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Geomorphology and Sediment Transport

Powder River: Data for Cross-channel profiles at 22 sites in southeastern Montana from 1975 through 2014

Moody, J.A., and Meade, R.H., 2014, Powder River: Data for cross-channel profiles at 22 sites in southeastern Montana from 1975 through 2014, Washington: U.S. Geological Survey Data Set, doi:10.5066/F70Z719C.

Photo PR120_16Oct2012CloseUpC.jpg

Powder River rises in the Bighorn Mountains of Wyoming and flows northward through a semi-arid landscape in Wyoming and Montana to the Yellowstone River. The river drains an area of 34,700 km2 and has an average discharge of about 500 million m3 y-1 or 16 m3 s-1. This view of the river looking northward, and hence downstream, was taken in October 2012 (see study reach map), about 20 km north of the Wyoming-Montana state line, about 4 km downstream from an operating gaging station at Moorhead, Montana (USGS station number 06324500), and about 80 river km upstream from a discontinued gaging station at Broadus, Montana (USGS station number 06324710). The river is emerging from a narrowly-confined reach, and the valley widens northward, bordered by hills of the coal-bearing Fort Union Formation.

The river in this photo is at about bed-full flow (12 m3 s-1, Moody and others, 1999), and several riffles with disturbed water can be seen downstream between smooth glassy reaches of the river. A narrow band (~2-4 m wide) of reddish sedge (Scirpus spp.) grows just above the bed-full level along the edge of water with a wider band of mixed grasses (Agropyron repens, A. pauciflorum, Bromus inermis, Elymus canadenis, Spartina pectinata, and S. cynosoroids), willow (Salix exigua), tamarisk (Tamirix ramosissima) and small cottonwood seedlings and trees (Populus sargentii) on the flood plain. Three terrace levels have been identified along the river (Leopold and Miller, 1954; Moody and Meade, 2008). The first is the Lightning terrace with small cottonwood trees (seen here without leaves) adjacent to the floodplain in the right-center of the photo. The second is the Moorcroft terrace seen best forming the left bank and extending as a flat surface to the left (west) with a few large cottonwood trees still retaining their green leaves. The third is the colluvial Kaycee terrace that grades slowly upwards and meets the hills of the Fort Union Formation. It can be seen on the right side at the base of the hills and in the far distance on the left side, west of the white ranch buildings.

Powder River has no dams or other large-scale human modifications, which, combined with its substantial suspended-sediment load (2-3 million metric tons per year), makes it an optimal outdoor laboratory for studying natural fluvial processes (Moody and Meade, 1990; Hubert, 1993; Moody and others 2002). A research program was started in 1975 and, by 1977, 20 channel cross sections had been established in the 93-km reach, with the uppermost (PR113) just upstream from the Moorhead gage and the lowermost (PR206, see map) just downstream from the Broadus gage. Cross section PR120 crosses the river in this photo at a point near where the shadows from the large cottonwood trees on the left bank meet the river downstream from the apex of the nearer bend (Moody and others 1999; Pizzuto and others, 2008). An extreme flood in 1978 (779 m3 s-1) (Moody and Meade, 2008; Meade and Moody, 2013) was a major disturbance that widened the channel, caused two meander cutoffs (not visible in this photo), and deposited fresh sediment on the Lightning and Moorcroft terraces. Two additional cross sections (PR 122A and PR141A) were established on the cutoffs in 1979, and the post-flood response has been monitored at most channel cross sections through 2012. Elevation datum is NGVD29, and all cross-sectional data (1975-1998) also are available in the references listed below.

Study Reach Map

image of Powder River

The above map shows locations of 20 channel cross sections and the tributaries of Powder River in the study reach. The dashed line indicates the approximate boundary of the visually-obvious valley. Longitude and latitude tick marks are on the outside of the border, and tick marks for the universal transverse mercator (UTM) gride are on the inside of the border. DA and DV are the identification letters for the 100,000-meter-square grid. "Forty-fifth parallel (45o 00' N) is the Montana-Wyoming state line. "PR113" is the cross section identification".

Daily Discharge Data for Moorhead, MT Open as an excel spreadsheet (429k)

Project Staff

John Moody
Research Hydrologist
U.S. Geological Survey
3215 Marine Street, Suite E-127
Boulder, CO 80303-1066
Telephone: 303-541-3011
Fax: 303-447-2505
email John A. Moody
Robert Meade
Scientist Emeritus
U.S. Geological Survey
28603 Meadow Drive
Evergreen, CO 80439
Telephone: 303-674-7001
email Robert Meade

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