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33 various limestones, sandstones, and shales below. Granite formations occur in places within the sedimentary rocks, such as the outcrop at the proposed dam site. Surface erosion at the higher elevations (generally above 8,000 feet) appears to be slight. Lower and particularly in the sed- imentaxy formations on the Sweetwater, ground cover is less effective in stabilizing the soils, and evidence of past gullying is abundant. Local ranchers report that periodic summer rains of high intensity have scoured nearly every gully below Sweetwater Lake at some time during the past 30 years. Rocks weighing several hundred pounds have been deposited in fans along the valley; finer materials have gone down the Colorado River. During the summer of 1962, there were no storms resulting in obvious erosion. ' Where the stream gradients are relatively high (5 percent or more), spring runoff results in considerable channel scouring. Turret Creek above the Currier Ranch with an average gradient of 7 percent is subject to considerable channel scouring and bottom rock movement each year. Mr. Tom Currier reports that a noticeable part of the wet meadow at the upper end of Sweetwater Lake was open water 20 years ago. Between. the Currier Ranch and. Sweetwater Lake there is evidence that the stream channel has shifted back and forth considerably over past years, probably the result of bed-load movement and log jams. _ In May or June of 1962, a land slide occurred on the Y-Z Ranch • several miles above Stillwater Bridge changing the channel of-the South Fork materially. This has been attributed to the saturation of unstable sub-surface formations. Other slides have. occurred in the past. Swede Creek, particularly, shows evidence of instability where