U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011-3099

November 2011

A Dryland River Transformed—The Little Colorado, 1936–2010

The Little Colorado River, in northeastern Arizona, is a 

major tributary of the Colorado 

River. Over a span of 74 years, the 

U.S. Geological Survey (USGS) has 

mapped substantial migration of 

the river channel between the City 

of Winslow and the Navajo Nation 

community of Leupp (Tólchíí kooh). In 

a human lifetime, the river has moved 

more than 1 mile across its valley 

floor. Channel migration and flooding 

pose a considerable risk to the life 

and property of people living near the 

river. USGS scientists are working 

to better understand the potential 

for further channel adjustments and 

flooding to help provide communities 

at risk with the information they need 

to address these threats and make 

future development decisions.

Map showing the Little Colorado River watershed in Arizona.

Flooding along the Little Colorado River poses a serious threat to communities between Winslow and Leupp, Arizona. This 

photograph shows the intersection of Indian Routes 2 and 71 in the Navajo Nation, which was closed by flooding along the 

Little Colorado River in January 2008. Because there are few main roads and bridges in the region, such closures can have 

serious consequences. Nearby homes were also threatened by the flooding. (USGS photo by Lee Amoroso.)

The Little Colorado River is a 

major northwest-flowing tributary of the 

Colorado River in northeastern Arizona. 

Water flows year round in the headwaters 

and where there is groundwater discharge. 

Above Winslow, minor spring and seep 

inflow rises from bedrock fractures in 

the Little Colorado River channel and a 

large artesian spring wells up above the 

mouth of a perennial tributary stream. 

This groundwater discharge sustains base 

flow in the range of 4 to 5 cubic feet per 

second near Winslow. However, between 

the City of Winslow and the Navajo 

Nation community of Leupp (Tólchíí 

kooh), streamflow depends on runoff from 

rainfall and snowmelt, and the channel is 

frequently dry. 

U.S. Geological Survey (USGS) 

scientists have documented changes in the 

channel position, length, and width of the 

Little Colorado River using a sequence 

of aerial photographs taken from 1936 to 

2010. In 1936, the river meandered for 

43 miles between Winslow and Leupp, a 

straight-line distance of 30 miles. In 2010, 

the river meandered for 57 miles between 

the same locations. In addition, the average width of the channel decreased from 

1,250 to 110 feet between 1936 and 2010, 

a reduction of more than 90 percent. Thus, 

the river became longer, narrower, and 

more sinuous over this 74-year period.

The USGS is working to gain a better understanding of changes in the Little 

Colorado River channel morphology 

(shape and pattern) to evaluate the potential for further channel adjustments. This 

information may be used to help aid in risk 

abatement and guide future development 

decisions and planning by Winslow and 

the Navajo Nation communities of Leupp 

and Birdsprings (Tsidii to ́ii). Many people 

in these communities live within 1 mile of 

the river channel, where channel change 

and flooding pose a considerable risk to 

life and property. 

Recent flood events have caused 

substantial damage to infrastructure in the 

region. For example, a flood control levee 

was overtopped and breached in several 

locations by flooding and channel migration in December 1978. A new levee was 

constructed in 1989. However, despite 

improvements to the levee in 1991, 

breaching again occurred during flood 

events in January 1993, January 1995, 

and December 2004. The levee improvements were intended to provide 100-year 

flood protection, but peak discharge (the 

highest rate of flow reached during a 

flood event) in each of these floods was 

well below the 100-year flood level of 

65,000 cubic feet per second (U.S. Army 

Corps of Engineers, 1976).

ARIZONA NEW MEXICO

UTAH COLORADO

Col

Cameron Cameron orado River

GRAND

CANYON Hopi

Little 

Colorado

River 

watershed

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Navajo Nation

Little

Colorado

River

Leupp

Winslow

Little

Colorado

River

Leupp

Winslow
Channel Movement Across the 

Valley

In just 74 years, the Little Colorado 

River channel moved laterally more than 

1 mile across the valley floor between 

Winslow and Leupp. Three processes 

account for the shifting of the Little 

Colorado River across its flood plain—(1) 

erosion of channel banks and deposition 

of sediment, (2) meander cutoff, and (3) 

avulsion. A meandering channel migrates 

across its valley floor by eroding the outer 

bank of each bend and depositing sediment 

on the inner bank of the next meander 

bend downstream. Channel abandonment 

can occur through either meander cutoff 

or avulsion. Cutoff is the breaching of 

the concave banks of adjacent meanders, 

producing a shorter, straightened river 

segment. Avulsion is the breaching of the 

channel bank and the establishment of a 

new channel at a different location on the 

flood plain. From 1936 to 2010, there were 

notable increases in meander cutoff events 

along the Little Colorado River between 

Winslow and Leupp, while two major 

avulsions resulted in considerable changes 

in the position of the channel. 

There have also been significant 

changes in the surface area of the Little 

Colorado River between Winslow and 

Leupp. Here, the Little Colorado River 

occupied more than 10 square miles of 

surface area in 1936, when it flowed in a 

broad, largely unvegetated channel. By 

2010, the river occupied only 1 square 

mile of surface area and flowed in a much 

narrower channel through extensive stands 

of nonnative tamarisk (Tamarix spp). 

Tamarisk, woody vegetation native to 

Eurasia, began to noticeably colonize flood 

plains in the Southwest in the 1930s.

Dense vegetation can stabilize stream 

banks and promote sedimentation. The 

tamarisk invasion of stream banks and 

channels in the Western United States 

has long been assumed to cause channel 

constriction through dense growth that 

increases bank resistance to erosion 

and through excessive consumption of 

groundwater. However, these assumptions 

may not always hold true. Established 

tamarisk thickets have been removed by 

flood flows of even moderate magnitude 

along the Little Colorado River between 

Winslow and Leupp. Moreover, recent 

studies indicate that native species use equal 

or greater amounts of water when compared 

to tamarisk (Nagler and others, 2009).

Using a sequence of aerial photographs taken from 1936 to 2010, U.S. Geological Survey scientists have documented 

changes in the channel of the Little Colorado River between Winslow and Leupp, Arizona. On this map, varying colors 

represent the position of the river channel over the past 74 years. These aerial photographs, taken in 2010, show 

enlarged examples of areas of meander cutoff and avulsion shown on the map. Cutoff is the breaching of the concave 

banks of adjacent meanders, producing a shorter, straightened river segment. Avulsion is the breaching of the channel 

bank and the establishment of a new channel at a different location on the flood plain.

Flood Events and Dryland Rivers

Spatial and temporal variability 

of precipitation is particularly high in 

dryland drainage basins like that of the 

Little Colorado River. Because dryland 

rivers often have little or no continuously 

flowing water, flood events have the 

potential to move large amounts of 

sediment and significantly change the 

morphology or shape and position of 

channels. Scientists assessing river 

channel instability in arid and semiarid 

regions have found that erosion caused by 

channel migration resulted in economic 

losses that were five times greater than 

potential flood inundation losses (Graf, 

1984). However, potential channel 

migration resulting from flood events 

is rarely accounted for in flood risk 

assessment. This poses a problem for 

flood-hazard mitigation. 

Flood-frequency analyses, used 

for flood-plain management and 

infrastructure design, provide estimated 

flood magnitudes for selected recurrence 

intervals such as 5, 10, and 100 years. The 

recurrence interval, or return period, is an 

average time interval within which a flood 

of a given size will recur as the annual 

maximum. These analyses are based on 

streamgage records of peak discharges. 

For locations that have no streamflow 

data, basin characteristics such as drainage 

area, mean elevation, and mean annual 

precipitation are used for predicting 

discharge as a function of recurrence 

interval. Flood hazard mapping is typically 

based on predicted 100-year flood levels. 

Statistical methods of flood risk 

assessment make assumptions that are 

generally incorrect for dryland rivers. Two 

such assumptions are (1) that individual 

flood size is directly related to the size 

Meander Cutoff and Avulsion Along the Little Colorado River

Winslow 

Leupp

Chapter Birdsprings

Chapter

Navajo Nation

Boundary

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0.5 1.0 MILE

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0

0

Meander cutoff Avulsion

1936

1953

1979

1992

1997

2007

2010

YEAR
0 0.25 MILE 0 0.25 MILE

2007 2010

These aerial photographs taken in 2007 and 2010 

show the migration of a meander bend on the Little 

Colorado River in northeastern Arizona (USDA 

National Agriculture Imagery Program). White dots 

in the 2007 image show the location of the channel 

bank in 2010. Yellow dots in the 2010 image show the 

location of the bank in June 2011. From June 2010 

to June 2011, the axis of the meander bend migrated 

at least 325 feet. The inset photo shows channel 

bank erosion despite dense tamarisk (Tamarisk spp.) 

growth. (USGS photo by Debra Block.)

A storm beginning on December 29, 2004, caused significant 

flooding on the Little Colorado River in northeastern Arizona. 

This graph shows the daily mean discharge of the river recorded 

at USGS streamgages at Winslow (which records drainage from 

an area of 16,192 square miles) and downstream at Cameron 

(which records drainage from a much larger area of 26,091 square 

miles). It took 4 days for the flood wave to reach Cameron, about 

90 miles downstream of Winslow, at a greatly reduced volume. 

The estimated volumetric difference in flow, for the period of the 

hydrograph, is calculated from the area under the “curves” on the 

graph. The difference of 14,580 cubic feet amounts to a downstream 

transmission loss of 38%. The large reduction in flood peak occurs 

downstream because flow is rapidly diminished by infiltration into 

the unconsolidated sediments of channel beds and banks.

of the area drained by the stream and (2) 

that discharge increases downstream. 

The record for the Little Colorado 

River, however, shows that floods are 

often relatively localized, that no clear 

relationship exists between flood size and 

drainage area, and that discharge typically 

decreases downstream. For example, 

during a storm event with widespread 

precipitation on December 30, 2004, the 

USGS streamgage at Winslow (which 

records drainage from an area of 16,192 

square miles) recorded a daily mean 

discharge of 15,200 cubic feet per second 

(cfs), whereas the USGS streamgage at 

Cameron (which records drainage from a 

much larger area of 26,091 square miles) 

recorded a much smaller daily mean 

discharge of 134 cfs on that same day. It 

took 4 days for the flood wave to reach 

Cameron, about 90 miles downstream of 

Winslow, at a greatly reduced volume. 

An estimate of the total flow volume for 

this storm shows a downstream reduction 

of 38% between the two gages. Water 

is typically lost downstream in dryland 

channels as a result of infiltration into 

channel beds and banks.

Recent overbank flooding between 

Winslow and Leupp is likely related to 

the decrease in channel width there. On 

January 29, 2008, peak discharge recorded 

at Winslow was 11,200 cfs and the stage, 

or elevation of the water surface, was 

17.46 feet. Flood stage is considered to 

be 19 feet for the Little Colorado River 

at Winslow by the Advanced Hydrologic 

Prediction Service (http://www.weather.

gov/oh/ahps/). However, about 22 miles 

downstream, where two bridges provide 

access for the Navajo community of 

Birdsprings, the river crested at or near the 

decking beneath the bridges and spread 

for nearly 2 miles across the flood plain. 

As the flood water receded, sediment 

was left piled against the bridge piers and 

abutments, requiring dredging. 

Over the past century, changes in the 

amount and timing of precipitation across 

the Colorado Plateau region have been 

notable (Hereford and others, 2002). The 

Little Colorado River, like other channels 

in semiarid regions, is particularly 

sensitive to changes in precipitation and 

runoff, and therefore changes in climate 

affect its channel characteristics.

Implications

The trend toward a hotter and drier 

climate in the Southwest is superimposed 

on the inherent seasonal, annual, and 

decadal climate variability of the 

Little Colorado River region (http://

globalchange.gov/publications/reports/

scientific-assessments/us-impacts/

regional-climate-change-impacts/

southwest). Increased temperatures, 

earlier snowmelt timing, a reduction 

in the relative amount of snowfall 

to rainfall, and decreased peak 

streamflow have already been observed. 

As temperatures rise, more surface 

water evaporates. More moisture in 

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

27 28 29 30 31

December 2004 January 2005

Daily mean discharge, in cubic feet per second

1 2 3 4 5 6 7 8 9 10

Winslow

(38,221 cubic feet)

Cameron

(23,641 cubic feet)
Field work on the Navajo Nation was conducted with the 

cooperation of, and under written permit from, the Navajo 

Nation Minerals Department. All scientific study on the 

Navajo Nation requires a permit from the Navajo Nation 

Minerals Department, P.O. Box 1910, Window Rock, 

Arizona 86515, (928) 871-6587.

References

Graf, W.L., 1984, A probabilistic approach 

to the spatial assessment of river channel 

instability: Water Resources Research, v. 20, 

p. 953–962.

Hereford, R., Webb, R.H., and Graham, S., 

2002, Precipitation history of the Colorado 

Plateau region, 1900–2000: U.S. Geological 

Survey Fact Sheet 119-02, 4 p., available at 

http://pubs.usgs.gov/fs/2002/fs119-02/.

Nagler, P.L., Morino, K., Didan, K., Erker, 

J., Osterberg, J., Hultine, K.R., and Glenn, 

E.P., 2009, Wide-area estimates of saltcedar 

(Tamarix spp.) evapotranspiration on the 

lower Colorado River measured by heat 

balance and remote sensing methods: 

Ecohydrology, v. 2, p. 18–33.

U.S. Army Corps of Engineers, 1976, Flood 

plain information, Little Colorado River, 

vicinity of Winslow, Navajo County, 

Arizona: prepared for City of Winslow by 

Corps of Engineers, U.S. Army, Los Angeles 

District, California, March 1976, 27 p., 

27 plates.

Flooding along the 

Little Colorado River in 

northeastern Arizona in 

January 2008 reached 

the decking of the 

Birdsprings Bridge in the 

Navajo Nation (photo at 

left). The photo at right 

taken in March 2008 

shows the large amount 

of sediment deposited 

against the bridge by 

the flood. (USGS photos 

by Lee Amoroso.)

This Moderate Resolution Imaging 

Spectroradiometer (MODIS) satellite 

image taken on April 3, 2009, shows 

a dust storm (tan, northeast-trending 

streaks in middle of image) originating 

in the Little Colorado River valley, 

Arizona. In the image, dust from the dry 

channel and flood plain of the river is 

blown into Colorado. Dust deposited on 

mountain snow accelerates the rate of 

snowmelt by increasing the amount of 

solar radiation absorbed. In the Little 

Colorado River valley, sand and dust 

storms threaten housing, health, and 

transportation, moving northeastward 

across the Colorado Plateau. (NASA 

image; http://earthobservatory.nasa.

gov/IOTD/view.php?id=37791.)

the atmosphere brings more intense 

precipitation events. These conditions set 

the stage for floods in a time of drought. 

Flood models, however, cannot 

effectively simulate changes in channel form, 

which affect hydrological behavior. USGS 

scientists have mapped substantial changes in 

the width and position of the channel of the 

Little Colorado River over a short historical 

period—74 years. Decreasing streamflow 

and channel narrowing have transformed 

the Little Colorado River into a laterally 

unstable river that is susceptible to increased 

incidences of meander cutoff and channel 

avulsion. Reduction in channel carrying 

capacity through narrowing has also likely 

increased the risk of overbank flooding. 

Not only has the behavior of the river 

changed, the availability of fine sediment 

for wind transport has been amplified. Dust 

from the dry channel and flood plain of the 

For more information, contact:

Debra Block

U.S. Geological Survey

2255 North Gemini Drive

Flagstaff, AZ 86001

Tel. (928) 556-7138

dblock@usgs.gov

http://geomaps.wr.usgs.gov/

This Fact Sheet and any updates to it

are available at 

http://pubs.usgs.gov/fs/2011/3099/

Little Colorado River has traveled as far 

as Colorado. Dust deposited on mountain 

snow accelerates the rate of snowmelt by 

increasing the amount of solar radiation 

absorbed. In the Little Colorado River valley, 

sand and dust storms threaten housing, 

health, and transportation. The combination 

of water and wind erosion and sediment 

transport processes, in an increasingly 

arid climate, are leaving the land of the 

Little Colorado River valley susceptible to 

accelerated degradation and related hazards.

The work of USGS scientists studying channel change and flood hazards in 

the Little Colorado River valley is helping 

residents better understand and prepare for 

natural hazards in the region. This work is 

only part of USGS efforts to understand 

natural hazards in the United States and to 

help protect the lives and property of our 

Nation’s citizens.

Debra Block and Margaret Hiza Redsteer

Edited by James W. Hendley II

Layout by Jeanne S. DiLeo

January 2008 March 2008

UTAH

ARIZONA

COLORADO

NEW

MEXICO

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Little

Colorado

River

D ust