Near Dark Gully is a small, ephemeral discontinuous gully located on the south side of U. S. Highway 14 and 16, 1 mile east of the Arvada road junction or 0.8 mile east of the Powder River bridge on U. S. Highway 14 and 16. Its coordinates are lat. 44°41'42" N., long. 106°05'00" W. in the NE 1/4 of T.54 N., R. 77 W. It is included on the topographic map published by the U. S. Geological Survey entitled "Sheridan, Wyoming; Montana," scale 1:250,000, part of which is included in this file (figure 1).
Near Dark Gully comprises the drainage system for a watershed of about five acres. The average elevation is about 3800 feet above sea level and relief within the drainage area is about 100 feet. The vegetation consists of various range grasses, primarily western wheatgrass (Agropyron), and sagebrush (Artemisia). The average annual precipitation is about 13 inches per year.
At the time of preparation of this file, five field surveys had been made: July 17, 1950, July 29-30, 1962, June 6, 1963, August 6-7, 1963 and July 4, 1968. The 1950 survey consisted of a planetable map showing the general configuration of Near Dark Gully, location of the largest headcuts, and a few spot elevations, see figure 5. No permanent bench marks were installed during this survey. The 1962 survey consisted of a more detailed topographic map by plane table survey, scale 1 inch = 100 feet, a simplified version of which appears as figure 2 of this file.
Twelve permanent reference points were installed, each reference point being a four-foot length of 1/2 inch diameter steel bar driven into the ground and protruding about six inches above the ground surface. Each reference point has a metal tag affixed to it on which is imprinted the pin description and elevation. The reference points, or bench marks (BM) are shown on figure 2. The triangulation net in table 2 will help enable the observer to find the reference points. Nine of the bench marks are used as end points for five cross-sectional surveys of ground-surface elevation. Cross-sectional and reference points information are listed in table 1 and the cross-sections were resurveyed in 1968; cross-section elevations are listed in tables 3-7. Note that distances between end pins for cross-sectional surveys are not always with a taut tape. Distances used in future surveys should be the same as used in initial surveys. A longitudinal profile was surveyed in 1962 up the main wash for a distance of 660 feet to the watershed divide and up tributaries "A" and "B" for distances of 800 feet and 760 feet respectively. Profile elevations are listed in table 8; tributaries "A" and "B" are defined on figure 2.
Three of the bench marks are used to determine the location of major headcuts. The position of headcuts in 1962 and 1968 are listed in table 9. In June 1963, a crest-stage gage was installed in the channel on line with section BM 11 - BM 1. The 1968 survey indicated the gage datum head changed so no reliable measurements have been obtained, but highwater marks indicated that depths of flow from one-half to one foot are possible. In August, 1963, two vegetation quadrats were established. Each is a five foot square with 10-inch spikes marking the corners. One is located 12 feet south of BM 6 and the other is located 16 feet west of BM 10. The distribution, size, and species of plants are shown on figures 3 and 4 for the two quadrats.
The file of original data includes both original planetable maps and black and white and color ground photographs (1963). These items are on file with William W. Emmett, U.S. Geological Survey, Washington, D.C. 20242, U.S.A.