, section, quarter section) Mark classification Location Mark Elevatio

in feet (NGVD 1929) 

North Fork Maquoketa River—Continued T87N R01W 31 SW (1) BM At Cascade, on 1st Avenue West bridge over North Fork Maquoketa River, on corner of right downstream wingwall. Iowa Department of Transportation bench mark 828.54 

T87N R01W 31 SW (2) RP At Cascade, on 1st Avenue West bridge over North Fork Maquoketa River, on downstream side of cyclone fence centered between 8th and 9th fence posts from right downstream end of bridge. Edge of concrete sidewalk 825.52 

T87N R01W 31 SW (3) RP At Cascade, on 1st Avenue West bridge over North Fork Maquoketa River, on upstream side of cyclone fence centered between 8th and 9th fence posts from right upstream end of bridge. Edge of concrete sidewalk 825.53 

T87N R02W 36 NE (1) BM About 0.4 mile north of Cascade, on east bound lane of U.S. Highway 151 bridge over North Fork Maquoketa River (downstream bridge), on con- crete rail at left downstream end of bridge. Iowa Department of Transportation bench mark 835.61 T87N R02W 36 NE (2) TBM About 0.4 mile north of Cascade, on east bound lane of U.S. Highway 151 bridge over North Fork Maquoketa River (downstream bridge), on con- crete rail at right downstream end of bridge. Chiseled square 850.31 T87N R02W 36 NE (3) RP About 0.4 mile north of Cascade, on east bound lane of U.S. Highway 151 bridge over North Fork Maquoketa River (downstream bridge), on down- stream concrete rail between 8th and 9th drains from right end of bridge. Chiseled arrow 843.28 T87N R02W 26 NW (1) BM About 2 miles northwest of Cascade, on State Highway 136 bridge over North Fork Maquoketa River, on left downstream wingwall. Iowa Department of Transportation bench mark 843.72 T87N R02W 26 NW (2) BM About 2 miles northwest of Cascade, on State Highway 136 bridge over North Fork Maquoketa River, on right downstream wingwall. Iowa Department of Transportation bench mark 843.64 T87N R02W 26 NW (3) RP About 2 miles northwest of Cascade, on State Highway 136 bridge over North Fork Maquoketa River, on concrete platform behind downstream concrete barrier wall across from 4th drain from either upstream end of bridge. Chiseled square 841.75 T87N R02W 18 SW (1) TBM About 3.5 miles south of Worthington, on 305th Street bridge over unnamed 

tributary to North Fork Maquoketa River, in post near right downstream wingwall of small wooden bridge.

Top of horizontal lag bolt 864.43 

T88N R03W 36 NE (1) BM About 0.5 mile west of Worthington, on County Road D35/272nd Street 

bridge over North Fork Maquoketa River, on left upstream wingwall.

Delaware County bench mark 904.62 
Table 1. Bench marks and reference points used in the July 23–26, 2010, Little Maquoketa River, North Fork Little Maquoketa River, Maquoketa RiverRiver flood profiles.—Continued[Bench marks and reference points are listed in upstream order. BM, bench mark; TBM, temporary bench mark; RP, reference point; GPS, Global Positioning System; USGS, Utownship; R, range; N, north; W, west; S, south; E, east; RM, reference mark; a number in parentheses following the quarter-section designation indicates the sequence number oparticular quarter section]

Public Land Survey 

System 

(township, range, section, 

quarter section)

Mark 

classification Location Mark

Elevatio

in feet 

(NGVD 

1929)

North Fork Maquoketa River—Continued

T88N R03W 36 NE (2) RP About 0.5 mile west of Worthington, on County Road D35/272nd Street 

bridge over North Fork Maquoketa River, on concrete barrier wall between 13th and 14th concrete posts from left downstream end of bridge.

Chiseled square 904.32 

T88N R02W 06 NW (1) BM At Dyersville, on eastbound lane of U.S. Highway 20 bridge over North Fork 

Maquoketa River (downstream bridge), on left upstream end of concrete barrier wall.

Iowa Department of Transportation 

bench mark 

959.79 

T88N R02W 06 NW (2) TBM At Dyersville, on eastbound lane of U.S. Highway 20 bridge over North Fork 

Maquoketa River (downstream bridge), on right upstream end of concrete barrier wall.

Chiseled cross 961.81 

T88N R02W 06 NW (3) RP At Dyersville, on eastbound lane of U.S. Highway 20 bridge over North Fork 

Maquoketa River (downstream bridge), on concrete barrier wall at 9th drain from left downstream end of bridge.

Chiseled square 960.67 

T89N R02W 05 SW (1) BM At New Vienna, on State Highway 136/Columbus Street bridge over North 

Fork Maquoketa River, on left upstream end of concrete barrier wall.

Iowa Department of Transportation 

bench mark 

1,005.28 

T89N R02W 05 SW (2) BM At New Vienna, on State Highway 136/Columbus Street bridge over North 

Fork Maquoketa River, on right downstream end of concrete barrier wall.

Iowa Department of Transportation 

bench mark 

1,003.01 

T89N R02W 05 SW (3) RP At New Vienna, on State Highway 136/Columbus Street bridge over North 

Fork Maquoketa River, on concrete barrier wall between 2nd and 3rd drains from either downstream end of bridge.

Chiseled square 1,004.25 

T90N R02W 23 NE (1) BM About 1.5 miles east of Luxemburg, on U.S. Highway 52 bridge over North 

Fork Maquoketa River, on right downstream concrete rail.

Iowa Department of Transportation 

bench mark 

1,067.30 

T90N R02W 23 NE (2) RP About 1.5 miles east of Luxemburg, on U.S. Highway 52 bridge over North 

Fork Maquoketa River, on downstream concrete lip at middle of bridge.

Chiseled arrow 1,065.24 
46 Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa

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P.O. Box 1230

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(319) 337–4191

Or visit the Iowa Water Science Center Web site at:

http://ia.water.usgs.gov

Eash—Floods of July 23–26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa—Open-File Report 2011-1301

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