This was a reconnaissance study for information on suspended-sediment concentrations and basin yields at 21 sites on selected streams in the Yakima Indian Reservation in Washington, and two sites on nearby streams. Suspended-sediment yields were generally low relative to those indicated by data for other streams on southeastern Washington, the southern Cascade Range, and the upper Columbia River basin. The highest long-term sediment yield on the reservation probably is from the Big Muddy Creek basin; the estimated annual yield is about 150 tons per square mile. The suspended sediment transported by this stream is largely from glacial outwash from Mount Adams. Other yields in the basin were estimated to be from 10 to 50 tons per square mile. Mass wasting is considered the principal cause of sediment transport in the streams studied. Some evidence of accelerated sediment production due to road construction was found along Surveyor Creek.
During the flood of January 1974, which has a calculated recurrence interval of more than 100 years, the maximum observed suspended-sediment concentration was 7,830 milligrams per litre, in the North Fork Simcoe Creek. During that flood, an estimated 70,000 tons of sediment was transported from the upper Toppenish Creek basin; this was nearly 600 tons per square mile. However, the long-term average annual yield was estimated to be only about 30 tons per square mile.
Additional Publication Details
USGS Numbered Series
Reconnaissance study of sediment transport by selected streams in the Yakima Indian Reservation, Washington, 1974 water year
iii, 12 leaves :map (folded) ;28 cm.; (20 p. - PGS)