U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5107

Prepared in cooperation with the Village of Homer, Nebraska, 

and the Papio-Missouri River Natural Resources District

Estimated Flood Discharges and Map of Flood-Inundated 

Areas for Omaha Creek, near Homer, Nebraska, 2005

Estimated Flood Discharges and Map of 

Flood-Inundated Areas for Omaha Creek, 

near Homer, Nebraska, 2005

By Benjamin J. Dietsch, Richard C. Wilson, and Kellan R. Strauch

Prepared in cooperation with the Village of Homer, Nebraska, and the 

Papio-Missouri River Natural Resources District

Scientific Investigations Report 2008–5107

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Suggested citation:

Dietsch, B.J., Wilson, R.C., and Strauch, K.R., 2008, Estimated flood-inundation map for Omaha Creek, near Homer, 

Nebraska, 2005: USGS Scientific Investigations Report 2008–5107, 10 p.
iii

Contents

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

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

Purpose and Scope .......................................................................................................................................1

Description of the Study Area .....................................................................................................................2

Hydrologic Analysis..............................................................................................................................2

Hydraulic Analyses...............................................................................................................................2

Delineation of Areas Inundated by a Flood with 1-Percent Annual Probability..................................6

Estimated Flood Discharges and Map of Flood-Inundated Areas.........................................................6

Summary and Conclusions...........................................................................................................................8

References Cited..........................................................................................................................................10

Figures

1–2. Maps showing:

1. Location of Omaha Creek Basin and the study area in Dakota and Thurston Counties, 

northeastern Nebraska................................................................................................................3

2. Location of U.S. Geological Survey streamflow-gaging station, survey cross sections, 

and study area...............................................................................................................................4

3. Comparison of streambed elevations at locations surveyed in 1993 and 2005 along 

Omaha Creek at Homer, Nebraska ............................................................................................5

4. Frequency of selected flooding events for Omaha Creek near Homer, Nebraska, 

determined by log-Pearson Type III analysis for the systematic record (1946–2004) and 

historic data...................................................................................................................................8

5. Areas at risk for inundation by the 1-percent annual probability flood (100-year flood) 

on Omaha Creek, at Homer, Nebraska......................................................................................9

Tables

1. Summary of flood frequency for Omaha Creek at Homer, Nebraska, determined by logPearson Type III analysis of the systematic record (1946–2004) and historical data .......6

2. Water-surface elevation for estimated discharges and flood-recurrence intervals 

at U.S. Geological Survey streamflow-gaging station on Omaha Creek near Homer, 

Nebraska (06601000) ....................................................................................................................7
iv

Conversion Factors, Abbreviations, and Datum

Multiply By To obtain

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

inch (in) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2) 

cubic foot (ft3) 28.32 cubic decimeter (dm3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

foot per second (ft/s) 0.3048 meter per second (m/s)

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).
Abstract

Repeated flooding of Omaha Creek has caused damage 

in the Village of Homer. Long-term degradation and bridge 

scouring have changed substantially the channel characteristics of Omaha Creek. Flood-plain managers, planners, 

homeowners, and others rely on maps to identify areas at risk 

of being inundated. 

To identify areas at risk for inundation by a flood having a 1-percent annual probability, maps were created using 

topographic data and water-surface elevations resulting from 

hydrologic and hydraulic analyses. The hydrologic analysis for 

the Omaha Creek study area was performed using historical 

peak flows obtained from the U.S. Geological Survey streamflow gage (station number 06601000). Flood frequency and 

magnitude were estimated using the PEAKFQ Log-Pearson 

Type III analysis software. The U.S. Army Corps of Engineers’ Hydrologic Engineering Center River Analysis System, 

version 3.1.3, software was used to simulate the water-surface 

elevation for flood events. The calibrated model was used to 

compute streamflow-gage stages and inundation elevations for 

the discharges corresponding to floods of selected probabilities. Results of the hydrologic and hydraulic analyses indicated that flood inundation elevations are substantially lower 

than from a previous study.

Introduction

Flooding of Omaha Creek has caused damage in the Village of Homer, Nebraska, since the 1920’s. To mitigate flood 

damages financially and to manage development within the 

regulatory floodplain, the village entered into the National 

Flood Insurance Program administrated by the Federal Emergency Management Agency (Federal Emergency Management 

Agency, 1983). This program provides maps for identifying 

areas at risk for flooding and helps flood-plain managers, planners, homeowners, stakeholders, and others make decisions 

about areas that are at risk for flooding. The Flood Insurance 

Study for the Village of Homer in Dakota County, Nebraska, 

was issued by Federal Emergency Management Agency 

(FEMA) in 1983 (Federal Emergency Management Agency, 

1983) and was revised in 1996 (Federal Emergency Management Agency,1996). Since the 1996 revision, additional 

streamflow data have been collected to aid in estimating the 

frequency of large floods. In addition, the Omaha Creek channel has undergone long-term general degradation and localized 

scour near bridges that may have affected the hydraulic properties of the channel near Homer since it was last surveyed 

in 1993. As channel characteristics of Omaha Creek continue 

to change, the Village of Homer and the Papio-Missouri 

River Natural Resources District entered into a cooperative 

agreement with the U.S. Geological Survey (USGS) to study 

the effects of these changes on the areas at risk for flooding 

around Homer, Nebraska.

Purpose and Scope

The purpose of this report is to estimate flood discharges 

to update the 1996 FEMA Flood Insurance Study for the Village of Homer, Nebraska, (FEMA, 1996) and the map of the 

area inundated by the flood having a 1-percent annual probability using additional streamflow data and recent (2005) 

topographic data (Nebraska Department of Natural Resources, 

written commun., 2005). 

Topics addressed for this report included peak-flow 

analyses of records from the USGS streamflow-gaging station on Omaha Creek at Homer, Nebraska, (station number 

06601000; fig. 2); collection of topographic and channelgeometry data; hydraulic analysis of Omaha Creek using the 

U.S. Army Corps of Engineers’ (USACE) Hydrologic Engineering Center River Analysis System (HEC-RAS) computer 

software (U.S. Army Corps of Engineers, 2001); and mapping 

flood-inundation areas that correspond to the flood having a 

1-percent annual probability by comparing hydraulic results 

with topographic data. 

The geographical scope of this report was limited to areas 

near Homer, Nebraska, where cross sections from previous 

studies were available. This includes the reach of Omaha 

Creek from Elma Road, located about 1 mile (mi) east of 

Homer, to Grant Road, located approximately 1.5 mi south 

of Homer.

Estimated Flood Discharges and Map of Flood-Inundated 

Areas for Omaha Creek Near Homer, Nebraska, 2005

By Benjamin J. Dietsch, Richard C. Wilson, and Kellan R. Strauch
2 Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, Near Homer, Nebraska, 2005

Description of the Study Area

Omaha Creek is a northeasterly flowing tributary of the 

Missouri River and is located in Dakota and Thurston Counties in northeastern Nebraska (fig. 1). The total drainage area 

is 175 square miles (mi2) at the gaging station at Homer. Soils 

in the basin are derived primarily from glacial tills capped 

with loess (Elder, 1969). The climate of Dakota and Thurston 

Counties is classified as continental, consisting of a subhumid moisture regime and moderate temperatures. The normal 

annual rainfall is approximately 26 inches at Sioux City, Iowa 

(National Weather Service, 2005). 

The study area (fig. 2) surrounds the Village of Homer 

and its extent corresponds to the available hydraulic cross section data; the downstream limit is located about 2 mi upstream 

(north) from the mouth of Omaha Creek. It is a deeply incised 

channel that is widening in some parts of the study area and 

exhibits steep banks, bank failures, and streambed degradation (Rus and others, 2003). The stream channel slope is about 

8.5 feet per mile (ft/mi) through the 4-mi study reach. Bed 

materials at the site are composed of silty clays. Vegetation 

along the downstream part of the reach generally is sparse 

because of steep bank angles and recent bank failures; however, grass, shrubs, and small trees line the upstream areas of 

the reach. 

Extensive straightening and channel modification of 

streams in the Omaha Creek Basin have occurred since the 

early 20th century (Nebraska Department of Roads and 

Irrigation, 1954). These changes in channel alignment may 

have triggered a degradation response in the lower part of the 

Omaha Creek Basin, including most of the study area. From 

1952 to 1996, the streambed degraded approximately 2.6 ft at 

Omaha Creek at Homer, but the migration of this bed elevation change may have been limited by the construction of a 

rock riffle near the gage in the 1950’s (Rus and others, 2003). 

Field inspections indicate that severe scour has occurred 

around bridge piers along the study reach. 

Flooding has occurred in the Village of Homer since 

it was incorporated in 1871 (Federal Emergency Management Agency, 1996). Significant flooding occurred in June, 

1875; June, 1900; September, 1903; March, 1909; May, 1920; 

June, 1940; February, 1971; and July, 1996. The most severe 

documented floods occurred in 1920 and 1940. On May 31, 

1920, excessive rainfall occurred, which caused widespread 

flooding. Newspaper and historical accounts of the 1940 flood 

describe severe damage to many homes and businesses with 

water elevations higher than any flood since 1920. The USGS 

began operating a streamflow-gaging station located on 

Omaha Creek near Homer (station 06601000) in 1940. The 

maximum peak flow for the period of record occurred June 4, 

1940, at a gage height of 34.50 ft (2005 gage datum) with a 

discharge of 51,000 cubic feet per second (ft3/s) estimated 

from indirect measurements. Other significant floods occurred 

in 1971 (18,100 ft3/s) and 1996 (21,500 ft3/s). 

Hydrologic Analysis

The hydrologic analysis for the Omaha Creek study area 

used historical data for peak flows obtained at the stream 

gage. Historical data for peak flows were available from the 

instantaneous-discharge records for the USGS streamflowgaging station at Homer (station 06601000) which includes 

the period of streamflow gage operation from 1946 through 

2004, and the estimate of peak discharge in 1940, which 

was the greatest peak discharge since 1920. Flood frequency 

and magnitude were estimated using the USGS PEAKFQ 

log-Pearson Type III analysis software (Flynn and others, 

2006). The PEAKFQ software (version 5.0.0) was used for 

standard log-Pearson Type III analysis as outlined in Bulletin 17B (Interagency Advisory Committee on Water Data, 

1982). The systematic-record analysis computed by PEAKFQ 

utilizes the mean, standard deviation, and skew coefficient 

of the log-transformed annual peak flow series, or systematic 

record, to fit a log-Pearson distribution function to the data. 

The frequency curve derived from the systematic-record 

analysis is an initial estimate of the Bulletin 17B frequency 

curve. Additional analyses are used to adjust the frequency 

curve for historic data, regional (generalized) skew information, and high and low outliers; historic data, or flood 

information outside that contained in the systematic records, 

can be used to extend the period of analysis. The analytical 

techniques to adjust for historic data are described in Bulletin 

17B (Interagency Advisory Committee on Water Data, 1982) 

and implemented in PEAKFQ. PEAKFQ provides a routine 

for weighting the computed skew coefficient with a regionalized skew coefficient. Because the skew coefficient computed 

from historical streamflow data for a station can be sensitive 

to extreme events, guidance in Bulletin 17B recommends 

weighting skew coefficients computed for stations with natural 

streamflow regimes with a generalized skew coefficient 

computed for an entire region or similar set of sites. For the 

PEAKFQ analysis for the USGS streamflow-gaging station at 

Homer (station 06601000), the generalized skew coefficient of 

-0.539 was used (Soenksen and others, 1999). PEAKFQ also 

computes outliers, or extremely high and extremely low peak 

flows in a record, that can disproportionately affect the results 

of flood frequency analysis. Thresholds for determining outliers are computed based on the sample size (Flynn and others, 

2006). Peak streamflows were estimated for floods of the 50-, 

20-, 10-, 4-, 2-, 1-, and 0.2-percent annual probabilities.

Hydraulic Analyses

The U.S. Army Corps of Engineers HEC-RAS, version 3.1.3, software was used to simulate the water-surface 

elevation for floods (U.S. Army Corps of Engineers, 2001). 

Simulated water-surface elevations of Omaha Creek within 

the study reach were calculated by the HEC-RAS hydraulic 

flow model that requires topographic data, channel and bridge 

geometry and characteristics, and steady, gradually varied 
Description of Study Area 3

Figure 1. Location of Omaha Creek Basin and the study area in Dakota and Thurston Counties, northeastern Nebraska.

Homer

Enlarged

area

NEBRASKA

Index map

Homer

Macy

Walthill

Rosalie

Winnebago

Thurston

Pender

42°20'

15'

10'

42°5'

Study area

Omaha Creek

Cow Creek

South Omaha Creek

North Omaha Creek

Morgan Creek

Turtle Creek

Fiddlers Creek

Wigle Creek

Missouri RiverIOWA

NEBRASKA

96°25'

96°40' 35' 30'

Boundary of Omaha Creek Basin

Boundary of Omaha Creek Basin

Dakota County

Thurston County

Cuming County

S87A

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

Base from U.S. Geological Survey digital data, 1987, 1:100,000

Universal Transverse Mercator projection

Zone 14

Horizontal coordinate information is referenced to the North American

 Datum of 1983 (NAD 83)

O

maha Creek
4 Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, Near Homer, Nebraska, 2005

Figure 2. Location of U.S. Geological Survey streamflow-gaging station, survey cross sections, and study area. 

0 .1 .2 .3 .4 .5 MILE

0 .1 .2 .3 .4 .5 KILOMETER

Omaha Creek

Fiddlers Creek

Wigle Creek

O

maha

Creek

1000

1120

5140

6800

8375

10352

12087

12787

16278

15538

14738

14338

14098

13687

19278

22198

10080

9840

42°20'30"

20'

30"

19'

30"

42°18'

96°30' 30" 29' 30" 28' 30" 27' 96°26'30"

06601000

Homer

Base from U.S. Geological Survey digital data, 1987, 1:100,000

Universal Transverse Mercator projection

Zone 14

Horizontal coordinate information is referenced to the North American

 Datum of 1983 (NAD 83)

13737

EXPLANATION

06601000

River station cross section—Number is main channel distance in feet

upstream from model original near Elma Road plus 1,000 feet

U.S. Geological Survey gaging station

 and number 

22198

Grant Road

Elma Road

John Street
Description of Study Area 5

streamflow as inputs. Energy losses were computed using friction and contraction/expansion calculations. 

Topographic data were field surveyed in 1993 and 2005 

by the Nebraska Department of Natural Resources (Nebraska 

Department of Natural Resources, written commun., 2005). 

Twenty-two river station cross sections were surveyed in 

the Omaha Creek channel in the study reach. Land-surface 

elevations of the areas within and adjacent to the channel 

were surveyed in 1993. In 2005, field surveys were limited to 

parts of the cross section including and between the tops of 

stream banks. The cross sections used in the HEC-RAS model 

were a composite of the topographic points surveyed in 1993 

(overbank areas) and in 2005 (channel areas between tops 

of banks). 

Comparison of 1993 and 2005 survey data indicated 

channel widening throughout the study reach and extensive 

scouring had occurred near bridges (fig. 3). 

Geometric data included hydraulic characteristics of the 

stream, such as friction coefficients, expansion and contraction 

ratios, reach distances, and hydraulic properties of structures, 

such as bridge dimensions. Manning’s roughness coefficients 

were estimated from field observations, aerial photographs, 

and previous studies (Federal Emergency Management 

Agency, 1996) using methods described in Barnes (1967) 

and Arcement and Schneider (1989). Manning’s roughness 

coefficients ranged from 0.036 to 0.050 in the channel, and 

from 0.065 to 0.175 in areas adjacent to the channel. Bridge 

geometry was obtained from aerial photographs and previous 

studies (Federal Emergency Management Agency, 1996). 

Steady-flow input data included results of the hydrologic 

analysis and downstream boundary conditions. Peak discharges estimated from the hydrologic analysis were used as 

steady-flow input values of streamflow for simulations of the 

floods. Two downstream boundary-condition scenarios were 

simulated for the peak discharge with 1-percent annual probability: normal depth was assumed at the downstream boundary; and alternatively the water-surface elevation at the downstream boundary was assumed to be equal to the water-surface 

elevation of the Missouri River corresponding to its peak 

discharge with 1-percent annual probability. Energy slope for 

the normal-depth boundary-condition simulation was assumed 

to be 0.0006 ft/ft, based on the previous study (Federal Emergency Management Agency, 1996). The results of the simulation using this boundary condition and slope were compared 

Figure 3. Comparison of streambed elevations at locations surveyed in 1993 and 2005 along Omaha Creek at 

Homer, Nebraska. 

0 5,000 10,000 15,000 20,000 1,050

1,060

1,070

1,080

1,090

1,100

1,110

1,120

Main channel distance upstream from Elma Road, in feet

Elevation, in feet

5140

5140

680083759840

10091

10352

12087127871368714098

14338 14738 15538

162781927822198

RIVER-1 Reach-1

22,000

John Street bridge

US Highway 77 and 75 bridge

Elma Road bridge

Burlington Northern Santa Fe

Railroad bridge

Thalweg, 1993 streambed 

Thalweg, 2005 streambed 

East South

1-percent annual probability water surface

Bend instream

EXPLANATION

River station cross section—Number is main channel distance in feet

upstream from model original near Elma Road plus 1,000 feet
6 Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, Near Homer, Nebraska, 2005

to simulation using the channel slope surveyed in 2005 and the 

normal depth boundary conditions and were determined to be 

similar. The downstream water-surface elevation corresponding to the peak discharge of the Missouri River with 1-percent 

annual chance flood was 1096.6 ft above the National Geodetic Vertical Datum of 1929 (NGVD 29) (Federal Emergency 

Management Agency, 1996). 

The hydraulic model for Omaha Creek was calibrated 

to the stage and discharge that was measured on August 30, 

1993, at the USGS streamflow-gaging station at Homer (station 06601000). The measurement was selected because it 

was the most recent direct measurement of a discharge near or 

exceeding the peak flow with 50-percent annual probability. 

The measured discharge on that date was 3,530 ft3/s at a stage 

of 9.06 ft (1,089.51 ft NGVD 29). The hydraulic model was 

calibrated by iteratively making small adjustments to Manning’s roughness coefficients until the water-surface elevation 

computed by the model closely agreed with the measured 

flood discharge and stage values at hydraulic cross section 12787 (fig. 2). 

The calibrated model was used to simulate stages and 

inundation elevations for the discharges with 50-, 20-, 10-, 

4-, 2-, 1-, and 0.2-percent annual probabilities, which is the 

annual probability multiplied by 100 (0.5, 0.2, 0.1, 0.04, 0.02, 

0.01, 0.002).

Delineation of Areas Inundated 

by a Flood with 1-Percent Annual 

Probability

The areas at risk for inundation by a flood with1-percent 

annual probability were mapped using topographic data 

and water-surface elevations from the hydraulic analyses. 

A triangulated irregular network (TIN) representation of the 

three-dimensional land surface was constructed from surveyed 

cross sections and longitudinal lines (Nebraska Department of 

Natural Resources, written commun., 2005), and 10-ft interval 

elevation contours (U.S. Geological Survey, 1976). A watersurface elevation model (as a TIN) was constructed from the 

results of the hydraulic analyses for a flood with 1-percent 

annual probability under the condition in which the watersurface elevation at the downstream boundary was assumed to 

be equal to the water-surface elevation of the Missouri River 

corresponding to its peak discharge with 1-percent annual 

probability. The water-surface elevation TIN represents the 

flood profile for a flood with 1-percent annual probability 

interpolated linearly between the cross sections used in the 

hydraulic model. The water-surface elevation TIN was overlaid digitally onto the land-surface TIN, and areas where the 

estimated water-surface elevation was greater than the landsurface elevation were considered to be at risk for inundation 

by a flood with a 1-percent annual probability. The outlines 

of the inundated areas were smoothed to remove unnatural 

corners and edges. The outline of the areas at risk for 

inundation was overlaid on high-resolution aerial photography 

of the study area. 

Estimated Flood Discharges and Map 

of Flood-Inundated Areas

Peak streamflows were estimated for floods of 50-, 20-, 

10-, 4-, 2-, 1-, and 0.2-percent annual probabilities (table 1). 

The results of the PEAKFQ analysis are shown in table 1 and 

figure 4. One low outlier and one high outlier were removed 

from the analysis. The high outlier is the discharge estimated 

for the flood of 1940. An annual peak of 230 ft3/s in 1970 was 

treated as a low outlier.

The calibrated hydraulic model was used to simulate 

stages and inundation elevations for the discharges with 

50-, 20-, 10-, 4-, 2-, 1-, and 0.2-percent annual probabilities. Near the stream gage at Homer, the simulated stage for 

the discharge with 1-percent annual probability was 24.4 ft 

(1104.8 ft, NGVD 29), which was derived by interpolation 

between hydraulic cross sections 12787 and 13687. The results 

of these analyses are shown in table 2 and figure 4. 

Results of the hydraulic analysis indicated that flood 

inundation elevations are substantially lower than elevations 

published in the previous study (Federal Emergency Management Agency, 1996). The most important reason for these 

differences is the set of lower flood discharges resulting from 

the hydrologic analysis completed for this study. In addition, 

channel cross-section area has increased because of degradation and channel widening. At river station cross section 10352 

(fig. 2) located upstream from the highway bridge, the flood 

inundation elevation was 3.7 ft lower than that in the previous 

study. At river station cross section 13768 located upstream 

from the bridge on the road entering the Homer from the east, 

Table 1. Summary of flood frequency for Omaha Creek at 

Homer, Nebraska, determined by log-Pearson Type III analysis of 

the systematic record (1946–2004) and historical data.

[—, no published value available]

Recurrence interval, in years Annual chance

Estimated peak 

flow, in cubic 

feet per second

Estimated peak 

flow for 1993 

flood insurance 

study1, in cubic 

feet per second

2 0.5 3,630 —

5 .2 7,050 —

10 .1 9,710 10,800

25 .04 13,400 —

50 .02 16,330 21,600

100 .01 19,370 27,600

500 .002 26,840 45,700

1

 Determined using the systematic record from 1946 to 1981 and historical 

data as published in Federal Emergency Management Agency (1996).
Estimated Flood Discharges and Map of Flood-Inundated Areas 7

Table 2. Water-surface elevation for estimated discharges and flood-recurrence intervals at U.S. Geological Survey streamflowgaging station on Omaha Creek near Homer, Nebraska (station 06601000).

[ft3/s, cubic feet per second, NGVD 29, National Geodetic Vertical Datum of 1929]

Estimated 2-year 

flood recurrence 

interval

Estimated 10-year 

flood recurrence 

interval

Estimated 50-year 

flood recurrence 

interval

Estimated 100-year 

flood recurrence 

interval

Estimated 500-year 

flood recurrence 

interval

River station 12787 is located near 

the streamflow gage

Annual probability

0.500 0.100 0.020 0.010 0.002

Percent annual probability (%)

50 10 2 1 0.2

Estimated discharge for indicated flood, in ft3/s

3,630 9,710 16,330 19,370 26,840

River station cross section number Simulated water-surface elevation, in feet above NGVD29

1000 1,078.76 1,085.44 1,087.29 1,087.98 1,089.49

1120 1,078.87 1,085.44 1,087.16 1,087.82 1,089.29

1138 1,078.89 1,085.49 1,087.53 1,088.37 1,090.08

5040 1,080.92 1,088.40 1,091.52 1,092.37 1,093.97

5140 1,081.00 1,088.46 1,091.54 1,092.35 1,093.98

6800 1,082.39 1,090.36 1,094.40 1,095.27 1,096.68

8375 1,083.27 1,091.64 1,095.62 1,096.38 1,097.60

9840 1,083.89 1,092.56 1,097.06 1,098.20 1,100.71

9887 1,083.93 1,092.64 1,097.21 1,098.40 1,101.06

10080 1,084.03 1,092.80 1,097.45 1,098.71 1,102.00

10102 1,086.04 1,093.83 1,098.58 1,100.04 1,103.34

10352 1,086.45 1,094.10 1,098.85 1,100.32 1,103.55

12087 1,087.74 1,095.85 1,101.11 1,102.89 1,107.80

12787 1,088.27 1,096.39 1,101.96 1,103.90 1,108.45

13687 1,090.28 1,097.28 1,102.62 1,104.45 1,108.58

13737 1,090.42 1,097.39 1,102.73 1,104.56 1,108.65

13768 1,090.84 1,098.17 1,103.62 1,105.53 1,110.90

14098 1,091.77 1,099.30 1,104.82 1,106.79 1,112.65

14338 1,092.15 1,099.59 1,105.03 1,107.00 1,112.84

14738 1,093.19 1,100.49 1,105.87 1,107.82 1,113.41

15538 1,094.68 1,101.79 1,107.19 1,109.22 1,113.94

16278 1,095.87 1,103.05 1,108.46 1,110.53 1,114.65

19278 1,099.89 1,106.80 1,111.91 1,113.94 1,117.10

22198 1,103.76 1,110.83 1,115.77 1,117.74 1,121.13
8 Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, Near Homer, Nebraska, 2005

the flood inundation elevation was 8.2 ft lower than that in the 

previous study. 

The final-flood inundation map for the 1-percent annual 

probability flood is shown in figure 5.

Summary and Conclusions

A map of the areas at risk for inundation by a flood with 

1-percent annual probability was produced for the study area 

by the U.S. Geological Survey in cooperation with the PapioMissouri Natural Resources District and the Village of Homer, 

Nebraska. The map allows resources at risk of being inundated 

along Omaha Creek at Homer, Nebraska, to be identified. 

The hydrologic analysis for the Omaha Creek study 

area was performed using historical data for peak flows 

recorded at the USGS streamflow-gaging station at Homer 

(station 06601000). Flood discharges were estimated for 

events with annual probabilities ranging from 0.5 to 0.002. 

The U.S. Army Corps of Engineers Hydrologic Engineering 

Center’s River Analysis System (HEC-RAS) version 3.1.3 

software was used to simulate the water-surface elevation 

for selected flood discharges. The calibrated model was used 

to compute stages and flood-inundation elevations for the 

selected discharges. The areas at risk for inundation by a flood 

with 1-percent annual probability were mapped using topographic data and water-surface elevations resulting from the 

hydraulic analyses. 

Results of the hydraulic analysis indicated that flood 

inundation elevations are substantially lower than elevations 

published in a previous study. The most important reason for 

these differences is the set of lower flood discharges resulting 

from the hydrologic analysis completed for this study. 

Bulletin 17−B frequency

Systematic frequency

Confidence limit

Systematic peak

Historical adjusted peak–Peakfq 5 

run January 13, 2007, 16:08

102

103

104

105

Annual peak discharge, in cubic feet per second

Annual exceedance probability, in percent

Omaha Creek at Homer, Nebraska (Station 06601000) 

99.5 98 95 90 80 70 50 30 20 10 5 2 1 .5 .2

EXPLANATION

1970 low outlier 

1940 flood 

Figure 4. Frequency of selected flooding events for Omaha Creek near Homer, Nebraska, determined by log-Pearson Type III 

analysis for the systematic record (1946–2004) and historic data.
Summary and Conclusions 9

0 .1 .2 .3 .4 .5 MILE

0 .1 .2 .3 .4 .5 KILOMETER

Omaha Creek

Fiddlers Creek

Wigle Creek

O

maha

Creek

42°20'30"

20'

30"

19'

30"

42°18'

96°30' 30" 29' 30" 28' 30" 27' 96°26'30"

Homer

Base from U.S. Geological Survey digital data, 1987, 1:100,000

Universal Transverse Mercator projection

Zone 14

Horizontal coordinate information is referenced to the North American

 Datum of 1983 (NAD 83) EXPLANATION

Estimated 100-year floodplain

Extraterritorial Limits

Extraterritorial Limits

Grant Road

Elma Road

John Street

Limit of study area

Limit of study area

Limit of study

area

Limit of study area

Limit of study area

Figure 5. Areas at risk for inundation by the 1-percent annual probability flood (100-year flood) on Omaha Creek, at Homer, 

Nebraska.
10 Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, Near Homer, Nebraska, 2005

References Cited

Arcement, G.J., Jr., and Schneider, V.R., 1989, Guide for 

selecting Manning’s roughness coefficients for natural channels and floodplains: U.S. Geological Survey Water-Supply 

Paper 2339, 38 p.

Barnes, H.H., Jr., 1967, Roughness characteristics of 

natural channels: U.S. Geological Survey Water-Supply 

Paper 1849, 213 p.

Elder, J.A., 1969, Soils of Nebraska: University of NebraskaLincoln, Institute of Agriculture and Natural Resources, 

Conservation and Survey Division, Resource Report No. 2, 

60 p.

Federal Emergency Management Agency, 1983, Flood insurance study, Village of Homer, Dakota County, Nebraska: 

Washington, D.C., Federal Emergency Management 

Agency, 15 p.

Federal Emergency Management Agency, 1996, Flood insurance study, Village of Homer, Dakota County, Nebraska: 

Washington, D.C., Federal Emergency Management 

Agency, 15 p.

Flynn, K.M., Kirby, W.H., and Hummel, P.R., 2006, User’s 

manual for program PeakFQ, Annual flood frequency analysis using Bulletin 17B guidelines: U.S. Geological Survey 

Techniques and Methods Book 4, Chapter B4, 42 p. 

Interagency Advisory Committee on Water Data, 1982, Guidelines for determining flood flow frequency: Reston, Virginia, U.S. Geological Survey, Office of Water Data Coordination, Bulletin 17–B of the Hydrology Subcommittee, 

183 p.

National Weather Service, 2005, Sioux City area climatic summary: Sioux City, Iowa, National Weather Service Forecast 

Office, accessed March 6, 2007 at http://www.crh.noaa.gov/

fsd/climate/archive.php.

Nebraska Department of Roads and Irrigation, 1954, Thirtieth 

biennial report of the Department of Roads and Irrigation, 1953–1954, volume II: Lincoln, Nebr., Department of 

Roads and Irrigation, 801 p.

Rus, D.L., Dietsch, B.J., and Simon, Andrew, 2003, Streambed adjustment and channel widening in eastern Nebraska: 

U.S. Geological Survey Water-Resources Investigations 

Report 03–4003, 63 p.

Soenksen, P.J., Miller, L.D., Sharpe, J.B., and Watton, J.R., 

1999, Peak-flow frequency relations and evaluation of the 

peak-flow gaging network in Nebraska: U.S. Geological 

Survey Water-Resources Investigations Report 99–4032, 

47 p., 3 appendixes.

U.S. Army Corps of Engineers, 2001, HEC-RAS, River analysis system, user’s manual, version 3.0: Davis, Calif., U.S. 

Army Corps of Engineers Hydrologic Engineering Center. 

U.S. Geological Survey, 1976, Homer quadrangle, Nebraska: 

U.S. Geological Survey Topographic Quadrangle Map, 

scale 1:24,000.
Publishing support provided by:

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Nebraska Water Science Center

5231 South 19 Street

Lincoln, NE 68512

(402) 328–4100

Or visit the Nebraska Water Science Center Web site at:

http://ne.water.usgs.gov
Dietsch and others—Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, 2005—Scientific Investigations Report 2008–5107

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