Vigil Network Site: Forsaken Gully Near Moneta, Wyoming, U.S.A.
Submitted by: William W. Emmett
U.S. Geological Survey, Washington, D.C. 20242
Forsaken Gully is located near Graham Reservoir about two miles north of Moneta, Wyoming, in sections 10 and 11, T. 37 N., R. 91 W. (lat. 43°11'24" N., long. 107°44'07" W.). It is included on the topographic maps published by the U.S. Geological Survey entitled "Moneta, Wyo.," scale 1:24,000 and "Arminto, Wyo.," scale 1:250,000 (parts of both appear in the folder, figures 1 and 2). To reach the site of Forsaken Gully, one turns northward on the Moneta-Lysite gravel road at the small town of Moneta. At a distance of 3/4 mile, one turns left on an unimproved road, drives over the earth dam of Graham Reservoir, continues for another one mile and drives over the earth dam of West Fork Reservoir. From here, one continues to drive another one mile along the east and north side of West Fork Tributary, an ephemeral channel. At this distance, Forsaken Gully is 800 yards away in the left corner of a cove-like scarp approximately 200 feet high. With a four-wheel drive vehicle, one may continue another 500 yards over rough terrain toward Forsaken Gully, but at this point, deeply incised channels prohibit further driving.
Forsaken Gully is an ephemeral tributary to the West Fork Tributary of West Fork Reservoir within the area known as Graham Draw. The upper half of the mapped reach is characterized by a steeply sloping channel bed and steep side slopes, both of which are probably downcutting. The lower half is characterized by a lessening of bed slope and probably is actively aggrading. The topography from the end of the mapped reach is essentially a flat blanket of alluvium incised by a number of stream channels. The topsoil is mostly silt and clay and overlies shale, siltstone, and sandstone which crop out occasionally on the side slopes and in the channel at headcuts. Vegetation density in the vicinity of the mapped reach is only about one percent, but scattered throughout the alluvial fill area are densities of grasses and low sagebrush approaching ten percent cover. The drainage area within the mapped reach of Forsaken Gully is about ten acres, the average elevation is 5700 feet above sea level, and the relief between the watershed divide and the alluvial fill is 137 feet in the 1000-foot length of Forsaken Gully.
At the time of preparation of this file, six field surveys had been made: August 8-11, 1962, June 8, 1963, July 28, 1965, June 20, 1966, September 7, 1967, and July 6, 1968. The 1962 survey consisted of installing 20 permanent reference points, each being a four-foot length of 1/2-inch diameter steel rod driven into the ground and protruding about six inches (or more in some instances) above the ground surface. These reference points are shown on a planimetric map by planetable survey (scale one inch equals 100 feet), see figure 3 for simplified reproduction. Eighteen of the reference points are end pins for nine cross-channel land-surface profiles surveyed at locations specified in table 1 of this file and are also shown on the planimetric map of figure 3. The other two reference points are end bench marks for a mass-movement line located on figure 3. The left bank references points at stations 0, 200, 400, 600, 800, and 1000 feet, and the two at the mass-movement line, have a metal tag attached to them on which is imprinted the pin description and elevation. The cross-sections at stations 600, 800, and 1000 feet are instrumented with 10-inch long steel pins driven into the ground at given locations. Values of erosion can be determined accurately at these pins as long as proper maintenance and surveilance is continued. The mass-movement line consists of 10-inch long pins driven into the ground and surveyed to determine their position from the line of sight between the two end bench marks. A longitudinal profile was surveyed from the watershed divide to the alluvial flat. The surveys of 1963, 1965, 1966, 1967, and 1968 consisted of resurveys of the cross-sections and mass-movement line and checks on the erosion pins. Elevations from the cross-sectional surveys are listed in tables 2-10. Actual values of erosion at stations 600, 800, and 1000 feet are shown in lieu of elevations from annual resurveys, tables 8-10. The longitudinal profile data are listed in table 11, and mass-movement data are listed in table 12. A crest-stage gage was installed in 1963 at station 300 feet. An incomplete record shows only two flows, both recorded in 1967 and indicating depths of flow of 0.85 and 0.40 feet.
The file of original data includes the original planetable map (1962) and black and white and color ground photography (1962, 1963, 1965, and 1966) and low altitude aerial photography (1963). Original data are on file with William W. Emmett, U.S. Geological Survey, Washington, D.C. 20242, U.S.A.
The following publication is partly devoted to information about Forsaken Gully:
Emmett, W.W., 1965, The Vigil Network: Methods of measurement and a sampling of data collected: Symposium of Budapest, Internat. Assoc. Sci. Hydrology Pub. 66, p. 89-106.