Floodflows and peak states of floods were measured and channel cross sections were surveyed at sites along the Sacramento River and in Butte Basin, Sacramento Valley, California, during 1980-90 to document magnitudes of flooding and channel changes. The study reach extends from rivermile 200 near Hamilton City to rivermile 134 near Meridian. Data were collected for each flood at about 70 sites that include streamf-flow gages, crest-stage gages, bridges and road overflows on State Highway 162 east of Butte City, and locations of historical high- water marks. Six cross sections of the river between rivermiles 193.7 near Big Chico Creek and 183.3 near Ordbend were surveyed annually during calendar years 1981-84, and 1986-90. Floodflows (peak flow 157,000 cubic feet per second) almost equaled the design flow capacity of the river at Butte City on March 2, 1983, when the peak stage of 93.0 feet was 5 feet below the top of the levee. This was the largest flood recorded at Butte City during 1980- 90. The most recent flood occurred February 18-19, 1986, when the peak stage in the river at Butte City was 92.0 feet and the peak flow was 145,000 cubic feet per second.
