U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5008

Prepared in cooperation with the Nebraska Game and Parks Commission

Geomorphic Segmentation, Hydraulic Geometry, and 

Hydraulic Microhabitats of the Niobrara River, Nebraska—

Methods and Initial Results
Front cover. Canoeists paddling the Niobrara River in the Niobrara National Wildlife Refuge, Nebraska, April 9, 2008. (photograph taken by 

Jason Alexander, USGS)
Geomorphic Segmentation, Hydraulic 

Geometry, and Hydraulic Microhabitats of 

the Niobrara River, Nebraska—Methods 

and Initial Results

By Jason S. Alexander, Ronald B. Zelt, and Nathaniel J. Schaepe

Prepared in cooperation with the Nebraska Game and Parks Commission

Scientific Investigations Report 2009–5008

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Alexander, J.S., Zelt, R.B., and Schaepe, N.J., 2009, Geomorphic segmentation, hydraulic geometry, and hydraulic 

microhabitats of the Niobrara River, Nebraska—Methods and initial results: U.S. Geological Survey Scientific Investigations Report 2009–5008, 51 p. 
iii

Contents

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

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

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

Description of the Niobrara River Basin...........................................................................................3

Background............................................................................................................................................4

Approach and Methods................................................................................................................................6

Inventory and Compilation of Available Data...................................................................................6

Surface-Water Inventory............................................................................................................6

Ground-Water Inventory.............................................................................................................8

Geomorphic Segmentation of the Niobrara River...........................................................................8

Classification Scheme for Longitudinal Segmentation .........................................................9

Longitudinal Profile Analysis ...................................................................................................10

Hydraulic Geometry Characterization.............................................................................................12

At-A-Station Hydraulic Geometry Relations .........................................................................12

Downstream Hydraulic Geometry Relations.........................................................................14

Hydraulic Habitat at a Streamflow-Gaging Station.......................................................................14

Initial Results ................................................................................................................................................17

Summary of Available Data...............................................................................................................17

Stream Hydrology and Sediment ............................................................................................17

Ground-Water Hydrology .........................................................................................................17

Characteristics of Geomorphic Segments .....................................................................................19

Longitudinal Segmentation ......................................................................................................19

Longitudinal Profile Characteristics of the Niobrara River.................................................20

Hydraulic Geometry............................................................................................................................21

At-A-Station Hydraulic Geometry Relations for Selected Niobrara River StreamflowGaging Stations ............................................................................................................21

Downstream Hydraulic Geometry of Niobrara River...........................................................25

Hydraulic Microhabitat: An Example from the Niobrara River near Sparks, Nebraska .........29

Summary and Conclusions.........................................................................................................................31

Acknowledgments.......................................................................................................................................32

References Cited..........................................................................................................................................32

Appendix 1: Description of Niobrara River Streamflow-Gaging Stations ..........................................36

Appendix 1 Summary..........................................................................................................................36

Niobrara River near Hay Springs ............................................................................................36

Niobrara River near Gordon.....................................................................................................36

Niobrara River near Cody.........................................................................................................37

Niobrara River near Sparks .....................................................................................................37

Niobrara River near Norden ....................................................................................................37

Niobrara River at Mariaville.....................................................................................................38

Niobrara River near Spencer...................................................................................................38

Niobrara River near Verdel ......................................................................................................40

Appendix 2: Scatter Plots of At-A-Station Hydraulic Geometry Relations.........................................43

Appendix 2 Summary..........................................................................................................................43
iv

Figures

1–2. Maps showing:

1. Study area, basin boundary, and National River reaches of the Niobrara River...............2

2. Dams, surface-water diversions, and large tributary drainages within the Niobrara 

River Basin.....................................................................................................................................5

3. Example of cross-section layout and subsections for point measurements used to calculate discharge and channel hydraulic geometry for a typical river streamflow-gaging 

station .............................................................................................................................................8

4. Map showing streamflow-gaging stations in the Niobrara River Basin selected for data 

inventory.......................................................................................................................................13

5. Graph showing flow-duration curves for selected streamflow gages and periods of 

record of the Niobrara River between Dunlap Diversion Dam and the Missouri River, 

Nebraska..................................................................................................................................... 15

6–7. Maps showing:

6. Ground-water well density in the Niobrara River study area ............................................ 19

7. Ground-water observation wells and geologic test holes in the Niobrara River study 

area ...............................................................................................................................................21

8–11. Graphs showing:

8. Longitudinal profile of the Niobrara River from the Missouri River upstream to Dunlap 

Diversion Dam.............................................................................................................................23

9. At-a-station hydraulic geometry relations for selected streamflow-gaging stations on 

the Niobrara River ......................................................................................................................26

10. Downstream hydraulic geometry relations for the Niobrara River between the streamflow-gaging station near Hay Springs, Nebraska, and the streamflow-gaging station 

near Verdel, Nebraska.............................................................................................................. 28

11. Channel geometry, velocity distribution, and microhabitat extent 

over a range of flow-exceedance frequencies for the Niobrara River near Sparks, 

Nebraska......................................................................................................................................30

Tables 

1. Data categories and scopes for Niobrara River data inventory and summary .................7

2. Niobrara River tributaries and their percentage of contributing basin drainage area at 

their confluence with the main channel ...................................................................................9

3. Segment-scale geomorphic classification system for the Niobrara River, Nebraska....11

4. Flow-exceedance frequencies and associated discharges used for downstream 

hydraulic-geometry calculations .............................................................................................15

5. Matrix of depth and velocity combinations used to define hydraulic-habitat niches for 

microhabitat analysis using streamflow measurement data..............................................16

6. Discharge measurements and associated flow frequencies at Niobrara River near 

Sparks, Nebraska, used in hydraulic-microhabitat calculations .......................................17

7. Active and inactive streamflow-gaging stations of the Niobrara River Basin 

study area ....................................................................................................................................18

8. Inventory of hydrographer’s discharge measurement notes at Niobrara River Basin 

gaging stations with records after 1963..................................................................................20
v

9. Inventory of ground-water wells and test holes in the Niobrara River study area by 

state and usage type..................................................................................................................22

10. Geomorphic segments of the Niobrara River between Dunlap Diversion Dam and the 

Missouri River, Nebraska ..........................................................................................................24

11. Summary of longitudinal channel slopes in fluvial geomorphic provinces of the Niobrara River, Nebraska ................................................................................................................25

12. At-a-station hydraulic geometry relations for selected Niobrara River streamflowgaging stations............................................................................................................................27

13. Downstream hydraulic geometry relations for the Niobrara River between Hay Springs 

and Verdel, Nebraska.................................................................................................................29

Appendix Figures

1-1–1-7. Photographs showing:

1-1. The Niobrara River near Gordon streamflow-gaging station reach..................................36 

1-2. The Niobrara River near Cody streamflow-gaging station reach ......................................37 

1-3. The Niobrara River near Sparks streamflow-gaging station reach.................................. 38

1-4. The Niobrara River near Norden streamflow-gaging station reach................................. 39

1-5. The Niobrara River near Mariaville streamflow-gaging station reach .............................40 

1-6. The Niobrara River near Spencer streamflow-gaging station reach............................... 41

1-7. The Niobrara River near Verdel streamflow-gaging station reach....................................42 

2-1–2-9. Scatter plots showing:

2-1. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Hay Springs, Nebraska (06456500)............................ 43

2-2. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Gordon, Nebraska (06457500).....................................44

2-3. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Cody, Nebraska (06459000)......................................... 45

2-4. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Sparks, Nebraska (06461500)......................................46 

2-5. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Norden, Nebraska (06462000).................................... 47

2-6. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Mariaville, Nebraska (06463720) ............................... 48

2-7. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Spencer, Nebraska (06465000) .................................. 49

2-8. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Verdel, Nebraska (06465500) for water years 

1964 to 1985................................................................................................................................. 50

2-9. The at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Verdel, Nebraska (06465500) for water years 

1986 to 2007................................................................................................................................. 51
vi

Conversion Factors

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

) 259.0 hectare (ha) 

Volume

quart (qt) 0.9464 liter (L) 

gallon (gal) 3.785 liter (L) 

million gallons (Mgal) 3,785 cubic meter (m3

)

acre-foot (acre-ft) 1,233 cubic meter (m3

)

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3

/s)

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

cubic foot per second (ft3

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

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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

The Niobrara River of Nebraska is a geologically, ecologically, and economically significant resource. The State 

of Nebraska has recognized the need to better manage the 

surface- and ground-water resources of the Niobrara River so 

they are sustainable in the long term. In cooperation with the 

Nebraska Game and Parks Commission, the U.S. Geological Survey is investigating the hydrogeomorphic settings and 

hydraulic geometry of the Niobrara River to assist in characterizing the types of broad-scale physical habitat attributes that 

may be of importance to the ecological resources of the river 

system. This report includes an inventory of surface-water and 

ground-water hydrology data, surface water-quality data, a 

longitudinal geomorphic segmentation and characterization of 

the main channel and its valley, and hydraulic geometry relations for the 330-mile section of the Niobrara River from Dunlap Diversion Dam in western Nebraska to the Missouri River 

confluence. Hydraulic microhabitats also were analyzed using 

available data from discharge measurements to demonstrate 

the potential application of these data and analysis methods. 

The main channel of the Niobrara was partitioned into 

three distinct fluvial geomorphic provinces: an upper province characterized by open valleys and a sinuous, equiwidth 

channel; a central province characterized by mixed valley and 

channel settings, including several entrenched canyon reaches; 

and a lower province where the valley is wide, yet restricted, 

but the river also is wide and persistently braided. Within the 

three fluvial geomorphic provinces, 36 geomorphic segments 

were identified using a customized, process-orientated classification scheme, which described the basic physical characteristics of the Niobrara River and its valley. Analysis of the 

longitudinal slope characteristics indicated that the Niobrara 

River longitudinal profile may be largely bedrock-controlled, 

with slope inflections co-located at changes in bedrock type 

at river level. Hydraulic geometry relations indicated that 

local (at-a-station) channel adjustments of the Niobrara River 

to changing discharge are accommodated mainly by changes 

in velocity, and streamwise adjustments are accommodated 

through changes in channel width. Downstream hydraulic 

geometry relations are in general agreement with values previously published for rivers of the Great Plains, but coefficients 

are likely skewed low because the locations of the streamflowgaging stations used in this analysis are located at natural or 

engineered constrictions and may not be accurately representing downstream adjustment processes of the Niobrara River. 

A demonstration analysis of hydraulic microhabitat attributes 

at a single station indicated that changes in velocity-related 

habitat types is the primary microhabitat adjustment over a 

range of discharges, but the magnitude of that adjustment for 

any particular discharge is temporally variable. 

Introduction

On the Great Plains of the central United States, groundand surface-water resources are the foundation of the agriculture-based economies. These same water resources provide the 

foundation of the aquatic food chain that sustains the fisheries 

of the Missouri River ecosystem and the wading birds and 

waterfowl of the central flyway of North America. The juxtaposition of economic interests and natural resources requires 

an accurate understanding of water resources so they can be 

managed to sustain both. 

The Niobrara River of Nebraska (Nebr.) is known in 

the Great Plains region as an ‘ecologic crossroads’ where 

five major terrestrial ecosystem types converge, creating a 

locally diverse array of flora and fauna (Johnsgard, 2001). The 

76-mile (mi) reach of the river east of Valentine, Nebraska, 

also called the “scenic reach,” is registered and protected 

within the National Wild and Scenic River System and is 

renowned for its scenic canyons, abundant waterfalls, and 

superb canoeing opportunities (fig. 1). Although the scenic 

reach is the most renowned, it constitutes only about 14 percent of the total river length. The reaches upstream from the 

scenic reach are less well known but contain a diverse array of 

fluvial environments that have largely gone unstudied. 

The lush beauty of the Niobrara bottomland in the scenic 

reach has given the river a reputation as a relatively undisturbed ecosystem; however, the present body of data and 

Geomorphic Segmentation, Hydraulic Geometry, 

and Hydraulic Microhabitats of the Niobrara River, 

Nebraska—Methods and Initial Results

By Jason S. Alexander, Ronald B. Zelt, and Nathaniel J. Schaepe
2 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results Figure 1. Study area, basin boundary, and National River reaches of the Niobrara River. 

!

!

!

!

!

!

!

!

Cherry County

Holt County

Custer County

Sioux County Sheridan County

Niobrara County

Goshen County

Tripp County Shannon County

Garden County

Todd County

Fall River County

Morrill County

Dawes County

Brown County

Lincoln County

Mellette County

Rock County

Jackson County

Bennett County

Keith County

Laramie County

Gregory County

Cheyenne County Kimball County

Box Butte County

Grant County

Charles Mix County

Arthur County

Blaine County

Banner County

Hooker County

Brule County

Thomas County Loup County

McPherson County

Knox County

Antelope County

Boyd County Keya Paha County

Logan County Valley County

Lyman County

Boone County

Weston County

Scotts Bluff County

Greeley County

Howard County

Garfield County

Aurora County

Wheeler County

Sherman County

Deuel County

Douglas County

Nance County

Pennington County

Cornell Dam

Merritt Dam

Spencer Dam

Box Butte Dam

NEBRASKA

SOUTH DAKOTA

Dunlap Diversion Dam

WYOMING

Niobrara

River

Missouri River

Snake River

Keya Paha River

Verdigre Creek

Hay Springs

Gordon Valentine Norden

Long Pine O'Neill

Spencer Cody

Scenic Reach

Recreational Reach

98° 99° 100° 101° 102° 103° 104°

43°42°41°

figure01final.ai

EXPLANATION

Sand hills (Soller and Reheis, 2003)National River Reaches (reaches managed by  U.S. National Park Service)Niobrara Basin boundary within study areaNiobrara Basin boundary outside study areaLarge dams

Boundary oflarger map 

NE

KS

Index map

CO

WY

MT ND

SD MN

IA

MO

0

0 20 40 60 KILOMETERS

20 40 60 MILES Base from USGS National Elevation Dataset, 2006; National Hydrography Datset, 2007; 

 State boundaries, 2005, 1:2,000,000Basin boundary based on United States Department of Agriculture-NaturalResource Conservation Service (2008), Watershed Boundary DatasetUniversal Traverse Mercator projection, zone 14Horizontal coordinate information is referenced to  the North American Datum of 1983 (NAD 83)
Introduction 3

information is inadequate to document the actual condition of 

the riverine ecosystem today. The persistence of below-average annual and peak flows since 2002, and the recent designation of the hydraulically connected ground- and surface-water 

resources of most of the Niobrara Basin as “fully appropriated” (Nebraska Department of Natural Resources, 2007), 

have emphasized the importance of understanding and sustainably managing the flow regime in the Niobrara River. 

The U.S. Geological Survey (USGS), in cooperation with 

the Nebraska Game and Parks Commission (NGPC), is working to characterize the hydrogeomorphic settings and associated processes of the Niobrara River system from the Dunlap 

Diversion Dam in Dawes County to the confluence with the 

Missouri River in Knox County more than 330 mi downstream 

(fig. 1). Among the key questions identified for the study are:

1. What flow regime is needed to maintain the present quantity and diversity of stream physical habitats that distinguish the Niobrara as a healthy ecosystem?

2. What frequency, duration, and timing of infrequent hydrologic disturbances (floods, droughts, ice jams) is needed 

to maintain a dynamic equilibrium of fluvial geomorphic 

processes to sustain the present channel character?

An abundance of hydrologic, hydraulic, and sediment 

data for the Niobrara River has been recorded at different 

intervals by various federal and state agencies. These data, 

however, have not been compiled and synthesized for the purpose of addressing the questions stated above. Given the scale 

of the study area, and the spatial and temporal complexity of 

river systems in general, an initial attempt at characterizing 

the hydraulic and geomorphic elements of the Niobrara River 

must be appropriately broad, yet encompass enough physical 

detail to build an informational foundation for future, more 

detailed investigations. 

Purpose and Scope 

The purpose of this report is to document the methods 

for, and present the initial results from, a data inventory and 

hydrogeomorphic characterization of the Niobrara River 

of Nebraska and selected tributaries for the approximately 

330-mi reach from Dunlap Diversion Dam to its confluence 

with the Missouri River (fig. 1). The inventory performed 

was more detailed than that necessary for the data analysis 

and includes existing hydrologic, hydraulic, geologic, and 

sediment data for the basin. The goal of the inventory was to 

identify the types and spatial distribution of available data that 

could be used in future geomorphic, hydrologic, and hydrogeologic investigations. An analysis of the Niobrara River 

channel morphology using the longitudinal profile of the river 

and a process-orientated classification scheme to segment 

the river is presented. The purpose of the segmentation is to 

characterize the types and extents of river channel and valley 

settings within the Niobrara River Basin. The principles of 

hydraulic geometry are applied at several streamflow-gaging 

stations of the Niobrara River to describe the hydraulic adjustment mechanisms at the local and basin scales. In addition, 

an example application of the relation between streamflow 

variability and hydraulic microhabitats at a streamflow-gaging 

station using a semi-automated method is demonstrated. 

Description of the Niobrara River Basin

The Niobrara River Basin is a component of the Greater 

Missouri River Basin and originates in the tablelands of northeastern Wyoming (University of Nebraska-Lincoln, Conservation and Survey Division, 1986). The Niobrara River begins at 

an altitude of approximately 5,500 feet (ft) and flows eastward 

nearly 560 mi through Wyoming and northern Nebraska, dropping 4,280 ft before its confluence with the Missouri River in 

Knox County, Nebr. Draining a total area of approximately 

13,480 square miles (mi2) along its course, the Niobrara River 

flows alternately through open valleys, valleys bound by 

escarpments, and narrow canyons. Average annual precipitation in the basin varies from approximately 16 inches (in.) in 

the west to 24 in. in the east. The northernmost extent of the 

basin drains the tablelands of South Dakota (University of 

Nebraska-Lincoln, Conservation and Survey Division, 1986). 

Much of the southern part of the river basin is in the Nebraska 

Sand Hills, whose underlying aquifers contribute a steady flow 

of ground water to the river and its tributaries (Bentall and 

Shaffer, 1979). The effects of flashier, rainfall-runoff hydrology steadily increase east of Norden, Nebr., resulting from 

changes in soil types, reductions in aquifer thickness, and 

increases in average annual precipitation (Bentall, 1991). On 

average, the Niobrara River contributes 1.2 million acre-feet 

(acre-ft) of water to the Missouri River annually (Bentall and 

Schaffer, 1979). Much of the land of the Niobrara River Basin 

is undeveloped. Cattle ranching is the dominant land use in the 

more arid western region and gives way to row-crop agriculture in the eastern region (Dappen and others, 2007).

Sedimentary rock units along the Niobrara River in 

Nebraska range in age from the Cretaceous to Tertiary periods. 

Bedrock units in the Niobrara River Basin are gently sloping 

to flat lying, except in Sheridan and western Cherry Counties, 

where the Niobrara River Basin crosses the Chadron Arch, 

an area of local compression and uplift of Cretaceous-age 

rocks (Hearty, 1978). Cretaceous-age Niobrara Chalk underlies the Niobrara River from the mouth to approximately 

10 mi upstream. Where present, the Niobrara Chalk forms the 

nearly vertical bluffs of the valley wall. Between the upstream 

extent of Niobrara Chalk and Norden, Nebr., the dominant 

rock at river level is the Cretaceous-age Pierre Shale, which 

is a mix of black mudstones, shales, and chalks (Condra and 

Reed, 1943). The overlying Tertiary-age sedimentary units are 

broadly divided into three groups: White River Group, Arikaree Group, and Ogallala Group. Each of these rock groups 

include several formations within them. The details of the 

lithologies of each formation are spatially complex and outside 

of the scope of this document. Formations of the White River 
4 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Group generally consist of easily eroded fine silt and clay, 

with occasional resistant gravel and sand that form ledges 

and steep slopes. The Arikaree Group consists of siltstone, 

tuffaceous siltstone, and clay units, many of which are ash 

layers deposited by wind and/or water. The Ogallala Group is 

spatially complex, but in general consists of sand and gravel, 

with occasional ash beds. The Ash Hollow Formation is the 

uppermost unit of the Ogallala Group and is well-cemented 

beds of silt, sand, and gravel, forming the resistant capstone 

of the Niobrara canyon in the scenic reach. (Condra and Reed, 

1943; Hearty, 1978). 

The Niobrara River in the scenic reach purveys the 

appearance of a wild river; however, the river basin has many 

engineered structures and streamflow diversions (fig. 2). 

Along the main channel, Box Butte Reservoir at Box Butte 

Dam (fig. 1), in Dawes County, Nebr., began storing water for 

irrigation as part of the Mirage Flats Project in 1945 (Shaffer, 

1975). Water is released from the dam and diverted at Dunlap 

Diversion Dam 8 mi downstream. Immediately below Dunlap 

Diversion Dam (fig. 1), average annual streamflow in the main 

channel is reduced by up to 90 percent relative to upstream 

from Box Butte Reservoir (Shaffer, 1975). Merritt Dam, on the 

Snake River, which is the third largest tributary to the Niobrara by drainage area, began operations in 1964 as part of the 

Ainsworth Irrigation Project. Merritt Reservoir at Merritt Dam 

(fig. 1) can store up to one-half of the total annual discharge 

of the Snake River. Operations at Merritt Reservoir have 

affected the high-frequency (low-magnitude) flows, reducing 

base flows (flows generally exceeded 99 percent of the time) 

by more than 90 percent in the Snake River (Shaffer, 1975). 

Merritt Reservoir operations also have affected streamflows on 

the Niobrara River below the Snake River confluence, reducing mean monthly flows at Norden, Nebr., by up to 15 percent 

(Buchanan, 1981). In addition to water-storage dams, there are 

two dams on the Niobrara main channel that were constructed 

for power generation. Cornell Dam (fig. 1), located east of 

Valentine, Nebr., was built in 1915, and remained an active 

hydropower site until 1985. Spencer Dam (fig. 1), located 

south of Spencer, Nebr., was built in 1927 by the Nebraska 

Public Power and Irrigation District and currently (2008) is 

active. Both dams act as sediment barriers, although the reservoir behind Cornell Dam has filled completely with sediment 

since the ceasing of hydropower operations, and likely much 

of the upstream sediment supply passes through.

The Niobrara River flows mainly through private property, although several miles of river are owned and managed 

by state and federal natural resources agencies, and others 

by private land trusts. Two sections of the river are federally 

protected under the Wild and Scenic Rivers Act of 1968 (Interagency Wild and Scenic Rivers Council, 2008), and cooperatively managed with private landholders and State entities by 

the U.S. Department of the Interior, National Park Service: the 

76-mile reach designated as “scenic” beginning a few miles 

upstream from Cornell Dam, near Valentine, Nebr., and ending in Rock County, Nebr.; and the 28-mi reach designated as 

“recreational” between the western border of Knox County, 

Nebr., and the Missouri River (fig. 1). The 76-mi scenic reach 

has more than 40,000 tourists per year, who come to float the 

river and enjoy the beauty of the Niobrara Valley (Whittaker 

and Shelby, 2008). 

Background

Alterations in the natural flow regime of any river or 

stream can result in adjustments to the overall planform 

(geometry), cross-sectional channel geometry, bed configuration, and channel-bed slope (Leopold and Wolman 1957; Brice 

and Blodgett, 1978; Williams and Wolman, 1984; Knighton, 

1998). These changes in the hydrogeomorphic attributes of 

a river channel may cascade into degradation of its physical 

habitat attributes, which are important for aquatic and riparian 

life (Poff and Ward, 1990; Power and others, 1995; Hupp and 

Osterkamp, 1996; Poff and others, 1997). The term ‘hydrogeomorphic’ is used in this report to encompass the host of form 

characteristics and processes associated with the interactions 

of water (hydro) and the landscape through which it flows 

(geomorphic). 

One of the existing management approaches for the 

conservation of river ecosystems is the determination of the 

hydrologic regime necessary to maintain a dynamic interaction 

between the physical and biological characteristics of a river 

system (Jowett, 1997; Poff and others, 1997). Thus, an integrated study of the hydrology and hydraulics of a river system 

will recognize and be coupled with a biological analysis using 

a common set of variables. River discharge, often considered 

the primary determinant of physical and ecological processes 

in river systems, is a powerful and accessible choice among 

a suite of variables commonly used across these disciplines 

(Resh and others, 1988; Junk and others, 1989; Power and others, 1995; Doyle and others, 2005). 

Hydraulic geometry relations use the hydrographer’s 

streamflow discharge-measurement notes from individual 

streamflow-gaging stations (at-a-station geometry) to relate 

wetted-channel geometry and water velocity to river discharge 

through a series of empirical models in the form of power laws 

as presented by Leopold and Maddock (1953):

w = aQb (1)

d = cQf (2)

v = kQm (3)

The variables w, d, and v are wetted-channel top width, 

mean depth, and mean velocity of the cross section, respectively; a, c, k, b, f, and m are numerical constants; and Q is a 

reference discharge. The product of w, d, and v are equal to Q, 

an equation known to hydrologists as “continuity,” because 

over short distances, the discharge of a river must be the 
Introduction 

5

G

G

G

G! Valentine

Dam and diversion locations from Nebraska Department of Natural Resources

99° 98° 101° 100° 102° 103° 104°

43°42°

EXPLANATION

0 20 40 60 MILES

0 20 40 60 KILOMETERS

Base from USGS National Elevation Dataset, 2006; National Hydrography Datset, 2007;  State boundaries, 2005, 1:2,000,000Basin boundary based on U.S. Department of Agriculture-NaturalResource Conservation Service, Watershed Boundary Dataset (2008)Universal Traverse Mercator projection, zone 14Horizontal coordinate information is referenced to  the North American Datum of 1983 (NAD 83)

NEBRASKA

SOUTH DAKOTA

WYOMING

Niobrara River

Tributary contributing at least 5 percent drainage  area addition at confluence with NiobraraNiobrara Basin boundary within study areaNiobrara Basin boundary outside study areaDamSurface-water diversion

Rush Creek

Minnechaduza Creek

Bear Creek

Keya Paha River

Leander Creek

Box Butte Creek

Pine Creek Snake RiverGordon Creek Plum Creek Fairfield Creek

Long Pine Creek

Eagle Creek

Redbird Creek

Verdigre Creek

Big Sandy Creek

Missouri River

Antelope Creek

Medicine Creek

Figure 2. Dams, surface-water diversions, and large tributary drainages within the Niobrara River Basin.
6 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

same, even if the geometry of the river changes. By continuity, the exponents of equations 1–3 must sum to unity, and the 

products of the coefficients of equations 1–3 must be unity. 

The magnitude of the exponent for each equation describes 

the slope of a best-fit (least-squares regression) line through 

a logarithmically scaled scatter plot of the relation, with 

discharge as the independent variable. The magnitude of the 

slope is a measure of the rate of adjustment of each variable 

at a cross section over a range of discharges. For the United 

States, rivers of the semi-arid Southwest and Great Plains, 

Leopold and Maddock (1953) reported averages of 0.26, 0.40, 

and 0.34 for exponents b, f, and m, respectively, although these 

values have been shown to be highly variable depending on 

regional climate and physiography (Park, 1977). 

 Hydraulic geometry relations also can be developed for 

a river basin using data from multiple streamflow-gaging stations, common measurement increments, and common periods 

of record. Leopold and Maddock (1953) referred to such models as “downstream hydraulic geometry” relations. These relations are examined to understand how a stream channel adjusts 

and accommodates gains of water and sediment with increases 

in drainage area. Downstream hydraulic geometry relations 

use equations 1 to 3, but the reference discharges used for the 

independent variable are populated with daily flows of common exceedance frequencies (percentage of time exceeded) 

for all gages. Although a range of values for the downstream 

hydraulic geometry coefficients and exponents have been 

reported, investigators consistently have reported that channel 

width varies approximately in proportion to the square root 

of discharge (that is, b = 0.5) for alluvial rivers (Parker, 1979; 

Parker and others, 2007). Hydraulic geometry relations assist 

in understanding channel adjustment processes but are limited 

in their predictive capabilities and require cautious application 

for such purposes (Simon and Castro, 2003). 

In addition to cross-sectional adjustments, the planform 

and profile (longitudinal slope) characteristics of a river also 

adjust to changing water and sediment inputs. Although a 

few studies of the Niobrara River have provided details of the 

modern river’s physical characteristics at the local or reach 

scale (Hearty, 1978; Buchanan, 1981; Cole, 1996; Skelly, 

1998; Etheridge and others, 1999), no consistent descriptive 

procedure has been applied at the system or basin scale. An 

objective description of the river at such a scale can provide 

a benchmark for future comparative studies, and is useful 

as a means of identifying the locations of particular types 

of riverine habitats, broad-scale controls on channel form, 

or specific fluvial geomorphic processes within the basin. 

Classification schemes, which involve ordering objects into 

classes based on pre-defined sets of characteristics, are useful 

as a means of describing the condition or character of a river 

at a point in time. Numerous classification schemes for fluvial 

systems have been developed by investigators and applied for 

a range of purposes. The most useful classification schemes, 

however, are tailored to meet the specific goals or objectives of the project (Kondolf and Downs, 1996; Juracek and 

Fitzpatrick, 2003). 

Approach and Methods

Given the spatial scale of this initial study, the approach 

must be broad yet provide enough detail to serve as a foundation for future, more focused investigations. This approach to 

initial characterization of the hydraulic and geomorphic attributes of the Niobrara River used existing data. The approach 

had three main components: inventory and compilation of 

available hydrogeomorphic data; geomorphic segmentation 

by stratification and characterization of the Niobrara River 

and its valley; and hydraulic geometry analysis. Whereas the 

inventory was intended to provide an informational foundation, the geomorphic stratification and hydraulic geometry 

analyses sought to characterize the types of valley and channel 

environments and channel-adjustment processes in the study 

area. Finally, an example application of the relation between 

streamflow variability and hydraulic microhabitats using a 

semi-automated method was conducted. 

Inventory and Compilation of Available Data

An ancillary component of any scientific investigation is 

an inventory of data available for analysis within the spatial 

and temporal scopes. Because this initial investigation was 

intended to provide an informational foundation, an inventory 

over and above that necessary for the accompanying investigation was performed. The inventory can generally be divided 

into two categories: surface-water and ground-water hydrology. Included in the inventory are stream discharge, water 

quality, ground-water elevation, and geologic test-hole data 

(table 1). 

Surface-Water Inventory 

Stream-discharge and water-quality data were compiled 

for streamflow-gaging stations throughout the study area. 

These data included hydrographer’s discharge-measurement 

records and sediment-discharge information. Station information was compiled from internal USGS databases, as 

well as from the Nebraska Department of Natural Resources 

(NDNR) streamflow-gage database. In the case of stream 

hydrology, continuous-record stations and crest-stage stations 

were inventoried. Continuous-record stations are hydrologic 

gaging stations that continuously record river stage, which 

is then converted to river discharge by using a statistical 

rating relation maintained by a hydrologic technician. Creststage gages record only the maximum elevation of the water 

surface from the most recent high flow, which is then used 

to calculate an associated river discharge. For sedimentdischarge data inventory, data retrieval was performed 

within the USGS National Water Information System (NWIS) 

(http://waterdata.usgs.gov/nwis). The same process was used 

for water-quality data. Only sediment and water-quality data 

collected at streamflow-gaging stations were included in 

the inventory.
Approach and Methods 7

Continuous-record streamflow-gaging stations provide 

a valuable record of channel geometry for a gage’s period 

of operation. This record is maintained because the hydraulic relations between river stage (water level) and discharge 

occasionally must be checked by a technician, and adjusted 

(shifted) when changes in the channel shape result in subsequent changes in the stage and discharge statistical relation. 

The relation between stage and discharge is checked when 

a hydrographer makes a manual measurement of discharge 

near the streamflow gage. Stream-discharge measurements 

consist of measuring current velocity at stations along a cross 

section of the river (fig. 3). The depth of the point velocity measurements at any distance across the cross section is 

determined in part by water depth, and in part by velocity, 

and as such requires measurements of depth at each station 

(Rantz and others, 1982). The authors refer to these records 

of discharge measurements as the hydrographer’s “dischargemeasurement notes.” 

Discharge-measurement notes for measurements up to 

the early 1990s typically are stored as hard copies within 

the archives of local USGS Water Science Centers; thus, 

the inventory for streamflow gages with records before that 

time is a manual counting process. Because of the size of the 

study area, the inventory of discharge-measurement notes 

was limited to main-channel stations and tributaries that were 

most likely to exert a significant effect on the hydrologic and 

geomorphic character of the Niobrara main channel. Under 

the assumption that drainage area is a proxy for discharge, the 

spatial scope of the inventory was limited to tributaries whose 

drainage area constitutes at least 5 percent of the basin area 

at the confluence (hereinafter referred to as “large” tributaries) (fig. 2). The drainage areas for the Niobrara River and its 

tributaries were based on the U.S. Department of AgricultureNatural Resources Conservation Service (2008) Watershed 

Boundary Dataset. The dataset was used to compile and sum 

tributary drainage areas, which were compared to the total 

drainage area of the Niobrara River Basin at the tributary 

confluence (table 2). Because the scope of this study is limited 

to characterizing the post-development river, the inventory 

generally was limited to streamflow-gaging stations that had 

records after 1963, the first year of operation of Merritt Reservoir, located on the Snake River, a large tributary. Some main 

channel streamflow-gaging station records that were critical 

to the analysis had records limited to periods before 1963. 

These records only were used for streamflow-gaging stations upstream from the Snake River confluence. Some of the 

tributaries had multiple streamflow-gaging stations that fit the 

selection criteria. In those cases the most downstream stations 

were selected for inventory. The inventory was expanded to 

include Eagle, Redbird, and Verdigre Creeks which, although 

they did not meet our drainage-area criterion, were recognized 

as ecologically important by project cooperators.

Once the stations were selected, individual dischargemeasurement notes were counted manually and inventoried 

according to water year. Measurement summaries, including channel discharge, top width, average velocity, and 

hydraulic control, from stations along the main channel of 

the Niobrara were entered into the USGS NWIS database 

(http://waterdata.usgs.gov/nwis). In addition to measurements from continuous-record stations, measurement notes 

also were available for sites monitored by the Nebraska 

Department of Environmental Quality (NDEQ). Three NDEQ 

stations fit some of our selection criteria. One of these sites 

(Pine Creek near Rushville, Nebr.) was not co-located with 

a former continuous-streamflow-gaging station; the site was 

included in the discharge-measurement notes inventory but 

not in the inventory of streamflow-gaging stations. Discharge 

measurements by NDEQ also were available from two other 

Table 1. Data categories and scopes for Niobrara River data inventory and summary. 

[USGS, U.S. Geological Survey; NDNR, Nebraska Department of Natural Resources; NDEQ, Nebraska Department of Environmental Quality; NNRD, 

Nebraska Natural Resources Districts; SDDENR, South Dakota Department of Environment and Natural Resources; CSD, University of Nebraska, Conservation and Survey Division]

Data category Temporal scope1 Spatial scope Data sources

Stream discharge 1964–present Main channel from Dunlap 

Diversion Dam to mouth; 

tributaries with 5 percent or 

greater of drainage area at 

confluence.

USGS, NDNR, NDEQ

Water quality period of record Main channel and tributaries 

downstream from Dunlap 

Diversion Dam to mouth.

USGS, NDNR, NDEQ

Ground-water elevation 1964–present Niobrara Basin from Dunlap 

Diversion Dam diversion to 

mouth.

USGS, NDNR, NNRD, 

 SDDENR

Geologic test hole period of record Niobrara Basin from Dunlap 

Diversion Dam diversion to 

mouth.

USGS, NDNR, CSD

1

Years refer to water year, which is defined as October 1–September 30 and ending in the calendar year shown.
8 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

directly contributing streams; however, these streams did not 

fit the drainage-area criterion and thus were not included in 

the inventory. 

Ground-Water Inventory 

For much of its length, the Niobrara River is a groundwater fed stream, with a steady discharge originating in the 

aquifers underlying the Nebraska Sand Hills (Bentall and 

Shaffer, 1979). Local streamflow gains and losses can result 

from stream-aquifer interactions, which may be dictated by 

the topography of local bedrock, ground-water pumping, 

and streambed substrate. Gains and losses of surface water 

in exchange with a shallow aquifer can result from or affect 

perturbations in channel form, and act as a nutrient source 

for aquatic organisms (Triska and others, 1993; Baxter and 

Hauer, 2000).

Geospatial databases of existing ground-water wells 

and geologic test holes were retrieved and inventoried for 

the entire study area from existing databases maintained by 

federal, state, and local entities including the USGS, NDNR, 

South Dakota Department of Environment and Natural 

Resources, and Nebraska Natural Resources Districts. Each 

database was first filtered by spatially selecting and exporting 

the point features into a geographic information system (GIS) 

using the Niobrara Basin boundary polygon (fig. 1) as a selection tool. Based on data attributes and guidance from officials 

responsible for the databases, the data were further filtered 

to eliminate abandoned or non-existent wells, identify and 

divide wells into use classes, and reduce redundancy between 

monitoring-well data sets. 

Geomorphic Segmentation of the Niobrara River

The most basic function of a river channel is as a conduit 

to transport water and sediment. As a rule, an alluvial river 

channel adjusts its geometry to accommodate its supplied 

loads of sediment and water (Huang and Nanson, 2000). 

Geometric adjustments may be in the form of cross-section 

geometry and characteristics (width, depth, roughness), planform geometry (bars, banks, sinuosity, curvature), or channelbed slope (Knighton, 1998). Thus, it follows that channelgeometry adjustments are the result of a dynamic interaction 

between imposed sediment and water loads, and constraints 

on adjustment, such as valley confinement, bedrock lithology, or biological effects such as the binding root strength 

of riparian plants (Montgomery and Buffington, 1997; Wohl 

and Merritt, 2001; Gran and Paola, 2001). These differences 

in channel geometries (morphology) act as the template for 

aquatic and bottomland ecological processes (Naiman and 

others, 1993; Scott and others, 1996). It can be inferred, then, 

that changes in channel morphology may result in changes in 

ecological processes. 

The Niobrara River channel in the study area is approximately 330 mi long and changes dramatically in size and 

shape over its course. A goal of this investigation is to document and describe the segment-scale characteristics of the 

Niobrara River channel and its valley corridor within the study 

area. The authors use the term “segment” to describe a length 

of river that has a relatively uniform host of hydrologic and 

morphologic characteristics. River segments contain several 

channel reaches, which are variously defined, but commonly 

refers to a repeated sequence of hydraulic characteristics, such 

Figure 3. Example of cross-section layout and subsections for point measurements used to calculate discharge and channel 

hydraulic geometry for a typical river streamflow-gaging station (adapted from Ginting and Zelt, 2008). 0 (Datum) 6080105 120 150 175 190 201 233 245 270

285320

DISTANCE FROM DATUM, IN FEET

Left edge 

of water

Left edge of sandbar

Left edge of island

Right edge of island

Right edge of sandbar

Right edge 

of water

EXPLANATION

Edge of subsection

Interior subsections

Sounding at subsection center
Approach and Methods 9

as a pool-riffle coupling (Frissell and others, 1986). The intention of the description is to provide an interpretive hydrogeomorphic framework to guide future, more detailed, scientific 

investigations. Geomorphic description and characterization of 

the Niobrara River was approached in three parts: (1) longitudinal segmentation using a geomorphic, process-oriented 

classification scheme; (2) longitudinal analysis of channel 

slope (hereinafter referred to as the “longitudinal profile”); and 

(3) longitudinal morphometric characterization. Within this 

report, the methods and some results from parts 1 and 2 are 

presented. Plans for complete results from part 2 and methods 

and results from part 3 are ongoing. 

Classification Scheme for Longitudinal 

Segmentation

Classification, in general, is the process of grouping 

objects based on a pre-defined set of characteristics (Kondolf, 

1995). River classification schemes range from purely form 

(shape)-based schemes, to inductive statistical procedures 

(Kondolf and others, 2003). Channel pattern classification 

schemes, such as those of Leopold and Wolman (1957), 

Schumm (1963), and Brice and Blodgett (1978), divide river 

channels into broad generalized types based on characteristics 

in channel planform. These channel types commonly are 

one of four: straight, meandering, braided, or anastomosing. 

These form-based schemes can be widely applied, and have 

a physical basis under the assumption that channel morphology is the integration of several physical processes including hydrologic, sediment, and vegetative effects. However, 

because these schemes are quite general, they are inadequate 

to describe other important effects on channel morphology, 

such as valley confinement or bedrock lithology. Some other 

form-based classification schemes, such as those of Rosgen 

(1994), provide more details of river and valley setting, but 

are, again, limited in their descriptive flexibility over large 

scales (Kondolf and Downs, 1996; Juracek and Fitzpatrick, 

2003). Process-based classifications, similar to those of 

Montgomery and Buffington (1997), are more focused on the 

geologic and physiographic setting, and the host of associated 

physical processes that may affect the form of the river. Inductive statistical techniques such as those used by Elliot and 

Jacobson (2006), are process-orientated, and the most objective of techniques; however, such techniques are cumbersome 

to apply at the basin-scale, and best used when applied in 

combination with an analysis of temporal variation in channel 

form and process. 

Because of the potentially unique qualities of the Niobrara River, a custom, process-orientated, classification scheme 

Table 2. Niobrara River tributaries and their percentage of contributing basin drainage area at their confluence with the main 

channel. 

[All drainage area data based on United States Department of Agriculture-Natural Resource Conservation Service (2008) Watershed Boundary Dataset; mi, 

miles; DA, drainage area; mi2, square miles; --, not determined]

Drainage

(fig. 2)

Distance upstream 

from mouth of 

Niobrara 

(mi)

DA 

(mi2

)

Noncontributing 

DA 

(mi2

)

DA1

 as percentage of 

Niobrara DA at 

confluence 

DA1

 as percentage of 

total Niobrara 

DA 

Niobrara DA 

at confluence 

(mi2

) 

Tributary drainage 

Box Butte Creek 312.1 253 -- 12.2 1.88 2,071

Pine Creek 300.1 1,916 221,631 46.7 14.2 4,106

Rush Creek 286.5 282 -- 6.29 2.09 4,488

Bear Creek 210.1 382 -- 6.79 2.84 5,630

Medicine Creek 200.5 268 60,657 4.49 1.99 5,963

Snake River 173.2 862 26,422 12.2 6.40 7,064

Gordon Creek 165.0 536 -- 7.01 3.98 7,646

Minnechaduza Creek 150.3 414 -- 5.00 3.08 8,285

Plum Creek 108.6 524 -- 5.65 3.89 9,263

Long Pine Creek 96.6 519 43,846 5.26 3.86 9,884

Keya Paha River 59.3 1,720 -- 14.4 12.8 11,981

Eagle Creek 33.8 217 -- 1.73 1.61 12,521

Redbird Creek 27.8 157 -- 1.24 1.17 12,701

Verdigre Creek 5.0 555 -- 4.13 4.12 13,440

Main channel drainage

Niobrara River -- 13,473 352,556 -- 100 --

1

 Drainage area includes non-contributing drainage area.
10 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

was developed to segment the river in the study area longitudinally. The purpose of the scheme was to act as a descriptive 

tool to assist in documenting the general range of channel and 

valley settings within the study area. The classification scheme 

and some of its results are presented herein as preliminary 

data. The final Niobrara River segments from the classification scheme are being derived and characterized as part of the 

ongoing study. 

After careful examination of the Niobrara River using 

combinations of aerial photography, topographic maps, and 

professional judgment, four descriptive elements were chosen 

as the basic framework for the Niobrara River classification 

scheme: degree of valley confinement; channel planview 

pattern; channel width variation; and bar configuration. Each 

descriptive element contains three to four classes, which 

describe a range of conditions (table 3). Valley confinement 

was chosen to describe the affect of the valley width on channel shape, sediment supply, and overall channel adjustability. 

For example, in canyon reaches, the shape of the valley is the 

primary determinant of the channel shape, whereas in open 

meandering reaches, the valley shape has little to no effect. 

In canyon reaches, hillslope processes, such as landsliding, 

deliver sediment directly to the channel, whereas in openvalley settings, landslides are delivered to the floodplain 

(Montgomery and Buffington, 1997). Sinuosity was chosen 

as a descriptor of the degree of variation in channel direction. 

Whereas sinuosity is variously defined (Bridge, 2003), it is 

defined here as the ratio of the length of the channel centerline between two points to the length of a straight line drawn 

between the same two points. The authors use boundaries of 

1.05 and 1.5 between straight and sinuous, and between sinuous and highly sinuous, respectively. Although these numerical boundaries have been used in other investigations (Wolman and Leopold, 1957), for the purposes of this study they 

were assigned based on natural data breaks, and have been 

calculated and named differently than those used previously. 

Because the Niobrara River is dominantly a ground-water-fed 

stream, the river may have significant gains in discharge, without a confluence from a major tributary. As such, the river also 

may have changes in width, without apparent changes in valley setting, curviness, or bar configuration. After examination 

of aerial photos of the Niobrara River, the authors also noted 

that several segments of the river had large shifts in channel 

width over short distances, potentially indicating loss or gain 

of discharge. Thus, width variation was chosen to describe 

changes in planform width within a segment. Finally, the 

configuration of sandbars is an important descriptor of channel processes such as a wandering thalweg, river meandering, multiple thalwegs, or anastomosing (Bridge, 2003). The 

authors use the terms alternate, lateral, braided, and islands 

respectively to indicate a dominance of one of these processes 

(Bridge, 2003). 

Segmentation of the Niobrara River was accomplished 

by examination of the 2003 Farm Service Agency (FSA) 

natural color digital aerial photographs (1-meter (m) (3.28 ft) 

resolution) (U.S. Department of Agriculture, 2004) in a GIS. 

Boundaries of segments were digitized as points, and their 

associated classification conditions were attributed wherever 

a pronounced and persistent change in one of the four elements was recognized. In some cases, segment boundaries 

were not pronounced. In such cases, professional judgment 

was used, and the boundary placed near the midpoint of the 

gradient. The authors did not, as a rule, use tributary junctions 

as segment boundaries unless a morphologic change coincided 

with it. Whereas tributaries commonly are used as hydrologic 

boundaries, the effect of ground water in the Niobrara study 

area diffuses hydrologic boundaries. The authors recognize 

the fact that some, arguably all, of the descriptive elements 

are discharge-dependent, and therefore limit segmentation 

results to the condition and discharge of the river as viewed in 

the 2003 FSA digital aerial photographs. Because of the vast 

area covered by the aerial photographs, and the dominance of 

ground-water accretion as the main source of flow in the Niobrara River, flow rates varied in the area by both the date and 

location of the photographs. That said, the authors acknowledge that the dominance of ground-water discharge in the 

upper two-thirds of the study area buffers temporal variability 

in flow rates.

Longitudinal Profile Analysis

One of the ways a river may adjust its morphology to 

inputs of sediment and water is by variation in channel slope. 

Bedrock lithology, tributary deposits, and hillslope processes 

may act as first-order controls on channel slope (Montgomery 

and Buffington, 1997; Montgomery and Gran, 2001; Hanks 

and Webb, 2006). To examine the broad-scale slope characteristics of the Niobrara River, the longitudinal profile of the 

main channel of the Niobrara was plotted and compared to 

available geologic and topographic digital datasets that also 

spanned the study area. To create the longitudinal profile, the 

channel centerline was digitized between the high banklines 

using the 2003 FSA aerial photographs. The centerline was 

addressed using a linear referencing tool in a GIS with the 

starting point (0.0 mi) at the former Chicago and Northwestern railroad bridge near the confluence of the Niobrara and 

Missouri Rivers. Where possible in this document, the authors 

have used English units because these are the most familiar 

and practical units used by the focus audience; however, for 

the purposes of this section we use metric units when referring 

to analysis of digital data sets, which are the most common 

native units of the data sets, and therefore the units in which 

the data were analyzed. 

The channel centerline was overlaid on the 1998 USGS 

National Elevation Dataset 10-m (32.8-ft) digital elevation 

model (DEM) (http://seamless.usgs.gov), and elevations were 

sampled at points every 20 m (65.6 ft) along the channel 

centerline. In addition, elevation statistics were computed at 

the same points using a 15-m (49.2 ft) radius buffer. An algorithm was applied in the downstream direction to eliminate 

elevation gains. This correction was necessary because the 

10-m DEM did not have the elevational precision to capture 
Approach and Methods 11

macro-scale channel bedforms such as pool-riffle sequences, 

and thus it was assumed that downstream elevational spikes 

were spurious. The algorithm applied the spatial statistics for 

any downstream point that was higher in elevation than its 

adjacent upstream point. The algorithm used trial and error, 

first assigning the mean, then the minimum of the elevation 

statistics; if neither the mean nor the minimum were lower 

than the elevation of the adjacent upstream point, the identical elevation of the upstream point was assigned. Whereas 

this correction forces a slope of zero between some points, 

it did not change the dominant local or broad-scale shape of 

the uncorrected original longitudinal profile. The longitudinal 

profile shape constructed from the USGS DEM also compares 

favorably with a more generalized profile constructed by 

Bentall (1991), which used the stream centerline and contour 

intervals from USGS 7.5-minute quadrangles.

Vertical position accuracy of the 10-m (3.28-ft) DEM 

is approximately equivalent to the root-mean-square error 

(RMSE) of the DEM. A RMSE less than one-half of the contour interval on the 7.5-minute quadrangle used was the maximum reported by the USGS and NDNR. Contour intervals for 

the study area vary, but typically are less than 20 ft, making 

Table 3. Segment-scale geomorphic classification system for the Niobrara River, Nebraska.

Scale Condition Class Definition

A. Degree of valley confinement

Valley

Entrenched 1

Valley confinement such that the river pattern is forced by the valley configuration making 

the river and valley pattern nearly identical, and as such the river persistently flows parallel 

to the valley direction, and adjustment of the broad-scale channel pattern is not possible. 

Floodplains are present but commonly are less than one channel width across. 

Restricted

Phase 2

Valley confinement such that the planview river pattern largely is controlled by valley pattern, 

valley width irregularities, or tributary alluvial fans. The valley is generally wide enough for 

a floodplain of several channel widths, but the river is intermittently entrenched. The river 

commonly flows in parallel to the valley direction and impinges on the valley wall at most 

outer bends. 

Width 3

Valley confinement such that the valley is wide enough for a floodplain of several channel 

widths and the effect of the valley pattern on river channel pattern generally is limited to 

redirection of the channel towards the opposite valley wall at outer bends. 

Open 4

Valley pattern has little to no affect on the dominant river pattern. Channel interaction with the 

valley wall is infrequent. Channel form adjustments such as large meander-loop cutoffs or 

long anabranching channels are possible. 

B. Channel planview pattern

Reach

Straight 1 Channel pattern such that the channel centerline length between two endpoints divided by the 

straightline length between the same two endpoints is less than or equal to 1.05.

Sinuous 2 Channel pattern such that the channel centerline length between two endpoints divided by the 

straightline length between the same two endpoints is between 1.06 and 1.49.

Highly sinuous 3 Channel pattern such that the channel centerline length between two endpoints divided by the 

straightline length between the same two endpoints is greater than or equal to 1.5.

C. Channel-width variation

Reach

Equiwidth 1 Channel width generally does not vary by more than a factor of two for the length of the reach.

Irregular 2 Channel width varies progressively or intermittently along the reach by more than a factor of 

two.

Highly irregular 3 Channel width varies by a factor of two for lengths as short as a single channel width, with the 

appearance as a series of bulges and narrows in planview. 

D. Bar configuration

Bar

Alternate 1

Bar configuration such that a single thalweg is dominant and flows alternately between bars 

that migrate freely within the channel banks. Alternating bars may be covered with immature vegetation.

Lateral 2 Bar configuration such that a single thalweg flows around stable laterally deposited bars that 

grow oblique or orthogonal to the dominant flow direction. 

Braided 3 Bar configuration such that several thalwegs exist and migrate between complexes of emergent 

and submerged channel sandbars.

Island 4 Bar configuration such that several thalwegs exist and flow between sandbars with mature 

vegetation and whose dimensions generally are proportional to the active channel width.
12 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

the vertical accuracy of the DEM plus or minus 10 ft (about 

3 m). At the scale of the study area, this constitutes less than 

0.4 percent of the total longitudinal profile relief. 

Comparisons of the Niobrara River longitudinal slope 

characteristics were made with two existing digital geographic 

data sets, both published by the University of NebraskaLincoln, Conservation and Survey Division (CSD) (1986): 

generalized bedrock geology of Nebraska and topographic 

regions of Nebraska. Contacts between bedrock lithologies 

and divisions between topographic regions were digitized and 

attributed along the channel centerline in a GIS. The point 

features were attributed with longitudinal locations using 

the address system of the Niobrara River channel centerline 

described above. 

Hydraulic Geometry Characterization 

To begin to understand how a river may adjust its geometry to changing discharges, examination of its current and 

historical behavior is a logical starting point (Kondolf and 

Downs, 1996). USGS and other agency streamflow-gaging 

stations provide a valuable, often temporally rich, empirical record of channel adjustment for a range of discharges 

at the local (cross-section) scale. The data contained in the 

basic field notes from a hydrographer’s discharge measurement provide observations of water-top width, channel area, 

and average channel velocity, all of which are related to a 

particular discharge. Average channel depth can be calculated by dividing channel area by the water top width. Using 

the conventional methods described (see Background section in this report), these measures of channel geometry can 

be used to develop statistical models, termed “hydraulic 

geometry,” which illustrate how a river channel at a particular location adjusts its geometry to accommodate a range of 

water discharges. 

Other reports have documented that simple hydraulic 

geometry relations are inadequate to describe the changing 

conditions at a particular river reach, and have employed 

more complex relations (Rhodes, 1977; Eschner, 1983). Some 

authors have documented temporal trends in stream-rating 

relations with implications for hydraulic geometry (Chen and 

others, 1999). For the purposes of this report, the authors carefully employ simple hydraulic geometry relations to provide 

a baseline understanding of Niobrara River behavior relative 

to discharge at the basin scale. No attempt was made to track 

temporal trends, or adjustments relative to a particular stressor 

at any particular streamflow gage. 

Although hydraulic geometry relations provide empirical evidence of channel adjustments, and hence a model of 

how a channel may respond to future changes in discharge, 

they are by no means a definitive predictor of such responses. 

The development and use of hydraulic geometry relations has 

several problems and limitations (Knighton, 1974; Park, 1977; 

Juracek and Fitzpatrick, 2008), some of which the authors 

encountered and wish to recognize here. First, discharge 

measurements are not always made at the same location. At 

stations where technicians measure discharge by wading the 

channel, the measurement location often is chosen based on 

safety and error considerations rather than the location of a 

previous measurement. The location of the measurement typically is recorded, but most often it is an estimate of distance 

from a local landmark (the gage house or a bridge), and is, 

therefore, neither accurate nor necessarily precise. This is 

particularly the case between distance estimates by different 

technicians. Thus, wading measurements may not be made at 

the same cross section, and differences in geometry between 

measurements made at a common discharge may be the result 

of natural spatial variability in channel dimensions rather than 

actual morphologic changes. At locations where measurements 

are made from a cableway or bridge, the problem of spatial 

variability is more limited, although differences in location 

can occur when technicians use different velocity measurement tools (Ginting and Zelt, 2008). 

A second limitation of hydraulic geometry is the fact 

that streamflow-gaging station locations may not necessarily 

be representative of the channel environments upstream and 

downstream. Examples of this are gages located at bridges, 

which often are built at locations that are naturally narrower 

than the surrounding river, or may have causeways or elevated 

approaches, forcing the channel to narrow. Another example 

is a streamflow-gaging station downstream from a dam, which 

reduces sediment supply and, again, may not represent the 

channel environments upstream or further downstream, where 

sediment supplies are more in balance with the flow regime. 

A third limitation of hydraulic geometry are the measurements themselves, which may be limited in range of flows, 

have varying degrees of uncertainty, and may be greatly 

affected by environmental conditions such as ice or debris. 

Although the quality of the measurement condition typically 

is rated by the hydrologic technician (Rantz and others, 1982), 

the rating is based on best professional judgment which is, 

again, subjective. 

Finally, there is the fact that observations of past behavior 

are not a guarantee of future behavior, especially given the 

complexity of river systems and the uncertainty of prediction 

in natural systems (Simon and Castro, 2003). Even with these 

limitations in mind, the fact that measurement data are actual 

observations of past river behavior lends some credence to 

their value in assessing, at a minimum, the potential direction 

of channel adjustment associated with changing discharges in 

the future. 

At-A-Station Hydraulic Geometry Relations

At-a-station hydraulic geometry relations describe how a 

river channel at a particular location (a cross section) adjusts 

to changing discharges. Hydraulic geometry relations were 

developed for eight individual streamflow-gaging stations 

located along the main channel of the Niobrara River in 

the study area (fig. 4). The relations were developed using 

methods first outlined in Leopold and Maddock (1953), using 
Approach and Methods 13

the forms of equations 1 through 3 described in the Background section of this report. The at-a-station relations of the 

form of equations 1 through 3 were developed using ordinary 

least-squares (OLS) regression of x/y data pairs from hydrologic technician’s measurement notes. In all cases “x” was 

the discharge calculated from the measurement, and “y” was 

either the channel-top width, the average channel depth (channel area divided by top width) or average channel velocity 

(discharge divided by channel area). The regression line slope 

value (exponent), regression line intercept value (coefficient), 

probability (p) values, and coefficients of determination 

(COD) for all OLS at-a-station hydraulic geometry relations 

were generated using standard statistical tools in Microsoft 

Excel®. OLS regression slope values were tested for statistical 

significance at the 90-percent confidence level; probability (p)

values less than 0.10 were interpreted to indicate that the slope 

coefficient generated for the at-a-station hydraulic geometry 

relation was significantly different than zero (a slope of zero 

would generally indicate that “x” is a poor or weak predictor 

of “y”). The COD values for the OLS model, which indicate 

the fraction of the variance in the “y” variable explained by a 

statistical model generated using the “x” variable as a predictor, was used as a secondary indicator of model goodnessof-fit. Raw data graphs of measurement data x/y pairs, and 

90-percent confidence bounds for all OLS at-a-station hydraulic geometry regression relations, were generated in S-plus 

statistical software and are presented in Appendix 2. 

For streamflow-gaging stations downstream from the 

Snake River confluence, only measurements recorded after 

water year 1963 were used because operations of Merritt Dam 

began in water year 1964. A water year is defined as beginning 

on October 1 and ending on September 30 of the year indicated. Upstream from the Snake River confluence, post-1963 

records were used where available; however, in most cases, 

only pre-1963 records were available. 

 Measurement data used to develop the at-a-station 

hydraulic geometry relations were the end result of a data filtering process intended to reduce data uncertainty. The initial 

data filter eliminated measurement data rated by the technician 

as “poor.” Data with a poor rating are assumed to have greater 

than 10-percent uncertainty in the discharge magnitude (Rantz 

and others, 1982). The second filter eliminated measurement 

data that were made when the channel itself was not considered the main hydraulic control by the technician. Examples of 

this are when the channel is choked with ice or heavy debris. 

A final filter step was applied that varied depending on 

whether or not the measurements were predominantly wading 

or from a bridge or cableway. If most of the measurements 

were wading, and the measurements included larger-magnitude flows (flows with lower exceedance frequencies), wading 

measurements were used in the hydraulic geometry relations. 

In such cases it was desirable to filter the data based on the 

hydrologic technician’s note of the measurement location 

relative to a landmark. Location data were filtered by first 

Valentine

EXPLANTION

Crest-stage gage

Niobrara River gage discontinued before 1964

Small-tributary gage

Large-tributary gage

Niobrara River gage with records after 1963

[Gaging stations with station number labels correspond to 

gages used for the hydraulic-geometry analysis (table 4)]

104° 103° 102° 101° 100° 99° 98°

43°

42°

0 20 40 60 KILOMETERS

Base from USGS National Elevation Dataset, 2006; National Hydrography Datset, 2007; 0 20 40 60 MILES

 State boundaries, 2005, 1:2,000,000

Basin boundary based on U.S. Department of Agriculture-Natural

Resource Conservation Service, Watershed Boundary Dataset (2008)

Universal Traverse Mercator projection, zone 14

Horizontal coordinate information is referenced to 

 the North American Datum of 1983 (NAD 83)

06456500

06457500

06459000

06461500 06463720

06462000

06465000

06465500

Figure 4. Streamflow-gaging stations in the Niobrara River Basin selected for data inventory. 
14 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

obtaining the statistical mode (the most frequently occurring observation) of the location data. The mode was then 

compared to other comments of location. For example, at one 

gage, two different measurement notes read “wading measurement 10 ft below gage under cableway” and “wading measurement 50 ft below gage under cableway.” These two measurements would appear to have been made under two different 

cableways located 40 ft apart; however, the location of the 

cableway did not change. In such cases, where two landmarks 

were used, it was assumed that all data with the label “under 

cableway” were at the same location, and therefore all data 

between 10 and 50 ft in the same direction (upstream or downstream) away from the first landmark, the gage, were used for 

hydraulic-geometry analysis. 

For measurements where no second landmark was noted, 

wading measurements were assumed to be at the same cross 

section if the measurement was within one-half the value of 

the statistical mode of measurement locations in either direction (upstream or downstream). For example, if the statistical 

mode was “50 ft below the gage,” all measurements between 

25 ft below the gage and 75 ft below the gage were used. In 

some cases, no location data were readily available for wading 

measurements, and the location filter could not be applied. 

For stations where bridges or cableways were the 

dominant location of measurements, only data from either the 

bridge or cableway were used. At one location, the Niobrara 

River near Verdel, bridge measurements were moved from 

a decommissioned bridge to a new bridge upstream in water 

year 1986. In this case, the measuring locations were considered as two different stations, and two separate at-a-station 

hydraulic-geometry relations were developed; one for the 

1964 to 1985 period of record, and one for the 1986 to 2007 

record.

Downstream Hydraulic-Geometry Relations

Downstream hydraulic geometry relations describe how a 

river adjusts its geometry to gains in discharge in the downstream direction (as drainage area increases). Downstream 

hydraulic geometry relations were developed for the Niobrara 

River using methods described by Leopold and Maddock 

(1953) and using the simple power equations 1 through 3 

(in the Background section of this report) as statistical models. Average daily discharge for each at-a-station streamflowgaging station was used to generate flow-duration curves 

(fig. 5). With the exception of the Verdel gages, the same periods of record as the measurement data used for the at-a-station 

relations were used to generate the flow-duration curves. 

At the Verdel gages, the authors assumed that, although the 

location of the streamflow-gaging station moved in water 

year 1986, the flow record applied to both locations because 

of their close proximity. Therefore, the entire post-1963 

period of record was used to generate a flow-duration curve, 

which was applied to both of the Verdel at-a-station hydraulic 

geometry relations. 

Three exceedance frequencies, 10, 50, and 75 percent, 

were chosen to represent the high-, median-, and low-flow 

magnitudes respectively (table 4). Mean annual flow (also 

known as mean daily flow) also was calculated for the period 

of record for each gaging station. Common exceedance flows 

were used as predictor variables to generate hydraulic geometry values (channel-top width, average depth, and average 

velocity) using the at-a-station hydraulic-geometry relations 

from each streamflow-gaging station. Downstream hydraulicgeometry relations were then generated for each exceedance 

frequency using OLS regression of the “x” (discharge of 

common exceedance frequency) and “y” (at-a-station width, 

average depth, or average velocity) data pairs from each of 

the streamflow-gaging stations. OLS regression slope values, 

coefficient values, p values, and COD were generated using 

procedures identical to those described above for the at-astation hydraulic-geometry relations. 

Hydraulic Habitat at a Streamflow-Gaging 

Station

At the scale of a river reach, hydraulic variables such as 

flow depth and velocity exert important effects on the types 

of aquatic habitat available for organisms, and even moderate 

alteration can produce significant shifts in habitat availability (Stalnaker and others, 1996; McKenny, 1997; Maddock, 

1999). For the purposes of demonstration, hydraulic microhabitat calculations were performed using the automated 

computational tool presented in Ginting and Zelt (2008). 

The tool characterizes the extent of hydraulic habitat niches 

along the cross section using a matrix of three depth and three 

velocity classes (table 5). Depth classes are defined as shallow, intermediate, and deep, corresponding to class boundaries 

of less than 1 ft, 1 to 2 ft, and deeper than 2 ft, respectively. 

Velocity classes are defined as slow, moderate, and swift, 

corresponding to class boundaries of less than 1 ft per second, 

1 to 2 ft per second, and greater than 2 ft per second, respectively. The hydraulic habitat nomenclature uses the respective 

depth and velocity class names. For example, an area of the 

channel with depth less than 1 ft and velocity between 1 and 

2 ft per second would be classified as “shallow-moderate.” 

Although the hydraulic habitat niches originally were defined 

for fish species of the Platte River (Peters and Holland, 1992), 

many of the same fish species have been sampled in the main 

channel and tributaries of the Niobrara National Scenic River 

(Dietsch, 2007). 

To compare differences in habitat types and distributions, 

three different flow magnitudes were chosen to represent the 

upper decile (less than 10-percent exceedance), median quantile (25- to 75-percent exceedance), and lower decile (greater 

than 90-percent exceedance) of flows at the USGS streamflowgaging station on the Niobrara River near Sparks, Nebraska 

(station number 06461500). This gage was chosen because 

of its location within the 76-mi National Scenic River Reach 

and its representativeness of the narrow canyon environments 
Approach and Methods 15

Table 4. Flow-exceedance frequencies and associated discharges used for downstream hydraulic-geometry calculations. 

[%, percent; ft3/s, cubic feet per second; all place names mentioned are in the State of Nebraska]

Streamflow gaging-station name Station 

number

Period of 

record1

Mean annual2

discharge in 

ft3

/s

10% 

exceedance3

discharge in ft3

/s

50% exceedance3

discharge in ft3

/s

75% exceedance3

discharge in ft3

/s

Niobrara River near Hay Springs 06456500 1951–1963 29 40 24 18

Niobrara River near Gordon 06457500 1964–1990 110 155 102 85

Niobrara River near Cody 06459000 1949–1956 315 400 302 258

Niobrara River near Sparks 06461500 1964–2007 738 1,000 726 567

Niobrara River near Norden 06462000 1964–1983 816 1,120 800 623

Niobrara River at Mariaville 06463720 1986–1990 1,360 1,875 1,250 1,080

Niobrara River near Spencer 06465000 1964–2000 1,536 2,375 1,400 1,060

Niobrara River near Verdel4 06465500 1964–2007 1,708 2,695 1,540 1,180

1

Period of record is given in water years, defined as October 1 to September 30 and ending in the calendar year indicated.

2

Mean annual discharge refers to the average of daily mean discharge values over the course of a water year.

3

Exceedance refers to the percentage of days annually that mean daily discharge exceeds the given value.

4

Gage near Verdel moved in water year 1985; exceedance-frequency values computed using entire period of record.

PERCENTAGE OF TIME STREAMFLOW WAS EXCEEDED

10

0 20 40 60 80 100

3

100

1,000

10,000

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

30,000

Near Hay Springs (1951−63)

Near Gordon (1964−90)

Near Cody (1949−56)

Near Sparks (1964−2007)

Near Norden (1964−83)

At Mariaville (1986−90)

Near Spencer (1964−2000)

Near Verdel (1964−2007)

Niobrara River

EXPLANATION

Figure 5. Flow-duration curves for selected streamflow gages and periods of 

record of the Niobrara River between Dunlap Diversion Dam and the Missouri 

River, Nebraska. 
16 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Table 5. Matrix of depth and velocity combinations used to define hydraulic-habitat niches for microhabitat analysis using 

streamflow measurement data (from Ginting and Zelt, 2008).

[Depth and velocity classes and associated species based on Peters and Holland (1992), except where indicated; ft/s, feet per second; ft, foot]

Water depth Current velocity

Slow (slower than 1 ft/s) Moderate (1–2 ft/s) Swift (faster than 2 ft/s)

Shallow Notropis blennius Hybognathus placitus Aplodinotus grunniens

(shallower than 1 ft) (River shiner) (Plains minnow) (Freshwater drum)

Cyprinella lutrensis

(Red shiner) Hybognathus argyritus

Notropis stramineus (Silvery minnow)

(Sand shiner) 

Hybognathus placitus Platygobio gracilis

(Plains minnow) (Flathead chub)

Hybognathus argyritus

(Silvery minnow) Ictalurus punctatus

Platygobio gracilis (Channel catfish)

(Flathead chub)

Carpiodes cyprinus

(River carpsucker)

Carpiodes carpio

(Quillback)

Intermediate Cyprinella lutrensis Ictalurus punctatus

(1-2 ft) (Red shiner) (Channel catfish)

Ictalurus punctatus

(Channel catfish) Aplodinotus grunniens

Aplodinotus grunniens (Freshwater drum)

(Freshwater drum)

Deep Cyprinella lutrensis lctalurus punctatus Ictalurus punctatus

(deeper than 2 ft) (Red shiner) (Channel catfish) (Channel catfish)

 Ictalurus punctatus Aplodinotus grunniens Aplodinotus grunniens

(Channel catfish) (Freshwater drum) (Freshwater drum)

Scaphirhynchus sp.1

(Sturgeon)

1

 Based on studies by Bramblett and White (2001) and Wildhaber and others (2007); the Deep-Swift niche is the preferred habitat requirements by pallid 

sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus) during their adult life.
Initial Results 17

within the basin. Three flows from water year 1988 were chosen because they referenced the same cross-section location 

in the same year, and all three measurements occurred after 

winter ice breakup (table 6). Comparisons also were made 

with time at the Sparks gage, using lower-decile and medianquantile flows from water year 2003. The upper-decile flow 

measurements were not made at a common cross section in 

2003, and therefore could not be used in the analysis. 

Initial Results

Summary of Available Data

Stream Hydrology and Sediment

All active and inactive streamflow-gaging stations for 

the Niobrara study area are listed in table 7. The inventory 

includes 45 streamflow-gaging stations. Of those, 29 gages 

were, at one time or another, continuous-record stations, 

where daily flows were recorded using a stage recorder, and 

where discharge measurements were made several times 

annually. Sixteen of the 45 stations are listed as crest-stage 

gages. Crest-stage gages within the study area generally are 

located in smaller basins, along intermittent creeks, and loworder streams (fig. 4). Of the 29 continuous-record stations, 

13 have records of suspended sediment; 8 are along the main 

channel of the Niobrara River; and 5 are within large tributaries. In addition, all but one of the continuous-record stations 

had available discharge-measurement field notes, and many 

have at least some water-quality data. Of the 28 gages with 

discharge-measurement field notes available, 15 have notes 

available after 1963 (table 8); most of these sites are in the 

downstream portion of the study area.

Ground-Water Hydrology

At the time of publication, more than 11,400 groundwater wells were identified as “active” (not including geologic 

test holes) within the Niobrara study area (table 9). Watersupply wells, which include irrigation, commercial, industrial, 

and minor-use wells (domestic, stock, and aquaculture supply 

wells) constitute most of the wells in the basin. Irrigation and 

commercial-supply wells are concentrated in the Nebraska 

Sand Hills region south of the river, near O’Neill, Nebr., and 

south of Dunlap Diversion Dam (fig. 6A). Domestic and stocksupply wells, which the authors refer to as “minor-use” wells, 

are focused in the area immediately around Valentine, Nebr., 

and to the southeast near Long Pine, Nebr. (fig. 6B).

Approximately 1,400 wells were identified as “active” 

within the USGS NWIS database. These wells have been 

used for various scientific observations (ground-water levels, 

aquifer tests, water-quality sampling). Nebraska wells in the 

NWIS database have the potential to be redundant with wells 

contained in the NDNR well database; however, without a 

common identifier between the two databases, no mechanism 

exists to readily eliminate redundancy. 

A network of ground-water elevation monitoring wells 

is maintained in the study area (fig. 7A). In South Dakota, the 

Department of Environment and Natural Resources monitors ground-water levels in approximately 39 wells several 

times a year (Ken Buhler, South Dakota Department of 

Environment and Natural Resources, oral commun., 2008); 

these wells are concentrated mainly in the Keya Paha River 

Basin. In Nebraska, three Natural Resources Districts (Upper 

Niobrara-White, Middle Niobrara, and Lower Niobrara) maintain 218 observation wells throughout the study area, which 

are monitored for ground-water elevation in the spring and 

fall annually (Lynn Webster, Upper Niobrara-White Natural 

Resources District, oral commun., 2008). The records for 

these wells generally are limited to the past 10 years, although 

several of the monitoring wells have records extending back 

several decades. 

Within the study area, 2,162 boreholes were identified as 

geologic “test holes” (table 8). Within Nebraska, University of 

Nebraska-Lincoln Conservation Survey Division (CSD) maintains a database of geologic test holes. Within the Nebraska 

part of the study area, 255 geologic test holes were identified; 

many of the geologic test holes are aligned in north-south 

series, and have been drilled since 1930 by CSD and used to 

identify bedrock geologic contacts and define aquifer physical 

and hydraulic properties (fig. 7B). The South Dakota Geological Survey maintains a public database of geologic test holes 

specifically drilled for the purpose of describing lithology; 

within the South Dakota part of the study area, 1,907 wells 

were identified. The South Dakota database of well-completion reports also contains lithologic logs for water-supply 

and explorations wells, although these were not included in 

the inventory. 

Although numerous wells and geologic test holes exist in 

the Niobrara study area, well density along the main channel 

and tributaries is approximately one per square mile. Such 

density provides little value for tests of stream-aquifer interactions; however, broad-scale piezometric surfaces may be 

generated and identify generalized locations of gains or losses, 

or recent temporal trends in ground-water table elevations.

Table 6. Discharge measurements and associated flow 

frequencies at Niobrara River near Sparks, Nebraska, used in 

hydraulic-microhabitat calculations. 

[ft3/s, cubic feet per second]

Date Discharge 

(ft3

/s)

Percent 

exceedance

Flow frequency 

quantile

8/17/1988 467 92 Lower decile

9/9/2003 446 95 Lower decile

7/20/1988 605 78 Median quantile

6/20/2003 749 57 Median quantile

4/28/1988 1,030 8 Upper decile
18 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Table 7. Active and inactive streamflow-gaging stations of the Niobrara River Basin study area. 

[Gages listed in order from upstream to downstream; trib., tributary; USGS, U.S. Geological Survey; NDNR, Nebraska Department of Natural Resources; 

present, record through water year 2007; unless indicated otherwise, all stations are located in Nebraska; *, gage reinstated in water year 2008; records available: 1 - daily discharge, 2 - peak streamflow, 3 - discharge-measurement field notes, 4 - suspended sediment, 5 - water quality, 6 - water 

temperature]

Station name Station number Period of record 

(water years) Operator Records available

Continuous-record stations

Niobrara River near Hay Springs1 06456500 1950–64 USGS 1, 2, 3, 4, 5

Niobrara River near Colclesser 06457000 1940–45 USGS 3, 5, 6

Niobrara River near Gordon1 06457500 1928–32, 1946–93 USGS, NDNR 1, 2, 3, 4

Bear Creek near Eli 06458500 1948–53 USGS 1, 2, 3

Niobrara River near Cody1 06459000 1948–57 USGS 1, 2, 3, 4

Snake River at Doughboy 06459175 1982–2004 USGS, NDNR 1, 2, 3

Snake River above Merritt Reservoir 06459200 1962–81 USGS 1, 2, 3, 6

Snake River near Burge 06459500 1947–2004 USGS, NDNR 1, 2, 3, 4

Niobrara River near Valentine 06460500 1928–32 USGS 3

Minnechaduza Creek near Kilgore 06460900 1958–74 USGS 1, 2, 3

Minnechaduza Creek at Valentine 06461000 1947–94 USGS, NDNR 1, 2, 3

Niobrara River near Sparks1 06461500 1949–Present USGS 1, 2, 3, 4

Niobrara River near Norden1 06462000 1953–83, 1986 USGS 1, 2, 3, 4, 5, 6

Plum Creek at Meadville 06462500 1948–75, 1977–94 USGS 1, 2, 3, 5, 6

Niobrara River at Meadville 06463000 1951–52 USGS 1, 3, 4, 6

Long Pine Creek near Long Pine 06463080 1980–91 USGS 1, 2, 3

Long Pine Creek near Riverview 06463500 1948–Present USGS, NDNR 1, 2, 3, 4, 5, 6

Niobrara River at Mariaville1 06463720 1986–91 USGS 1, 2, 3, 4, 5, 6

Keya Paha River near Hidden Timber, South Dakota 06464000 1948–52 USGS 1, 2, 5, 6

Keya Paha River near Keya Paha, South Dakota 06464100 1981–Present USGS 1, 2, 3, 4, 6

Keya Paha River at Wewela, South Dakota 06464500 1938–40, 1947–Present USGS 1, 2, 3, 4, 5, 6

Keya Paha River near Naper 06464900 1958–2004 USGS, NDNR 1, 2, 3

Niobrara River near Spencer1 06465000 1908–2002* USGS 1, 2, 3, 5, 6

Eagle Creek near Redbird 06465310 1979–92 USGS 1, 2, 3, 5, 6

Redbird Creek at Redbird 06465440 1981–94 USGS 1, 2, 3

Niobrara River near Verdel1 06465500 1938–40, 1958–Present USGS 1, 2, 3, 4, 5, 6

North Branch Verdigre Creek near Verdigre 06465680 1980–92 USGS 1, 2, 3

Verdigre Creek near Verdigre 06465700 2002–Present USGS 1, 3, 4

Niobrara River at Niobrara 06466000 1954–58, 1999–Present USGS 1, 2, 3

Crest-stage gages

Pebble Creek near Esther 06456200 1953–78 USGS 2

Pebble Creek near Dunlap 06456300 1953–70 USGS 2

Cottonwood Creek near Dunlap 06456400 1948–78 USGS 2

Point of Rocks Creek near Marsland 06457100 1970–78 USGS 2

Berea Creek near Alliance 06457200 1953–78 USGS 2

Antelope Creek at Gordon 06457700 1953–70 USGS 2

Antelope Creek trib. near Gordon 06457800 1953–78 USGS 2

Bone Creek trib. near Ainsworth 06463100 1956–68 USGS 2

Bone Creek trib. No. 2 near Ainsworth 06463200 1958–68 USGS 2

Sand Draw tributary near Ainsworth 06463300 1956–74 USGS 2

Antelope Creek near Mission, South Dakota 06463900 1990–2006 USGS 2, 6

Sand Creek near Olsonville, South Dakota 06464120 1999–2007 USGS 2, 6

Honey Creek near O’Neill 06465200 1958–68 USGS 2

Camp Creek near O’Neill 06465300 1958–78 USGS 2

Blackbird Creek trib. near O’Neill 06465400 1958–68 USGS 2

Bingham Creek near Niobrara 06465850 1968–78 USGS 2 1

Gage used in hydraulic geometry analysis.
Initial Results 19

Characteristics of Geomorphic Segments

Longitudinal Segmentation

Using the descriptive elements outlined in table 3, the 

portion of the Niobrara River in the study area was divided 

into 36 individual segments (table 10). Three fluvial geomorphic provinces can be inferred based on natural breaks in the 

condition classes of the segments: an upper province dominated by open valleys and a sinuous, equiwidth channel; a central province with mixed valley and channel settings, including 

several entrenched canyon reaches; and a lower province with 

a wide, yet restricted, valley and a wide, persistently braided, 

or island-dominated channel. In this report, these provinces are 

called the meandering bottoms (MB), canyons and restricted 

bottoms (CRB), and braided bottoms (BB), respectively. 

The boundaries of these provinces roughly correspond to the 

boundaries of the “valleys” and “escarpments and bluffs” 

topographic provinces published by University of NebraskaLincoln, Conservation Survey Division (1986) (fig. 8). 

Additionally, the boundary between CRB and BB roughly 

corresponds to the boundary between bedrock of Tertiary and 

Cretaceous age, also published by University of NebraskaLincoln, Conservation Survey Division (1986). 

Mean segment length increases in the downstream direction, with MB segments averaging 5.3 mi, CRB segments 

averaging 7.1 mi, and BB segments averaging 20.8 mi long 

(table 9). Width-restricted valley settings are the most frequent 

!

!

!

O'Neill

Valentine

Long Pine

O'Neill

Valentine

Long Pine

104° 103° 102° 101° 100° 99° 98°

43°

42°

104° 103° 102° 101° 100° 99° 98°

43°

42°

NEBRASKA

SOUTH DAKOTA

B.

A.

NEBRASKA

SOUTH DAKOTA

WYOMING WYOMING

EXPLANATION

Number of wells per square mile

Boundary of Niobrara Basin 

within study area

Boundary of Niobrara Basin 

within study area

Boundary of Niobrara Basin 

outside study area

Boundary of Niobrara Basin 

outside study area

Missouri River

Niobrara River

Missouri River

Niobrara River

figure06final.ai

Dunlap Diversion

Dam

Dunlap Diversion

Dam

0 20 40 60 KILOMETERS

0 20 40 60 MILES

Figure 6. Ground-water well density in the Niobrara River study area (A) Irrigation and commercial-supply wells; and 

(B) minor-use wells (domestic, stock, and aquaculture supply wells).
20 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

type of segment and the most widespread within the study 

area. Open valleys are intermittent downstream from the MB 

province, occurring as abrupt convexities in valley bottom 

width. Nearly all segments are sinuous in channel pattern 

and none meet the criteria of “straight.” Three reaches meet 

the criteria of “highly sinuous:” two in open valleys, and one 

within an entrenched canyon segment. Irregular width patterns 

are the most frequent among channel segments, although 

highly irregular width patterns dominate the extent of the 

study area. Finally, alternate bars are the most frequent bed 

forms present among geomorphic segments, but braided bars 

cover most of the channel bed in the study area. Island-dominated reaches are uncommon, occurring mainly in the backwater segments above Spencer Dam and the delta region near the 

Missouri River (Etheridge and others, 1999). 

Longitudinal Profile Characteristics of the 

Niobrara River

Channel slope of the Niobrara River study area varies 

between 0.05 and 0.25 percent among segments, with a studyarea mean of 0.15 percent (tables 10 and 11). Among geomorphic provinces, channel slope is steepest and most variable 

in the MB; however, the CRB province has the widest range 

among segment slopes. The BB province exhibits the mildest, 

least-variable slopes among the three provinces, with a maximum slope approximately equivalent to the study-area mean. 

Slope characteristics and perturbations of slope in the 

longitudinal profile of the Niobrara River indicate that bedrock 

may be an important control in channel form. At least two 

knick zones (locations of channel steepening) exist within 

the study area, both within the CRB province, and both 

roughly corresponding to bedrock contacts (fig. 8). Within the 

upstream knick zone, between Antelope and Bear Creeks, the 

Niobrara flows through a long series of entrenched meanders. 

Upstream from this knick zone, no major bedrock contacts 

occur in the study area, and the slope of the river is approximately the study-area mean. Near the downstream knick zone, 

between Medicine Creek and Snake River, several small, 

denuded tributaries deliver sediment directly to the river from 

the tablelands north of the river. An additional indicator of the 

effect of bedrock on Niobrara channel slope is the reduction in 

slope, and reduced slope variation, downstream from the contact between the White River Group and the Pierre Shale. This 

location also roughly corresponds to the boundary between 

the CRB and BB geomorphic provinces. Additional analysis is 

necessary to verify the effect of bedrock on channel geometry.

In addition to the effect of bedrock on channel slope, 

tributary alluvial sediment contributions also may cause local 

perturbations in slope. Within the CRB geomorphic province 

the longitudinal profile has a consistent stair-step pattern. 

Visual examination of the longitudinal profile indicates that 

many of the tributary confluences are located at or near the 

top of steps. Although this pattern has been shown in other 

Table 8. Inventory of hydrographer’s discharge measurement notes at Niobrara River Basin gaging stations with records after 1963. 

[Gages listed upstream to downstream; USGS, U.S. Geological Survey; NDNR, Nebraska Department of Natural Resources; NDEQ, Nebraska Department of 

Environmental Quality; no., number; --, no data; all stations are located in Nebraska]

Station name Station identification 

code or number

Period of record available (water years)

Total no. of 

measurements Custodian of measurement notes

USGS NDNR NDEQ

Pine Creek at Rushville SNI4PINEC107 -- -- 2002–07 79

Niobrara River near Gordon1 06457500 -- 1964–1994 2003 721

Snake River near Burge 06459500 1964–93 1994–2007 -- 697

Minnechaduza Creek at Valentine 06461000 1964–95 -- 2003 549

Niobrara River near Sparks1 06461500 1964–2007 -- -- 618

Niobrara River near Norden1 06462000 1964–87 -- -- 388

Plum Creek at Meadville 06462500 1967–95 -- -- 450

Long Pine Creek near Riverview 06463500 1964–2007 -- -- 672

Niobrara River at Mariaville1 06463720 1985–92 -- -- 92

Keya Paha River near Naper 06464900 1964–95 1998–2007 -- 670

Niobrara River near Spencer1 06465000 1964–2003 -- -- 515

Eagle Creek near Redbird 06465310 1979–92 -- -- 208

Redbird Creek at Redbird 06465440 1977–78, 

1981–95

-- -- 211

Niobrara River near Verdel1 06465500 1964–2007 -- -- 648

Verdigre Creek near Verdigre 06465700 2002–07 -- -- 49

1

 Gage used in hydraulic-geometry analysis. 
Initial Results 21

locations to be the result of tributary sediment contributions 

(Grams and Schmidt, 1999; Hanks and Webb, 2006), the low 

precision of the 10-m DEM and the forcing of local slope 

values by the slope algorithm did not allow this hypothesis to 

be verified. 

Hydraulic Geometry

The magnitude of the coefficients calculated for hydraulic-geometry models depend largely on the geometry and 

adjustability of the cross section (Turowski and others, 2008). 

For example, a box culvert will have no relation between 

increasing discharge and width for any discharge above that 

which fully covers the bottom with water. The same culvert 

will, however, have a strong relation with depth. To provide 

the reader with some visual and quantitative context for 

the hydraulic-geometry relations described below, detailed 

descriptions, photos, and detailed hydraulic-geometry plots for 

each streamflow-gaging station are included in the appendixes. 

At-A-Station Hydraulic-Geometry Relations 

for Selected Niobrara River StreamflowGaging Stations 

The graphical summaries of at-a-station hydraulicgeometry relations for Niobrara streamflow-gaging stations 

Valentine

104° 103° 102° 101° 100° 99° 98°

43°

42°

104° 103° 102° 101° 100° 99° 98°

43°

42°

NEBRASKA

0 20 40 60 KILOMETERS

0 20 40 60 MILES

Valentine

B.

A.

SOUTH DAKOTA

WYOMING

NEBRASKA

SOUTH DAKOTA

WYOMING

Boundary of Niobrara Basin 

within study area

Boundary of Niobrara Basin 

within study area

Boundary of Niobrara Basin 

outside study area

Boundary of Niobrara Basin 

outside study area

Missouri River

Niobrara River

Missouri River

Niobrara River

Geologic test hole (map B)

EXPLANATION

Observation well with at least annual measurements (map A)

Base from USGS National Elevation Dataset, 2006; National Hydrography Datset, 2007; 

 State boundaries, 2005, 1:2,000,000

Basin boundary based on U.S. Department of Agriculture-Natural

Resource Conservation Service, Watershed Boundary Dataset (2008)

Universal Traverse Mercator projection, zone 14

Horizontal coordinate information is referenced to 

 the North American Datum of 1983 (NAD 83)

Figure 7. Ground-water observation wells and geologic test holes in the Niobrara River study area. (A) Active groundwater observation wells monitored at least annually for water-table elevation; and (B) Geologic test holes with depth-tobedrock data.
22 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

are shown in figure 9. Values for the coefficients and exponents associated with the at-a-station relations for each 

streamflow-gaging station, using the models of equations 1 

through 3 (see Background section of report), are given in 

table 12. Although the coefficients (a, c, k) for each relation 

generally are associated with local physical setting, sediment, 

and vegetation conditions, the exponents (b, f, m) describe the 

rate at which each of the variables (width, depth, and velocity, 

respectively) adjust to changing discharges (Knighton, 1998). 

The exponents are the most widely scrutinized of published 

values (Park, 1977). Exponent values reported for streams of 

the midwestern United States by Leopold and Maddock (1953) 

average 0.26 (b), 0.40 (f), and 0.34 (m) for width, depth, and 

velocity, respectively. 

Width exponents of at-a-station hydraulic-geometry 

relations among selected gages of the Niobrara River average 0.14, but range between 0.00 and 0.32. Depth exponents 

average 0.40 and range from 0.31 to 0.46. Velocity exponents 

average 0.45 and range between 0.34 and 0.57. The average 

at-a-station exponent values indicate that at the local scale, 

the Niobrara River adjusts to changing discharges mainly 

through variation in flow depth and velocity. These data are 

in general agreement with an analysis by Buchanan (1981), 

which indicated that the stage of the lower Niobrara River did 

not increase proportionally to increases in discharge, but rather 

discharge was accommodated through increases in velocity by 

coincident decreases in channel-boundary roughness. 

The at-a-station hydraulic geometry velocity exponent 

values have a wide range, and the average value of 0.45 is 

affected by the narrow reaches near the Mariaville, Verdel 

(1963–1985 water years), Sparks, and Cody streamflowgaging stations. Whereas Mariaville and Verdel likely are not 

representative of their adjacent river reaches because of their 

locations near channel constrictions, Cody and Sparks are 

similar to many of their surrounding reaches. These findings 

indicate that the at-a-station velocity exponent average may be 

skewed high, but the range is within the natural variation of 

the Niobrara River. 

Coefficients of determination for hydraulic geometry 

relations indicate that between zero and 80 percent of the 

variance in width, depth, or velocity can be explained by 

discharge. The lowest coefficients of determination were all 

associated with the variance in channel width, further indicating a relatively weak relation between discharge and wettedTable 9. Inventory of ground-water wells and test holes in the Niobrara River study area by state and usage type. 

[NDNR, Nebraska Department of Natural Resources; CSD, University of Nebraska-Lincoln, Conservation and Survey Division; NRD, Nebraska Natural 

Resources Districts; USGS, U.S. Geological Survey; NWIS, National Water Information System; SDDENR, South Dakota Department of Environment and 

Natural Resources]

Usage type Count Source Description

Nebraska

Irrigation, commerical, industrial 5,635 NDNR Irrigation, commerical, and industrial-use water-supply wells.

Minor-use water supply 3,164 NDNR Domestic, livestock, aquaculture, and “other” uses as defined by 

NDNR; does not include State observation or water-quality 

monitoring wells.

Geologic test hole 255 CSD Test holes to define physical and chemical properties of bedrock and 

aquifers.

Regional ground-water observations 218 NRD, USGS Cooperative network of ground-water-level observation wells. Most 

wells in this network have at least one measurement of groundwater elevation per year. Period of record is variable, although all 

are currently active.

Various scientific observations 666 USGS Wells included within the USGS NWIS database with at least one 

observation after 1963. Excludes wells within the cooperative 

network.

South Dakota

Irrigation, commerical, industrial 29 SDDENR Irrigation, commerical, and industrial-use water-supply wells.

Minor-use water supply 619 SDDENR Domestic and livestock water-supply wells.

Geologic test hole 1,907 SDDENR Test holes to define physical and chemical properties of bedrock and 

aquifers.

Regional ground-water observations 39 SDDENR, USGS Cooperative network of ground-water-level observation wells. Some 

wells are cooperative with USGS and SDDENR. Wells have at 

least one measurment annually.

Various scientific observations 799 USGS Wells included within the USGS NWIS database with at least one 

observation after 1963. Excludes wells within the cooperative 

network.
Initial Results 23

40003500300025002000150010005000

0 50 100 150 200 250 300 350 400

Distance from mouth, in miles

Elevation above mean sea level, in feet

Bed ElevationGeomorphic Segment BoundaryConfluence with 5% increase in D.A.Confluence with less than 5% increase in D.A.

Braided Bottoms

Meandering Bottoms

Canyons and Restricted Bottoms

4,0003,5003,0002,5002,0001,5001,000500

*UNL-University of Nebraska-Lincoln, Conservation and Survey Division 

4

4

Open RestrictedEntrenched

3

ValleysEscarpments and bluffs 

EXPLANATION

2

2

3

Ogallala GroupArikaree GroupWhite River GroupPierre ShaleNiobrara Chalk 

Tertiary AgeCretaceous Age

1

1

Bed elevationGeomorphic segment boundary (table 10)Confluence with at least 5-percent increase in drainage areaConfluence with less than 5-percent increase in drainage areaStraight line slope between mouth and head of study areaKnick zone

Niobrara River longitudinal profile (this study)

Bedrock at river level (Burchett, 1986)

Topographic regions (UNL*, 1986)

Valley condition (table 3)

Fluvial geomorphic province

Dunlap Diversion Dam

Rush Creek

Antelope Creek

Bear Creek

Snake River

Cornell Dam

Norden Chute

Keya Paha River

Spencer Dam

Pine Creek

Box Butte Creek

Leander Creek

Medicine Creek

Gordon Creek

Minnechaduza Creek

Fairfield Creek

Plum Creek

Long Pine Creek

Big Sandy Creek

Eagle Creek

Redbird Creek

Verdigre Creek

400 350 300 250

DISTANCE FROM MOUTH OF RIVER, IN MILES

200 150 100 50 0

0

ELEVATION ABOVE MEAN SEA LEVEL, IN FEET

Figure 8. Longitudinal profile of the Niobrara River from the Missouri River upstream to Dunlap Diversion Dam, showing (1) bed elevation, location of major tributaries, manmade structures, and boundaries of geomorphic segments; (2) bedrock at river level; (3) topographic regions; and (4) valley conditions and fluvial-geomorphic provinces. 
24 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Table 10. Geomorphic segments of the Niobrara River between Dunlap Diversion Dam and the Missouri River, Nebraska. 

[no., number; River mile, miles upstream from the Missouri River; S.A., percent of total length of Niobrara mainstem channel in study area; condition 

classes A through D refer to the channel degree of confinement, planview pattern, width variation, and bar configuration, respectively, as described in the 

geomorphic classification system included in table 3; “Mode” refers to the most frequently occuring condition among segments; “Per unit length” refers to 

the condition that is most frequent when considering total channel length within the study area]

Segment no. River mile Percent of 

S.A.

Descriptive elements and assigned condition classes No. of bridges 

within 

segment

Segment 

average 

channel slope 

(percent)

A B C D

Braided bottoms

1 12 3.6 3 2 3 4 2 0.13

2 34 6.6 3 2 3 3 2 .13

3 39 1.6 3 2 2 1 0 .11

1

4 60 6.2 3 2 3 4 1 .13

5 107 14.2 3 2 3 3 2 .15

6 125 5.4 2 2 3 3 4 .15

Canyons and restricted bottoms

7 134 2.7 2 2 1 2 1 .16

8 150 5.0 1 2 1 2 5 .14

1

9 156 1.8 1 2 2 3 2 .13

10 159 .9 3 2 2 3 1 .05

11 166 2.1 3 2 2 1 1 .14

12 171 1.2 3 2 3 3 0 .12

13 178 2.1 2 2 2 1 1 .15

14 182 1.4 3 2 2 1 2 .17

15 188 1.8 2 2 2 1 2 .20

16 195 2.1 3 2 2 1 1 .15

17 208 3.9 2 2 2 1 3 .15

18 213 1.6 1 2 2 1 0 .15

19 224 3.4 3 2 3 3 2 .13

20 232 2.2 2 2 2 1 1 .15

21 234 .8 4 3 1 2 1 .15

22 236 .4 3 2 1 2 1 .25

23 262 7.8 1 3 1 2 1 .19

24 265 .8 3 2 2 1 0 .14

25 275 3.0 1 2 3 3 2 .15

26 281 1.9 3 2 2 1 2 .12

27 284 .8 1 2 3 1 0 .14

28 289 1.6 3 2 2 1 1 .14

29 294 1.4 2 2 2 1 1 .15

30 298 1.4 3 2 2 1 1 .14

31 300 .6 4 2 2 1 1 .15

32 307 2.1 3 2 2 2 2 .16

33 316 2.6 2 2 1 2 3 .18

Meandering bottoms

34 326 3.2 4 2 1 2 1 .17

35 330 1.0 4 3 1 2 0 .13

36 332 .6 4 2 1 2 0 .20

Mode

3 2 2 1

Per unit length

3 2 3 3

1

Reach includes backwater of main channel dam.
Initial Results 25

channel width at the local scale. The probability (p) values for 

slope-coefficient significance indicate that all but two of the 

calculated at-a-station power models have regression slopes 

that are significantly different from zero at the 90-percent 

confidence level, and most models are highly significant 

(table 12). The hydraulic-geometry relations between width 

and discharge at the Mariaville gage and original site of the 

Verdel gage have power coefficients of nearly zero, indicating 

that channel-top width is virtually invariant over a range of 

discharges. Both of these gages were located at bridge reaches 

in which the channel narrowed significantly before passing 

under the bridge deck. 

At one streamflow-gaging station only, Niobrara River 

near Gordon, did the at-a-station hydraulic-geometry coefficients and exponents have products and sums that varied 

from unity by more than 0.05. This lack of compliance with 

continuity likely is the result of measurements being made at 

several different cross sections, a problem that could not be 

resolved because many of the original hydrographer’s measurement notes were not available at the time of publication. 

Additionally, the median of discharges among measurement 

notes was 114 cubic feet per second (ft3/s), and more than 98 

percent of the discharges measured by technicians were less 

than 300 ft3

/s, but the range of measurements meeting the filter 

criteria includes values up to 1,380 ft3/s. Thus, in addition 

to the problem of measurement location, there are too few 

measurements at high-magnitude flows to represent the natural 

hydraulic variation; therefore, coefficient and exponent values 

may be skewed. 

Downstream Hydraulic Geometry of Niobrara 

River

Downstream hydraulic-geometry relations for the study 

area indicate that the Niobrara River adjusts its geometry to 

gains in drainage area and discharge mainly through increases 

in channel width. This is indicated by the exponents of the 

width relation, which are more than double the magnitude of 

depth and velocity exponents for all flow conditions analyzed (table 13). The width exponents in the study area are 

only slightly higher than the most commonly cited value of 

0.5 for alluvial rivers (Parker and others, 2007). Downstream 

hydraulic-geometry relations agree with geomorphic segmentation data, which described a river that increases in width, 

and width variation downstream from the contact between 

Tertiary and Cretaceous bedrock units. Downstream hydraulic 

geometry data also are in general agreement with an analysis 

performed by Buchanan (1981), which determined that the 

Niobrara River channel decreased in width after installation of 

Merritt Reservoir on the Snake River reduced mean monthly 

flows. Coefficients of determination for hydraulic geometry 

models indicate that between 61 and 79 percent of the variance 

in downstream geometry is explained by increasing discharge. 

All downstream hydraulic geometry regression models have 

slope coefficients that are significantly different from zero 

at the 90-percent confidence level. In addition, the products 

of coefficients and sums of model exponents are all within 

0.05 of unity, indicating the relations conform with continuity. 

The graphical summaries of downstream hydraulicgeometry relations over a range of flow frequencies are shown 

in figure 10. The wide scatter in hydraulic geometry values for 

higher-magnitude discharges indicates that geometry in the 

most downstream reaches of the Niobrara has a large degree 

of variability. Although this result is in general agreement 

with the geomorphic segmentation data for the lower Niobrara (table 10), the large degree of width variation also is the 

consequence of site selection for streamflow-gaging stations. 

Whereas much of the lower Niobrara is characterized by a 

wide, braided channel, streamflow-gaging stations generally 

are located at natural or engineered channel constrictions. As 

mentioned above, the Niobrara channel near the Mariaville 

and Verdel (for 1963–1985 period of record) streamflowgaging stations is much narrower than reaches immediately 

upstream and downstream. The Niobrara River near Norden is 

located at a bedrock constriction that is, again, much narrower 

than nearby upstream and downstream channel environments. 

The Niobrara River near Spencer streamflow gage is located 

on a single-thalweg channel with alternate bars, a condition 

that likely results from the local sediment and hydrologic 

regimes regulated by the upstream dam. 

Table 11. Summary of longitudinal channel slopes in fluvial geomorphic provinces of the Niobrara River, Nebraska. 

[n, number of geomorphic segments within province; S.D., standard deviation of segment slopes; max., maximum; min., minimum] 

Fluvial geomorphic province 

(fig. 8)

Province 

mean slope, 

in percent1

Summary of segments by province

n Mean slope, 

in percent2

Slope S.D., 

in percent

Median slope, 

in percent

Max. slope, 

in percent

Min. slope, 

in percent

Meandering bottoms 0.17 3 0.16 0.04 0.17 0.20 0.13

Canyons and restricted bottoms3 .15 27 .15 .03 .15 .25 .05

Braided bottoms3 .14 6 .13 .01 .13 .15 .11

Total study area3 .15 36 .15 .03 .15 .25 .05 1

 Mean slope of fluvial geomorphic province computed as difference between upstream and downstream elevations divided by along-channel length of the 

province.

2

 Mean of mean bed slopes of individual geomorphic segments within province; individual segment-mean slopes were computed using the difference 

between upstream and downstream elevations divided by the along-channel length of the segment.

3

 Province includes reaches of dam backwater, but these reaches were not included in slope calculations.
26 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

0.1

1.0

10

100

Near Hay Springs

Near Gordon

Near Cody

Near Sparks

Near Norden

At Mariaville

Near Spencer

Near Verdel (pre-1985)

Near Verdel (post-1985)

EXPLANATION

Niobrara River

10 100 1,000 10,000 100,000

DISCHARGE, IN CUBIC FEET PER SECOND

AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

AVERAGE CHANNEL DEPTH, IN FEET

10

100

1,000

AVERAGE CHANNEL-TOP WIDTH, IN FEET

B.

C.

A.

0.1

1.0

10

Figure 9. At-a-station hydraulic geometry relations for selected streamflow-gaging stations on the 

Niobrara River, showing relations between discharge and (A) channel width; (B) average cross-sectional 

depth; and (C) average flow velocity. (All records used in the analysis are from post-1963 period except 

those stations near Hay Springs and Cody, which are upstream from the Snake River confluence).
Initial Results 27

Table 12. At-a-station hydraulic geometry relations for selected Niobrara River streamflow-gaging stations. 

[Period of record for each streamflow-gaging station expressed in water years; period of record used for hydraulic geometry analysis may differ from total 

available period of record for streamflow gage listed; a, width coefficient; b, width exponent; c, depth coefficient; f, depth exponent; k, velocity coefficient; m, 

velocity exponent; ft3/s, cubic feet per second; --, not applicable]

Parameter 

or statistic

Station name, number, and period of record1

Niobrara 

River near 

Hay 

Springs, 

06456500, 

1951–631

Niobrara 

River near 

Gordon, 

06457500, 

1964–90

Niobrara 

River near 

Cody, 

06459000, 

1949–56

Niobrara 

River near 

Sparks, 

06461500, 

1964–2007

Niobrara 

River near 

Norden, 

06462000, 

1964–83

Niobrara 

River near 

Mariaville, 

06463720, 

1986–90

Niobrara 

River near 

Spencer, 

06465000, 

1964–2000

Niobrara 

River near 

Verdel2

, 

06465500, 

1964–85

Niobrara 

River near 

Verdel2

, 

06465500, 

1986–2007

Average of 

nine 

stations

Number of measurements used in hydraulic-geometry analysis3

35 589 142 485 196 34 331 238 117 241

Maximum discharge of included measurements, in ft3

/s

168 1,380 3,340 3,940 3,990 3,520 12,500 8,680 7,610 5,014

Minimum discharge of included measurements, in ft3

/s

10 49 197 203 357 946 540 474 975 417

Width coefficients and exponents (equation 1)

a 27 21 53 81 24 292 34 230 53 91

b .12 .22 .05 .10 .19 .00 .27 .01 .32 .14

p value4 .05 <.0001 <.0001 <.0001 <.0001 .82 <.0001 .14 <.0001 --

COD5 .11 .11 .42 .12 .24 .00 .20 .01 .12 --

Depth coefficients and exponents (equation 2)

c .11 .22 .17 .11 .10 .06 .15 .07 .08 .12

f .46 .31 .39 .40 .46 .44 .34 .46 .34 .40

p value4 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 --

COD5 .70 .25 .69 .58 .70 .52 .23 .73 .24 --

Velocity coefficients and exponents (equation 3)

k .34 .31 .11 .11 .41 .06 .19 .07 .23 .20

m .42 .39 .57 .51 .35 .55 .39 .53 .34 .45

p value4 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 --

COD5 .78 .47 .73 .79 .48 .60 .41 .80 .34 --

Product of coefficients

1.00 1.48 .97 1.00 1.00 1.00 0.99 1.03 1.00 1.05

Sum of exponents

1.00 .92 1.01 1.00 1.00 1.00 1.00 1.00 1.00 .99

1

Measurement record for gage near Hay Springs was unavailable for water years 1956–1960.

2

Verdel gage was moved in 1985.

3

Number of measurements used in hydraulic-geometry calculations (number retained after filter criteria were applied).

4

Probability (p value) that regression slope is zero (no correlation between discharge and geometric variable); values less than 0.10 indicate model significance at the 90-percent confidence level.

5

Coefficient of determination for least-squares estimate of regression equation.
28 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Vertical dash line

identifies two Verdel 

gaging-station 

hydraulic geometries

A.

B.

C.

Mean

10-percent exceedance

50-percent exceedance

75-percent exceedance

Fitting line − Mean

Fitting line − 10-percent exceedance

Fitting line − 50-percent exceedance

Fitting line − 75-percent exceedance

EXPLANATION

Streamflow condition

1

10 100 1,000 10,000

10

0.1

1.0

10

10

100

1,000

DISCHARGE, IN CUBIC FEET PER SECOND

AVERAGE CHANNEL VELOCITY, 

IN FEET PER SECOND

AVERAGE CHANNEL DEPTH, IN FEET CHANNEL WIDTH, IN FEET

Figure 10. Downstream hydraulic geometry relations for the Niobrara River between the streamflowgaging station near Hay Springs, Nebraska, and the streamflow-gaging station near Verdel, Nebraska, 

showing downstream relations between discharge and (A) channel width; (B) channel depth; and 

(C) flow velocity. (All records used in the analysis are from post-1963 period except those stations near 

Hay Springs and Cody, which are upstream from the Snake River confluence. Data include two different 

geometry values for the station near Verdel, which was at two different locations since 1963). 
Initial Results 29

The Niobrara River near Verdel (1986–2007 period) is 

the only station on the lower Niobrara River that has channel 

dimensions similar to those upstream and downstream, and 

is likely the station that most accurately represents channel adjustment processes in the wider, braided sections. The 

differences in adjustment processes are well illustrated when 

the two periods of record for the two different locations of 

the Verdel streamflow-gaging station are compared. For 

every exceedance frequency in figures 10A–C, there are two 

data points that have exactly the same discharge; these data 

points represent the geometries of the two different Verdel 

streamflow-gaging station locations. For all flow regimes, 

the channel is wider, shallower, and slower at the new (1986-

2007 period) Verdel streamflow-gaging station relative to the 

old station location at the channel constriction. The disparity 

in width between the two stations increases for increasing 

discharge and is an artifact of the large differences in at-astation width exponents between locations. The effect of narrow channels at streamflow-gaging locations on downstream 

hydraulic-geometry relations, and differences between the Verdel at-a-station exponents, indicate that downstream hydraulic 

geometry width exponents actually may be skewed lower than 

those that would be computed from natural cross sections, and 

may not be accurately representing downstream adjustment 

processes of the Niobrara River. 

Hydraulic Microhabitat: An Example from the 

Niobrara River near Sparks, Nebraska

Comparison of cross-section geometries, between lowerdecile, median-quantile, and upper-decile flows of the 1988 

and 2003 measurements, indicates that the bed of the Niobrara 

River channel scours even with moderate increases in discharge (fig. 11A). The scouring is accompanied by increases in 

the magnitude and variability of velocities, especially between 

median-quantile and upper-decile flows (fig. 11B). Comparison of the distributions of depths and velocities between 

median-quantile and upper-decile flows indicates that the 

increase in velocity with increasing discharge is accompanied 

by only minor increases in channel depth. For example, visual 

examination of figure 11B indicates that the depth distribution 

during the 1988 upper-decile flow was not altogether different 

from the depth distribution during the 2003 median-quantile 

flow. The velocity distribution of the 1988 upper-decile flow, 

however, was dominated by velocities that were at least 1 foot 

per second (ft/s) greater than the 2003 median-quantile flows 

(fig. 11B), confirming that velocity is the dominant mode of 

hydraulic adjustment. These analyses are in general agreement 

with the at-a-station hydraulic-geometry relations for the Niobrara River near Sparks, Nebr., which indicate that, at the local 

scale, velocity increase is the primary hydraulic adjustment to 

increased discharge (table 12). Bedform roughness changes 

are the physical mechanism associated with this hydraulic 

adjustment (Buchanan, 1981). Additionally, the magnitude 

of scour depth with increasing discharge is limited near the 

Sparks streamflow-gaging station because of the presence of 

shallow bedrock.

Analysis of hydraulic microhabitat types at the Sparks 

streamflow-gaging station indicates that combinations of water 

depth and velocity are variable with discharge and time. Measurements analyzed from 1988 indicate that the upper-decile 

discharge redistributed microhabitats by increasing the availability of deep-moderate and deep-swift microhabitat niches 

(figure 11C). Conversely, measurements analyzed from 2003 

indicate that the median-quantile flow had similar microhabitat 

distributions to those of the 1988 upper-decile flow. The differences in microhabitat distributions between the median-quantile flows of 1988 and 2003 may be because of the slightly 

higher magnitude of flow in 2003, or differences in the amount 

of sand on bed. Shallow-slow, intermediate-slow, and intermediate-moderate microhabitat niches all show a decrease in 

Table 13. Downstream hydraulic geometry relations for the 

Niobrara River between Hay Springs and Verdel, Nebraska.

[%, percent; ft3/s, cubic feet per second]

Parameter or 

statistic

Mean 

annual 

discharge

Flow exceedance1

10% 50% 75% 

Maximum discharge used in regression model, in ft3

/s 

1,708 2,695 1,540 1,180

Minimum discharge used in regression model, in ft3

/s 

29 40 24 18

Width coefficients and exponents (equation 1)

a 4.72 4.08 5.29 5.95

b .54 .54 .53 .52

p value2 <.001 <.001 <.001 <.001

COD3 .76 .77 .75 .75

Depth coefficients and exponents (equation 2)

c .28 .29 .26 .25

f .25 .25 .26 .26

p value2 .01 .01 .01 .01

COD3 .61 .62 .63 .63

Velocity coefficients and exponents (equation 3)

k .76 .81 .73 .69

m .21 .21 .21 .21

p value2 <.001 <.001 <.001 <.001

COD3 .77 .79 .77 .77

Product of coefficients

.99 .97 1.00 1.01

Sum of exponents

1.00 1.00 1.00 1.00

1

Refers to the percentage of days from period of record that flow 

exceeded a particular magnitude. See table 4 for values associated with a 

particular streamflow-gaging station; exceedance was calculated for each 

gaging station for its particular period of record and used to develop the data 

values to which hydraulic-geometry relations were fitted. 

2

Probability (p value) that regression slope is zero (no correlation between 

discharge and geometric variable); values less than 0.10 indicate model 

significance at the 90-percent confidence level.

3

Coefficient of determination for least-squares estimate of regression 

equation.
30 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Figure 11. Channel geometry, velocity distribution, and microhabitat extent over a range of flow-exceedance 

frequencies for the Niobrara River near Sparks, Nebraska. (A) Cross-sectional form; (B) velocity and depth 

distributions; and (C) hydraulic microhabitat distributions. (Hydraulic microhabitat classes are defined in 

table 5).

Shallow-

 slow

Shallow-

 moderate

Shallow-

 swift

Intermediate-

 slow

Intermediate-

 moderate

Intermediate-

 swift

Deep-

 slow

 Deepmoderate

DeepOther

 swift

 niche

0

10

20

30

40

50

60

70

80

90

HYDRAULIC-MICROHABITAT NICHE CATEGORY

PERCENTAGE OF WIDTH

EXPLANATION

1988 Lower-decile flow (407 cubic feet per second [ft3/s])

1988 Median-quantile flow (605 ft3

/s)

1988 Upper-decile flow (1,027 ft3

/s)

2003 Lower-decile flow (446 ft3

/s)

2003 Median-quantile flow (749 ft3

/s)

C.

Solid lines correspond to velocity

Dashed lines correspond to water depth

0

1.0

2.0

3.0

4.0

5.0

0

1

2

3

4

5

CUMULATIVE WIDTH, IN PERCENT 

0

0.5

1.0

1.5

2.0

2.5

-10 10 30 50 70 90 110 130 150 170

0 10 20 30 40 50 60 70 80 90 100

DISTANCE FROM LEFT BANK FACING DOWNSTREAM, IN FEET

ELEVATION, IN FEET BELOW

WATER SURFACE 

VELOCITY, IN FEET PER SECOND

DEPTH, IN FEET

B.

A.
Summary and Conclusions 31

extent from lower to median-quantile discharges. The creation 

of the deep-swift niche in 1988 and 2003 came mainly at the 

expense of the intermediate-moderate and intermediate-swift 

hydraulic microhabitat niches. These data indicate that higher 

median-quantile to upper-decile discharges are important for 

the creation of deeper hydraulic microhabitat niches.

Of the flows analyzed, the upper-decile flow of 1988 

had the broadest range of hydraulic microhabitats, including the highest percentage of the shallow-slow niche, and the 

only occurrence of the deep-moderate niche. The increase in 

the extent of the shallow-slow microhabitat niche during the 

upper-decile discharge in 1988 could be because of a number 

of reasons: inundation of low-floodplains or shelves, prompting an increase in shallow and slow habitat; an increase in 

near-bank velocities prompting the technician to make a 

velocity measurement closer to the bank; or an increase in 

the affect of bank vegetation as stage rises, which may create 

slower, more turbulent hydraulic zones in their wake. Because 

the width of the channel did not change dramatically over the 

range of flows measured, the increase in the shallow-slow 

niche is likely because of the latter two possibilities.

Distributions of microhabitat classes at any given point in 

time are dependent on several factors, including the preceding hydrologic context, which may have persistent effects on 

channel geometry. Thus, habitat distributions are best viewed 

and compared in a broader temporal and hydrologic context 

before conclusions can be drawn (Ginting and Zelt, 2008). A 

more detailed analysis of inter-year, between year, and decadal 

comparison of changes in microhabitat likely would provide a 

better description of the temporal variability of microhabitats 

in the Niobrara River. Further, an analysis of microhabitat 

trends over short, drought periods may provide indications 

of the direction of microhabitat distributions from future 

water depletions. 

Summary and Conclusions 

An inventory and initial analysis of the hydrogeomorphic 

data and characteristics of the Niobrara River between Dunlap 

Diversion Dam in Dawes County, Nebr., and the Missouri 

River confluence was completed. The goal of the inventory 

was to provide an informational foundation for ongoing or 

future scientific investigations, and thus provided information over and above that which was necessary for the hydrogeomorphic analysis. The objective of the hydrogeomorphic 

analysis was to describe the Niobrara River channel and valley 

characteristics, divide the main channel into segments of differing potential physical habitat characteristics, and understand how the channel and physical habitats of the Niobrara 

River adjust to changing discharges. 

The inventory of available hydrogeomorphic data indicates that many of the tributaries to the Niobrara River have 

at least some hydrologic data, which, at a minimum, include 

estimates of peak discharges in isolated years. In addition, 

several larger tributaries (tributaries that contribute at least an 

approximate 5-percent drainage area increase at their confluence) have water-quality data that include measurements of 

suspended sediment. Ground-water well spacing currently is 

too sparse for a relevant analysis of existing ground-water and 

surface-water interactions at the scale of a river segment.

Thirty-six geomorphic segments were identified and 

described along the Niobrara River in the study area using a 

customized classification system. Three geomorphic provinces 

were identified using natural boundaries within the geomorphic characteristics of the segments: an upper province characterized by open valleys and a sinuous, equiwidth channel; 

a central province characterized by mixed valley and channel 

settings, including several entrenched canyon reaches; and a 

lower province characterized by a wide, yet restricted, valley 

and a wide, persistently braided channel. The coincidence of 

channel slope perturbations and bedrock contacts indicates 

that channel slope, and consequent attributes of geomorphic 

segments of the Niobrara River in the study area, may largely 

be controlled by the properties of bedrock.

At-a-station hydraulic-geometry relations indicate that 

cross-sectional adjustments to changes in discharge are accommodated primarily by changes in flow velocity. Downstream 

hydraulic-geometry relations for eight streamflow-gaging stations along the main channel indicate that the Niobrara River 

in the study area adjusts its geometry to changing discharges 

primarily by changes in channel-top width. At-a-station and 

downstream hydraulic-geometry relations are in general agreement with previously published hydraulic- and channel-adjustment data. Downstream hydraulic-geometry relations also are 

in agreement with the geomorphic segmentation data, which 

describe a river that increases in width and width variation, 

especially downstream from the contact between Tertiary and 

Cretaceous bedrock units. Although the at-a-station hydraulic geometry values used to create the downstream hydraulic 

geometry relations represent the natural variation in channel 

width in the lower Niobrara River, the downstream width 

exponents (m) are likely skewed low because the locations 

of many of the streamflow-gaging stations are at natural or 

engineered constrictions. 

Analysis of hydraulic microhabitats at a gage within the 

National Scenic River reach of the Niobrara indicated that 

velocity changes are the primary adjustment in hydraulic-habitat characteristics over a range of discharges. Comparison of 

microhabitat distributions over a range of discharges indicates 

that shallow and intermediate hydraulic microhabitat niches 

are available over all flows, but deeper hydraulic niches are 

only available during higher median-quantile and upper-decile 

discharges. Comparison of microhabitat distributions at similar 

flow-exceedance frequencies separated by 15 years indicated 

that microhabitat is temporally variable, although the total 

scale of this variability was not captured by the initial analysis. 

A more detailed temporal analysis of hydraulic microhabitat, 

including analysis of drought periods, would likely provide a 

better description of the temporal variability of microhabitats 

and the potential direction of microhabitat changes caused by 

future water depletions. 
32 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Acknowledgments

This report is one of several produced in cooperation with 

the Nebraska Game and Parks Commission to provide sound 

scientific information for managing the Niobrara River. The 

authors thank Larry Hutchinson and Richard Holland of the 

Nebraska Game and Parks Commission for their thoughtful 

questions, suggestions, and support of this project. Bethany 

Zelt volunteered numerous hours to enter stream dischargemeasurement data for the hydraulic-geometry analysis. 

References Cited

Baxter, C.V., and Hauer, F.R., 2000, Geomorphology, hyporheic exchange, and selection of spawning habitat by bull 

trout (Salvelinus confluentus): Canadian Journal of Fisheries 

and Aquatic Science, v. 57, p. 1,470–1,481.

Bentall, R., and Shaffer, F.B., 1979, Availability and use of 

water in Nebraska, 1975: Lincoln, University of Nebraska, 

Conservation Survey Division, Nebraska Water Survey 

Paper 48, 121 p.

Bentall, R., 1991, Facts and figures about Nebraska rivers: 

Lincoln, University of Nebraska, Conservation and Survey 

Division, Water Supply Paper No. 73, 16 p. 

Bramblett, R.G., and White, R.G., 2001, Habitat use and 

movements of pallid and shovelnose sturgeon in the Yellowstone and Missouri Rivers in Montana and North Dakota: 

Transactions of the American Fisheries Society, v. 130, 

p. 1,006–1,025.

Brice, J.C., and Blodgett, J.C., 1978, Countermeasures for 

hydraulic problems at bridges: Federal Highway Administration Report No. FHWA-RD-78-162, v. 1, 169 p.

Bridge, J.S., 2003, Rivers and floodplains—forms, processes, 

and sedimentary record: Oxford, England, Blackwell Publishing, 491 p.

Buchanan, J.P., 1981, Channel morphology and sedimentary 

facies of the Niobrara River, north-central Nebraska: Fort 

Collins, Colo., Colorado State University, M.S. Thesis, 

126 p.

Burchett, R.R., comp., 1986, Geologic bedrock map 

of Nebraska: Lincoln, Nebraska Geological Survey, 

scale 1:1,000,000.

Chen, A.H., Rus, D.L., and Stanton, C.P., 1999, Trends 

in channel gradation in Nebraska streams, 1913–95: 

U.S. Geological Survey Water-Resources Investigations 

Report 99–4103, 29 p.

Cole, J.M., 1996, Aggradation, degradation, and levels of 

heterogeneity of the braided Niobrara River, Nebraska: 

Fort Collins, Colo., Colorado State University, M.S. Thesis, 

83 p. 

Condra, G.E., and Reed, E.C., 1943, The Geological Section 

of Nebraska: Nebraska Geological Survey Bulletin No. 14, 

82 p.

Dappen, P., Merchant, J., Ratcliffe, I., and Robbins, C., 2007, 

Delineation of 2005 land use patterns for the State of 

Nebraska Department of Natural Resources: Lincoln, Nebr., 

University of Nebraska, Center for Advanced Land Management Information Technologies, 80 p.

Dietsch, B.J., 2007, Water-quality and fish-community data 

for the Niobrara National Scenic River, Nebraska: U.S. 

Geological Survey Fact Sheet 2007–3098, 6 p.

Doyle, M.W., Stanley, E.H., Strayer, D.L., Jacobson, R.B., and 

Schmidt, J.C., 2005, Effective discharge analysis of ecological processes in streams: Water Resources Research, v. 41, 

16 p. 

Elliot, C.M., and Jacobson, R.B., 2006, Geomorphic classification and assessment of channel dynamics in the 

Missouri National Recreation River, South Dakota and 

Nebraska: U.S. Geological Survey Scientific Investigations 

Report 2006–5313, 66 p.

Eschner, T.R., 1983, Hydraulic geometry of the Platte River 

near Overton, south-central Nebraska: U.S. Geological 

Survey Professional Paper 1277–C, 27 p.

Etheridge, F.G., Skelly, R.L., and Bristow, C.S., 1999, 

Avulsion and crevassing in the sandy, braided Niobrara 

River—Complex response to base-level rise and aggradation: Special Publication of the International Association of 

Sedimentology, v. 28, p. 179–191.

Frissell, C.A., Liss, W.J., Warren, C.E., and Hurley, M.D., 

1986, A hierarchical framework for stream habitat classification—Viewing streams in a watershed context: Environmental Management, v. 10, p. 199–214.

Ginting, D., and Zelt, R.B., 2008, Temporal differences in 

flow depth and velocity distributions and hydraulic microhabitats near bridges of the lower Platte River, Nebraska, 

1934–2006: U.S. Geological Survey Scientific Investigations Report 2008–5054, 99 p.

Grams, P.E., and Schmidt, J.C., 1999, Geomorphology of 

the Green River in the eastern Uinta Mountains, Dinosaur 

National Monument, Colorado and Utah, in Miller, A.J., 

and Gupta, Avijit, Varieties of fluvial form: New York, John 

Wiley and Sons, p. 81–111.

Gran, K., and Paola, C., 2001, Riparian vegetation controls on 

braided stream dynamics: Water Resources Research, v. 37, 

p. 3,275–3,283.
References Cited 33

Hanks, T.C., and Webb, R.H., 2006, Effects of tributary debris 

on the longitudinal profile of the Colorado River in Grand 

Canyon: Journal of Geophysical Research, v. 11, 13 p. 

Hearty, P.J., 1978, The biogeography and geomorphology of 

the Niobrara River Valley near Valentine, Nebraska: Omaha, 

University of Nebraska, M.S. Thesis, 108 p. 

Huang, H.Q., and Nanson, G.C., 2000, Hydraulic geometry 

and maximum flow efficiency as products of the principle of 

least action: Earth Surface Processes and Landforms, v. 25, 

p. 1–16.

Hupp, C.R., and Osterkamp, W.R., 1996, Riparian vegetation 

and fluvial geomorphic processes: Geomorphology, v. 14, 

p. 277–295.

Insightful Corporation, 2005, S-Plus 7 for Windows—users 

guide: Seattle, Wash., 80 p.

Interagency Wild and Scenic Rivers Council, 2008, National 

Wild and Scenic Rivers System— Niobrara River, 

Nebraska: accessed November 21, 2008, at 

http://www.rivers.gov/wsr-niobrara.html

Johnsgard, P.A., 2001, The nature of Nebraska—ecology and 

biodiversity: Lincoln, Nebr., University of Nebraska Press, 

402 p. 

Jowett, I.G., 1997, Instream flow methods—a comparison of 

approaches: Regulated Rivers—Research and Management, 

v. 13, p. 115–127.

Junk, W.J., Bayley, P.B., and Sparks, R.E., 1989, The flood 

pulse concept in river-floodplain systems: Canadian Special 

Publication of Fisheries and Aquatic Science., v. 106, 

p. 110–127.

Juracek, K.E., and Fitzpatrick, F.A., 2003, Limitations and 

implications of stream classification: Journal of the American Water Resources Association, v. 39, p. 659–670.

Juracek, K.E., and Fitzpatrick, F.A., 2008, Geomorphic applications of stream-gage information: River Research and 

Applications—internet publication, doi: 10.1002/rra.1163.

Kennedy, E.J., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of WaterResources Investigations 03–A13, 53 p.

Knighton, A.D., 1974, Variation in width-discharge relation 

and some implications for hydraulic geometry: Geological 

Society of America Bulletin, v. 85, p. 1,069–1,076. 

Knighton, A.D., 1998, Fluvial forms and processes: Chichester, England, John Wiley and Sons, 383 p. 

Kondolf, G.M., 1995, Geomorphological stream classification 

in aquatic habitat restoration—uses and limitations: Aquatic 

Conservation—Marine and Freshwater Ecosystems, v. 5, 

p. 127–141.

Kondolf, G.M., and Downs, P.W., 1996, Catchment approach 

to planning channel restoration, in Brookes, A., and Shields, 

F.D., Jr., River channel restoration—Guiding principles for 

sustainable projects: Chichester, England, John Wiley and 

Sons, p. 129–148.

Kondolf, G.M., Montgomery, D.R., Piegay, Herve, and 

Schmitt, Laurent, 2003, Geomorphic classification of rivers 

and streams, in Kondolf, G.E., and Piegay, H., eds., Tools in 

fluvial geomorphology: Chichester, John Wiley and Sons, 

p. 171–204.

Leopold, L.B., and Maddock, T., Jr., 1953, The hydraulic 

geometry of stream channels and some physiographic implications: U.S. Geological Survey Professional Paper 252, 

57 p. 

Leopold, L.B., and Wolman, M.G., 1957, River channel patterns; braided, meandering, and straight: U.S. Geological 

Survey Professional Paper 282–B, 85 p.

Maddock, I., 1999, The importance of physical habitat assessment for evaluating river health: Freshwater Biology, v. 41, 

p. 373–391.

McKenny, R., 1997, Formation and maintenance of hydraulic 

habitat units in streams of the Ozark Plateaus: University 

Park, Penn., Pennsylvania State University, State College, 

unpublished Ph.D. Dissertation, 340 p.

Montgomery, D.R., and Buffington, J.M., 1997, Channel-reach 

morphology in mountain drainage basins: Geological Society of America Bulletin, v. 109, p. 596–611.

Montgomery, D.R., and Gran, K.B., 2001, Downstream variations in the width of bedrock channels: Water Resources 

Research, v. 37, p. 1,841–1,846.

Naiman, R.J., Decamps, H., and Pollock, M., 1993, The role 

of riparian corridors in maintaining regional biodiversity: 

Ecological Applications, v. 3, p. 209–212.

Nebraska Department of Natural Resources, 2007, 2008 

Annual evaluation of availability of hydrologically connected water supplies, determination of fully appropriated—

final report: Lincoln, Nebraska Department of Natural 

Resources, 145 p.

Park, C.C., 1977, World-wide variations in hydraulic geometry 

exponents of stream channels—an analysis and some observations: Journal of Hydrology, v. 33, p. 133–146.

Parker, G., 1979, Hydraulic geometry of active gravel rivers: 

Journal of the Hydraulics Division, v. 109, p. 1,185–1,201.

Parker, G., Wilcock, P.R., Paola, C., Dietrich, W.E., and 

Pitlick, J., 2007, Physical basis for quasi-universal relations 

describing bankfull hydraulic geometry of single-thread 

gravel bed rivers: Journal of Geophysical Research, v. 112, 

21 p.
34 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Peters, E.J., and Holland, R.S., 1992, Shallow-water fish community abundance and habitat use in the lower Platte River, 

Nebraska: University of Nebraska-Lincoln, Department of 

Forestry, Fisheries and Wildlife, Journal Series No. 9109.

Poff, N.L., Allen, J.D., Bain, M.B., Karr, J.R., Prestegaard, 

K.L., Richter, Brian, Sparks, R.E, and Stromberg, J.C., 

1997, The natural flow regime—a new paradigm for 

riverine conservation and restoration: Bioscience, v. 47, 

p. 769–784.

Poff, N.L., and Ward, J.V., 1990, The physical habitat template of lotic systems—recovery in the context of historical 

pattern of spatio-temporal heterogeneity: Environmental 

Management, v. 14, p. 629–646.

Power, M.E., Sun, A., Parker, G., Dietrich, W.E., and Wooton, 

J.T., 1995, Hydraulic food chain models—An approach to 

the study of food-web dynamics in large rivers: Bioscience, 

v. 45, p. 159–167.

Rantz, S.E., and others, 1982, Measurement and computation of streamflow: U.S. Geological Survey Water Supply 

Paper 2175, v. 1, 284 p.

Resh, V.H., Brown, A.V., Covich, A.P., Gurtz, M.R., Li, H.W., 

Minshall, G.W., Reice, S.R., Sheldon, A.L., Wallace, J.B., 

and Wissmar, R.C., 1988, The role of disturbance in stream 

ecology: Journal of the North American Benthological Society, v. 7, p. 433–455.

Rhodes, D.D., 1977, The b-f-m diagram—graphical representation and interpretation of at-a-station hydraulic geometry: 

American Journal of Science, v. 277, p. 73–42.

Rosgen, D.L., 1994, A classification of natural rivers: Catena, 

v. 22, p. 169–199.

Schumm, S.A., 1963, A tentative classification of alluvial rivers: U.S. Geological Survey Circular 477, 10 p.

Schumm, S.A., 1985, Patterns of alluvial rivers: Annual 

Reviews in Earth and Planetary Sciences, v. 13, p. 5–27.

Scott, M.L., Friedman, J.M., and Auble, G.T., 1996, Fluvial 

processes and the establishment of bottomland trees: Geomorphology, v. 14, p. 327–339. 

Shaffer, F.B., 1975, History of irrigation and characteristics of 

streamflow in northern Nebraska: U.S. Geological Survey 

Open-File Report 7501, 114 p.

Simon, A., and Castro, J., 2003, Measurement and analysis 

of alluvial channel form, in, Kondolf, G.E., and Piegay, 

H., eds., Tools in fluvial geomorphology: Chichester, John 

Wiley and Sons, p. 291–322.

Skelly, R.L., 1998, Evolution and facies architecture of modern braided river deposits—The Niobrara River, northeast 

Nebraska: Fort Collins, Colo., Colorado State University, 

M.S. Thesis, 239 p.

Soller, D.R., and Reheis, M.C., 2003, Surficial materials in 

the conterminous United States: United States Geological 

Survey Open-File Report 2003–275, map. 

Stalnaker, C.B., Bovee, K.D., and Waddle, T.J., 1996, Importance of the temporal aspects of habitat hydraulics to fish 

population studies: Regulated Rivers—Research and Management, v. 12, p. 145–153. 

Triska, F.J., Duff, J.H., and Avanzino, R.J., 1993, The role of 

water exchange between a stream channel and its hyporheic 

zone in nitrogen cycling at the terrestrial-aquatic interface: 

Hydrobiologia, v. 251, p. 167–184.

Turowski, J.M., Hovius, N., Wilson, A., and Horng, M.J., 

2008, Hydraulic geometry, river sediment, and the definition 

of bedrock channels: Geomorphology, v. 99, p. 26–38.

U.S. Department of Agriculture, 2004, Farm Service AgencyAerial Photography Field Office, FSA Digital Orthophoto2003-UTM-Index for the State of Nebraska, Salt Lake City.

U.S. Department of Agriculture-Natural Resources Conservation Service, 2008, Watershed boundary dataset for 

HUC 101500, Nebraska: Natural Resources Conservation 

Service digital data, accessed online October 22, 2008 at 

http://datagateway.nrcs.usda.gov

University of Nebraska-Lincoln, Conservation and Survey Division, 1986, The ground water atlas of Nebraska: 

Lincoln, University of Nebraska, Conservation and Survey 

Division, Resource Atlas No. 4, 32 p. 

Whittaker, D., and Shelby, B., 2008, Flows and recreation on 

the Niobrara National Scenic River, Nebraska—final report: 

Lincoln, Nebraska Game and Parks Commission, 27 p.

Wildhaber, M.L., Delonay, A.J., Papoulias, D.M., Galat, D.L., 

Jacobson, R.B., Simpkins, D.G., Braaten, P.J., Korschgen, 

C.E., and Mac, M.J., 2007, A conceptual life-history model 

for pallid and shovelnose sturgeon: U.S. Geological Survey 

Circular 1315, 18 p.

Williams, G.P., and Wolman, M.G., 1984, Downstream effects 

of dams on alluvial rivers: U.S. Geological Survey Professional Paper 1286, 83 p.

Wohl, E.E., and Merritt, D.M., 2001, Bedrock channel morphology: Geological Society of America Bulletin, v. 113, 

p. 1,205–1,212.

Wolman, M.G., and Leopold, L.B., 1957, River flood plains: 

some observations on their formation: U.S. Geological 

Survey Professional Paper 282–C.
Appendixes
36 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Appendix 1: Description of Niobrara 

River Streamflow-Gaging Stations

Appendix 1 Summary

During the operational life of a streamflow-gaging 

station, the USGS maintains a running description of the 

location, establishment date, drainage area, types of gages 

used, elevation of reference datum and benchmarks, channel 

and hydraulic controls, environmental conditions, history, 

floods, and other miscellaneous information (Kennedy, 1983). 

After a streamflow gage is decommissioned, the description is finalized and archived. These descriptions serve to 

stratify measurement data if hydraulic conditions changed at 

a streamflow gage, or a gage was moved from one location 

to another. Excerpts of these descriptions are included in this 

report for Niobrara River streamflow-gaging stations used 

in the hydraulic-geometry analysis to set the context for the 

hydraulic-geometry relations. The descriptive excerpts have 

been paraphrased for clarity and consistency, and are presented below upstream to downstream for the Niobrara study 

area. The authors have included photos of the cross sections 

and bridges typically used for discharge measurement at the 

streamflow-gaging stations. Photos were unavailable for the 

streamflow-gaging station near Hay Springs, Nebr., and the 

streamflow-gaging station near Verdel for the 1963 to 1985 

water years. The terms “left river bank” and “right river bank” 

refer to the direction of the river banks when a theoretical 

observer is in the middle of the river channel facing directly 

downstream. 

Niobrara River near Hay Springs

The USGS maintained a streamflow-gaging station on the 

Niobrara River near Hay Springs, Nebr., from 1950 to 1964. 

The streamflow gage was located 14 mi south of Hay Springs 

and approximately 4 mi upstream from Box Butte Creek. On 

July 31, 1951, the gage was moved 500 ft downstream from its 

original location. For the period of record the Niobrara channel generally was shallow, with low, vegetated banks, a mild 

slope, and a sandy bottom. The channel was uniform directly 

upstream and downstream from a nearby bridge. Because of 

the mild slope and shallow depths, wading measurements were 

made for most flow conditions. 

Niobrara River near Gordon

At a bridge crossing, located 11 mi south of Gordon, 

Nebr., and approximately 16 mi downstream from the Pine 

Creek confluence, the USGS and NDNR operated a streamflow-gaging station from 1946 to 1993. The original streamflow gage was located 4 mi downstream from this location 

and operated intermittently between August 1928 and September 1932. Channel width varied considerably upstream and 

downstream from the bridge, but the channel itself was fairly 

straight and shallow. The streambed consisted of sand and silt 

and shifted considerably. The left bank was high and did not 

have a significant amount of vegetation. The right bank was 

low, covered in woody vegetation, and subject to overflow at 

higher magnitude discharges. Most measurements were made 

while wading. Only a few high-magnitude discharge measurements were made; these measurements were made from 

the bridge.

Figure 1-1. Photograph of the 

Niobrara River near Gordon 

streamflow-gaging station 

reach. Photograph was taken 

looking downstream. The gage 

house is in the foreground. 

Many of the measurements 

were made near the upstream 

face of the bridge. (USGS file 

photograph)
Appendixes 37

Niobrara River near Cody

The USGS operated a streamflow gage 10 mi south of 

Cody, Nebr., from 1948 to 1957, located 5 mi downstream 

from the Bear Creek confluence, and a quarter mile upstream 

from an unnamed county road bridge. The channel was 

straight and uniform 500 ft upstream and downstream from 

the gage. The right bank was low and was overtopped during 

high-magnitude discharges, whereas the left bank was higher 

in elevation and rarely overtopped. The bed of the channel was 

gravel and the slope was steep enough to produce increased 

velocities during average flow conditions. A bedrock and 

gravel riffle extended from 50 ft below the gage on the left 

bank to about 200 ft below the gage on the right bank. The 

riffle was fairly persistent but subject to some shifting. During 

low flows the stream was waded, but during high-magnitude 

flows a cableway located 40 ft downstream from the gage was 

used for measurements.

Niobrara River near Sparks

The Niobrara River near Sparks streamflow-gaging 

station is operated by the USGS, and is located within the 

National Scenic River reach approximately 5.5 mi downstream 

from the Minnechaduza Creek confluence. The gage was 

established in October 1949 and presently is active. The right 

bank terminates at a high, forested bluff; the left bank has 

sparse vegetation. The banks are subject to overflow only 

during very high-magnitude discharges. The channel is shallow and straight with a mild slope. There is one thalweg only, 

but the location shifts occasionally. Most of the flows are 

measured by wading about 300 ft downstream from the gage. 

High-magnitude discharge measurements can be made from a 

bridge located approximately 18 feet upstream from the gage. 

Niobrara River near Norden

The USGS operated a streamflow-gaging station along 

the Niobrara River at a bridge approximately 1.5 mi downstream from the Fairfield Creek confluence from 1953 to 1986. 

The gage was established in October 1952 and was discontinued temporarily in September 1983. The gage was reestablished in October 1985 and then discontinued again in September 1986. Although the streamflow gage was never moved, 

the original bridge crossing was washed out on May 28, 1962, 

and a new bridge was constructed 75 ft upstream from the 

old bridge between March and May of 1963. The gage was 

located in a constricted section that has a steep bedrock bottom 

Figure 1-2. Photograph of 

the Niobrara River near Cody 

streamflow-gaging station reach. 

Photo was taken looking upstream. 

The gage house can be seen 

on the left river bank (right side 

of photo). The cableway can be 

seen one-third distance down 

from the top of the photo. Most 

measurements were made by 

wading underneath the cableway. 

High-flow measurements were 

made using the cable car. (USGS 

file photograph)
38 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

composed of shale. The constricted section is slowly changing because of headward erosion of a knick point of the bed. 

Above the bedrock section there is a shifting layer of sand and 

gravel alluvium. The channel was straight from approximately 

150 ft upstream from the gage to approximately 400 ft downstream from the gage. The right bank was steep, whereas the 

left bank was low with sparse woody vegetation. The channel 

was considerably wider upstream and downstream from the 

constriction where the streamflow gage was located. Most 

of the measurements were made at the bridge because of the 

depths and velocities in the constricted area, although some 

low-flow conditions allowed wading measurements. 

Niobrara River at Mariaville

The USGS operated a streamflow-gaging station on 

the Niobrara River at a bridge approximately 17 mi downstream of the Long Pine Creek confluence and about 20.5 mi 

upstream from the Keya Paha River confluence from water 

years 1986 to 1991. The channel upstream and downstream 

from the bridge reach is extremely braided and approximately 

one-half mile wide. Within the bridge reach the channel is narrower, but subject to frequent shifting, and commonly flows 

in more than one thalweg. Both banks are fairly steep and 

vegetated. The bridge was used for high-magnitude discharge 

measurements, but because of the wide and shallow nature of 

the channel, wading measurements also were common. 

Niobrara River near Spencer 

The USGS operates a streamflow-gaging station on the 

Niobrara River downstream from Spencer Dam, 5 mi southeast of Spencer, Nebr., and approximately 5 mi upstream from 

the Eagle Creek confluence. Temporary gages were used in 

the area exclusively to record river stage as early as 1908. 

Stage was related to daily discharge by computing the flow 

through the dam power house and spillgates. From October 

1944 to November 1954, a water-stage recorder was in place 

275 feet downstream from the dam. From November 1954 to 

September of 1957 a water-stage recorder was located 0.3 mi 

Figure 1-3. Photograph of the Niobrara River near Sparks streamflow-gaging station reach. Photo was taken looking 

downstream. The gage house is on the left bank, immediately downstream from the bridge. Most discharge measurements 

were made by wading downstream from the bridge. High-flow measurements are made from the bridge. (Photograph taken 

by Ronald Zelt, USGS).
Appendixes 39

Figure 1-4. Photograph of the Niobrara River near Norden streamflow-gaging station reach. Photo was taken looking 

upstream from the right river bank. The gage house can be seen on the left river bank (right side of photo), just downstream 

from the bridge. Discharge measurements were made by both wading and using the bridge. However, only bridge 

measurements were used for the hydraulic geometry relation. The bedrock notch is now located several meters upstream 

from the bridge. (USGS file photograph)
40 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

downstream. The most recent streamflow gage during the 

study period was established in August of 1963, and was in 

operation until October 2002. Most measurements were made 

from a cableway located downstream from the dam. A bridge 

is located approximately 0.25 mi downstream from the dam. 

The left tower of the cableway was located 460 ft downstream 

from the bridge, and its right tower was located 375 ft downstream from the bridge. During some lower flows, wading 

measurements could be made downstream from the bridge in 

the vicinity of the cableway. The reach downstream from the 

dam has a single thalweg flowing between shifting sandbars. 

The gage was reinstated in April 2008. 

Niobrara River near Verdel

The USGS operates a gage located approximately 

7.5 mi upstream from the Verdigre Creek confluence on the 

downstream side of a county road bridge. The gage was 

established in April 1938 at an old county road bridge 2,600 

ft downstream from the current bridge. In June 1939 the gage 

was moved 250 ft downstream to an old bridge abutment on 

the right bank. No records were collected between May 1940 

and June 1958. From June 1958 until July 1985 the gage was 

located near the old county road bridge; it was then moved to 

the new bridge, where it currently is located. The channel at 

the current location is approximately 3 times wider than the 

section used before 1986. The channel is wide and has several 

thalwegs in the vicinity of the current streamflow gage. Both 

banks are approximately 4 ft high and are heavily vegetated. 

Most measurements are made from the bridge, but lower flows 

can be measured by wading in the vicinity of the bridge. 

Figure 1-5. Photograph of the Niobrara River near Mariaville streamflow-gaging station reach. Photo 

was taken from the left river bank looking toward the right river bank. Gage house can be seen on 

opposite side of river. Flow is from right to left. Discharge measurements were made by both wading 

and using the bridge. However, only bridge measurements were used for the hydraulic geometry 

relation. (Photograph taken by Mark Nelson, Nebraska Department of Natural Resources)
Appendixes 41

Figure 1-6. Photograph of the Niobrara River near Spencer streamflow-gaging station reach. Photo was 

taken from the right river bank looking toward the left river bank. Flow is from left to right. Only cable-car 

measurements were used for the hydraulic geometry relation. (USGS file photograph)
42 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

Figure 1-7. Photograph of the Niobrara River near Verdel streamflow-gaging station reach. Photo was taken from 

the right river bank looking toward the left river bank. Flow is from left to right. Only bridge measurements were used 

for the hydraulic geometry relation. The gage was moved to this location in 1986. Prior to 1986, the gage was located 

approximately one-half mile downstream at a narrower channel section. (USGS file photograph)
Appendixes 43

Appendix 2: Scatter Plots of At-AStation Hydraulic-Geometry Relations

Appendix 2 Summary

This appendix includes the scatter plots used to generate the at-a-station hydraulic-geometry models for each 

streamflow-gaging station. The ordinary least-squares regression lines shown on each plot correspond to the individual 

fitting lines shown in figure 9 of this report. The regression 

lines and data are shown with 90-percent confidence bounds. 

The coefficients of the models (equations 1 to 3 in Background

section of this report), coefficients of determination for each 

least-squares regression line, and probability values for slope 

significance are shown in table 12 of this report. 

10

100

0.1

1.0

10

0.1

1.0

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

10 1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-1. Scatter plots of the at-a-station hydraulic geometry relations for the USGS 

streamflow-gaging station on the Niobrara River near Hay Springs, Nebraska (06456500). 

(A) Relations between discharge and wetted channel-top width; (B) relations between 

discharge and average channel depth; (C) relations from discharge and average channel 

velocity. The relations are shown for the period of record from water years 1951 to 1963, 

excluding water years 1956 to 1960. The solid line through the data points is the ordinary leastsquares regression fit. The dashed lines running nearly parallel to the regression line are the 

90-percent confidence bounds of the regression model. 
44 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

1,000

10

100

0.1

1.0

10

0.1

1.0

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1 10 1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-2. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflowgaging station on the Niobrara River near Gordon, Nebraska (06457500). (A) Relations between discharge 

and wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations 

between discharge and average channel velocity. The relations are shown for the period of record from 

water years 1964 to 1990. The solid line through the data points is the ordinary least-squares regression fit. 

The dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of the 

regression model. 
Appendixes 45

10

100

1

10

1

100

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

Least-squares 

regression line

90-percent 

confidence 

interval

Figure 2-3. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Cody, Nebraska (06459000). (A) Relations between discharge and wetted 

channel-top width; (B) relations between discharge and average channel depth; (C) relations between 

discharge and average channel velocity. The relations are shown for the period of record from water years 

1949 to 1956. The solid line through the data points is the ordinary least-squares regression fit. The dashed 

lines running nearly parallel to the regression line are the 90-percent confidence bounds of the regression 

model. 
46 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

10

100

1,000

1.0

0.1

10

1.0

0.1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-4. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflowgaging station on the Niobrara River near Sparks, Nebraska (06461500). (A) Relations between discharge 

and wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations 

between discharge and average channel velocity. The relations are shown for the period of record from 

water years 1964 to 2007. The solid line through the data points is the ordinary least-squares regression fit. 

The dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of the 

regression model. 
Appendixes 47

10

100

1,000

1

10

1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-5. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflowgaging station on the Niobrara River near Norden, Nebraska (06462000). (A) Relations between discharge 

and wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations 

between discharge and average channel velocity. The relations are shown for the period of record from 

water years 1964 to 1983. The solid line through the data points is the ordinary least-squares regression fit. 

The dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of 

the regression model. 
48 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

10

100

10,000

1,000

1

10

1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-6. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Mariaville, Nebraska (06463720). (A) Relations between discharge and 

wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations from 

discharge and average channel velocity. The relations are shown for the period of record from water 

years 1986 to 1990. The solid line through the data points is the ordinary least-squares regression fit. The 

dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of the 

regression model. 
Appendixes 49

10

100

1,000

10,000

0.1

10

1.0

1.0

0.1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000 100,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-7. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Spencer, Nebraska (06465000). (A) Relations between discharge and 

wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations from 

discharge and average channel velocity. The relations are shown for the period of record from water 

years 1964 to 2002. The solid line through the data points is the ordinary least-squares regression fit. The 

dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of the 

regression model. 
50 Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Methods and Results

10

100

1,000

1

10

1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-8. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflow-gaging 

station on the Niobrara River near Verdel, Nebraska (06465500). (A) Relations between discharge and 

wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations from 

discharge and average channel velocity. The relations are shown for the period of record from water years 

1964 to 1985. The gage moved upstream approximately one-half mile after water year 1985 (see figure 2-9 

for post-1985 relations). The solid line through the data points is the ordinary least-squares regression fit. 

The dashed lines running nearly parallel to the regression line are the 90-percent confidence bounds of the 

regression model. 
Appendixes 51

10

100

1,000

10,000

0.1

10

1.0

1

10

WETTED CHANNEL TOP-WIDTH, IN FEET AVERAGE CHANNEL DEPTH, IN FEET AVERAGE CHANNEL VELOCITY,

IN FEET PER SECOND

1,000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

A.

B.

C.

100

90-percent 

confidence 

interval

Least-squares 

regression line

Figure 2-9. Scatter plots of the at-a-station hydraulic geometry relations for the USGS streamflowgaging station on the Niobrara River near Verdel, Nebraska (06465500). (A) Relations between discharge 

and wetted channel-top width; (B) relations between discharge and average channel depth; (C) relations 

from discharge and average channel velocity. The relations are shown for the period of record from 

water years 1986 to 2007. The gage moved upstream approximately one-half mile after water year 

1985 (see figure 2-8 for pre-1986 relations). The solid line through the data points is the ordinary leastsquares regression fit. The dashed lines running nearly parallel to the regression line are the 90-percent 

confidence bounds of the regression model. 
Publishing support provided by:

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Nebraska Water Science Center

5231 South 19th Street

Lincoln, NE 68512

(402) 328–4100

Or visit the Nebraska Water Science Center Web site at:

http://ne.water.usgs.gov
Back cover. Upper left photograph is the Niobrara River near Cody streamflow-gaging station reach and was taken looking upstream. 

Upper right photograph is the Niobrara River near Norden streamflow-gaging station reach and was taken looking upstream from the 

right river bank. Bottom photograph is the Niobrara River near Verdel streamflow-gaging station reach and was taken from the right 

river bank looking toward the left river bank. (USGS file photographs)
Alexander and others—Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River—Scientific Investigations Report 2009–5008